Help! DIY 4 amp L297/6203 driver

[Ross77]

Wow thanks guys, thats a great help, now if i could just get someone to convert the schematic to a pcb and mill it for me.....:lmao:

Irving
The short circuit protection is for the the output chips, (see below)

Tribbles
Thanks for the very kind offer, Unfortunatly I have no idea where to start with the code. I can only guess that an output needs to modulate (or switch low) the vref line to set the hold current (possibly adjustable from a trim pot) and then an input needs to look for the clock pulse to reset full current when a signal is seen?

I would imagine that the timing's are going to be the hardest bit as it might loss the first step whilst switching back to full current?

Is there any reason why this couldnt be put on a separate board and just send the Vref lineto the driver board with the other signals?

Thanks again

[tribbles]

Wow thanks guys, thats a great help, now if i could just get someone to convert the schematic to a pcb and mill it for me.....

I can do the conversion of the schematic - I've done a fair number of PCBs myself (using Eagle PCB). Just send me the schematic, an idea as to what size you want (and also any heatsinks - most of the stuff I do is low-current digital, although the fan control was high current).

However, milling it... I photo-etch them myself, since I have the capability.

http://www.tribbeck.com/electronics/pcbs/

If you're interested

If you want to do it yourself, then there are a few rules to follow - graffian's advice is sound, but Eagle does have a "DRC" (Design Rule Check) which makes sure you don't break common ones (such as tracks too small, crossing over, pads too small, objects too close together). If you run this every so often as you're designing it, then it'll help you get along.

The photo-etching I do performs better than Eagle's built-in rules, so I've modified my rules to allow me to etch to within very tight tolerances.

Tribbles
Thanks for the very kind offer, Unfortunatly I have no idea where to start with the code. I can only guess that an output needs to modulate (or switch low) the vref line to set the hold current (possibly adjustable from a trim pot) and then an input needs to look for the clock pulse to reset full current when a signal is seen?

I would imagine that the timing's are going to be the hardest bit as it might loss the first step whilst switching back to full current?

Is there any reason why this couldnt be put on a separate board and just send the Vref lineto the driver board with the other signals?

Thanks again

I actually meant discuss with Irving

Looking at his (later) reply with the rough idea of the code, that looks sane to me, and roughly how I'd go about it.

INT0 would be the interrupt from the INT pin; INT1 would be the Timer0/1 interrupt.

DIP switches for the timeout's a neat idea - especially if it'll be used by someone who doesn't have reprogramming capability.

I have a slight concerna about using the PWM - if the PWM controls the direction control (i.e. oscillates between output 0 and open-collector), then that would be fine. However, from memory, it'll only oscillate between 0 and 1, then you'd need to be careful of the PWM pulse width - you could end up going too high with the VREF signal. Still doable though.

There's nothing stopping you from putting it on a separate board.

[irving2008]

....
I have a slight concerna about using the PWM - if the PWM controls the direction control (i.e. oscillates between output 0 and open-collector), then that would be fine. However, from memory, it'll only oscillate between 0 and 1, then you'd need to be careful of the PWM pulse width - you could end up going too high with the VREF signal. Still doable though.

There's nothing stopping you from putting it on a separate board.

Depends on the chip and whether an O/C output is available. If not, a single NPN small signal transistor and base resistor on the output would suffice.

Having said that, if you are using a transistor, why not put a trimmer on the output side and not use PWM at all... would simplify the code and you could adjust the holding current to your hearts content.

[Ross77]

Thanks graffian, I think I was about to make that mistake. I'll have to look for that thread, will it still apply to the L297?

I can do the conversion of the schematic

I will definatly take you up on that offer, If you make the board bigger than 4"x3" will i be able to veiw and output it myself? Good info on the PCB fabrication but think it will be too costly for a one off, as i plan to mill future pcbs.

I actually meant discuss with Irving

You've got me sussed, I'll go and sit in the corner then.:heehee:

a single NPN small signal transistor and base resistor on the output would suffice.

Wouldnt this then be the same as using a 555?

[graffian]

Thanks graffian, I think I was about to make that mistake. I'll have to look for that thread, will it still apply to the L297?

From what I remember, Mariss had just noticed the A3986 thread and it started with a comment he could programme a CPLD, pretty much as the gecko stepper drives minus mid band resonance, to do what the A3986 was meant to do. Then another post suggested he would be able to sell them for $5! I imagine you would drive bridge drivers[ir2184?] from the cpld?

[tribbles]

I will definatly take you up on that offer, If you make the board bigger than 4"x3" will i be able to veiw and output it myself? Good info on the PCB fabrication but think it will be too costly for a one off, as i plan to mill future pcbs.

I'll try to fit into 100x80mm (this is the maximum size for the free version). However, I think you would be able to load the larger size in, but you probably won't be able to move the components that are outside the area around.

There are techniques to squeeze it into a smaller space, but I'll avoid them (basically, moving to surface mount components) unless you've got a particular desire to solder really small components

Send me a PM (let me know when you've done it - I think the last one didn't arrive), and I'll give you the details. I can have a rough idea as to whether it'll fit or not probably in an hour or so.