L-Cheapo Mk1

Download the Gerber files here. I recommend Sunstone Circuits if you want to get it made.

L-Cheapo Mk2 and 3

Download the Gerber files here. I recommend 4pcb if you want to get it made.

The schematic is obvious, however -- the L-Cheapo only works properly if assembled according to the working drawings! Thermal conductivity is important. If you are building this on a prototyping board, be sure that the LM338 is properly soldered to the board in such a way that heat can transfer between it and the laser diode.

Do not use a single 0.7 ohm resistor instead of the eight 5.6 ohm resistors: having eight in parallel is important to let tolerances even out, and spread out the heat over a larger area.

Do not use a LM317 instead of a LM338, even if you can get a LM317 that can handle the current; the thermal coefficient is important.

Remember that the power plane in this circuit is NOT ground!

If you make this on a 2 layer board, the bottom copper should mirror the top copper (for thermal conductivity).

The design is provided for free, but on the explicit condition that you email if you implement it; we can help, and we'd love a picture!

Thanks to Ruwan Janapriya for the diagram above!

Page last modified on October 12, 2017, at 01:44 AM
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