External power supplies/chargers

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External power supplies/chargers

Simon Walters 05 Feb 2014 18:27

I'm connecting a RaspberryPi to my Thymio and getting a few lockups on my RPi when I make the Thymio move.
This is when powering the RPi from a USB hub.

When I power my RPI from 4xAA NiMH - the lockouts are not happening.

I was wondering if there was information on how much current is being drawn via the Thymio USB port when it is connected to a computer.

Both stationary and with motors at full speed and all the LEDs on.

What happens if the motors stall - is the USB interface protected from a 2A demand?

regards

Simon

Last edited on 05 Feb 2014 18:28 by Simon Walters Show more

Re: External power supplies/chargers

Simon Walters 10 Feb 2014 16:48

it happens on batteries as well and it seems to be a software issue instead :( Maybe my Python script - maybe a D-Bus lib issue - maybe Asebamedulla - I'm trying to narrow it down

Re: External power supplies/chargers

Michael Bonani 10 Feb 2014 20:49

Hi,
Normally Thymio II respect USB standard.
When you plug it will take maximum 100mA until it is recognized by the host.
It is then allow to get up to 500mA.
For charging when you plug it to a wall charger it will go up to 1A.

But as you know the robot can need more, but the chip which control the power switch automatically to the battery to not ask more than 500mA on a USB host.
If the robot consume less it will charge the battery, if more it will ask the battery the needed power.

I don't know how RPi works but powering it from a USB hub could be problematic. It could be that the hub is limited at 500mA too and than all the current is taken by Thymio and there is no power left for RPi.

From a battery it should work if the battery are enough charged.

Finally just to know:

• each led are asking at maximum 20mA (they are 40) so you can have 800mA for the leds.
• Each motor can draw maximum 400mA (a little more for a short time, but than there is a protection when they are stall)
• the IR sensor are pulsing at 500mA (very short pulse)
• uControler around 60-80mA
• the laud speaker can also ask 500mA max

Re: External power supplies/chargers

Simon Walters 13 Feb 2014 21:52

Thank for for that detailed answer. I have bought a little USB power monitor just to monitor current and voltage :)

Simon