u/DatCheeseBoi

MOSFET switching time advice.

Hello, I am building an H-bridge to drive a peltier cooler, and I am trying to figure out what switching time should I aim for. Now I know some may consider it a cardinal sin, but I use GPT, I'm a wall and breakers kind of sparky, my finer electronics knowledge is rusty, and somewhat basic. My idea is that since I have a few analog sensors around, and the faster a MOSFET switches the more noise it produces, I'd want it to switch slower. Power losses are not that significant, because at most I'd be switching it once or twice a second, more likely every few minutes. I look at the Safe operating area graph, and see that at my loads 10ms would still be well within safe margins for the MOSFETs I'm using, and decide to go with much lower time like 1ms just to be sure, I calculate the current I need to achieve it, triple it because switching MOSFETs is supposedly inefficient when slow, although I can't find exact estimates on just how inefficient, I end up with a huge resistor, when GPT has been telling me to use something orders of magnitude smaller. I know that the bot is limited and sometimes quite irrational, but he keeps insisting on couple hundred ohm resistors no matter what, which makes me think that everyone uses them, hence the training data, which makes me think there's a big reason that I'm missing. Can someone much better versed in this explain to me exactly what pro knowledge that's missing from the datasheet is eluding me? I have spare parts, and they are pretty cheap, but I'd prefer not to build the whole thing and immediately destroy it because I'm missing a key insight or because an AI has hallucinated me into the wrong solution. Thanks for reading, and thanks for any advice you'll provide me.

reddit.com
u/DatCheeseBoi — 3 days ago

How do you guys deal with huge hordes?

I've had moderate success with soldier's ability, but in some of the recent expeditions the hordes just feel so oppressive.

reddit.com
u/DatCheeseBoi — 8 days ago

Hello everyone, I'm working on a project that needs a good chunk of power, and the only affordable thing I could get is the pile of old PC power supplies in my closet. They work well because I need 5V and 12V. Thing here is that I have a MAX7219 8 digit 7 segment display to show some sensor readings, and my Uno R4 seems fine at first, but when I try to change the numbers too frequently the whole thing just loses it, and I believe it's due to the Arduino not being able to provide enough power on it's own. No worries I thought, I'll just need to pull that big PSU out early, so I connect the Arduino ground and the PSU ground since that should get them to equalize right? Run both, and the display is now working even worse. I check just out of curiosity and there seems to be about 0,4V difference between the two grounds. So here's the real question: can I make a setup where the Arduino is powered by USB from my computer and the attached devices are not, work? Or will I be forced to hack together a plug that powers the board straight from the power supply to get useable conditions. I've only done little projects on Arduino before, so feel free to state the obvious, I still have a lot to learn.

reddit.com
u/DatCheeseBoi — 21 days ago