DC Power Supply LM317

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Peacock
Posts:5
Joined:Wed Feb 22, 2017 12:57 pm
DC Power Supply LM317

Post by Peacock » Wed Feb 22, 2017 1:31 pm

Hopefully someone with more knowledge of power supplies can answer this. I've built a variable DC power supply based on the LM317 regulator to power my guitar effects. I have a wall wart with 20VAC output connected to a full bridge rectifier I made from individual diodes. The rest of the circuit is one of the designs I've seen for the LM317. Some of the designs I've seen have additional diodes across the 3 pins of the regulator and some don't. Mine doesn't. When I power the circuit up, the DC voltage out responds well (~2-24VDC) when I turn the adjustment pot. The problem is that I also have an AC component that also responds to turning the pot. I understand that ripple can occur, but the AC voltage goes a high as 70v! Is this normal? I'd hate to fry one of my guitar effects. Any thoughts would be greatly appreciated.

Junaid_Shahid
Posts:110
Joined:Tue Feb 14, 2017 9:00 am

Re: DC Power Supply LM317

Post by Junaid_Shahid » Wed Feb 22, 2017 1:32 pm

Peacock wrote:
Wed Feb 22, 2017 1:31 pm
Hopefully someone with more knowledge of power supplies can answer this. I've built a variable DC power supply based on the LM317 regulator to power my guitar effects. I have a wall wart with 20VAC output connected to a full bridge rectifier I made from individual diodes. The rest of the circuit is one of the designs I've seen for the LM317. Some of the designs I've seen have additional diodes across the 3 pins of the regulator and some don't. Mine doesn't. When I power the circuit up, the DC voltage out responds well (~2-24VDC) when I turn the adjustment pot. The problem is that I also have an AC component that also responds to turning the pot. I understand that ripple can occur, but the AC voltage goes a high as 70v! Is this normal? I'd hate to fry one of my guitar effects. Any thoughts would be greatly appreciated.
do you have a schematic? dont hook any load up to it before you figure out whats happening. something is wrong.
The diodes are for protection (some of the protection is for the LM317 and some is for the load.
you might have a capacitor that is either bad or has a loose connection.

what is the output voltage and current draw supposed to be for this effects generator?
design a DC power supply using LM317

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