Adjustable voltage regulator for varying current?

noobydoob

I have tried to regulate 7.5V to my servo controller using LM317, but it's not working. The servos won't turn. Is this because of the voltage divider? What are my options?

Franklin

How do you have the servo hooked up and what are you driving it with? Could you attach the code you are using?

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- Stephen

noobydoob

It's a Parallax PSC. All servos work fine with 7.5 batteries connected. When I use the regulator (which I measure to 7.5 volt with a meter, they don't work.

Franklin

Sounds like you are not getting enough current out.

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- Stephen

noobydoob

The LM317 is rated at 1.5A, should be plenty for 4 servos. They are not under load at the moment, and should only draw a few milliamps. I have a 2300 mAh, 13.8V battery pack going into the regulator. Is it not a problem to use a voltage divider when you have varying currents? How are people powering their PSC?

Mike Green

What is your output voltage?

There's nothing wrong with using a voltage divider for controlling the output voltage of an LM317. That's how the regulator is supposed to be used. If the voltage divider is set wrong or the values are wrong, you won't get the output voltage you expect. What are the capacitor values? The LM317, like all regulators, has certain minimum input and output capacitor requirements.

noobydoob

Thanks Mike. I added a 1uf to the output (had only a 10nF) and now it works! Great thanks.