I made a power supply using two 47uf electrolytic (aluminum, I believe) caps and a L7805CV 5v power regulator. I also added a 100ohm resistor and an led to vout. I'm using a battery pack of 4 NiMH AA batteries. The pack reads 5.43 on the multimeter with no load. When I hook up a motor to vout and ground, I get 3.85v instead of the expected 5v.
I'm wired up like so:
- battery positive -> vin
- battery negative -> ground
- vout -> 100ohm resistor -> led -> ground
- vin -> 47uf cap -> gnd
- vout -> 47uf cap -> gnd
Here's a pic:
The L7805C has a dropout voltage of 2v typical.
So with 5.43 volts input you can expect an output of 3.43 volts typical.
(Although dropout is not really spec'd when the output is below regulation voltage.)Tweet