Reed switches and turnouts.

[Anonymous]

Hello everyone,
I need to automate my atlas tunouts (snap switches) to change the points to the proper direction just before the loco arrives at the frog end of the switch points. I have been told that reed switches , mounted on the track,and magnets mounted under a car in the line will do this for me. So I was thinking that some of you must have done this already and maybe could give the names and or style of the reed switch I might need and also what and where to get the right sized magnet. I run DC. Thanks for your help. Jon

[NZRMac]

I'm thinking along the same lines as you, I repair Fisher & Paykel refrigerators and they use reed switches in the door for light and fan control. I think any normally open reed switch would do the trick, security alarms use them too for window, door detection.

I'm going to wire mine in parallel with control panel pushbuttons, which use a capacitor discharge circuit so it won't matter if the train stops over the reed switch.

Ken.

[willy6]

Try Jameco Electronics @ www.jameco.com

[Anonymous]

Hi Jon. I had done the same thing on my first layout. I used a mechanical type trigger, but a reed switch will work as well. You want reed switchs that are normally open, single pole, single throw and are can be mounted low enough between the rails without interfering with coupler trip pins or loco trucks. The MAGNET has to be small enough to clear the guard rails on turnouts and grade crossings and not interfere with truck rotation. Placing them on the loco frame could be a problem. The reed switch will work in either direction, so the control device you make, to work the turnout solenoid, will need a circuit for each direction or polarity. If not, the relay would trip the switch as it passes the opposite reed switch.A capacitor discharge circuit is a must, or you'll burn up the solenoid. The units I built had two capacitor discharge circuits per control unit, one for each direction. The voltage in should be 14 -18 volts AC and at least two amps and 18 gage wire, or larger, to operate the Atlas solenoids. Otherwise the solenoid won't throw the points completely.
If clearence is a problem, other alternatives to the reed switch is a light or infrared detector circuit. If using a light detector circuit, photocells are more sensitive than photo resistors. My sources for electronics are DIGI-KEY and ALL ELECTRONICS

(p.s. Click on highlighted words for links)

[cwclark]

reed switches are not very reliable because you have to have really strong magnets that pull them up to complete the circuit that have to be glued to the bottom of your engine (and there isn't a lot of clearence for that)...you may want to build a train detection circuit that sets off a relay to throw the switch..the only problem with this is that you need motor driven turnout machines (like tortoise) because a train detetion circuit will apply power through the relay the entire time the train is in the block which will burn up the coils on an atlas switch machine...might be better if you re-think the entire scheme...reed switches aren't very reliable, they need contant adjustment, and are a bugger to intall under the track...Chuck