Powering up ATtiny85 based microcontroller via a 3.7V LiPo battery?

Projects General Guidance
1

Hi,
First of all, sorry if this is in the wrong section.
I am building something that is very weight critical, using Adafruit's Trinket (5V), which is an ATtiny85 based microcontroller. Right now i am powering it up via a lithium battery that provides around 4.7V when fully charged and a "step-up" module, which converts lower voltages to regulated 5V.
The microcontroller will have to support a bluetooth module and 2 small 5V servos.

Do you think it is possible to power it up through a watch battery (button cell) and/or a 3.7V LiPo battery? (of course i will be using the step up module and not powering it directly from the battery)

Thanks! :slight_smile:

edit: Tried the watch battery, does not work! How about the 3.7V LiPo battery?

2

It would be better to include a link to something descriptive about your "step-up" module. That photograph is very limited in information.

3

I am afraid i don't have much more information than that. The shop I got it from just says it will boost the voltage. Manufacturer's website isn't much more enlightening either. :confused:

4

It certainly looks a sweet little module. Probably quite efficient too. but no real way of knowing. Even bluetooth devices vary in their power demands. It's all guesswork. I honestly haven't a clue. Try it and see, but be prepared to accept you may need a bigger power source.

5

Alright, i guess i'll go and buy a button cell battery and just try it out. Thanks for your input. By the way, I tried to power it up with a simple AA battery (~1,5V), but that didn't work. :frowning:

6

kuruki:
Alright, i guess i'll go and buy a button cell battery and just try it out. Thanks for your input. By the way, I tried to power it up with a simple AA battery (~1,5V), but that didn't work. :frowning:

Oh dear. The prognosis isn't good :frowning: According to their site it should work from 0.9 Volts. Good luck.

7

I have used similar cheap "step up" modules, they are nice for small projects (e.g. here) - but under no circumstances will a button cell be enough for servo motors!

8

@igendel That's a really cool little project. Did you consider having text blowing across the LED array?

9

KenF:
@igendel That's a really cool little project. Did you consider having text blowing across the LED array?

Thanks :slight_smile: I guess I could squeeze character bitmaps in there and all, but truth is, I needed this as something quick & dirty to show off somewhere, so I didn't put too much effort into the visual effects.

10

igendel:
I have used similar cheap "step up" modules, they are nice for small projects (e.g. here) - but under no circumstances will a button cell be enough for servo motors!

nice project you made there! 8) Well, I decided not to take your word for it :grin:, so since you managed to power yours up, i am on my way to buy a button cell. Worse case scenario, this will set me back 3 dollars. :stuck_out_tongue:

11

kuruki:
nice project you made there! 8) Well, I decided not to take your word for it :grin:, so since you managed to power yours up, i am on my way to buy a button cell. Worse case scenario, this will set me back 3 dollars. :stuck_out_tongue:

If it doesn't work, you could always sell the button battery on ebay, or just buy a watch to go with it.

12

kuruki:
nice project you made there! 8) Well, I decided not to take your word for it :grin:, so since you managed to power yours up, i am on my way to buy a button cell. Worse case scenario, this will set me back 3 dollars. :stuck_out_tongue:

That's ok, next time you'll listen :grinning:
The point is not about being able to get 5V - that will probably work - but getting enough current.

Edit: Oh, and just in case there's a terminology confusion - my project was powered with a AA battery, not a button cell.

13

I appreciate that it's not a very technical approach, but judging from the size of the components and comparing them to similar devices I suspect that it will be rated about 300mA.

14

igendel:
That's ok, next time you'll listen :grinning:
The point is not about being able to get 5V - that will probably work - but getting enough current.

Edit: Oh, and just in case there's a terminology confusion - my project was powered with a AA battery, not a button cell.

It appears you were unfortunately correct. It doesn't power up properly. Any clues whether this will work with a 3.7 lipo battery like this?

15

Have you tried that battery direct (without the step up)

16

KenF:
Have you tried that battery direct (without the step up)

if you are referring to the button cell, no, i haven't tried that. However at this moment it's only possible to power up the board via USB.

17

Well the ATTiny should be happy on anything above 1.8volts. It's just a matter of whether the other devices would cope.

18

kuruki:
It appears you were unfortunately correct. It doesn't power up properly. Any clues whether this will work with a 3.7 lipo battery like this?

I wouldn't use that, either. Too small, doesn't look like it can provide enough current - especially considering the inevitable loss in the step-up. Even if it held up somehow, it won't be for long (how long should it work, anyway?)

You see, "weight critical" kind of conflicts with "two servo motors"... perhaps you should measure how much current these motors take while operating, that will give you a better idea about feasible power sources.

19

igendel:
The point is not about being able to get 5V - that will probably work - but getting enough current.

i've also got the same remark from another person i asked. How can I know in advance which power source provides enough current?!

20

kuruki:
i've also got the same remark from another person i asked. How can I know in advance which power source provides enough current?!

They key is the battery's "Discharge rate", although that parameter isn't always obvious either. Here's a relevant-looking article I just found :slight_smile: :