Comment on Schematic review
Norodix@lemmy.world 2 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.
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.
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.
Thanks again for the advice. I made a working prototype and attached it to my pump: Image
For now I’ve used just optocouplers to drive the mosfets, since pulling p-type gates down to above -24V seemed like a hassle. I’ve ordered some IR2210 gate drivers and intend to use those with PWM later to not have to use a buck converter.
Here’s a video of the pump. drive.google.com/file/d/…/view?usp=sharing
No problem :) Let me know if you need any help!
Well, the whole setup is a semi automatic greenhouse. It has a 12 channel peristaltic pump, grow lights, heater and a plant shaker for pollination. I’m attempting to grow indoor tomatoes and chili’s. Not weed although I have learned a lot from weed growers.
The system runs on a 24V power supply so that is easily accessible. The 18V comes from an LM7818 and the motor speed will be regulated with a buck converter module.
I also worry about the LM7818. It drops about 6V, so at 330mA it burns 2W, which seems like the maximum for the package that I quickly pulled up. If you have a very efficient buck converter that gives you at most about 1A to drive the motor. Not a lot of overhead.
Also as I said already, you could just skip the whole thing and make everything work from the 24V using PWM. Since you want to drive it with an arduino that is not a difficult thing.
If I were you, I would not step down the 24V, but use that to drive the motor with pwm. It requires a bit different H bridge but overall it would be simpler. But if you already have a converter module that is good enough this works too.
abominable_panda@lemmy.world 2 months ago
This looks like the web simulator falstad…
Rolive@discuss.tchncs.de 2 months ago
Proto on Android.