Pi not powering on 12v


 
I

I Roots

New member
Hi, this is my first post here so apologies if this has been asked before (I did search but found nothing!)

Just got my heatermeter (v4.2) I bought the ready built version as I'm more used to soldering heavier duty things than circuit boards. Assembled it with my Pi B, tested with the USB supply and all works fine. Tried it with a 12v supply and while the heatermeter powers up ok the raspberry pi doesn't.

The trouble with not building it myself is not knowing where to start testing to find the problem, can anyone point me in the right direction?

Thanks!
 
I would definitely talk to the person whom made it for you. He may need to fix it.

If you don't see any lights on the pi, when you power up with 12v then either it's not getting the 5v from the heatermeter or the pi has an issue. But sounds like the 5v issue on the heatermeter board. If you can post some good lighted close ups of the front and back of the board and maybe we could see a problem.

John
 
I Roots said:
Hi, this is my first post here so apologies if this has been asked before (I did search but found nothing!)

Just got my heatermeter (v4.2) I bought the ready built version as I'm more used to soldering heavier duty things than circuit boards. Assembled it with my Pi B, tested with the USB supply and all works fine. Tried it with a 12v supply and while the heatermeter powers up ok the raspberry pi doesn't.

The trouble with not building it myself is not knowing where to start testing to find the problem, can anyone point me in the right direction?

Thanks!
Click to expand...

By any chance did you power it with 12v at the same time you had the Pi powered over USB? If so, that could critically damage the Pi.
 
Are you sure you don't have the parts misaligned or something? The board was tested before shipping and it has to work powered by the 12V line because that's the only way it is powered during final assembly (which is where the Pi boots up and flashes the ATmega). If the HeaterMeter works powering from USB, that means the 5V connections between the boards is functional. If the HeaterMeter works on 12V, that means the 12V -> 5V -> 3.3V power supply chain is working. Therefore, everything checks out electrically.

Is the power LED on the Pi not even turning on at all? I can't imagine how it wouldn't if the 5V power connections between the two are connected.

Testing Procedure is as follows:
-- Combine Pi and HeaterMeter boards, power up with 12V
-- Wait ~50s for AVR to be flashed, adjust contrast pot
-- Plug in blower / servo, set HeaterMeter to manual mode using device buttons (tests all 4 button directions)
-- Test ramp up from 0% to 100% and back down to 0%
-- Enter webui and switch Probe 0 to Thermocouple, verify display switches to No Pit Probe
-- Insert thermocouple, verify temperature around room temp
-- Insert thermistor probe into each successive food probe jack, verify each reads within 1F after settling (2-3s)

So there's no way the HeaterMeter isn't passing 5V to the Pi, otherwise it would never boot to be flashed or have its probe config changed.
 
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Solved it, my bench power supply was running at 13.8v rather than 12v. Changed it to 12v and lol and behold the pi powered up again as it should.
If I were writing a fault report this would go down as "fault exists at user interface"!
 
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