Let's Make Robots!

Voltage regulator problem

Hi, i recently added a sharp ir sensor, a servo, and a picaxe 8m to my robot, trix. The power supply i made for the picaxe board and sharp ir sensor assembly was simple and should have worked i thought, it was a five volt regulator from parallax, a 9volt bettery clip, and a 3 pin header for the power out (5volt reg, un regulated 9v, ground), However when i plugged the power supply into the picaxe board, my multimeter read only like 2.5 volts across the picaxe and the voltage regulator heat sink got so hot i burt my finger quite a bit.

i was wondering if i needed any supplimental circuitry with the voltege regulator?

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Okay. I'm finished with it and I tried putting in a mylar speaker. Then, everthing stopped. I did change the code but nothing happened. I am not sure if the board is fried. I can plug it into the computer and program it. Everything is in properly but I don't know what happened. I had a Bourns 330ohm resistor in a DIL package.


Thanks for all the help! i looked at my circuit and i did find i had gotten the pinout turned around. oops! Now i have one more question: do picaxes have reverse polarity protection?

I hope you didn't fry the Picaxe board.  If you did, count it as a lesson learned.

It's a really, really, really, good idea to test your regulator circuit before hooking it up the the microcontroller or anything sensitive. I know this may be advice coming too late, but take heart in the knowledge that most of us have learned this the hard way. ; j

I remember years ago working with some radio systems we had borrowed for a project from the US Marines (this was for work). We had no documentation for the units, and we fried 3 of them before realizing we were hooking up the power backwards.  There was no reverse voltage protection built in.  My boss got to explain this to an angry Marine officer. ; j

I just finished my own regulator a few days ago, and almost hooked it up without testing in my enthusiasm. Then I remembered lessons like the one above and checked the voltage outputs, double-checked the pinout for the Picaxe, etc. before hooking it up.


not usually, did you fry it?

just built new voltage regulator and it works perfectly. i have a gnawing feeling i  fried my picaxe though because the program wont find it. i made sure i did a reset too.


yup. i just checked and the way i incorrectly wired it reversed the ground and 5 volt regulated, which would have made the power on the picaxe backwards and fried it. oh shucky darns.

I wonder what bits got fried? Most sensitive would be the microcontroller. If you had a motor contoller or other supporting ICs installed, they may or may not be OK. I'd guess most of the discrete components are fine.

Anyone else have any educated guesses as to what Pixelator can salvage on his PICAXE board?

the only thing that was supplied by the regulated 5v was the picaxe and a sharp ir sensor. it was on a home made board that also has a servo and a serial connection to a bs2 that was left unconnected when i was trying my voltage regulator that was bad. didnt know if the board was good before i made the bad regulator because its the only power source.

It sounds a bit inconclusive about whether you fried it or not. Did you have the serial in properly grounded when you tried to connect to it?


I havent tried connecting the serial link to the bs2 yet, but the cable to my pc was properly conected and grounded.I think im gonna order a new picaxe and see if that helps.

well, a few questions for ya. Do you know if the proc worked prior to it being possibly fried? Is it on a proto board or something similar(properly grounded serial ports)?

 just wondering as I've hooked my up backwards once, I think it was with 4AAA batteries so around 6 volts and it survived that abuse!

 Just throwing that out there...