Timeline for UPS for battery with minimum quiescent current
Current License: CC BY-SA 4.0
12 events
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| Sep 26, 2022 at 19:13 | comment | added | CaveScientist | Finally tests are done, PIR sensors are really weird, they can detect meters away motion with few volts. I could go as low as 2V without major problem. It started to false trigger at 1.5V. I focused on 3V as this is a good finish voltage and I did many tests. The detection sensitivity or the angle of view wasn't different than 5V input. I'll use direct connection to battery, still I'll remember your advice for some other time. MCU is Attiny24A which has around 1uA power-down current which is neglectable. | |
| Sep 26, 2022 at 15:58 | comment | added | Andy aka | I'm just proposing what seems to me a better method with less potential problems. I would "test" for the minimum voltage unless you want to take risks on a one-off build. There's also your MCU current consumption to consider maybe? | |
| Sep 26, 2022 at 15:56 | comment | added | CaveScientist | Ofc your method is better than boost converter option, but I compared your way with "connecting the PIR sensor directly to battery". Then it is a draw for now. I'm testing minimum working voltage of PIR sensor with LM317, I'll share the results. | |
| Sep 26, 2022 at 15:56 | history | edited | Andy aka | CC BY-SA 4.0 |
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| Sep 26, 2022 at 15:52 | comment | added | Andy aka | The important thing about it is that it clearly has no problems (even if the math says a draw) and, it is available and it doesn't leave you head-scratching about whether the boost will perform adequately and trying to figure out if you have enough hysteresis on your comparator so that you don't get into a state where it's switching back and forth. Less messing around I would say but, you can do the math and think about it @CaveScientist <-- also boost converters usually require a minimum load to get proper voltage regulation. | |
| Sep 26, 2022 at 15:45 | comment | added | CaveScientist | By using parallel cells I can certainly double the run time, but I waste %20 of the capacity. Can we make the analogy of a %80 efficient converter? You on the other hand can also approximately double the run time by drawing nearly half current from batteries but you are not %100 efficient either. The converter will use current itself and also conversion is %90 efficient at most. So we seem like we are going for a draw. The numbers I gave are assumptions that's why I am never sure. I just wouldn't bother adding extra part + shrinking battery life by discharging to 2.7V if it won't add much. | |
| Sep 26, 2022 at 15:18 | comment | added | Andy aka | You said parallel cells and that means at least two cells. I said series cells and that means at least two cells. Why does it double your cell count? | |
| Sep 26, 2022 at 15:17 | history | edited | Andy aka | CC BY-SA 4.0 |
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| Sep 26, 2022 at 15:16 | comment | added | CaveScientist | Good point of view. But this doubles my cell count. I can double my cell count now without any buck or boost and can still power until 3.4V with %100 efficiency. I think your solution is great for >=3.7 V applications. I will now test if the PIR sensor can really run with 3.4V when protection diode is shorted then decide to use buck converter or nothing at all. Because boost converter option doesn't really help much. | |
| Sep 26, 2022 at 15:04 | history | edited | Andy aka | CC BY-SA 4.0 |
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| Sep 26, 2022 at 14:57 | history | edited | Andy aka | CC BY-SA 4.0 |
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| Sep 26, 2022 at 14:50 | history | answered | Andy aka | CC BY-SA 4.0 |