Small project #7 — USB powered inspection light


Quite often I run into the problem of getting light to where I need it when inspecting SMD solder joints. The ring-light I built some time ago provides a lot of light, but is too large to get close to the objects of desire.

A slight variation of the schematic, smaller LEDs and a different layout now provides a quite small light source with brightness control. The ‘point source’ only consists of 6 0805 LEDs, 3 per side. Two LEDs point sideways, one points forward.


This will not provide anywhere near the amount of light the ring-light, but it is more concentrated and can get very close to the solder joints I need to inspect. There shouldn’t be any shadow problems as well. The light source is small enough to fit in-between the object and the magnifier without obscuring anything.



A few shots with the light in action:



Hints for assembly:


R8 and R9 are 1k, R7 is 150R (gate resistor), C1 is 4.7µF. The LED resistors are matched to the white LEDs used, in this case 110R. You may want to place a 10k resistor across the transistor’s gate-source pins (the ones pointing towards the USB connector).

Design files and code are available via the Projects section (see above).

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