LM317 Adjustable Regulator in a constant current configuration. The current value is set by the resistor value: Iout=1.25/R1. Mounting holes are tied to GND. The TO-220 package maybe soldered directly to the exposed pad to provide thermal relief for the regulator. The input voltage is dependent on the number of LED’s being driven and the forward voltage. Using the LM317 adjustable regulator allows most of the power to be dissipated from the regulator so you may not require a power resistor, but fixed output regulators can also be used but will likely require a high wattage resistor. Just do your power calculations. Altium Designer files are available on Github.

Project files are hosted on GutHub.com.

Micro Relay Board

I designed this to use a small signal relay () with a small package to use in many of my projects that need a relay without a log of space available. The silkscreen for the relay contacts are reversed and haven t had the motivation to update it as I am probably going to be the only person using it, but just in case I wanted any else to be aware of that. The board uses a sot-23 diode as a flyback diode across the relay coil, and it is input signal is active high which drives a transistor to pull the relay to ground. So the signal input does not directly drive the relay because that might pull more current than a microcontroller can provide from a single pin. The two pin header is there to easily check that the relay functions them out. Design is about as small as I could make so the fab costs are pretty low.

Dual Row Header Edge Conntector