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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It sounds like it may have been hooked up incorrectly. They will heat up like that when that happens. Check your wiring and verify that it's connected properly.


Sounds like there's a short somewhere. Make sure you've got things lined up right, double checking the datasheet for a sample schematic.

Does the power supply work as expected before you attach the other parts?

A quick glance at parallax.com seems to show only one through-hole 5V regulator, and its pinout (pins 1-3, left to right pins aiming down) is "unregulated9v-ground-5Vout" not "5v-unregulated9v-ground" as you described. Make absolutely certain you've got things wired up correctly.

Hi Pixelator,

 It sounds like a short, or you have something connected to the power rails backwards (i.e. grn ->+5 and +5 ->GND).

Some componets connected backwards will present a low reistance path, so your regulator is supplying all the current it can but cant pull it to 5V.