Is 5V necessary?
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@BetterAuto Yes, you cannot supply the WM01 differently. And with WIPy,. LoPy and SiPy, Vin is sufficient, because they have an on-board regulator, which can also be used to drive additional peripherals.
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Thanks much. Will use three D cells. And copious deep sleep time :-)
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@BetterAuto WM01 you still need a regulator. 3 D Cells will have a voltage of 4.8V down to ~3 V.
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@robert-hh Humm, hadn't thought of that. And two alkaline cells at a starting voltage of 1.65V could only power it for moments before dropping below 3.3V.
I want to run a long time on batteries, sleeping most of the time. Is there a recommended regulator (switching or linear) with a low quiescent and high efficiency?
I can go look at DigiKey, just wondering if there's one people often use and recommend.
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@BetterAuto I personally used a module from Pololu, model S7V8F3, which is a step down/step up regulator, which will output 3.3 with an input voltage between 2.7 and 11.8V. https://www.pololu.com/product/2122
The module (or chip) suits perfectly for your needs of a supply by battery.
The quiescent current of the module is specified a below 0.1 mA, but that varies with the input voltage & usage. The LM3281 used by Pycom ist specified with a quiescent current of 16 - 30 µA.
By the way: what do you call "a long time on batteries"? -
Six months to a year. How is it the LM3281 can output 3.3V with an input of 3V? I thought input voltage had to be higher than output for regulators.
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@BetterAuto the Lm3281 is step down only. If the input is too low, it will go into a pass-through mode.
At .1 mA for the regulator, it will use about 880 mAh alone for standby per year, plus the power needed for the circuitry. A D cell is rated at 5000 mAh, maybe more. -
Ahh, pass-through. Wasn't aware of that.
I had oopsed and read your comment as 1mA but 0.1mA is within my power budget. Obviously lower is better though.
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@BetterAuto I just gave it a try:
Pololu 7v8FA (which is the adjustable model):
Vin 4.5 V, Vout set to 3.3 V- Quiescent Current w/o load: 50 µA
- Input Current with a 100µA load: 130 µA
- Input Current with a 1 mA load: 860 µA
The input current is lower than the output current, because Vin is higher than Vout and it's a switching regulator.
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You rock.
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