(I've never heard of Totem Pole output stages, and a quick google makes me think I don't have anything like that in my circuitry)
1. With just LED's it works properly. Interestingly, I conected it up to the transistor driver (without the motor connected) and it worked as it should, making one wire to the motor high. However, upon conecting the motor it fails. I then disconected the motor and left the PIC conected to the transistor driver and the PIC started overheating. Conecting the PIC up to LEDs again made it work.
Furthermore, I did at one stage have it working with one motor. I left the other two motors disconected, hooked it up to the PC serial port and was able to control the motor. Afterwards I removed the decoupling cap (I'm pretty sure it was after, but I can't be sure... I should start writing this stuff down since my memory is appalling!) and everything seemed to go downhill to the current condition.
Also, if I use a wire connected to +ve and touch each socket (without the PIC installed, thus simulating the pins going high) I can make the motors step.
2. Yes, they are powered with the same supply. It's a fairly cheap and nasty supply (£15) - switching mode with selectable voltages. I've have it set to 4.5V, as it's either 4.5 or 6.
3. Motors are rated at 12V, but step perfectly well at 3V. Currently the output from the h-bridges are 4V after losses. I was planning on setting the power supply to 12V and then using a 5V regulator to power the PIC to give more torque, once I had got it working at 4.5V.
I will draw up some schematics tomorrowI will draw them up from the veroboard, checking each connection as it go to make sure you get exactly what I have on the board.
Last peice of info which may help: I remember that when I was running it with the PICAXE (driving just 2 stepper motors) it was somewhat flakey. It would ocassionally reset each time I sent serial data, if I remember correctly, and would have spells of simply refusing to work (for no apparent reason). The next day it would be fine though.
I'm now going to try powering the PIC with a battery and powering the rest of the circuit with the power supply.
Thanks again for your help
EDIT:
Did some digging - here is the schematic I used:
http://www.mcmanis.com/chuck/robotic...t-circuit.html
(Except I used TIP122's and TIP125's - the same but can't handle as much current).
However, I used no opto-isolators on the NPN's, but I did use some 2N3904's on the PNP's (instead of the isolators) as desribed here:
http://www.mcmanis.com/chuck/robotic.../bjt-impl.html
(half way down the page, the author describes it as the 'the high side problem')
I could probably fix the problem by using opto-isolators (since I can flash LED's!) but I would like to find out why it isn't working at the moment
Bookmarks