I'm trying to build a low power counter device. help

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I'm trying to build a low power counter device. help.

[Board specifications]

  1. Use 3.6V battery
  2. Used for about 2 years
  3. Use OLED 128x32 0.91
    url: How much current do OLED displays use?
  4. Arduino Pro mini: ATmega328P 3.3V 8MHz
  5. ‘Deep sleep’, ‘Interrupter wake up’
  6. DRV5012 Hall sensor

[Questions]
Q1. You need to convert '3.6VDC' to '3.3VDC'. Please recommend a suitable ‘SMPS Buck converter’. Is there something that is reasonably priced and efficient?

  • Must be low power.
  • It must be operated between -20℃ and 50℃.

Q2. I use 'OLED 128x32 0.91'. You can see the power consumption by looking at the ‘url’ above.
As of now, I plan to use 'BJT-pnp' power only when in use.
Is there a better way?

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Please. Show us a schematic if you can, or at least a block diagram of what you plan.

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@camsysca

figs
figs919×494 49.3 KB

Please advise.
The current concept is as follows:

4

All your devices can works on battery supply range 3.2-4.2v without voltage conversion, so you can get rid the buck converter from the design. The only possible exclusion is an OLED display, because there are a lot different versions of OLED and you have to choose the variant that compatible with battery voltage.

Getting rid of the converter is an important step to get a truly low-power device.

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@b707
@camsysca

Thank you for answer. Thanks for the great idea too.
@b707
As you said, the circuit can be implemented without 'SMPS'.

fig

Please look at the image above.

  1. If two batteries are inserted, a ‘diode’ must be inserted.
  2. I plan to use SS34 for the ‘diode’.
  3. Or, can you make a recommendation?
6

Why do you need a two batteries?

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However, if you do need two batteries, I don't think you need the diodes. The batteries need to be at the same voltage when first connected together, then never separated after that. They should discharge together without the diodes. But one larger battery would be better if it will physically fit.

(Edit: If the two batteries are lithium rechargeables, they should not have protection built in if used in parallel. The protection circuit would need to be elsewhere. Basically, life will be easier if you use one battery.)

I don't have any experience with these OLED displays, but I wonder if they aren't a very high current option for a "low power counter device".

While everything may run without using a buck converter, it's likely the devices will use less current at 3.3V than they will at 4.2V. So you may get better battery life if you use a regulator. But I think a linear regulator would be the best option because it can draw very little current when the load is very low. Something like an MCP1700.

I hope in the end you will post a regular detailed schematic of your circuit so we can help make sure it makes sense. For example, you don't show a base resistor on the PNP, which will be needed.

1 Like
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@b707 @ShermanP

Due to the device design and size,

  1. A large battery does not fit.
  2. So it uses two small batteries.
  3. It seems that the diode itself will consume a lot of power.

Battery full charge voltage is 3.6V.
Is it better to do 'SMPS'? Should I not do it?
(Please note that this is not a rechargeable battery. It is a disposable battery)

Thank you for your comments. It seems to be of great help.

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I guess I don't see a need for a regulator. It looks like everything you have will run directly on battery down to 3.0V or less. And I still don't see the need for the diodes.

2 Likes
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@ShermanP

Thank you.

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