MB102 Faulty?

Hi,

I have one of these MB102 power supplies:

http://www.petervis.com/Raspberry_PI/Breadboard_Power_Supply/YwRobot_Breadboard_Power_Supply.html

I was testing the output voltages with my multimeter and found that when the jumpers were on the 3.3v it indeed measured about 3.3v (was actually 3.1v), which was good.

When I put the jumpers on the 5v, it measured as about 12.9v!

The input was 9v 500ma, which seems within spec.

Any ideas?

The board has two voltage regulators. A 3.3volt and a 5volt one.
Did you try the 5volt rail with some load, e.g. a 1k resistor.
An "unloaded" regulator could oscillate, and throw your readings off.
Lineair regulators like this one can never produce a higher output voltage than what you put in.

Note that the 5volt regulator can only deliver ~200mA with 12volt on the DC jack.
And ~350mA with a 9volt supply.
The 700mA stated can only be reached with 6-7volt input.
Same or even less for the 3.3volt output.
Leo..

Suggest you have a few more tries at measuring the voltage.

12.9 V from a 9 V supply is rather unlikely. :grinning:

Indeed, though I tried all four pin pairs when on the 5v jumper and it very much came out every time the same.

This is why I am puzzled.. I can take a photograph to prove my innocence! :wink:

My thoughts were that perhaps the power supply isn't regulated so until I add some load (e.g. the resistor suggested above), then this might explain the odd behaviour?

If you read the datasheet of the 2 regulaturs used on the board (AM1117, as indicated on the document that you linked), you can see :

Ciao, Ale.

flipcode:
The input was 9v 500ma, which seems within spec.

Did you measure the input voltage?

I blew up a couple of these with a "12 V" wall-wart that was running somewhat higher than 12 V (around 18 V in reality). In my case the 1117-5 5 volt regulator blew but the 1117-3.3 3.3 volt regulator continued operating and replacing the 5 volt regulator brought the whole thing back in spec.