Thursday, 19 January 2012

New DIY UMT design

I've modified my Milestag UMT design to correct a problem with the original.

The problem is that the muzzle flash LED is wired in parallel with the infra red LED:

This is an issue because the forward voltage of the IR emitter is 1.35V, and that of the muzzle flash LED is 2.1V. This results in the muzzle flash illuminating far below its potential.

My new design has two outputs, one for the IR LED, and one for the muzzle flash LED. Both are driven from the same MOSFET but the current limit resistor is dedicated to the IR LED:

The muzzle flash LED will require its own current limiting resistor, but this matches the original Milestag design.

Here's the PCB, it will be available as a kit at TAGBITS in a few weeks:

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