Only 4.86 4.87v from Battborg?

Submitted by METTAUK on Wed, 07/13/2016 - 10:22

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I currently have a 1 PicoBorg Reverse and 1 UltraBorg connected to a Pi3b. On boot up (power on I don't get more than 4.9v it then drops to 4.86 with nothing running, no ultrasonics and no motors! The battery pack shows plenty of power :-)

Checked wiring and all seems fine (see pics in case I've messwe up on Borg's)

Proto hat only has temp sensor on at the moment, small servo was on pi and worked fine but when used the battborg it crashes the pi Never had this before, even with two small servos and USB supply to the pi, inc straining and stalling the small servos!

WiFi and Bluetooth are on but nothing else running and Bluetooth does not connect to anything.
The camera module is not running either.

Images: 
piborg's picture

piborg

Wed, 07/13/2016 - 11:23

The most likely explanation is that the two 3-pin cables the power has to travel down are providing enough resistance to cause the 0.1 ~ 0.14 V power drop.

I would suggest trying to make a short cable to go between the UltraBorg and the PicoBorg Reverse to reduce how much power is wasted here.
It may also be worth using slightly thicker cables as they will have less resistance as well, 22 AWG cable should work well.

If you need wire we sell some different colours of 22 AWG on our accessories page here.

METTAUK

Fri, 07/22/2016 - 00:14

Rewired with your rather ridged 22AWG single core wire and now get around 4.90v which is enough at the moment so thank you for the suggestion.

I wonder if there is any benefit in running a separate BattBorg to the PicoBorg Reverse rather than daisy chaining from the Ultraborg to PicoBorg Reverse and then to the Pi 3, all from the same 12x1.2v power pack?

Currently no servos, just USM's x4 ..
Each will be (not standard HC04) at
Operating voltage: DC 5V
Quiescent current: 5mA
Total current work: 30mA

piborg's picture

piborg

Fri, 07/22/2016 - 18:19

Unless you are really concerned about the slight voltage difference it will probably not be worth having a second BattBorg.

If you really want to try and improve on the 4.9 V the best thing to do is have the BattBorg as close to the Raspberry Pi as possible.
A TriBorg or TriBorg+ will help in that regard, connect the BattBorg to one header and the other boards to a second header.

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