Hello!
I need to power a 775 DC motor with arduino. So I ordered a driver from China, but to kill time decided to try and make my own driver. I made up a schematic like this:
I used my laser cutter to make a PCB, soldered everything in place and now comes the testing...
It's not working. I use a 12V power supply for VCC, and 5V from arduino for logic. Grounds are tied together.
When I give 5V to any EN pins, the power supply gets shorted.
Does anyone see a problem with my schematic, or is my pcb faulty? Should the schematic even work? Thanks!
10 ohms is an extremely low value for R1,R2. That's likely to exceed the maximum emitter current for Q3,Q4 (and maybe smoke the resistors, or the drive transistors).
Not to put too fine a point on it, but do you know Ohm's law?
Welp, when I was designing the circuit, it seemed a good value. Now I changed it to 1k, and it is in fact working. But, when I measure the voltage across the motor, its only 10.7V when the VCC is 12V. Is the 1k too much and the transitor isnt saturating, or is it normal with transistors? Thanks!
Well I had a really stupid mistake. I had the pcb on my table turned the other way, and so I was thinking I was connecting the 5V to EN pins, but actually I was connecting to PWM pins. That way I didnt think the small resistor values was the cause.
It looks like your top PNP are always ON or shorted, as @anon57585045 stated.
For simplicity you can remove the PWM driver transistors and connect the base of the top-left Darlington to the collector of the bottom-right Darlington, same for top-right and bottom left. Of course with resistors matching Vcc like 10k. This leaves one control input for each direction.
