This is an updated version of the LM317 kit we've been selling.

Based on the user feedback the following improvements have been made:

• Add mounting holes- a biggie! There are now three mounting holes sized for 4-40 screws (3.2mm diameter)
• Move LM317 regulator to board edge, so it can be mounted on a heatsink
• Add ability to adjust voltage: you now get a choice to either use an included 5K potentiometer for adjustable voltage or install a resistor instead to get fixed output. The values for 3.3V, 5V and 8V are still included
• Add protection diode to handle shorts on the input.
• Add cap to the feedback pin (together with a protection diode) to lower output ripple if desired.

Description:

Here is a simple LM317 power supply kit so that you don't have to build the regulator on the protoboard every time you need one! One handy application is a pre-regulator for Arduino when running from higher voltages, such as 12V or more. It is well known that at high input, Arduino power supply dissipates quite a bit of power and gets really hot, even to the point of shutting down. By dropping the input to 7-8V that can be easily avoided. (See the Arduino Survival Guide article by Ed Nisley in Circuit Cellar #269 for details)

The output voltage is adjustable by selecting the proper value of R2. The LM317 chip is at the edge of the board, so if higher currents are needed, you can add a heatsink (not included). Input voltage range is 3V to 40V, and the output can be set between 1.25V and 37V. Output current is limited to 1.5A, and depends on the power dissipation in the chip and cooling. You get all the parts pictured and a bare board. The formula for calculating resistor value is shown on the schematic as well as on the board silk. The input and output pins are on a 0.1" grid and can be used with breadboard if desired. Board size is 27x31mm