2

I am trying popped a transistor while trying to power my raspberry pi from a bread board. I have a 12v battery pack that I am going to use to power my raspberry pi and some servo's. Yesterday I checked the voltage coming out of the output voltage from one of the power rails on the breadboard and it was 5 volts. When I attached my raspberry pi it popped one of the transistors on the board that I used to convert the 12volt to 5 volt. BTW the odd thing is that after frying the transistor it was outputting 10 volts to the rails. Luckily it did not cook my pi :) . I am using a B+ and connected the first 5v pin and the 3rd pin which is ground on my pi. Counting pins only on the outside of of the header and not the board layout. Should I have used the second 5v (pin 2 on the outside of the header). BTW what is the second 5v pin for? I only have one 5v on my model B.

Any ideas would help as I am new to electronics and don't want to fry another board. I apologize if this is not the right forum maybe there is a better stackexchange site but I figured I would start here.

Here is the breadboard power supply that I was using. http://www.amazon.com/gp/product/B00GWIL0MQ/ref=oh_aui_detailpage_o02_s00?ie=UTF8&psc=1

Here is the power supply I was using. http://www.amazon.com/gp/product/B007RQW5WG/ref=oh_aui_detailpage_o04_s01?ie=UTF8&psc=1

Update

Found another option on amazon and it appears the mb102 max output is 700ma and the pi can pull 1.5A current so this is probably what happened.

http://www.amazon.com/Breadboard-Power-Supply-Module-Solderless/dp/B00BXWV2F6/ref=sr_1_1?s=electronics&ie=UTF8&qid=1412193923&sr=1-1&keywords=gino+breadboard

Chris Hinshaw
  • 145
  • 2
  • 7

2 Answers2

2

Why not connect the 12V supply to a 5V UBEC? A UBEC converts anything within a wide range of voltages (typically 5.5V-26V) to 5V and they are generally rated for 3-4 amps.

Search on eBay, a UBEC costs a couple of UK pounds.

You are lucky the Pi wasn't damaged.

Anything over 6V is likely to damage the Pi.

Anything over 5.25V could potentially damage anything connected to the Pi (like a USB device).

The Pi has always had two 5V pins. See http://elinux.org/RPi_Low-level_peripherals#General_Purpose_Input.2FOutput_.28GPIO.29

On early revisions they were marked Do Not Connect (DNC) but in fact were always 5V.

I feed 5V from a UBEC into a 5V pin and a ground pin (my UBEC is powered from a 12V laptop power transformer). I use the other 5V pin to feed power into a breadboard. Similarly I use a 3V3 pin to feed power into a breadboard if I'm using a component which needs 3V3.

joan
  • 71,852
  • 5
  • 76
  • 108
1

The exploding part you called "transistor" is most likely the integrated regulator itself. From the description given it is highly likely that that was caused by overcurrent/short circuit. To be honest I'd consider it a bad design that the regulator has no current limiter. But I doubt the current rating of 1500 mA for the RPi for any typical application given the reportet power consumption of less than 1.5 W (see How much energy does the raspberry pi consume in a day?). The 10 V output after the failure is also reported at amazon reviews for the product used.

Using a linear regulator for a portable solution however is not a good idea. If the input voltage is 12 V and output voltage is 5 V you're wasting more than half your energy used for the RPi just to heat your regulator (which seems to have little to none heatsink attached). So if you want to safe batteries you should really investigate Step-Down Converters. But maybe https://electronics.stackexchange.com/ would be more helpful concerning such issues.

Community
  • 1
Ghanima
  • 15,958
  • 17
  • 65
  • 125