| Electronics > Projects, Designs, and Technical Stuff |
| USB Battery Bank Auto Shutoff |
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| engrguy42:
--- Quote from: SilverSolder on May 12, 2020, 04:26:28 pm --- --- Quote from: Peabody on May 12, 2020, 04:14:39 pm ---I keep having to remind myself, because I'm old, that the new way to deal with this kind of problem is to get a little 8-pin microcontroller like an ATTiny or PIC or MSP430 with its own internal oscillator, and program it to drive the mosfet with the exact pulse duration and interval you want. That takes the place of all the 555 stuff, resistors, capacitors, pots, diodes, etc. Cheaper, easier, more precise, fewer parts, less space, less power. Anyway, I hope you'll report back with the final shortest, least frequent, lowest current, pulse you can get away with to keep the powerbank alive. It may be that the total mAh penalty isn't all that great. --- End quote --- That is exactly what to do for this kind of project, I think. I abandoned a 555 project and used a Pro Mini Arduino simply because the timing of the 555 was less accurate, and it didn't do exactly what I wanted, and ended up being a lot more work than knocking up the 3 lines of code needed... Welcome to 2020! --- End quote --- And sometimes accuracy is irrelevant, as is spending any money and ordering stuff and starting from scratch when I have a perfectly good design already. Changing from 50% to any other duty cycle, like I said, is a nice-to-have but largely irrelevant. Actually I'm kinda surprised there were no responses on how to design a PWM on an ever-so-popular 555. I thought you guys would be all over that. |
| SilverSolder:
--- Quote from: engrguy42 on May 12, 2020, 04:32:44 pm --- --- Quote from: SilverSolder on May 12, 2020, 04:26:28 pm --- --- Quote from: Peabody on May 12, 2020, 04:14:39 pm ---I keep having to remind myself, because I'm old, that the new way to deal with this kind of problem is to get a little 8-pin microcontroller like an ATTiny or PIC or MSP430 with its own internal oscillator, and program it to drive the mosfet with the exact pulse duration and interval you want. That takes the place of all the 555 stuff, resistors, capacitors, pots, diodes, etc. Cheaper, easier, more precise, fewer parts, less space, less power. Anyway, I hope you'll report back with the final shortest, least frequent, lowest current, pulse you can get away with to keep the powerbank alive. It may be that the total mAh penalty isn't all that great. --- End quote --- That is exactly what to do for this kind of project, I think. I abandoned a 555 project and used a Pro Mini Arduino simply because the timing of the 555 was less accurate, and it didn't do exactly what I wanted, and ended up being a lot more work than knocking up the 3 lines of code needed... Welcome to 2020! --- End quote --- And sometimes accuracy is irrelevant, as is spending any money and ordering stuff and starting from scratch when I have a perfectly good design already. Changing from 50% to any other duty cycle, like I said, is a nice-to-have but largely irrelevant. Actually I'm kinda surprised there were no responses on how to design a PWM on an ever-so-popular 555. I thought you guys would be all over that. --- End quote --- I guess the reason is that it can be a lot more work to get a 555 circuit to do certain things than a $2 Arduino. I tried this recently for a hobby project that needed something similar (a pulse every 15 - 30 minutes in my case) and it was surprisingly hard to get a 555 to do that. |
| engrguy42:
Houston, we have liftoff... Got me some yummy PWM goodness. Tried the latest circuit I showed, it gives me 25% duty cycle (5 seconds ON, delivering 120mA, then 13 seconds OFF), and it keeps the battery bank on continuously. Sweet. I think that's a wrap. |
| Peabody:
That's great, but how about 1 second on, 13 seconds off? Or 100mS on, or even 1mS on? |
| engrguy42:
--- Quote from: Peabody on May 12, 2020, 10:11:36 pm ---That's great, but how about 1 second on, 13 seconds off? Or 100mS on, or even 1mS on? --- End quote --- Do I owe you something?? :wtf: You're certainly welcome to do your own research, but personally I couldn't care less about what you seem interested in. |
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