power (amperage) issue

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steveheistand
 
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Joined: Sat Jun 28, 2014 4:23 pm

power (amperage) issue

Post by steveheistand »

hi folks,

I have put together a couple of lipoly batteries (the 6600mah ones you sell: https://www.adafruit.com/products/353)
As I needed more voltage then 1 can provide I wired everything up including the charges following the fabulous guide:
https://learn.adafruit.com/multi-cell-l ... ll-charger

Then the power is fed into the buck converter : https://www.adafruit.com/product/1385
and into a B+ raspberry pi.

Its all well and good except that I have a pi-pan board (from openelectrons) with light plugged into the gpio
header on the pi. When the light is on or the camera is moving the power led on the PI flashes like its not
getting enough power.

The batteries are charged and assuming the dc/dc converter isnt broken its supposed to be
able to handle 3A which is way more then the PI is needing.
I have plugged in a usb AC adapter that was rated at 5v/1.8A and the PI had no power issues.

Im not sure where the power limiting would be coming into play with the power supply
I have built.

A PI model B has no power issues with this battery setup and servo combo.
or at least it doesnt flash its power led at me.

thoughts?

thanks

steve

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zener
 
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Joined: Sat Feb 21, 2009 2:38 am

Re: power (amperage) issue

Post by zener »

So you have two different pi versions?

It would be helpful if you can sketch out a block diagram so we are all on the same page regarding the connections.

As a first step I would take the setup that works, and measure the voltage and current out of the battery, voltage and current out of the buck regulator, and voltage and current into the camera board. Then do the same with the setup that doesn't work. That should help identify where the trouble is occurring.

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steveheistand
 
Posts: 11
Joined: Sat Jun 28, 2014 4:23 pm

Re: power (amperage) issue

Post by steveheistand »

I have the RPI model B (works) and the B+ which is having issues.
The cabling system is all bundled up otherwise I would have taken
amp readings at the various places already. Will see if I can draw up a diagram.
But mostly its will be the images in the multi-cell charger page with a buck
converter on the load end of it then off to the RPI.
s

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zener
 
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Re: power (amperage) issue

Post by zener »

I think it will be hard to figure out without taking any measurements. Hopefully you can at least measure some voltages. Electronics trouble shooting requires doing tests and making measurements usually. Maybe someone else has an idea however.

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adafruit_support_bill
 
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Re: power (amperage) issue

Post by adafruit_support_bill »

Servos are electrically noisy devices with peaky current demands which further complicates issues. If you have access to an oscilloscope, you can have a look at what the power supply looks like when things are moving.

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