Help! DIY 4 amp L297/6203 driver

Can you program a pic at all?
What you actually want it to do is pretty trivial.

However I'd change the circuit slightly. In my experience you don't generally want the holding current to fall too much - to about 25% is about right.

So:
The current voltage across the VR is about 1v. Get another resistor which will give you approximately 0.25v and wire that up to the top of the VR. You now have two resistors which if either is connected to the supply will either give you the desired current or 1/4 or it.

Next take the two resistors and wire them to two of the output pins of the PIC (obviously the existing 3k9 will need disconnecting from the supply).

What we've got now is the ability of the PIC to pull either resistor high (+5v) and thus select the current as either 1x or 0.25x.




Some psuedo code for your pic.

Code:

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start:

loop:
 if (clock == valid)
  counter = 5Seconds;

 if (counter <> 0)
 {
    Line1x = high;
    Line0.25x = tri-state;
 }
 else
 {
    Line0.25x = high;
    Line1x = tri-state;
 }

 if (counter > 0)
    counter = counter - 1;

  goto loop;

---

As you can see, there's not a lot required...

If you've got interrupt on port change - that would be best for the clock (although it'd be unlikely in sampling it over 5 seconds that you'd miss an event).
counter can be done using a timer or in software - whatever your comfy with.

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Can you program a pic at all?

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No not at the moment. But tribbles has kindly offered to program one for me (and make the board :beer:) but wasnt 100% sure on the best way to go with the code so thanks vmuch.

Would it be ok to use 2 trim pots instead of resistors, so i can adjust for diferent motors/ applications? and is it feasable to to use a 1 sec or less timing?

Thanks again, I'll have a go at another schematic to see if I've got the the right idea.

The code could be pretty much as kwacker has suggested (obviously not pseudo-code though). I'd use timer interrupts.

Using two of the PIC's pins to control Vref is a neat idea - and two trimmers should be fine.. You could use a third pin with a trimmer for configuring the timeout (should be very easy to do).

Exellent. This is moving along nicley now.

Good idea on the trim pot for time out, I like it...

So the only decision now is what pic to use and the pin out? It looks like im not going to use the short circuit protection so the the tripple 3 input AND gate is wasted in this circuit.

Are there enough pins on the pic to implment the 1/2 step boost, or will it make the code difficult?

Last question. dose this need a crystal or can it be linked to the sync pin on the L297 for external clock?

The PIC doesn't really need a clock (it depends on which one you use).

Since I've got them, you may as well use 12F683 - it doesn't need an external crystal or clock (it's got an 8MHz clock built-in). It's 8-pin: 2 power, 1 input and 5 I/O.

If you're referring to replacing the 7415, then I would keep it as it is - you'd need to monitor the lines, and there would be a delay. But then, if you're not clocking the circuit very fast, then it would probably be okay. But, as you mention, it does save on code complexity :smile:

For the PIC, you can use any of the output pins (pins 2, 3, 5, 6 and 7) for the VREF generation signals, but use one of the analogue pins (5, 6 and 7) with a trimmer (between VCC and GND) to set the delay.

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For the PIC, you can use any of the output pins (pins 2, 3, 5, 6 and 7) for the VREF generation signals, but use one of the analogue pins (5, 6 and 7) with a trimmer (between VCC and GND) to set the delay.

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Ok think I've got it sorted. I'm not sure if the trim pots are configured properly as it looks like they will interfer with each other :naughty:. Just reread Kwakers post and I think i should have used the pic to pull them high not low. :whistling:

I've also left the 3.9 res in as I presume it will limit the Vref to 3v mav as per the data sheet. If the pots are pulled high could this be achived with a common 3v supply?

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Originally Posted by Ross77

Ok think I've got it sorted. I'm not sure if the trim pots are configured properly as it looks like they will interfer with each other :naughty:. Just reread Kwakers post and I think i should have used the pic to pull them high not low. :whistling:

I've also left the 3.9 res in as I presume it will limit the Vref to 3v mav as per the data sheet. If the pots are pulled high could this be achived with a common 3v supply?

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Just to clear any confusion - you the 3k9 res should be removed from the +5v line and connected to a port. The voltage at the other end will never exceed 1v.
Another resistor is connected the same (19k??) one end to the junction of the VR and the 3K9 the other to a second port.

Basically the PIC will pull either of the lines high - if it pulls the 3k9 one high you get whatever current you've set the VR for, if it pulls the 19k one high you get a quarter of that.
The pic avoids interference by essentially disconnecting the unused resistor (tri-stating the output).

I've also realised in my pseudo code there's no need to set the port pins high in the loop - this can be done outside - plus I don't show the pin being 'un-tri-stated' - which obviously it would need.

Just thinking about it - I don't think it's necessary to have two pins controlling VREF.

In the original circuit, there are three possible states:

GP 2is open circuit; VREF would range from 0 to ~1V (depending on R23)
GP2 is 0V; VREF would be 0
GP2 is 5V; VREF would be between 0 and 5V (again, depending on R23)

The last mode of operation isn't what I suspect is used, so I'll discount that.

However, GP2 can easily create a PWM signal by going from open-circuit to 0v, which at a 25% duty cycle would bring VREF from between ~0 and 0.25V. C23 is used to smooth the signal.

I'm beginning to have an idea about a (possibly) better way to do this.

GP2 is used for the CLOCK signal for the L297 - this is the PIC's interrupt pin, and would be easier to deal with there.

GP1 has a 10K trim resistor which is used to control the minimum hold voltage.

GP0 is connected DIRECTLY to VREF. This is used to monitor VREF.

GP5 is used to control VREF using the same circuit as the original does.

GP4 has a 10K trim to control the delay time for the circuit.

The advantages with this are:

1) The hold VREF can be easily adjusted, and measured with a volt meter
2) The PIC has voltage comparison circuits on GP0 and GP1, and this would be using them
3) Interrupts can easily be used for everything (VREF going below voltage, clock signal coming in, timeout occurring)
4) The PIC shouldn't need to be reprogrammed at all (once it's all working)

If there was a spare output pin, then the L297's RESET pin could be controlled (removing the need for R15, D12 and C16 on your circuit). If we didn't monitor the VREF signal (GP0), then this could be done instead - the trim for GP1 would actually control the minimum PWM duty cycle.

Hi tribbles,

Yep, all that would work - I was just demonstrating that what was required could be done simply.

In the past I've used PWM to modify the VRef voltage - however I've always spotted some ripple with a single stage of RC filtering (I think my PWM was at about 5khz) so always added another. Don't think it matters that much as long as the voltage is approximately right though.
Usually I didn't bother with the VR, having options in the PIC to set the current (either with links setting the most common values, or via a menu on whatever display device I'm using).

Monitoring the VRef voltage I've never found to be necessary - although my initial attempt did exactly that. I have in the past though (when building buck/boost converters to drive LED's) made self starting regulators using the PWM on the PIC and used the analogue inputs to monitor the voltage and adjust the PWM. That's a very interesting experiment in feedback loops... :eek:)

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Just to clear any confusion - you the 3k9 res should be removed from the +5v line and connected to a port. The voltage at the other end will never exceed 1v.
Another resistor is connected the same (19k??) one end to the junction of the VR and the 3K9 the other to a second port.

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See first attachment, is this what you meant? if not Im afraid I dont know what you mean, sorry :redface:

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The advantages with this are:

1) The hold VREF can be easily adjusted, and measured with a volt meter
2) The PIC has voltage comparison circuits on GP0 and GP1, and this would be using them
3) Interrupts can easily be used for everything (VREF going below voltage, clock signal coming in, timeout occurring)
4) The PIC shouldn't need to be reprogrammed at all (once it's all working)

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Sounds good, especially not needing to be reprogramed , see 2nd attachment. hope Ive at least got 1 right :smile:

If monitoring the vref isnt necessary then the reset option would be best. I see the data sheet says the reset must be initially be set low and then set high but this is the only circuit I have seen that dose this, all the others just tie it to +5v.

The only question is what can we make GP3 do? Flashy lights, make the tea? :smile:

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Usually I didn't bother with the VR, having options in the PIC to set the current (either with links setting the most common values, or via a menu on whatever display device I'm using).

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Nice idea but I think I'll save that for the next incarnation...

Okay - just one slight change - pull the reset low with a 10k resistor. That will ensure that the L297 is in a reset condition before the PIC starts up.

GP3 can only be used for a digital input, so there's not a lot you can do with it, I'm afraid!

Nope.

Connect one pin of the pic to a 3k9, the other to a 19k.

Now connect the other end of the resistors to the top of the VR, the bottom of the VR connects to 0v and the wiper to VRef.

That's it!

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Okay - just one slight change - pull the reset low with a 10k resistor. That will ensure that the L297 is in a reset condition before the PIC starts up.

GP3 can only be used for a digital input, so there's not a lot you can do with it, I'm afraid!

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Like so?

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Connect one pin of the pic to a 3k9, the other to a 19k.

Now connect the other end of the resistors to the top of the VR, the bottom of the VR connects to 0v and the wiper to VRef.

That's it!

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Thanks, think i under stood that better.

Ok so Kwackers option is easy to do and gives me adjustable vref with a fixed idle current at 25% (which could be changed by swapping out the 19 K resistor?) and Tribbles options uses a few more trim pots but means I can easily adjust Vref max, vref hold and the delay time. Correct?

For the trimmers am I looking at quality multiturn (£1 each) or will the cheap low wattage single turn (10p) be ok? would need 9 for 3 axis.

Thanks again. looks like its nearly there :dance:

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Originally Posted by Ross77

Like so?

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Yes (from my side :smile:).

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Originally Posted by Ross77

Ok so Kwackers option is easy to do and gives me adjustable vref with a fixed idle current at 25% (which could be changed by swapping out the 19 K resistor?) and Tribbles options uses a few more trim pots but means I can easily adjust Vref max, vref hold and the delay time. Correct?

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Yes - you could even put an open-ended trim instead of the 19K to make that variable.

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Originally Posted by Ross77

For the trimmers am I looking at quality multiturn (£1 each) or will the cheap low wattage single turn (10p) be ok? would need 9 for 3 axis.

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I don't see a problem with cheap.

If you were to put all 3 on the same board, you could use a single PIC to control them all - then there'd only be one pair of trimmers for the duration/hold...

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Yes (from my side :smile:).

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Hurray at last :heehee:

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If you were to put all 3 on the same board, you could use a single PIC to control them all - then there'd only be one pair of trimmers for the duration/hold...

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I thought we'd ruled out an all in one board? also wouldnt this also mean the control is global? I was hoping to be able to set up each motor separatly.

So just need to check the type and size of a few components and we should be good to go.

Are there any parts to look out for? I now the polar caps just have to be 50v and the sense resistors 2 watt. Can the caps be any type or is polyester or tantilum required?

I was being facetious about the all-on-one-board :smile:

The settings would be global, but it could control all three axes independently (I've done that on my parallel port interface - although the PIC is more of an override for the PC [I've got the capability of having an external keyboard to move the machine around if I'm not anywhere near the PC]).

Digital:

For the non-electrolytic caps (C17, C19), there isn't really too much to worry about (so almost anything). I normally use polyester ones, such as Farnell part 116-6036 (100nF), 116-6039 (220nF).

Eagle PCB 5.6 has these in the "rcl" library -> C-EU -> C-EU050-030X075 (or C-EU050-035X075 for 220nF).

Don't forget you'll need a cap for the supply to IC4 (and also the supply itself).

You haven't got any electrolytic caps on the digital supply side - I'd put one in, around 47µF. I'd normally choose an Aluminium 5mm radial over Tantalum (they can explode quite nastily if you're not careful - mainly if you solder it the wrong way around, but they are known to short internally over time). Farnell part 969-3572.

Eagle PCB 5.6 is rcl -> CPOL_EU -> CPOL_EUE2-5

(Hope you follow the nomenclature)

Resistors (R14, R19, R11, R10, R9) for the digital can be 0.25W quite happily. The smallest size for them to be mounted parallel to the board is rcl -> R-EU_ -> R-EU_0207/7

For the power side:

Non-electrolytics, I'd also use polyester, the 63V ones I mentioned above should be fine, but for the smaller values (15/22nF), then 121-5517 and 121-5518 respectively (they use the 030X075 package).

Electrolytics (only C13 and C11), then you could use Tantalum for them (Tants are good for small space and high capacitance). However, I'd stick with Aluminium. Farnell 969-3793, CPOL-EUE3.5-8.

The 2W resistors I take it are for R1/2/3 and R5/6/7. Not sure if you meant it for R4 and R8 as well, but I'd use them too.

I'm not sure if you could replace R1 and R2 with a single 0.25 ohm resistor (may need to be 4W). Anyway, Farnell only seem to have 0.5ohm 2W resistors in SMT form (they do have a 0.51 resistor, but it's in the US, and you'd need to pay £15.95 for delivery [!]). I'm guessing R-EU_0613/15 package for that one (based on the datasheet for the US item). You could use 4x1ohm resistors (Farnell 156-5440, same package as below).

The 1K resistor (Farnell 156-5434 seems the cheapest in stock), looks like it's R-EU_0411/12.

10R resistor - Farnell 156-5420 (same package as above).

I think you can guess where I get most of my components from :smile:

Note that the STTA8 diode does not appear to be available from Farnell, but they do offer the STTH8 instead (same current, but slightly lower Vf [I don't think that'll affect it much - they're only to prevent the back-EMF from the motors from damaging the drivers]).

Also note that I'm using an oldish catalogue for the capacitors (the 2W resistors I did use their website though).

Furthermore note that digital and audio analogue is really my realm, so feel free for people to correct my choices.

Have you decided what type of connectors to use? I really like Farnell 963-2735 style connectors for the motors (I'd used them before I saw them on the drivers I got from Zapp). There are bigger ones for more current if you need it.

Perfect, glad you chose Farnell.

I was hoping to save you the job but it looks like that idea failed. Shall I continue setting the components or will it be easier for you to choose sizes and orientation whilst laying out the pcb?

I've have a look at some similar designs and they use the larger 100v 7.5mm caps for the output bootstrapping etc. seen reasonable or over kill?

I already have the STTA8's that i can steal from the old board. :whistling: That pin spacing will still be ok if i need to replace them the traditional round diodes.

Thanks again

I like Phoenix connectors, Farnell part 304-1359. They are cheap and robust (41p for a 2 way, 83p for a 4way)

You can go larger with the caps. I'd generally not mess around with the caps with what you give me, but the resistors are easier to change the orientation, and pin spacing. I may need to be a bit inventive in order to get it onto two layers *

Send the schematic to me when you're done, and I'll have a play with the layout and then send it back for you to have a look (or even on here, if anyone wants to see).

* Edited: I meant one layer with wire jumpers (which would be shown as a two-layer board).

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Originally Posted by irving2008

I like Phoenix connectors, Farnell part 304-1359. They are cheap and robust (41p for a 2 way, 83p for a 4way)

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Yes, I used them for a bit (and even have some spare in both 3.81 and 5.08mm spacing [albeit 6 and 8-way]), however, I prefer the other ones because you can easily unplug them for replacement or testing.

I initially used the Phoenix ones on a steering control circuit for a crop sprayer, but the boards kept on getting water on them, causing problems (the board has now been moved), and the guy who was fitting them was getting a bit annoyed at having to unscrew them, replace the board, and remember which way around the cables needed to go.

Phoenix do make the same style as the one I indicated, but they're more expensive (the two do seem to mate though).

Ok I'll see what the smallest 100v caps are. The only bit I'm stuck with is the high power resistors. The Original dosnt show a rating and the similar Burger design shows the bootstraps as 2 watt and the sense res as 5 watt! dose this seem right?

The other problem is that although the original board used this configuration the motors are only 2 amp per phase so I will need to lower these values to set a temporary 2 amp max current. This shouldnt affect the pcb layout tho. maybe just use a large res mounted vertically?

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Originally Posted by Ross77

Ok I'll see what the smallest 100v caps are. The only bit I'm stuck with is the high power resistors. The Original dosnt show a rating and the similar Burger design shows the bootstraps as 2 watt and the sense res as 5 watt! dose this seem right?

The other problem is that although the original board used this configuration the motors are only 2 amp per phase so I will need to lower these values to set a temporary 2 amp max current. This shouldnt affect the pcb layout tho. maybe just use a large res mounted vertically?

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Vref = 0.5v, phase current = 4A therefore sense resistor is 0.5/4 = 0.125ohm and dissipates 0.5 * 4 W = 2W so need to be 5W rated.

Why would you need to reduce them for 2A, just turn down Vref to 0.25V. I would recommend a 10 turn pot for the Vref trimmer, makes it so much easier to set.

What have you planned for heatsinking the 6203s?

From the datasheet, at 4A you are going to dissipate between 10 and 15W. Max junction temp is 150, max case temp 90 so for an ambient of 25degC you'll need better than (90-25)/15 = 4degC/W heatsink per 6203 - I'd go for ~3degC/W. thats going to need a finned heatsink around 60mm x 100mm each chip...

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Vref = 0.5v, phase current = 4A therefore sense resistor is 0.5/4 = 0.125ohm and dissipates 0.5 * 4 W = 2W so need to be 5W rated.

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If it only = 2W then why do the res need to be 5W? I thought vref was up to 1v as well? if so then 1/4 = 0.25 hence the two 0.5r, but this would mean max current is 4W? probably got it wrong again :whistling:

Theres not much available in 2 or 5W resistors in that range as they cant be wirewound.......Why is it possible to get a 2W smd res 30p? dosnt make sense.

For the heat sinks I was going to reuse the originals, their about 50mm square and 140mm long with fan at each end. The 6203's mount on both sides with the fins top and bottom.

Does the shunt regulator have to be on each board or could I just put one on the PSU distribution board?

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Originally Posted by Ross77

If it only = 2W then why do the res need to be 5W? I thought vref was up to 1v as well? if so then 1/4 = 0.25 hence the two 0.5r, but this would mean max current is 4W? probably got it wrong again :whistling:

Theres not much available in 2 or 5W resistors in that range as they cant be wirewound.......Why is it possible to get a 2W smd res 30p? dosnt make sense.

For the heat sinks I was going to reuse the originals, their about 50mm square and 140mm long with fan at each end. The 6203's mount on both sides with the fins top and bottom.

Does the shunt regulator have to be on each board or could I just put one on the PSU distribution board?

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You are right, Vref for the L297 is 1v - I was confusing it with the TBA6560 chip on the other thread... so the sense resistor should be 1v/4A = 0.25ohm non-wirewound, rated at 1v x 4A = 4W you would derate by 25% - 50% so really you need something rated at 5W - 8W

Look at the datasheet for this 0.5ohm SMD resistor from Farnell (you'd need 2 in parallel to give 0.25ohm/4W). At its rated dissipation it needs, and I quote "2 Watts with total solder pad and trace size of 300 mm2" - I doubt you'll be close to that amount of copper, and even if you were the temp rise is 90degC above ambient... thats 105degC+ - ouch!

A better product is this nickel chrome metal resistor from Vishay, also from Farnell. This is rated at 5W and seemingly doesnt need a heatsink, but will hit 120degC at rated load so some airflow would help.

And this is why I like low-current digital electronics :smile:

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You are right, Vref for the L297 is 1v - I was confusing it with the TBA6560 chip on the other thread... so the sense resistor should be 1v/4A = 0.25ohm non-wirewound, rated at 1v x 4A = 4W you would derate by 25% - 50% so really you need something rated at 5W - 8W

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Phew I thought I was going mad. thanks for the smd links but I think I'll stay away from them at the mo. i just couldnt understand how such a small part was so powerful and cheap.....

Looks like digi-key are the best for this project. in fact they are cheaper on a lot of things, I just need to spend £50 for free delivery. Any body need parts? I can get 2watt res for 13p each, if I use 3No. 750 ohm in parralel = 250 ohm at 6 watt correct?

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Originally Posted by Ross77

Phew I thought I was going mad. thanks for the smd links but I think I'll stay away from them at the mo. i just couldnt understand how such a small part was so powerful and cheap.....

Looks like digi-key are the best for this project. in fact they are cheaper on a lot of things, I just need to spend £50 for free delivery. Any body need parts? I can get 2watt res for 13p each, if I use 3No. 750 ohm in parralel = 250 ohm at 6 watt correct?

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That is correct...

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Originally Posted by Ross77

Any body need parts?

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Let me know how short you are off your £50 - I may have some bits that I can order from Digikey.

Ditto, i need to order a few small bits, not urgent but if you need a couple of quid extra let me know... stuff i need can be posted to me with a 2nd class stamp...

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Let me know how short you are off your £50 - I may have some bits that I can order from Digikey.

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Ditto, i need to order a few small bits, not urgent but if you need a couple of quid extra let me know... stuff i need can be posted to me with a 2nd class stamp...

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Sure pm me with what you want. it would be good to help a little, after all the help you guys have given me. Dosnt matter if I go over, just said £50 min. :smile:

just about there with with the design. I've had a crack at laying out the pcb but I dont think it will fit on the 100x80 board in eagle, I'm sure you will prove me wrong.....

Ok so heres the final draft..........

The only thing I cant work out out is what the diodes (D9,D10) for the shunt reg need to be? Any over obvious problems?

Once its all confirmed and if anyone is interested I can post the eagle files.

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Originally Posted by Ross77

Ok so heres the final draft..........

The only thing I cant work out out is what the diodes (D9,D10) for the shunt reg need to be? Any over obvious problems?

Once its all confirmed and if anyone is interested I can post the eagle files.

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they are zener diodes. You need a total voltage of Vclamp - 1.4. By using 2 diodes you can get a bit more fine tuning of the voltage, for example a 30v and a 7.5would give a clamp of 30 + 7.5 + 1.4 = 38.9 which would be good for a 36v supply on 40V drivers...

Before you make any modifications, I've tweaked the schematic a bit to make the board a bit more sensible in layout.

Basically, I've renamed the components so that those beginning with "D" are the Digital part, those "A" are the bottom driver, "B" are the top driver (yeah, probably should've done them the other way around), and "P" is the power (top-right).

So when the board is laid out, it's easy to make sure that C13 (which is now BC3) is the smoothing capacitor to IC2 (now BIC1), rather than IC3 (AIC1).

Of course, that doesn't really matter if they're swapped, but I like it for symmetry :smile:

The other things are that R4 and R8 have been rotated through 180deg - you can see that the lines go through the middle of the resistors.

I'm not sure of your choice for PH1 and PH2 - 0.1" jumpers would be pushing it for the power consumption. I'd use the connectors that Irving and myself suggested. Also, the power connector may be a little too small as well (it looks the same kind of size as a 0.1" jumper).

I'll send you back the modifications I've made (there's also a custom library part which is a 100x80mm board that I designed; if you have problems with loading it, then let me know - I'll send you the library, although when it's done, I'll replace it with ordinary lines).

Ummm, wheres the RC network associated with the (OSC)illator? Obviusly if you have multiple boards you should minimise noise by connecting (SYNC) together and you have brought that out to a pin for that purpose... but one of the boards has to be the master oscillator... unless you are doing that externally somehow...

Good point - I hadn't spotted that in the datasheet.

It looks like all of the OSC pins can all be connected to ground - as long as you inject a signal into the SYNC pins.

That could be done from the parallel port, and could even part of the charge-pump circuit (if there's no signal, then don't clock the devices). Although I don't know how the L297 would cope in such a condition.

Although you could just use the ENABLE pin for that...

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they are zener diodes. You need a total voltage of Vclamp - 1.4. By using 2 diodes you can get a bit more fine tuning of the voltage, for example a 30v and a 7.5would give a clamp of 30 + 7.5 + 1.4 = 38.9 which would be good for a 36v supply on 40V drivers...

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Thanks. My supply is 41.5V unloaded so will this still work? or wil i need to up it to a 30+10? Im not to good with diodes, can you recomend a suitable part?

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I've tweaked the schematic a bit to make the board a bit more sensible in layout.

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That makes sense, I'll do that in the future. I think the resistors where 180deg out because i swapped the pins (vertical mount) in the pcb editor to make the lay out easier. i'll have to look out for that as I didnt think it also changed the schematic.....:redface:

Hands up about the connectors as well, I completelly forgot, definetly use the ones you suggested. as long as Digikey sell them, or something with the same pin spacing.

Well spotted on the missing clock/osc. I'm working on that now. There will be a master board that the 3 controllers connect to for signal, clock and power.

I found a driver for unipolar motors that used the l297 and the designer came up with a separate clock that was adjustable to help reduce the frying noise (see attached, not finnished tho.) I believe the noise is a result of the chopper cuircuit and clock freq. so by changing the freq you can make it less audible.

Thanks again.for the continuing support, I realise this is going on a bit now :beer:

For the resistors inputs to the 'HC14s that are pulled high, I'd use a resistor pack for that - makes the track laying a lot easier.

You've also got 3 enable inputs - any particular reason for having them individually enabled? I'd be tempted to have a single enable pin (which means you could have fewer 'HC14s - although unfortunately, you'd still need 3).

You could also not pair them up - the DIR would be the other way around (and CLOCK would be inverted), but the DIR can be corrected at the other end (i.e. how you wire the motors) - and the CLOCK probably wouldn't hurt. In fact, EMC2 allows you to invert the DIR should you need to (and I'd imagine Mach3 would too).

Jason has done an excellent job of the PCB, it even fits on a 100x80mm board, just need to to sort out the ground planes and star earthing then it finnished. :beer::beer::beer:

Heres the latest version of the BOB, think I've got a bit carried away and may have to bring it back to basic's. maybe put the 4th axis and Aux1 on a separate board as well. I'm a bit worried that ive mixed up the values on the optos and inverters so wont get the correct voltages :whistling:

waiting report from someone that built the driver by the diagram

No not yet I'm affraid. I've got all the parts be no time at the mo. I hope to start in a few weeks. The circuit above has been simplified a bit but I will post all files once I know it works.

Ross