Internal Resistance Of Various "Clickie" Switches

Internal Resistance Of Various \"Clickie\" Switches

This subject was brought up during a telephone conversation with Sonic earlier tonight, so I had to find out for myself.

I hooked up a constant voltage power supply running at 7.5V, at first directly across the leads of a multimeter to see what kind of current it was measuring, and got a reading of 1,068 ma.

Okay, so that was the control baseline. Then I introduced one by one into the circuit several switches from light mods I had laying around, just to see what kind of loss each switch sucked out. The results, expressed in milliamperes, follow in descending order from highest current still passing through (good), down to least (bad), although I am not sure what real effect these relatively small amounts would take away, as far as light output is concerned:

Baseline Current - 1,068

NoviGear (as used in Mini LGI) - 1,058

Legend 3AA (as used in LGI Classic) - 1,018

Legend LX - 998

The infamous Kroll switch - 983

Coleman 2AA - 976

NexStar 2C - 965

NexStar 2AA - 962


Wish I had more switches to compare, but that is all for now. These numbers are open to interpretive comments and discussion, so please have at it...

Re: Internal Resistance Of Various

Very very interesting data, I suspect the SF tailswitches will have a very small internal resistance?

-YC

Re: Internal Resistance Of Various

I would presume in the case of home made mods, the quality of solder joints in the bulb/lamp area would wipe out any benefits of a low resistant clickie switch.

Re: Internal Resistance Of Various

Charlie,
I think that I may be confused about what you actually did. You don't say so, but are these various switches being tested with a 5W Luxeon light powered by the 7.5V supply. Alternately, are you just essentially shorting across the supply output with the switch with meter in series. If the later case, it looks like you are just repeatedly measuring the current limit of your bench supply. There is a way to get a good measure of switch resistance if you have a bench supply with a consistant current limit. If you measured 1A from the supply when its output is shorted by the meter, if you then short the supply with the switch to be tested and measure the *voltage* directly across the switch, you can then compute the resistance. Example: supply limits at 1A, yoltage across switch measures .08V. Resistance=V/I [Ohms law] so R=.08/1.0 or .08 ohm.
On a related subject, I haven't done extensive testing of various clickies like you have. I did play around a bit with an LX clickie and one thing I noticed was that the switch resistance varied quite a bit from one actuation to another. If you set up again to do this testing, it might be interesting to check the range of values you get in some fixed number of actuations.

Re: Internal Resistance Of Various

I agree with Doug S. You can't set your bench supply for constant voltage and then measure amperage. If you do it like Doug says and set it to constant current, it should work to measure voltage. With a good true RMS multi-meter, just measure the resistance of the switch itself. I have noticed the Kroll's resistance varies a lot, and it even varies between different switches. However, the resistance I've seen with other switches are on par with the Kroll. I've tested various M*g switches in the AA and D models, the Legend LX, along with the Kroll. Of note is that sometimes the flashlight bodies themselves have more resistance than the switches do... /ubbthreads/images/graemlins/icon3.gif