Low Consumption Latching Circuit

Question

Low Consumption Latching Circuit

perts (Electrical)

(OP)

5 Jan 18 16:35

I am looking to make a very low consumption current led button just like in the picture below. The switch is a momentary switch. I want to press on to turn the led on and then press off to turn of the led. Simple latching circuit.

Do you guys how these cheap button led flashlights work? What circuit is under the black potting material. Trying to do the same.

BrianE22 (Specifier/Regulator) · Answer 1 · 2018-01-05 16:47:42

Do a search on "self-latching transistor circuits".

IRstuff (Aerospace) · Answer 2 · 2018-01-05 17:32:27

Conceptually, it's basically a toggle flip-flop

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VEBill (Military) · Answer 3 · 2018-01-05 20:16:59

This page has several examples.

Things to watch for:
1) The image you posted appears to be the usual CR2032 'battery' powered LED light. The CR2032 cell is only about 3 volts, at most. Some of the circuits to be found wouldn't work directly off 3 volts.
2) Watch for quiescent current consumption. If you're running it from a small battery, you want the OFF standby current to be essentially zero. Otherwise it'll be dead when you go to use it a month later.
3) The latched-running ON current is arguably less critical, since there's probably about 5-10mA going through the LED anyway. Another mA isn't a huge deal breaker.
4) Beware voltage drop in the switched path since you might be trying to run a White LED from a 3v battery. You probably can't afford to drop a volt (for example).

Compositepro (Chemical) · Answer 4 · 2018-01-05 21:11:11

There are plenty of micro LED flashlights which have momentary and latched switch already on the market. Most do not use circuit boards. The circuits are to regulate the LED current as temperature changes and the battery runs down.

IRstuff (Aerospace) · Answer 5 · 2018-01-06 00:58:09

A more interesting question is if that's all you need, why not use an off-the-shelf product?

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Low Consumption Latching Circuit