LM317 Variable Power Supply

LM317 Variable Power Supply

A very basic power supply that can be adjusted over a range of about 1.5 to 30 volts DC @ 2 Amps. This is a text book circuit using an LM317, which is a 3 terminal regulator in a TO-220 package. Input can be either AC or DC; DC input must be at least 2.5 V above the required voltage output. You can use a LM338T for up to 5 amps of current. We do not have the LM338T, but you can get one at just about any component supplier.


  • Dimensions: L: 2" W: 1-5/8" H: 7/8"
  • Input Voltage: AC or DC (32 Volts Max) has to be 2 volts above desired max output voltage.Not intended for use with Line or Mains Voltage.
  • Outputs up to 30 VDC at 2 Amps.
  • Includes all parts and components.

LM317 Variable Power Supply Reviews:

  • --> After the kit arrived, I laid out the parts and checked them against the parts list. Next, I tested all the parts with my multimeter and they were all satisfactory and high quality. I then soldered the components to the circuit board (CB) making sure that the diodes and other components were in the correct position in the circuit. This was my first soldering job. There is a knack to soldering but rereading the soldering instructions and following them exactly resulted in a successful job. Installing the LM317T regulator in the correct position was the most challenging. If it is installed backwards, it can burn up. The + and - sides of the capacitors were clearly marked on the CB. It would have been helpful if the same info was provided for the regulator. I anchored the assembled CB to a base plate with standoffs and connected the CB to a 30 volt ac/dc transformer which I had previously purchased. I screwed the base plate and the transformer to small wooden blocks glued to the bottom of a small, home-made, wooden plywood box which has a removeable top, a hole in one side for the potentiometer knob, and three exit holes on the end for ac, dc, and ground wires. The top of the box acts as a dust cover and is not secured so that it can be removed when the on/off switch is employed during experiments using the power supply. This kit is very educational and an excellent value if you are willing to do a little work. It is the only variable power supply I need to perform all the experiments in my electronic circuit analysis text.

  • --> Good kit, I have used two of them so far as part of an alternator circuit on an unmanned helicopter. It could be more verasatile if it used molex type headers for power in, power out, and the v-reg chip rather than solder points. I use the v-reg chip (lm338) out of the case on a 17watt heatsink. The offerred heatsink heated up very quickly on a minimal load. Apart from these details, this board has a lot of potential and quality. The power output is noise free and runs my radio equipment well.

    I would buy a five or ten amp equivalent of this if somebody offerred it, very hard to find however.

  • --> Kits arrived in a timely manner. All parts were in the kit. Directions were clear. Assembly went flawless and kit worked as advertized. This was an extremely pleasant experiance. Would by another kit without reservation.