Rooting around in the fascinating stuff at the bottom of a draw labelled 'Engineering - Junk Miscellaneous'. Delving amongst the delightful...
Two leds for one
That push button bistable I have still yet to get going is part of an attempt to replace an led in an existing lamp with a choice of two.
I thought I would reveal the rest of my circuit for scrutiny.
The idea is that the whole circuit connects directly into the lamp instead of the existing led, stealing a few microamps to run itself.
The pairs of diodes ensure that there is always a load on the power source, which is a dc-dc converter, even during switching.
I tried just one diode, but the Cree leds I am using seem quite happy to produce a significant amount of light, even with only 2.5V across them.
The two diodes cut this to about 2.2V when the active led is dropping 3V, leaving only a faint glow from the nominally ‘off’ one.
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I will keep it that way for as long as possible.