LM317 Variable Power Supply





Introduction: LM317 Variable Power Supply

The LM317 variable power supply is very popular and works well in many situations. It can take in up to 40 volts and vary the output voltage from 1.2 volts - 37 volts. While providing up to 1.5 amps of current with a proper heat sink installed. Its important to note the larger the difference between input and output voltage the hotter this voltage regulator will get. As of right now you can get 10 of these for a $1.30 on ebay.

Step 1: The Circuit

This circuit has very few parts and can be assembled on a breadboard in minutes for testing. In fact the capacitors can be left out and it will still work just fine. The capacitors are there to smooth any noise and provide a clean dc output. I used the toner transfer method along with vinegar, salt and hydrogen peroxide to etch the pcb. For more information on etching copper clad boards and making your own pcb's or this circuit search youtube for video tutorials which are readily available.

Step 2: LM317 Simple 3.3 Volt Power Supply

I needed a 3.3 volt power supply that was capable of 250ma for the esp8266 wifi thermometer I was working on. So in very little time I took two resistors and some wire and wired the lm317 as a fixed 3.3 volt supply. After making sure it worked I added a heat sink and hot glued the whole thing to a piece of stiff plastic. On the input of the LM317 I used a dollar store USB wall charger with a rating of 5 volts at 1 amp.



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The LM317 comes in a TO-3 steel can package too. The TO-220 like you have here can only dissipate 15 Watts. The steel can dissipates 20 Watts. The 1.5 amp spec is kind of worthless really. This is what the steel can looks like


Mo bigger is mo betterer.

That's good to know, too bad I already bought 10 of the to-220 spec ones for a $1.30 from ebay.

Yeah I have a bunch of TO-220 package LM317s myself. They do the job most of the time. Right now I am using a 78L05 on a breadboard for a circuit I am experimenting on. It is only good for 100ma. It is in a plastic transistor TO-92 package.

pfred2: I'm looking for a power supply where I can regulate DC to 12v up to 6 amps or more. Any suggestions on where to start?