Hi there
The purpose of this schematic is to control a DC motor that runs at 8V max. That is why I chose 4 N-channel mosfets in the H bridge. P-channels would not fully activate at voltages above -10Vgs but the N-channels can handle 18V at the gate.
The 5v switches represent an Arduino’s digital output pins. One to turn forward, one for reverse. To prevent a failure scenario where both pins are HIGH I added a transistor that prevents current from flowing through the optocoupler on the second half bridge.
Does this circuit make sense? I’m not an electronics engineer, just a hobbyist and have doubts about how effective the gate driving circuit is of the mosfets.
Thanks!
Norodix@lemmy.world 3 months ago
Please don’t use non perpendicular lines and draw in a clearer software if possible. Its quite hard to read.
What is the point of the push-pull BJTs? With the optocoupler you could drive the nmos gates directly. If you need more current to drive the gates (unlikely for a small motor), I suggest you buy dedicated gate drivers. They are tested and not expensive. If you have the 18V available already, using the optocouplers directly would be a lot simpler.
abominable_panda@lemmy.world 3 months ago
This looks like the web simulator falstad…
Rolive@discuss.tchncs.de 3 months ago
Proto on Android.
Rolive@discuss.tchncs.de 3 months ago
Right, sorry about that. I made the simulation on my phone with the Proto app.
I figured the push pull part is good practice with mosfets. It’s partially the learning experience and if the motor stalls it could draw several amps.
I won’t be doing PWM, just on and off so maybe just the optocoupler is good enough.
I’d have to order dedicated gate drivers and have a lot of 547 and 557 transistors in stock at home.
Norodix@lemmy.world 3 months ago
I would omit the extra transistors and use only the optocouplers.
What sort of application is this? Having 18V somewhere and a 5V supply too that can output several amps is quite unusual.