Arduino Voltage regulator gets hot when I connect a raspberry Pi to it.

The raspberry pi is already powered through it's micro USB port.

When I switch on the printer CPU and connect the PI to it, the voltage regulator gets to hot to touch within seconds. I think I found out the culprit. It was the power adapter dat was powering the PI. I replaced the power adapter with a different one and now the voltage regulator functions normally. Both power adapters were 5 volt 1.2 amp output.

How can a faulty adapter cause this? The PI was on and accessible when only connected to the power adapter. But somehow the PI still drawer power from the Arduino​?

Also this is a noob question but I'll ask it anyway. The voltage regulator, as the name suggests, regulates voltage and not current. So why does it get hot? Is it because the power consumption increases while the voltage stays the same, thus the current from the psu through the regulator to the Arduino has to increase?

Edited 1 time(s). Last edit at 05/02/2017 04:19AM by Nadim.

Some people reported molten USB cables from bad "ground loops". But that happened with 12V supplies.
The 5V regulator should switch off, when it sees 5V from USB. Maybe that circuit is broken on your arduino?

... if your PI-adapter was broken, then all the 5V-power was drawn from the Arduino regulator --- and this was definite too much to handle

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Viktor
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Aufruf zum Projekt "Müll-freie Meere" - [reprap.org] -- Deutsche Facebook-Gruppe - [www.facebook.com]

Call for the project "garbage-free seas" - [reprap.org]

I'd say the regulator would normally get a little hot as 12v to 5v requires the "excess voltage" to be shed as heat. The more current you are drawing the more heat this process produces.

I have a lm7805, a much larger and more capable regulator than fitted to an arduino, on one printer just running a 5v hotend fan regulating down from 12v and it gets quite hot despite current draw being miniscule.

If the raspberry pi is being under-supplied and I read that we should use 2A supplies for them, its pulling extra current from the arduino 5v regulator (which is suitable size for an arduino, but not for the rest of the 5v kit also attached like lcds) and therefore it gets hot, too hot and it dies.

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Simon Khoury

Co-founder of [www.precisionpiezo.co.uk] Accurate, repeatable, versatile Z-Probes
Published:Inventions