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The Digispark => Digispark (Original) Support => Topic started by: fbettinger on May 20, 2013, 05:31:53 pm

Title: powering on 5V with AAA ?
Post by: fbettinger on May 20, 2013, 05:31:53 pm

Hi,


I tried to power the digispark using the 5V pin. I assumed I should just plug about 5V and it would work fine (actually 4.8V since I used 4 AAA batteries).
When I mesure the voltage after starting the digispark, I got 2.7V. As far as I understood the green LED might explain that voltage drop, but I just want to make sure I'm doing things right and not fry my digispark. It's probably newbie questions, but I'm still wondering :
How can I get safely get 5V on that pin with AAA batteries ?
Is it better to power it with 4 AAA batteries and cut the trace for the LED or do I have to use more batteries (5 batteries? more? ) ?
Is it safe powering it on the 5V pin directly ?

Title: Re: powering on 5V with AAA ?
Post by: digistump on May 20, 2013, 08:14:44 pm

It is safe to power it via the 5v pin with anything from 4.5-5.5v


When you see 2.7v where are you measuring? The 5v pin? The LED does not affect the voltage on the 5v pin.


Are you using fresh batteries and did you connect the + side of the pack to the 5v and - side to the GND?

Title: Re: powering on 5V with AAA ?
Post by: fbettinger on May 20, 2013, 10:16:31 pm

Yes, I connect the - ont the GND pin and the + on the 5V.
I measure the voltage between the GND and 5V pins and get 2.7V.
If I measure the voltage directly an unconnected battery pack, I get around 4.8V.


I'm using rechargeable batteries (I recharged them 2/3 days ago, so those should be "fresh").


I try to light a 6V rated LED with this setup and, If I use the digispark it doesn't seem to light, but if I plug it directly to the 5V pack, it lights up without problems.
Now if I use a 9V battery on the digispark it lights correcly, and I measure 4.9V between the GND and 5V pins.


strange...

Title: Re: powering on 5V with AAA ?
Post by: Bluebie on May 21, 2013, 07:23:45 am

I think your batteries are not working properly - it sounds like they have a lot of internal resistance, causing a voltage drop (like a resistor voltage divider) when a load is attached. Can you try some different batteries in that pack?

Title: Re: powering on 5V with AAA ?
Post by: fbettinger on May 21, 2013, 11:30:01 am

Thanks Bluebie,


You were right, the accumulators didn't behave properly. I just bought new ones, and I got 4.95V instead of the 2.7V. I's still strange that lighting the led alone worked and plugging the led on the digispark gave such a drop in voltage. Anyway, the new batteries can light that led plugged on the digispark, so everything's fine and behaves properly now.