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They go bang because of excessive current not voltage...usually if upper and lower devices in the bridge are 'on' simultaneously... 40v across .5 ohms = 80A peak, 3200W instantaneously.... your PSU will do that for a few 100uS no problem!Quote:
Originally Posted by Ross77
Cheers, I did check the outputs when the onboard processor was controlling the motors and could see the logic highs and lows on the step and dir. pins, but when I tryed to inject a signal in to it my self nothing happened. I was just wondering if anyone knew if the enable pin can completely switch off the chip? as the board is double sided and very crowded it is difficult to see what is going on. (and after the last one went bang , I'm not keen to randomly test points) I was hoping that the enable switch is also controlled by the processor, which would explain why the motors wont work when I try to control them.Quote:
Opto's if none is found when you fire the circuit up it maybe because they require some voltage
Looks like I must have shorted something whist I was trying to get it to work. Is this driver set up usually Ok?Quote:
They go bang because of excessive current not voltage...usually if upper and lower devices in the bridge are 'on' simultaneously... 40v across .5 ohms = 80A peak, 3200W instantaneously.... your PSU will do that for a few 100uS no problem!
P.S if you are throwing them away KIP, my bin has plenty of space:beer:
Fair play, It was worth a try tho eh :naughty: Damm you yorkshiremen....Quote:
I have a good arm...although the bin in Devon is a throw too far for me :D
Im not one to be beaten so had another crack at the control board. Rewired the inputs to the L297, bypassed the output relays and it worked.............:dance:
......Until I turned the Vref pot the wrong way and fryed the output chips AGAIN. So at least I've found something i'm good at. :rofl:
Question time. If all 3 motors are 2 phase, 8 wire and configured in parallel, then why is one of the motors wired differently at the board plug? surley the phases cant change as the motor wouldnt turn...
Hope to make some real progress this weekend. so post some more pics soon
Forgot to ask if anyone knows of a good cuircuit to test stepper drives? I'm looking for an MPG type thingy that dosnt require a pc or mach, but will generate the correct pulse voltages, timings etc for step and direction
Maybe i should post In the drivers section?
Cheers
Funny you should say that, i was just thinking along those lines...Quote:
Originally Posted by Ross77
I'll post it up later...
For a really simple 'get you up & running testing a stepper nice & quick', it's really handy to have one of these in your component tray...
http://www.datasheetcatalog.org/data...stems/5804.pdf
They don't make 'em anymore so they're getting a little scarce, but still available here...
http://www.cricklewoodelectronics.co...0&cat=0&page=1
Pin 11 is the step input - switch that pin low/high - your steppers move. Job done.
Tell you what, Nottingham is nearer and I can take them down to Bristol on the 22nd when I go to the show.Quote:
Originally Posted by Kip
Let's shame the bastard :clap:
.
Ross, are you saying to exercise the stepper drivers directly without a PC, or to drive the motors without a stepper driver?Quote:
Originally Posted by Ross77
Cheers guys.
That sounds perfect for testing the motors, I was also after something to control the whole driver/ motor setup without a pc.Quote:
For a really simple 'get you up & running testing a stepper nice & quick', it's really handy to have one of these in your component tray...
http://www.datasheetcatalog.org/data...stems/5804.pdf
Good idea, he's not biting yet tho..... maybe have to offer some cash:heehee:Quote:
Tell you what, Nottingham is nearer and I can take them down to Bristol on the 22nd when I go to the show.
Let's shame the bastard
Is that a CNC/ machinery show?
Yes I would like to be able to control the whole driver and motor system without a pc. I was thinking along the lines of a varible pulse generator that could feed each axis as required by using a joystick, (like on a Playstation controller) That way i could control direction with the pad and the speed with a trim pot, If it works i might look at using a ps3 analouge type joystick so the speed it proportional to the stick movement.Quote:
Ross, are you saying to exercise the stepper drivers directly without a PC, or to drive the motors without a stepper driver?
Ive been looking on the the net at 555 timer circuits feeding a schitt trigger, but I'm not skilled enought to design it for the correct voltages and pulse timings:sad:
Oops...that'll be the speed reading. Sorry!Quote:
Originally Posted by Ross77
you wanna tread carefully there ....you could end up with a stinking mess :tongue:Quote:
Originally Posted by Ross77
No probs, still usefulQuote:
Oops...that'll be the speed reading. Sorry!
That will be my speed typing....:heehee: Or at least thats my excuse....Quote:
555 timer circuits feeding a schitt trigger
Another evening of tinkering and I think Ive finally got the board sorted so I'll leave it for now. Now my finger is better I can hopefully finish the honing and anti backlash nuts. Just got to hope I dont make a schitt job of it :rofl:
Ross,
Try the attached for size...
If you are driving opto-isolated inputs to the drivers let me know as it'll need a couple more parts...
Hi Irving,
on the small pic I think I can see the link to the dir out pin but it is missing if you enlarge the picture, I assume it goes to the divider part of the 2 resistors.
peter
Thanks Irving thats exactly what I was looking for. :beer:
For this board I'm going direct to the driver chip but it will be useful to have the opto verision as well if you dont mind. Is it posible to do single steps with this circuit as well :whistling:.
Thanks again
Peter, seems to be ok when I look at it, dir pin is linked to the resistors
Here is the opto version...Quote:
Originally Posted by Ross77
Single steps I need to think about (and why would you want them?)
well i dont understand whats going wrong with my pc display, I downloaded pictures and the links are there but not on the display!
Another fine point of MS IE7 I expect!
Peter
Thanks Irving, your a star. have a couple of beers :beer::beer:
The single steps are for fine tuning, I'm planning ahead really. Once it has built the machine I want, this mill will probably be redundant and not worth selling, so I thought that It might be useful if I just need a part skimmed or holes drilled at set distances. If I also fit a DRO of some discription I can manually control the machine as a stand alone without having to draw the part and produce g-code etc. etc.
Farnell will charge the first time you use them, I think (that's what happened to a mate of mine [who asked me to order the bits for him instead, since I tend to chuck about £200 a month at them] and my brother).
I'd also put RS in that list - although RS I've found are generally more expensive for components, except LCD displays where RS are about half the price.
I've used Digikey before, but not Rapid nor Cricklewood (yet).
Not as far as i am aware... just signed up, threw an order of about £30 at them, job done...Quote:
Originally Posted by tribbles
+1 to that.
I've only just started dealing with Farnell, as I'd always had in my mind that they were Draconian with their postal charges & minimum order requirements and made you jump through hoops as a private individual (they used to - & RS were worse from recollection!)
I'm actually pleasantly surprised at how they've changed (I guess it's 'adapt or die' in this new Global commercial market place we now live in) & I've put in some pitifully small orders with Farnell & never yet had a postage charge yet....normally get the stuff the next day too.
I think that's only if you don't order below £20 the first time.Quote:
Originally Posted by irving2008
Certainly they used to have an MOP of £20 (which meant I always over-ordered on items), but now they don't for me.
No, its because i used a debit card, the £20 MOP applies to credit cards only.Quote:
Originally Posted by tribbles
Ok In case your thinking this tread is getting a bit stale I'd better post some pic's. Again apologies for the quality, need a new camera really.
The motor mounts are finished as is the MK3 anti-backlash nut for the X axis. Its all a bit messy as Ive had to use alu angle and modify bits from the original machine. some bits are still mock up and I may remake them if I get time.
Thanks to John S for the idea for anti backlash solution. I had to change it slightly as the first incarnation of just sandwiching the orignal nut with delrin kept twisting slightly and producing more BL. This design uses the first to plates to sandwich to original nut, and prove a fixed base, whilst the delrin is fixed to the end plate, the spring in between means that i can back of the tension on the adjusters as well. Having played around with this there seems to be a very fine line between zero BL and too much friction. Comments and abuse welcome :heehee:
Quote:
Originally Posted by Ross77
Why have you got nuts behind the stator plate? If you tighten them the spring does nothing and the line will be fine :beer:
Hi RobinQuote:
Why have you got nuts behind the stator plate?
Not sure what you mean by a stator plate? in the 2nd picture the left hand and middle plate are clamping the original nut, tightened by the middle nuts (to resist rotation). the delrin nut is fixed to the right hand plate and is adjusted by the end nuts to compress both drive nuts to reduce backlash.
The spring is purley overkill and just pushes the delrin nut on to the adjuster nuts and also ensures that if I back of the adjuster nuts then the delrin nut moves with them to give positive control over the pre-tension.
Ive tried 3 or 4 different versions and this set up worked the best, is the easiest to align and easiest to adjust.
I presumed that there is always a fine line between eliminating backlash and excessive friction?
Made some good progress this weekend.
Gave up honing the ways as they were so far out of true and had to scrape them. I used a 60 deg. Carbide tipped lathe bit (held in a 3-4 MT adapter :whistling:)
I can see why people dont like doing it, very time consuming, repetative and hard work.
So with the ways sorted, motor mounts done and the antibacklash nuts finnished I decided to give it a lick of paint. :dance:
Amazing Ross, coming along nice mate !
What paint did you go with in the blue ?
Thanks Lee. Hope to get it assembled soon....Other projects and uni looming...........................
Can't remember the makers name but its supposed to be a hardwearing hammered finnish same as Hammerite. The casting was so so rough I thought a flat paint would look terrible.
This should be a good test for the paint. If it can resist way oil, coolant, grease and all the other nasties that will be thown at it.
After 2 months I've been able to fit in some workshop time:yahoo:
So the z axis is done and I've managed to hot-wire the controller board to work with step and direction so "IT WORKS" just need to find a better way to transfer the IC to another board.
Tested the x axis and there is no backlash, using a 0.001" gauge it always returned to the same place
The breadboard circuit is the stepper exerciser that Irvine designed for me. Thanks again it works great, no need the drag the pc out.
Now for the question........
Should steppers hum/crackle whilst holding? it only seems to happen on certain motor positions. It also gets worse/louder when I turn up the Vref to increase max current.
It also seems to buzz/miss steps at about 300 rpm, is that normal?
Thanks in advance.
Quote:
Originally Posted by Ross77
Steppers usually make their best noises when in action, on hold the current is usually cut because you don't need the pulling power.
300rpm is not bad for a stepper, but it isn't good either :nope:
Thanks Robin, not sure i understand, so is the buzzing/ frying noise when holding ok then? or Have I got problems?
I have basicly had to rewire the driver chip and followed the data sheet and other similar designs but I not sure about the control pin. It sets the chopper for either the 4 phases or on the inhibit wires, could this be causing the noise?
If the noise is ok (typical) then I can increase the vref to gain more current which seems to help with the missing steps at the higher speeds. At the moment its set at 0.5v which i think means I've only got 1amp going to the motor. As it uses 2 L602 output chips I belive it is capable of 4amp but I'm too chicken to just crank it up.
Thanks in advance
Quote:
Originally Posted by Ross77
The frying noise is probably a sympathetic vibration to the chopper frequency, possibly worse if you pause between half steps. Nothing to worry about so long as the motor isn't getting hot.
I'm no expert on this, my max stepper speed actually decreases if I wind up the current which seems totally wrong, so I am not understanding something. My motors clack out if I set the G0 to 12mm/s so I keep them set 8mm/s to avoid losing position. I'm waiting for Gary to send me some fancy 220 volt drivers which will hopefully make everything wonderful.
I suggest you wind up the current slowly, test the top speed and see if motors, or heatsinks on the driver start to get excessively hot.
Good luck :beer:
Robin
Thanks Robin, :beer:
The motors dont seem to get hot if left holding but they get dam hot in use, almost untouchable!! I'll have to see how it goes.
Thanks again
Get a cheap thermoprobe from Maplin (£19, here) and check motor case temp. Anything above 85degC and you need to be thinking cooling/heatsinks on the motors.
Thanks Irving, Already got that on my meter, and one of those infrared jobbies.....Just forgot to use them.:whistling:
So is it ok for the motors to get hot if i provde cooling to hopfully keep below 85 degC?
With regard to your L297/ 6203 driver do your motors buzz whilst hold?
Also have you got the contol pin set high or low?
Cheers
Quote:
Originally Posted by irving2008
D'uh :eek:
I've never run a stepper past comfortable to touch, usually lukewarm to tepid. Am I not trying hard enough :naughty:
Isn't there something about eddy currents heating things up? No possibility he's driving one coil with the other shorted out I suppose? That would be the perfect recipe for slow'n'hot :heehee:
Robin
Problem solved........:whistling:
It all went up in smoke tonite, flames an all. quite impressive :heehee:
Looks like I need a new 3 axis stepper driver.
2 steps forward 5 steps back eh.
Bit late for a photo i suppose :whistling:Quote:
Originally Posted by Ross77
Unless you chuck a bit of paraffin over it :naughty:
Glad you found it funny.:smile: I'm £50-60 out of pocket now to replace it tho :eek:
Could be arranged, and very tempting, but being a tight git i'm going to rob the heat sink ect from it first.:dance:Quote:
Unless you chuck a bit of paraffin over it :naughty:
I cant find any cheap drivers that work over 40v so looks like I cant even use the psu.
Sadly most stepper driver chips are 35 or 40v max... so 30 or 35v supplies. To go above that you need to be looking at discrete MOSFET drivers, but these tend to be are rare and expensive..Quote:
Originally Posted by Ross77