Newbie from NZ

[rjsutton]

Hi All
I was paralyzed 7 years ago by doctors negligence and have been adjusting to life in a wheelchair
there's a cool new machine on the market called an OMEO ( google if you like..... have to add NZ) which currently has no storing device in a vehicle unless its ramps or a hoist ( awkward and dangerous) it weights 70kg total.
Ive thought of a machine that sits in the back of a suv type vehicle and when the door opens the machine moves OUT 400mm so that the front has now cleared the boot-bumper-towbar.
a forklift like arm then lowers and picks up the omeo by its handles. this is then automatically locked to the arm
gears etc lift it up 650mm and then the whole lot moves back into the vehicle. No tiedows needed as its locked.
having problem with the "forks" moving from parked position ( right forward ) to the end of the 400mm overhang
Thats why im here
I need a ballscrew mounted on the side of the machine which is then attached to the fork base plate so as powered it moves the whole fork outwards 900mm
My background is building and no matter how many "calculators" i find online i just dont know what im doing to work out torque-rpm etc.
Jes sorry for the novel above

My name is Richard and i live in New Zealand. Thank you in advance for any help

[mekanik]

Hi Richard
Welcome to the forum, sorry to hear of your problems, I am sure someone will be able to help.
Have enclosed a link to the wheelchair.
Regards
mike
https://omeotechnology.com/

[John McNamara]

Hi Richard
Welcome to the forum, sorry to hear of your problems, I am sure someone will be able to help.
Have enclosed a link to the wheelchair.
Regards
mike
https://omeotechnology.com/

Hi Richard.

Welcome aboard from OZ.
I would like to think on this problem.

A couple of questions?

Is it possible to get 3D CAD drawings of the machine?
That would assist the person designing a manipulator for it.

If the machine was stored in the rear compartment of a vehicle. Would it be possible for the driver of the vehicle if disabled assuming that the degree of disability allowed the person to drive, to remotely control the chair and guide it to within reach of the driver? It would be great if the chair already had this capability. If not it could be retro fitted.

The chair would have to be returned to the storage unit in the same way. Not easy but doable. fortunately many vehicle manufacturers now offer automatically opening and closing rear doors so that part is easy.

The chair looks like a very well engineered unit, cool looking too, In spite of this no doubt you have a number if niggles regarding operation of the chair put them on paper.

Regards
John

[AndyUK]

Hi Richard

Have you considered long stroke linear actuators?

I suggest these because they're usually rated in terms of the force they can apply (which should be an easier calculation) and are often provided with 12/24V compatible systems which might be useful given the mobile environment. They should be cheaper than a ballscrew, because unlike a CNC you're not looking for a high degree of accuracy in this use case (1mm is probably close enough!).

The one disadvantage I can see is they might not be the quickest of options ;)

BW,
Andy

[Doddy]

Not to argue with the OP - just to ask you to review your statement: you say a hoist is awkward and dangerous - lifting 70kg into the boot. I'd suggest its probably the easier solution and can certainly be made safe. Awkwardness is more subjective.

Few solutions are going to "sit" in the boot - there's either going to be an awful lot of framework and counterweight, or you're going to have to bolt to the structure of the vehicle.

[AndyUK]

<Ignore my rant which missed the word hoist in the above post....>

[Doddy]

The point is that this is a one time thing to make a system which fits in to the back of a car, and then allows the user to be more independent.

Lifting 70kg in and out of a car boot is no joke for an able bodied adult male - I'm not even sure I'd be comfortable doing that alone, it's a big weight if you slip. Let alone when that's an awkward shape, and if the able bodied person who has to do it is a 50kg female, no chance in hell.

Sent from my SM-G950F using Tapatalk

We might misunderstand each other - the point I'm making is to manufacture a hoist, even on a sliding or swinging arm, is likely easier than a tail-gate lift type of system. I'm not suggesting for a second that manually lifting the OMEO is viable. Been there, tried it with similar (but heavier) weights and lost count of the number of lives I've lost.

[rjsutton]

Hi Andy
thanks for the reply
Actuators can t work as the amount of travel is 900mm +- and most actuators are 2s + ? and i only have 900mm to fit it in
It cant stick out the front or back
I use an actuator to push the initial platform out the 400mm which works well.
speed isn't a problem but i think fully in to out needs to be 15-20 secs or we could all be dead waiting for it to arrive
thanks Richard

[rjsutton]

Doddy
the hoists have to be bolted to the rear of the vehicle and when lifting the machine you have to put a cradle thru the handles then lift and rotate the chair at the same time. A major problem is you then have to tie the chair down in the boot which means reaching over and around and doing up ratchets etc . not easy for a person in wheelchair.
once the chair is locked to my forks that's it the mechanics do the rest.
My machine does in fact "Sit" in the back it has 2 simple metal straps which go behind the rear seat and secure to the rear safety belt anchor points. This is only to stop the machine "tipping" when fully extended out the boot.
also the width of the chair with outdoor kit tires is 830mm and a lot of normal suv wont fit that width wise as well as the hoist so must have the narrow tires which is a pain to change over ( change 2 wheels every time you want to off road!
My overall is 1000 and all the gear is clear of the chair which slides into a "pan" which is 850mm clear width so takes both sets of tyres.
Thanks For your comments

[rjsutton]

John
thanks for your interest and comments
The Omeo does in fact have a Bluetooth circuit which at the moment is used as a safety circuit
( no fob -no go.)
i have thought that this could be used to make the machine perform a tight left turn and park beside the drivers door . This would need alot of work and safety as when doing the reverse ( putting it back in the car)it would need sensors etc to make sure the Omeo was in correct position to be "picked up"
I have a machine called a Abiloader now which does just that with my manual chair. boot goes up chair comes out on arm and drops right buy my door. Brilliant but my chair weights 12 kg Not the 70 of the Omeo
have attached My drawings which is what i designed it on. Ive only done 12 hrs cad training but think ive done ok
Managed to get all the plates-pans etc made by engineering firm off them
dont seem to be able to load my dwg files!!!!! will try later
thanks Richard

[rjsutton]

Hi Mekanik
just wondering if the comments etc can be transferred to the mechanical general forum instead of the newbie thread? or doesnt it matter ?
thanks Richard

[rjsutton]

all
just a photo of the top of the panel where the ballscrew would attach, image screw fixed by bearings ( on its side) on the 60mm upstand
the ball housing fixed down where the 8 screws are
I took video but can find compatible file to attach here
thanks Richard

just noticed my other drawing didn't come over
might help visualize

[AndyUK]

So I've thrown your numbers roughly into our motor calc spreadsheet, which is only a guide, but has a few nice assumptions which lead to a wide safety margin.

Assuming your ballscrew is 900mm long (which obviously results in a travel less than 900mm), a 1610 screw (for speed rather than accuracy) and a moving mass of 90kg (you said 400N load, but the spreadsheet wants a moving mass - so lets take the chair plus ~20kg of frame).

If the screw is fixed-supported (i.e. BF and BK mount) we get a critical speed of 2200 ish rpm before whipping is an issue. That means we have a travel speed limit of 22m/min, well in excess of what we need. Assuming a 15s ish travel, lets say 6m/min which could travel the full distance in 10s but allowing time for acceleration and deceleration. That nicely translates to 600rpm on a directly coupled motor.

All in, you need a torque of 1.34nm (ish) at 600rpm to achieve that. Make it 4nm to allow for dynamic loads and a 3x safety factor.

Now, here comes the issue. Motor selection. I'm not great with low voltage motor selection - so I've used a 12.5nm nema34 stepper at 64ish volts. This easily gets you to the 3x safety margin that the spreadsheet suggests, but isn't exactly straight forward to use in a car. I'll let someone else chip in at this point :)

26411

[mekanik]

Hi Richard
Lee will move your post to the appropriate section if need be.

[John McNamara]

Hi RJSutton

The following link will assist you to find a 12V Gearmotor.

Armed with AndyUK's motor computations you will find a number that meet his specifications.

Beware of selecting the motor/gearbox on price alone You want your lift to long lived and reliable..

https://www.google.com/search?q=high+torque+12v+gearmotor&tbs=vw:l,ss:44,p_ord:pd&tbm=shop&ei=4L1wXf-AFNPfz7sP94OGmAU&start=60&sa=N&ved=0ahUKEwj_8KDqmLnkAhXT73MBHfeBAVM4KBDw0wMIpAQ&biw=1195&bih=731%22]https://www.google.com/search?q=high+torque+12v+gearmotor&tbs=vw:l,ss:44,p_ord:pd&tbm=shop&ei=4L1wXf-AFNPfz7sP94OGmAU&start=60&sa=N&ved=0ahUKEwj_8KDqmLnkAhXT73MBHfeBAVM4KBDw0wMIpAQ&biw=1195&bih=731

Regards
John

[rjsutton]

Andy
THATS why i joined this forum. It's all just numbers to me which i dont understand at all.
Thank you
My wife was interested in the "whipping " issue but told her it was for the machine in the garage. She soon lost interest.
The motor could be an issue as i dont think i can get to 64V in vehicle but well see if someone else can help out
appreciate your time spent on my dilemma

[mekanik]

The following link will assist you to find a 12V Gearmotor.


https://www.google.com/search?q=high+torque+12v+gearmotor&tbs=vw:l,ss:44,p_ord:pd&tbm=shop&ei=4L1wXf-AFNPfz7sP94OGmAU&start=60&sa=N&ved=0ahUKEwj_8KDqmLnkAhXT73MBHfeBAVM4KBDw0wMIpAQ&biw=1195&bih=731%22]https://www.google.com/search?q=high+torque+12v+gearmotor&tbs=vw:l,ss:44,p_ord:pd&tbm=shop&ei=4L1wXf-AFNPfz7sP94OGmAU&start=60&sa=N&ved=0ahUKEwj_8KDqmLnkAhXT73MBHfeBAVM4KBDw0wMIpAQ&biw=1195&bih=731

[rjsutton]

Thanks for the link
i need a unit with right angle drive ( takes up less horizontal space) so the only ones sort of max out at 470rmp but need an encoder to set limits (i think?????)maybe not i dont know on this part either
could someone please check this out. im still not sure about torque etc . so appreciate feedback-comments
Thanks in advance
Richard
https://www.ebay.com/itm/1pc-High-torque-worm-gear-motor-DC-motor-with-ENCODER-12V-470rpm/264289703688

[Doddy]

Thanks for the link
i need a unit with right angle drive ( takes up less horizontal space) so the only ones sort of max out at 470rmp but need an encoder to set limits (i think?????)maybe not i dont know on this part either
could someone please check this out. im still not sure about torque etc . so appreciate feedback-comments
Thanks in advance
Richard
https://www.ebay.com/itm/1pc-High-torque-worm-gear-motor-DC-motor-with-ENCODER-12V-470rpm/264289703688

Don't overestimate these Chinese motor/gearbox devices. I've used a couple in the past for raising a poly tunnel vent panel (28ft panel of polythene wrapped around a lower 1" steel tube... rotate the tube and the tension on the polythene sheet either raises or allows to lower the tube, opening or closing the panel). They are adequate provided that they're suitably rated but for my application I normally go for 0.5-2 rpm models to get the necessary torque. I have had to replace them, but the environment (heat, humidity) is pretty severe. Part of my selection criteria is the worm gear to allow it to hold position without power. I don't know the actual power output from these but a similar 470rpm 12V Chinese motor/gearbox here (https://www.ebay.com/itm/DC-12V-24V-Worm-Gear-Motor-3-470rpm-High-Torque-with-Self-lock-for-DIY-Design/172777200466?_trkparms=aid%3D333200%26algo%3DCOMP. MBE%26ao%3D1%26asc%3D20171012094517%26meid%3D86236 f21d8954b66a9c7ad6dc4e8acf5%26pid%3D100008%26rk%3D 1%26rkt%3D7%26sd%3D264289703688%26itm%3D1727772004 66%26pmt%3D1%26noa%3D0%26pg%3D2047675&_trksid=p2047675.c100008.m2219) claims 5kg.cm which translates to around 0.5nm.

Andy's recommendation of a 4nm rated motor is appropriate for a stepper motor - where you need to guarantee the step, or micro step in time to maintain a (potentially) rapid acceleration under load. In your case you're not quite so constrained and I think you can tolerate a lower torque to allow the motor to accelerate more gradually and less predictably. Even so, the order-of-magnitude difference is a little steep. Personally I'd trade the RPM for more torque (1rpm = 10mm with the 1610 screw, 900mm = 90 rotations, so the 260rpm motor would double the torque and give you a 900mm traverse in 20 seconds).

Limiting your choice to motors with integral encoders will reduce your choice of motor drastically. It's easy to add an encoder onto the shaft of any gearbox output (or better - if you get a twin-shaft one). The resolution of the encoder need not be so great - that one you link to is coupled to the motor shaft, not the gearbox shaft, so you're going to be counting small fractions of rotation of the output shaft - no need for this precision, provided that you have a positional sensor (e.g. micro switch) on the closed-position to avoid gradual drift in positional accuracy.

The motor controller is likely to be a dedicated device - a micro controller (maybe the Arduino range) with a H-bridge driver, and hook up the encoder accordingly. That's the easy part.

[rjsutton]

Doddy
i think you may mean don't "underestimate" Chinese motor-gearbox as you seem quiet happy with there performance. !
thanks for your input and your Logic seems sound
Loose a bit of rmp for Torque.
I came here to find out what parameters i need to make the Ballscrew work and i think im nearly there

I had a look on Arduino website and im more confused than ever..H-bridge driver ! STK500 Protocol ! ICSP Header.! loT Bundle......
i will have to join their forum to get answers on how i get the motor to stop at one end and reverse and stop and go forward and stop and reverse.......... I love your comment "That's the easy part " mmmmmmm.
I thought by buying a motor with a built in-on encoder then i would just pick up a controller with a few buttons to press when the limits were where i wanted. Not be be it seems ,
I was going to use 2 micro switches to limit travel but i still cant work out how they must be wired to stop travel and reverse the next time the controller button is pushed. My Bob the builder brain doesnt work very well in these situations
Thanks again
Richard

[Doddy]

Doddy
i think you may mean don't "underestimate" Chinese motor-gearbox as you seem quiet happy with there performance. !


No, I meant don't overestimate. These are very small devices, very small motors. They are reasonably rugged (the first that I stripped down was a mostly metal gearbox). I think these are particularly under specced for the numbers that Andy provided - but I'm trying to understand my gut-feel (rather than science) that they might just be worth a look at if the $30 cost is not prohibitive to you. But understand that you'd be in the realm of practical experimentation.


Doddy
I had a look on Arduino website and im more confused than ever..H-bridge driver ! STK500 Protocol ! ICSP Header.! loT Bundle......
i will have to join their forum to get answers on how i get the motor to stop at one end and reverse and stop and go forward and stop and reverse.......... I love your comment "That's the easy part " mmmmmmm.
I thought by buying a motor with a built in-on encoder then i would just pick up a controller with a few buttons to press when the limits were where i wanted. Not be be it seems ,
I was going to use 2 micro switches to limit travel but i still cant work out how they must be wired to stop travel and reverse the next time the controller button is pushed. My Bob the builder brain doesnt work very well in these situations
Richard

If you wanted I could provide the suitable software(or at least the basic framework that could be adapted by yourself) and help advise on the wiring. I'm not promoting Arduino as the only solution here - and at the end of the day these are simply based around COTS microcontrollers, but they do promote an accessible set of capable programmable hardware.

[rjsutton]

Doddy
Thanks for that
The $ cost of the motors etc is not a problem. But if these won’t work then I will be in another place [emoji30]
Appreciate any help in program and wiring diagrams. Any of your guys knowledge I can glean then that is a 100% more than I started with
Thanks
Richard

B


Sent from my iPhone using Tapatalk

[Doddy]

Doddy
Thanks for that
The $ cost of the motors etc is not a problem. But if these won’t work then I will be in another place [emoji30]

For clarity, I’m not convinced that these motors are big enough. I think they will be operating at their max power rating to get close to what you want, but then you’re only looking to run for 20 seconds at a time under load. This is why I say you’re in the land of practical experimentation

[rjsutton]

Doddy and All
Mate the next thing ive found is
https://www.aliexpress.com/item/32907624187.html?spm=a2g0o.productlist.0.0.78a91da csXtbKp&algo_pvid=000850c1-9a10-47a0-9d5c-c981134f01cc&algo_expid=000850c1-9a10-47a0-9d5c-c981134f01cc-28&btsid=8b83feca-f2ec-4d3f-80b9-a1de90815cec&ws_ab_test=searchweb0_0,searchweb201602_3,searchwe b201603_55

they reckon ( i think ) that @ 220rpm then torque is 24.25 kg.cm is this 2.4NM ?
alot more expensive but will see if i can source a cheaper supplier $NZ -$US not very good exchange ( thanks Trump)

I hope i could put an encoder somewhere ( can it go on the end of the ballscrew?)
Richard

[Doddy]

I’m not going to comment on the motor choice other than to say it looks much closer to the numbers that Andy suggested. I’m guessing the rating is more appropriate for continuous rating than peak (a good thing)

To answer your question: you essentially want to add an encoder to the gearbox output, either directly or on either end of the ball screw.

You will always want a “home” microswitch close to the home position for the mechanism to reset/calibrate the closed position... that allows you to include soft stops on the traverses by predicting position.

[rjsutton]

Thanks
Can You "suggest " an encoder and controller setup that would do what you mention. Im not sure where (or How) a Home microswitch would be wired into the circuit to reset-recalibrate.
If not too much bother could you please give me a diag (or lead me to where i would find one) with the encoder wire and microswitch.
I do think those chinese motors would not work as they just too small. I don't want to WASTE time and money . I will have to shorten the ballscrew slightly to fit the wider gearbox in as well

Andy if your still around do you think the new motor link above will be better choice of power for the ballscrew ?

[Doddy]

Thanks
Can You "suggest " an encoder and controller setup that would do what you mention. Im not sure where (or How) a Home microswitch would be wired into the circuit to reset-recalibrate.
If not too much bother could you please give me a diag (or lead me to where i would find one) with the encoder wire and microswitch.
I do think those chinese motors would not work as they just too small. I don't want to WASTE time and money . I will have to shorten the ballscrew slightly to fit the wider gearbox in as well

Andy if your still around do you think the new motor link above will be better choice of power for the ballscrew ?

I'm "thinking" that you're looking for an off-the-shelf solution, and there are such things readily available. For example.

https://www.amazon.com/uniquegoods-Wireless-Controller-Adjustable-Reversible/dp/B06W56X259/ref=sr_1_1?keywords=motor+controller+limit&qid=1567924478&s=gateway&sr=8-1

All you need are two limit switches. The instruction manual (linked at the bottom of the page on Amazon) shows how to attach two NPN proximity switches (https://www.amazon.com/Twidec-Inductive-Proximity-Detecting-LJ12A3-4-Z/dp/B07P3JX6J7/ref=sr_1_7?crid=10D4W3DIOQH97&keywords=npn+proximity+sensor&qid=1567925126&s=gateway&sprefix=npn+pro%2Caps%2C204&sr=8-7 and from the photo that you provided in post 12, I'd simply drill two holes in the side-wall an inch or so above the moving sled, one at each end of travel, and fit the proximity sensors there; Add a short piece of angle steel attached to the bolts on the linear blocks (you show 8 bolts in the image) to project up to provide a moving vane to actuate the proximity sensors when the sled is in the two end positions.

Job done.

[rjsutton]

cool
so i wouldnt need an encoder to check the revs moved if i just use the gear you show above?
bloody marvelous if thats the case ( can you please confirm my reasoning )
ive just ordered

https://www.ebay.com/itm/120W-High-Torque-Electric-RV-Gear-Motor-Worm-Gear-Reducer-Gearbox-DC12-24V/163817967776?_trksid=p2485497.m4902.l9144

with a ratio of 1:7.5 which should give me 3.21 NM as far as i can see
its a 120w motor so will be heaps better than the little ones
I hope im reading everything as i should be.
appreciate all your help.
Richard

[Doddy]

The purpose of the encoder is to allow the control system to determine where the sled physically is (actually, where it thinks it is, based on the number of [partial] revolutions and a knowledge of the screw pitch). That's one way of skinning the cat. The other is to simply think of what your actual use-case is - which is to understand when the sled is fully opened, and when it's fully closed - which the two proximity sensors will allow you to determine.

This simpler solution offers fewer bells and whistles (e.g. stall detection and acceleration/deceleration around limits), but also fewer things to go wrong - potentially higher reliability. You could introduce stall detection with a suitably rated circuit breaker. You'll have to tune the system with the actual position of the sense vane but it should be robust enough for your simple use-case.

I'm not a motors man - a bigger number looks better than a smaller number to me.

[Doddy]

...and one other thing - with heavy duty motors (or rather, heavy current draw on a low voltage supply) - remember Ohm's law. I'd personally slave a lead-acid battery close-by and trickle-charge it from the vehicle battery. Then use the shortest, beefiest cable runs to the controller and to the motor, maybe even bi/tri wiring it to reduce the power loss in the cable.

[John McNamara]

Hi RJ sutton

This link points to a 12v DC servo motor search.
Some of these units have an integral gearbox while others don't however if you make sure the shaft and flange mate up many will will work with a separate often right angle gearbox. Servo motors usually have an integrated encoder.

Leadshine offer a good range of servo controllers.and or motors. They are blatantly copied! and it is hard to tell the fakes are so similar. Make sure you are getting the genuine article.

You will need to control this setup with a micro, an Arduino for example.
This approach using servos better quality gearboxes and a dedicated controller will cost more but it should be very long lived and reliable.


Regards
John

https://www.google.com/search?q=12v%20dc%20servo%20motor%20-site%3Apinterest.*&rlz=1C1ASUT_enAU791AU791&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjo4fveocLkAhWUeisKHZaJAwYQ_AUIEigB&biw=1229&bih=633&oq=12v%20dc%20servo%20motor%20-site%3Apinterest.*

Worm reducer search

https://www.google.com/search?rlz=1C1ASUT_enAU791AU791&biw=1229&bih=633&tbm=isch&sa=1&ei=X4B1Xc-IBsz2vgSW1oSgDg&q=iso%20worm%20reducer%20%20gearbox%20-site%3Apinterest.*&oq=iso%20worm%20reducer%20%20gearbox%20-site%3Apinterest.*&gs_l=img.3...18800.25403..26892...0.0..0.218.2171. 0j12j2......0....1..gws-wiz-img.Q6wZEkGReBM&ved=0ahUKEwiPtKzwosLkAhVMu48KHRYrAeQQ4dUDCAY&uact=5

Leadshine servo controllers

http://leadshine.com/Pdf/Catalogs.pdf

[rjsutton]

Thanks John
interesting reading
appreciate your time
richard

[rjsutton]

Mate
looking at the install instructions
there's a "manual control" bit
i would use this instead of the wireless. Im not sure what type of switches etc or how it would work
assume simple off -on switch but what do 2 switches do
1 would turn motor on? below is chinese words in manual

Manual switch control Connect two manual switches.
Turn on the power,motor remotes on the corresponding direction.
When reach the limit switch,motor stops
.In manual working process,the remote controller is invalid

understand when use manual the remote doesnt work . Good because i want it all hard wired Not remote.
turn on power motor remotes on the cor.. direction... WHAT?
what is second switch for ?? im not very good with this wiring stuff
If i had a hand controller with 2 buttons ( 1 forward -1 reverse 12vdc operation) could these "buttons" be used to SWITCH thru the manual port and would a mere press ( not holding) keep the circuit going till the sensor stopped it? then press button 2 to reverse?

If you dont know this than totaly understand
i can try a different forum
cheers

One more quick thing please
the speed controller with reversable limit switch link you gave me
Im trying to find a similar piece of gear that would control another motor with 2 sensors ( 1 each end of travel) that onced reached would reverse direction
Sam as the larger one but dont need wifi etc just basic that can take the proximity switches. Have googled but nothing seems to have 6 connectors for the 2 sensors. plenty with speed and revers SWITCH but not for proximity . Anyway any help appreciated on this search

[Doddy]

I think you've included a marked up copy of the manual?, with Mac Preview I can't see the highlighted sections, so this reply is a little blind.

I agree - manual is likely a better system, but with the 30 minutes I spent looking I couldn't find a similar manual-only solution. Hide the remote.

The two switches - one for open, one for close. I'd look to a DPDT centre-off rocker switch (e.g https://www.amazon.co.uk/VASI4KO-Waterproof-Rocker-Switch-Centre/dp/B004J6PY2A)

That way you can use this single switch to actuate the open in one position, close in the other, and "nothing" with the switch in the centre position.

I don't think push buttons would work well - I think the inputs are non-latching (you'd have to hold the button down for the duration of travel). The rocker switch overcomes this. This applies to the hand-held pendant that you describe.

There are ways around this - without getting clever I'd use two separate 12V relays with diodes in series with the coil - one wired one way, the other reversed, wired across the motor - in one direction one relay actuates, in the other, the second relay actuates, and each relay is used to short the input to the corresponding demand input to the controller. I can sketch a diagram for this later when I'm not getting ready to go to work. But you'd have to understand how the controller behaves if you present two demands at once (e.g. what happens if you press open, when it's traversing to the closed position).

The biggest problem I have with that controller is understanding the connectors required for the manual switches and the potentiometer control. You could do with getting that information to get the switch/speed controller set-up.

Re. the last question - if your issue is the use of 3 wire proximity switches - you can replace these with microswitches for 2-wire interfaces, or use the proximity switch to actuate a relay and use the relay's NO contacts to provide the 2-wire interface to the controller.

[rjsutton]

Thanks I would appreciate a diagram when you have the time don’t really understand the relay-diode thing but maybe I see it I can do it
Richard

[Doddy]

Thanks I would appreciate a diagram when you have the time don’t really understand the relay-diode thing but maybe I see it I can do it
Richard

26430

Okay, hand-cranked over lunch. This is a very basic solution - I think you'd really be looking at a three button solution (the third being a "stop" button in case things went pear-shaped). But understand this one first...

SW1 and SW2 with open/close the sled. Not sure which will do which - everything depends on the wiring to the motor. Lets assume SW1 opens, and SW2 closes.

SW1 is pressed. The speed controller (central box) presents a PWM signal to the motor (M) with e.g. negative on M+ and positive on M-. That allows D1 to forward-conduct and RLY1 is actuated, closing the NO contacts within that relay. These are wired across the SW1 button pins, and essentially keep the button pressed whilst the motor remains driven. At the end of the travel, the proximity switch (not shown) causes the controller to stop driving the motor, and the voltage across M+ and M- falls to nothing. The motor stops, and the RLY1 de-energises, releasing the "Open" command.

Now, operator presses SW2 to close. The speed controller presents the PWM signal to the motor with positive on M+ and negative on M-. That allows D2 to forward-conduct (D1 is reverse-biased and does NOT conduct). That closes the NO contacts within that relay, wired across the SW2 button which keeps the button "pressed" whilst the motor remains driven to close. At the end of the travel the proximity switch (also not shown) commands the controller the stop driving the motor and the voltage across M+ and M- falls to nothing. The motor stops, and the RLT2 de-energises, releasing the "close" command.

Note, I'm making assumptions against the polatity of the PWM output to the motor depending on whether SW1 or SW2 is pressed. It's 50% certain that I've assumed wrongly and you'd have to reverse both D1 and D2 to get the circuit to work correctly.

Now, a third (stop) button?, would be very useful for when the sled jams and can't complete the traverse. You probably wouldn't want to interrupt the supply to the motor (big currents, inductive load = lots of wear-and-tear on the contactor) - but a suitably heavy duty relay could be used in-line with the output from either M+/M- from the controller - a NC contactor breaking either the M+ or M- signal, with the relay coil actuated by the "stop" button. You could also fiddle with a smaller relay with two NC contacts to break the signalling into the INPUT SIGNAL 1/2 inputs (actually, if the "NEGATIVE SIGNAL" on SW1 and SW2 are common for both switches, then you'd only need one NC contactor here... or a NC push button).

[rjsutton]

Doddy
Im a little bit concerned
the motor ive brought is a 120w 12vdc 13A motor ( see pic )
the controller i brought was
http://go.skimresources.com/?id=20518X781349&isjs=1&jv=3.22.5-stackpath&sref=http%3A%2F%2Fwww.mycncuk.com%2Fthreads%2F1300 4-Newbie-from-NZ%2Fpage3&url=https%3A%2F%2Fwww.amazon.com%2Funiquegoods-Wireless-Controller-Adjustable-Reversible%2Fdp%2FB06W56X259%2Fref%3Dsr_1_1%3Fkeyw ords%3Dmotor%2Bcontroller%2Blimit%26qid%3D15679244 78%26s%3Dgateway%26sr%3D8-1&xguid=01DK5Y5D0BTBBRB4BP1QP8KT2F&xs=1&xtz=-720&xuuid=597b140ffbc0d59f37bf6eee96225584

it says its 30A . ive just burnt out a 60 A variable speed controller
https://www.ebay.com/itm/PWM-Motor-Speed-Controller-Reversible-Regulator-Remote-Control-DC-10-55V-60A/113849071701?hash=item1a81eef855:g:F9IAAOSwhBVdTlh I
on another 12v motor (200W 9-12 amp)) and hoping that the new motor wont do same to the 30A wifi controller. I dont understand the amp-watt connection but i would think that a 60A controller should be able to handle the 9-12 A. am i missing something
Thanks]26438

[Doddy]

EDIT:
One very quick question to OP - are you confident that the wiring/polarity to the battery was correct?, it's the easy way to destroy a controller if reverse connected.

I was going to suggest also adding a TVS across the motor but this article https://www.modularcircuits.com/blog/articles/h-bridge-secrets/safety-features/ adds some interesting information. For reference, the h-bridge is essentially the output from the controller.
END-EDIT:

Rambling reply alert

In theory, nope, you're not missing a lot, apart from understanding the stall-current of the motor.

Before we get too involved, can I ask you to characterise how the controller failed? Did it fail immediately in a puff of smoke?, or did it fail after prolonged use? Was the motor output under significant load at the time, or just turning air through the gearbox? If it was under heavy load was the motor straining, or stalled? All this may help to understand what may have gone wrong with your first controller.

Before I forget to include this: sometimes s**t happens and a device will fail very quickly after initial power-up/test. Particularly power-devices such as those in your controller. I had this with a Seig mill brushless motor controller and a IGBT exploded within 20 minutes of operation on a brand-new mill - an otherwise expensive repair which was fortunately covered by the supplier. So, yeah, particularly with Chinese-sourced boards s**t sometimes does happen. Anyway, back to the main thrust of this reply...

The motor will often be described with two ratings for current draw (I noticed that with the earlier 90W motor). The lower of the two (around 1.5A?, from memory) would be the no-load current, and the higher value (6A?, from memory) would be the current draw under a quoted load (so many Nm... I think around 4, from memory?). Beyond that load the motor will draw more current. As the load increases, it will slow the speed of the motor and the current will increase. At the point that the motor stops (stalls) the current will be at a maximum, the stall current. That will be (significantly) higher than the rated power under load and will likely result in damage to the motor coils if power is not quickly removed. At the same time it's presenting more of a load to the speed controller which may be similarly stressed.

There's a slightly confusing labelling on the motor in the attached image, with V=12V, I=13A, and P=120W. I expect that the "P" output here is the mechanical output power at the rated voltage, current and RPM, somewhat lower than the computed 12*13 = 156W and the ratio to the rated power indicates the motor efficiency (120/156 = 77% efficient). Be warned, there will be further losses through the gearbox.

What you can do is measure the resistance of the rotor winding of the motor isolated from any supply - i.e. just on the bench-top. This is likely to be a rather low number of Ohms, but if you can measure this then that allows you to calculate the stall-current (it's essentially I(stall) = 12V / R(static)). This would tell you the maximum possible load that the motor would present if you stall it... or on start-up. Normally, of course, the motor would quickly come to speed and the current drawn would drop from the stall-current to the current appropriate for the mechanical load presented to the motor. For this reason a poorly designed, or under-specced speed controller may fail at the instant of turning the motor on. But, it must be expected that the motor has to start from stationary position in all but a few cases, and the speed controller should be designed to handle this instantaneous current surge.

So, the controller that failed is described with two primary ratings, a Voltage range 0-55V and a Current rating off 60A. Read through the advertising blurb and immediately you find that the 60A is a peak rating, and the continuous rating is 40A. So, a little bit of optimistic headline advertising there - to all intents that controller would be designed for 40A operation. But that doesn't explain the failure. What you might uncover if you stripped the controller down is that the rated current capacity is that in the manufacturer's data sheet for the power control devices (the output MOSFETS, or whatever devices are chosen), whereas the rest of the design could be poorly designed (for example, PCB traces could be too thin [localised heating, vaporisation of the PCB foil], inadequate heat sinking [the power devices would get too hot under load, overheat and fail], or inadequate protection from back-EMF from the motor [with PWM drives the motor will generate large voltage spikes which can damage semiconductors if not clamped]). All this comes under the banner of fitness for purpose. And, without wishing to appear too xenophobic or casting stereotypes, Chinese advertising. But, let's not kid ourselves, most of the electronics will come out of China and we, the consumer, drive the quality down by the price we want to pay.

Enough of the hypothesis, posturing and blame. Let's get practical.

I'm surprised that you managed to burn out the controller, but possibly not for the reason that you might expect. I'm going to throw some random numbers together to explain why...

*** ALL NUMBERS BELOW ARE PLUCKED OUT OF THIN AIR FOR EXAMPLE PURPOSES ONLY ***

Let's make a bold assumption on that motor. Rated 12V, an average of 12A, I'm going to make a rough-arsed guess that the rotor resistance (including brushes and terminals) comes out at 0.5 Ohm. That would give you a stall current of 24A. Still way below the maximum current that the controller is advertised as capable of sustaining, even under the stalled (or starting) condition.

But, the motor is only one component in the whole drive chain here. We need to consider the internal resistance of the battery, the resistance of the cable from the battery to the controller (both positive and negative supplies) and the resistance of the cable from the controller to the motor (again, both lengths). And in amongst that lot, the resistance of the terminals/connectors being used, and the internal resistance of the controller. Some not unreasonable numbers....

R(motor-stalled) = 0.5R
R(bat) = 0.05R
R(2m cable) = 0.2R. Imagine that you have four such lengths - source/return battery->controller, and controller->motor
R(controller) = 0.15R
R(terminal) = 0.0 - unrealistic, but it's just drawing out the numbers unnecessarily a this point

Your overall resistance would be 0.5 + 0.05 + 4x0.2 + 0.15 = 1.5R, and so the current draw from the battery would be 12V/1.5 = 8A (thereabouts). Definitely well within the advertised rating of the controller.

Further, you might expect the controller to be suffering under the short-load of 8A at 12V (around 100W of dissipated power), but it's not. Because of the internal resistance of the battery the battery terminal voltage has dropped...

V(terminal) = V(cell) - I * R(bat) = 12-8*0.05 = 11.6V

and then you have the voltage drop across the supply wires to the controller...

V(controller) = V(terminal) - I * R * (R(2m cable) * 2) = 11.6 - 8 * (0.2 * 2) = 8.4V at the controller, so the maximum power dissipated by the controller/motor/cables-between-these would be only 8.4 * 8 = 70W.

What I'm getting at here, is that with low voltage, high current designs, you get significant parasitic losses throughout the system that tend to degrade the performance significantly but in the same breath tend to be self-protecting.


I'm rambling now, and not coming to a conclusion...

My thoughts are with the advertised controller and motor, on paper they should work fine, and you've either been unlucky with a unit destined to fail due to manufacturing flaw, or that its design is either flawed, or underrated for the advertised specification. I'd approach the Chinese supplier for a refund or replacement.

For the new controller and motor... tread with caution. If you use a long supply wire from the battery to the controller (increasing the resistance) you should introduce a level of protection that you can use to test, and then start to reduce in length as you gain confidence that the controller isn't overheating etc, with the motor under load. Ultimately you do want that cable length to introduce as low an electrical resistance as possible to allow you to attain the power through the motor that you expect.

[rjsutton]

Doody
hi
the controller just stopped after about 15 seconds
no puff of smoke -no load on motor lead from battery was 300mm and had correct polarity
had worked 10 times but i was only running for a few seconds each time to test motor setup. Just stopped
Didnt buy from china but the nz supplier did as they are identical to ones on ebay etc.
ill try and digest your ather comments. i just didnt want to destroy the new controller as well

[Doddy]

Have a read here... https://medium.com/jungletronics/dc-motors-against-back-emf-589d8ed174cc, you might consider this a pragmatic approach.

[rjsutton]

Morning.!
Doody i want-(NEED) to protect these motors and electronics so thought i could use relays to protect each high amp motor circuit
would https://www.ebay.com.au/itm/MICTUNING-Relay-Harness-3040A-SPDT-Relay-12V-5-Prong-Harness-Socket-with-Colo/192899624547?hash=item2ce9b6ae63:g:7JsAAOSwjkJcwxx g&frcectupt=true
something like this work ?
or this?https://www.trademe.co.nz/electronics-photography/other-electronics/other/listing-2316521589.htm?rsqid=459af9141ab744ec9e9a8d45063f2 ae1-003

im not sure HOW large the amps-watts etc need to be but i just want to protect the electronics.
OR do i simply hardwire a 10-15-20 amp car fuse in the power supply feeds? this may be messier
trying to get smallest-neatest setup so i could fit them all in a protective case somewhere.
thanks if you can help
Richard

[Doddy]

Richard,

I need to understand your thinking. How do you perceive a relay will protect the motor and/or electronics? A relay is effectively a switch, so my question is really what quality is actuating the switch? Are you talking thermal overload? (a thermistor somewhere in the speed controller?) Some form of limit control? (already accommodated with the motor speed controller)? Sorry, I don't understand where you're coming from for "protection".

Similarly the timer module that you have there. From the outset I'd argue a couple of points - that module is likely (from a glance at the image of the board) to fry with the current draw from your motor (and I'm only talking of the principal motor in this thread). And in terms of "protection" you're only looking to introduce a timed on-state with that, and the only protection this effectively offers is against prolonged use (the quality here being the probability of over-temperature of the power devices in the speed controller). That presupposes that particular failure mechanism.


For the new controller and motor... tread with caution. If you use a long supply wire from the battery to the controller (increasing the resistance) you should introduce a level of protection that you can use to test, and then start to reduce in length as you gain confidence that the controller isn't overheating etc, with the motor under load. Ultimately you do want that cable length to introduce as low an electrical resistance as possible to allow you to attain the power through the motor that you expect This is what I recommended to avoid overheating. It's a heath-robinson solution but it's robust.

There is another potential failure mechanism of back-EMF from the PWM output to the motor frying the electronics (if poorly designed - pure speculation on my part) - which
Have a read here... https://medium.com/jungletronics/dc-...f-589d8ed174cc, you might consider this a pragmatic approach was intended to address. Here, add one or three capacitors across the motor terminals, or (I prefer, but seems to have limited traction in a number of articles) a TVS to suppress the back EMF.

[rjsutton]

Hi
i guess im just trying to stop any of the electronics from frying. MY THOUGHT is that if i put relays in the switches( realize a relay is a low voltage switch) then it MAY stop the electronics getting zapped by to much V or Amps when switched on. Maybe im not heading in the right direction.
On my unit i have a 200W geared motor with a 60 Amp fwd-rev-speed controller
, a 120w geared motor with the 2 proximity switches with the 30A speed-reversing controller
and 10A linear actuator.
Non of these will be run simultaneously they will go in sequence so the current draw is lower.
the whole units in the boot of the vehicle so i imagined running a fairly decent sized awg feed direct from battery to the boot and feed of a contact there . ( lessening power drop)
Nothing runs for more than 40 secs at a time either...
being overly cautious perhaps but this is a prototype and i cant-dont want weak points that could cause returns -claims etc.
at the moment the battery is on the floor 1m away from the electronics but obviously when installed it would be feed off the car battery ( with motor running) which gives slightly higher V. and could possibly cause problems?? ( or not)
Thats really where i am. it will probably fine with a few inline fuses but i dont know .During trials ive never over stressed any motor or controller as when i fried the last one it costs $ to replace ( $ which are running out)
I do need to put pressure on all parts as who knows what the purchaser may stupidly do. It needs to be pretty foolproof.( or protected)
Cheers

[rjsutton]

Hi anyone?
im nearly sorted BUT i just have one ? .
i have the motors-then the controller box ( which determines -speed- direction-PSD switches etc)
i also have a 12v dc hand control pad and a 12vd control box. this is all very light wireing and even the outlet plugs are designed for simple light actuators.
How do i wire the controller into the circuitry ie the outlet from controller is small wires, even thought the hand controller activates relays in the controller box the outlet is small.
( controller box has max 60A over 3 circuits ) do i just stick fatter wires into the outlet?
Hope someone can understand
Doody you gave me a circuit diagram before but i think this is already in the controller box
Thanks

[rjsutton]

I'm "thinking" that you're looking for an off-the-shelf solution, and there are such things readily available. For example.

https://www.amazon.com/uniquegoods-Wireless-Controller-Adjustable-Reversible/dp/B06W56X259/ref=sr_1_1?keywords=motor+controller+limit&qid=1567924478&s=gateway&sr=8-1

All you need are two limit switches. The instruction manual (linked at the bottom of the page on Amazon) shows how to attach two NPN proximity switches (https://www.amazon.com/Twidec-Inductive-Proximity-Detecting-LJ12A3-4-Z/dp/B07P3JX6J7/ref=sr_1_7?crid=10D4W3DIOQH97&keywords=npn+proximity+sensor&qid=1567925126&s=gateway&sprefix=npn+pro%2Caps%2C204&sr=8-7 and from the photo that you provided in post 12, I'd simply drill two holes in the side-wall an inch or so above the moving sled, one at each end of travel, and fit the proximity sensors there; Add a short piece of angle steel attached to the bolts on the linear blocks (you show 8 bolts in the image) to project up to provide a moving vane to actuate the proximity sensors when the sled is in the two end positions.

Job done.

Doddy
can you please help
ive installed 3 of the uniquegoods 30 amp controllers with npn switches each end
all works 100% BUT i want to get rid of the remotes and use a simple push button hand controller
ive wired this into the manual switch but i can only get it to work by using only 2 of the 4 wires. i think im grounding the circuit so infact closing the switch. trouble as soon as i release the button the motor stops ( with remote it stays ngaged until it hits the npn switch. is there a quick fix to turn this bit into a stay on system so when release the BUTTON it keeps moving until it hits the end then it reverses the direction. As said it works NOW with the remote as one press keeps it moving. Do i need to wire the handpiece differently or use the 2 other wires in the manual bit. ( says that using the manual makes the remote redundant but it doesnt do this . Any help cheers Richard

[Doddy]

Post #34, #36 cover this.

You could develop a more cunning solution with an Arduino at low cost.

[rjsutton]

Hi
reread 34 & 36 and see where you have supplied a solution to the switches. the hand controller does work when i hold down the button but it seems to deactivate the npn sensors.ie keeps traveling past the limits as long as its held down.. i would of thought they would still kick in.
ive googled and found that what you have said is what i need ( convert a momentary switch into a toggle switch) again the unit has relays everywhere so would i need to install a complete new set of relays simply to achieve this function ( 2 x 3 units = 6 extra relays!)
I pulled the handset to pieces and it just has 6 microswitches which obviously need to be held down to complete the circuit.
your reference to Arduino again sort of worries me. i cant really see on their site how-what sort of system i would use to achieve what i need.I dont think im smart enough to work with this product.
anyway .....thanks .....

[Doddy]

Do me a favour... measure the voltage, referenced to ground, of the two travel limit inputs, and similarly the voltage on the open/close inputs with reference to ground.

I’m trying to work out if you can directly couple a Logic device (typically 5v) to these inputs. The inputs are likely to float around either 12v or 5v (in the absence of an active switch input)

[rjsutton]

Hi
Mate i have no idea what you are asking
reference to ground , im just not that techy. im winging this on a hope and a prayer. i also dont have a voltage measurer.
i think im too much in the s..t to dig my way out
thanks for the help so far but i just cant get my head around how to do what you need . i really dont know where to go from here..............

[AndyUK]

Wonder on down to Mitre10, grab one of these:

https://www.mitre10.co.nz/shop/medalist-digital-multimeter-150x70mm-orange/p/464017

Its a must have if you're doing anything with electronics. Its like trying to cook without an oven otherwise.

Connect the black wire into the COM socket. Then the red wire into the V Ohm mA socket (like the picture). Turn the dial to Volts DC, range 20V (thats the area slightly counter clockwise from straight up).

Stick the black probe from the tester to a ground pin, or in the absence of a ground pin, stick it to anything big and bare metal that the electronics are connected to on the car. Stick the red probe from the tester onto each pin Doddy is talking about, it should give you some readings.

[rjsutton]

cheers will do tomorrow and get back
thanks for the input

[Doddy]

Cheers Andy, sometimes difficult for me to aim information at the appropriate level.

OP: My use of "referenced to ground" is, as Andy says, a way of saying with the black lead of the meter connected to ground/vehicle earth. I'd intended that (past midnight) to indicate to measure each input, not to measure with the two meter leads across the two inputs.

Where my thoughts are going on this is to understand if you could, with a diagram, connect an Arduino directly to the controller inputs or whether you'd need a relay board. I'm trying to keep this simple. I am prepared to write the software to host on an Arduino to give you the level of control that you've asked for, but in the first instance I want to see just what we can get away with with wiring. I can tell you that with UK prices, I could implement the control electronics for less than £20 (Arduino Uno, separate 2 relay board, probably a DC-DC convertor to protect the logic from the vehicle voltage spikes). The next challenge would be for you to install the Arduino IDE on a computer and demonstrate to yourself that you can flash/program an Arduino (connect via USB cable, press one button) - and check that a LED on the Arduino is flashing.

Your shout.

[opentoideas]

Something i dont think you have looked at yet is the end of travel can be variable. Think uneven ground, kerbs and even parked on a slope.

I have a hydraulic lift in the back of my van that does similar to your requirement moving a small platform from the rear floor out and down to the ground .

You will need to think carefully because the end point at one end (retracted into the boot) is fixed but the other end of the travel is not fixed.

The most likely is flat ground at the same level as the car verses reversed up to a pavement so 150mm or more higher than the surface the wheels are on.

If you have a fixed limit switch this will cause problems as the unit will keep driving even though its hit the deck.

Sorry to add another complication but hope it helps

[rjsutton]

Open to ideas
i Just reread your comment above and i think you may be misunderstanding the concept. There is NOTHING below the chair
all the lifting is done by 2 support arms which hook under the chairs main handle grips ( at top of machine )
no plate under it at all
thanks

[opentoideas]

I get there is no plate on your design but just wanted you to think about what happens if the chair touches down prior to the end of travel.

If the mechanism would continue without damage thats great but if it were to continue down damaging what i presume is an expensive chair not so much.

I couldnt see your sketches to see the interface between the machine and chair so you may well have this covered

[rjsutton]

Hi
I did write a novel length reply before but i lost the whole post somehow. i will rewrite it now
The machine is operated by a hand control which when the buttons are released it stops
As there is nothing under the chair as its lowered if the ground is higher ( say backed into the kerb with a 150mm high footpath ) then the operator
A if you can drive yourself then you can operate the wired remote
B if you dont drive then your carer will be in control of the remote...
Can stop the lowering of the pickup arms by simply releasing the finger off the button. There is a micro switch for when the machine is on a flat platform and it reaches "0" then it cant go lower.
This would be very unusual in New Zealand as we either drive into a parking space OR parallel park so the lowered machine height is the same as the vehicles standard height so 90 % of the time it will travel to its limit switch. Also if the car is parked on a slope OR road camber then the machine will still lower it parallel to the car ie the road surface. If its too steep then obviously drive around and find a more level park.
I have an abiloader in my current car for my manual chair and yes if the road is uneven it can jamb the chair in the loader . a good shake usually works but its not 70 kg of chair either :)
I dont ever want this to be autonomous as it will rip itself to pieces if something went wrong ( like a standard boot hoist if the hoist is lifted higher than the length of rope-cable it will snap the cable and drop 70 kg of machine on your feet ) common sense must prevail
Anyway
thanks fr your comments and i need all the brain power i can get to finalize this machine
Cheers
Richard