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LED current source based on LT3080, the modern LM317 replacement part, runs off USB or 9V or any voltage in between

This 20mA current source will operate from a USB 5V power supply. Using the LT3080 linear regulator makes it easy to get good voltage headroom. Only 200mV is needed in this version to sense the LED current – the old venerable LM317 required 1.25V just to get started – and that’s not including any drop-out voltage of the pass transistor.

There's no need for a heatsink since the regulator does not dissipate much power.










Here’s a link to the schematic, in pdf format, showing some details of the voltages and operating ranges.



This shows the simple package for the LED current source, ready for use in testing the spectra or providing a constant light source on our optical bench.

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Coffee source

Multitasking through massive coffee consumption, we find this tasty,

the Bizzarri Blend by Caffe Umbria.


best coffee in town, we think

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