I am trying to use reed switches to control atlas snapswitches. However, using a Bachmann power pack seems to be “frying” the Reed Switch. The reed switch, I have since learned, should be powered by more that 30v / 100ma. I know the voltage is 16v but do not know the amperage. If the amperage is too high how do I lower it and will it still operate the turnout?
I would appreciate any input, suggestions, and other options.[:(]
The amperage would be a function of the load. By Ohms Law (common electronics math formula), voltage equals current times resistance. You know the voltage output of your power pack, 16 volts, and you need to measure the resistance of the switch machine, a simple ohmmeter will tell you this, just measure across the center and either outside terminal of the switch machine. Then voltage divided by resistance equals amps. If you’re not familiar with the prefixes, “ma” stands for milliamps or 1/1000 of an amp. The formula works with full amps, full volts, and single ohms. Many times you’ll see resistance stated in kilohms, which is 1000 ohms.
However, this may not be your problem. The Atlas Snap Switches use a twin coil machine that requires a MOMENTARY CONTACT switch to operate them. Just a quick burst of electricity to throw the points, then off. If your reed switch is not set up to close for less than a second, then open again, this could be your problem.
The current level is your problem. Twin coil switch machines, as Tom said, are momentary devices using at least 500ma and sometimes more than 1000 ma while throwing. Atlas machines use less current than others, but are less powerful, and still draw over 500ma.
The only switch machines drawing less than 100ma I know of would be the stall-motor type such as Tortoise. But these are always on, just reversed when you want to throw the turnout.
It might be possible, but not sure - I’d have to think it through on how to put in the circuit - to use the reed switch in conjunction with a Capacitive Discharge power supply.
You other option is to have the reed contact control a relay (relay has to draw less than 100ma) or transistor driver circuit with contacts or output rated for at least 2 amps.
yours in electron flow
Or he could use the reed relay interfaced with a Darlington: ULN2003 or ULN2803, which can drive loads up to 500mA…and they have integrated diodes for snubbing transients…ULN2003 has 7 outputs…ULN2803 looks like it has 8…but I do think you should check into a cap. discharge P.S. as suggested…
Reeds are pretty fragile aren’t they? I have not played with one myself…
OOps, Posted this as a NEW Topic instead of a REPLY, SORRY GUYS! Lets try this again.
Here are a couple of links for DIY electronics, I spent most of this evening looking threw most of the stuff on this site for some cheap ways to do some ideas I may try to do. (Lots of Stuff) Some of the the guys just mentioned are at these links to.
http://home.cogeco.ca/~rpaisley4/CDPSU.html
http://home.cogeco.ca/~rpaisley4/ToggleTwin.html
Great site for DIY electronics.
Good Luck; John (Please excuse the New Guy)