Hi,
I've been buying RPi's (up to 6 now) since they were first available, so far used successfully as media centre devices, thin client to windows terminal server, and linux workstation (for the kids).
Now I've finally got around to trying to use one to control real things (especially motors) and after talking to element14 tech, they suggested I should get the gertboard and a couple of small motors (59911601 - 1.5V to 4.5V DC).
I was following the sample guide, and passed the led and button tests, and tried the motor test.
I hooked up my motor to the MOTA and MOTB as shown in the manual, and hooked up a old tranformer/plug pack which had an output of 4.5V/500mA (old portable CD player). This made the motor turn on, and running the sample program made it stop initially, stutter, and then run at normal speed (ie, it didn't seem to control the speed well, it was either on, or off). When the program tried to run it in reverse, it did not run at all.
I then hooked up an old PC fan to the MOTA/MOTB, and changed to another old plugpack which provided 12VDC/1A. This time, as soon as I connected the power supply, I saw a bright flash, and cried (OK, not literally). After some examination, I've clearly blown the fuse (I can see the wire inside the fuse is broken). The manual states it can handle up to 18V at 2A, so I'm not sure why the fuse blew.
Can anyone please advise what I did wrong (why the fuse blew)?
What fuse can I replace it with? Where to get it from?
Why didn't the motor run in reverse?
Why didn't the motor run at different speeds?
BTW, If I connect the old PC fan directly to the power supply, it works fine in one direction, and does not turn if I reverse polarity.
I was doing a test run before I tried to run through this with my kids on the weekend..... probably lucky I did 
