Reed-Switches and Hall-sensors

Special solutions for outdoor model railroading.
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Joined: 23.02.2008, 20:55
Location: Deventer Niederlande

Reed-Switches and Hall-sensors

Post by phg » 12.05.2013, 19:11

The use of Reed-Switches is fairly common in garden railroad environment. It is cheap but face a few problems.
First there is the 'contact dender', causing multiple contacts in one switch action.
Rocrail does not have any problem with that, as long as it is just a simple feed-back.
But using the switch as a wheel-counter (or magnet counter here) would give some problems.
And specially this wheel counter is a very nice option, so far hardly anywhere available but in Rocrail it is standard.
Second there is the fact that the contact given by a passing magnet is a rather short pulse.
Most units in LocoNet or CANBUS useually need a pulse-length of minimal 50-75 milliSec.
Abd the third fact is that reed-switches have a short functional life, when incorrent current is switched, either much too high or far too low.
The last issue can be improved by switcxhingthe correct current as given by the specifications of the reed-switch, which might be mostly very hard to find.

For all three problems, there will be one simple solution.
At the present moment I am finishing the development of GCA179 buffer board.
It has 8 isolated inputs, useable for reed-switch and/or hall-sensor. where a for the reed-switch 'healthy' current of approx. 25 milliAmp will be switched.
The hall-sensor does not have any problem with that current.
The isolated input enables the use of common Railpower wiring for the reed-switches, which mmakes it possible to use any existing wiring.
This GCA179 has a connection to GCA50 or CAN-GC2 which also provide the 5V supply for the on-board processor.
This processor will extend a minimal puls length in each input to a 0.1 Sec pulse for GCA50/CAN-GC2.
At the same time, this longer pulse will sufficiently suppress the multi pulses from çontact dender of a reed-switch.
Hall sensor do not provide contact dender at all.
More info about GCA179 :

The production of this board is not a fact yet.
It will only be made if I can find buyers for it.
Board only will be approx €6,50 and separate hall-sensor boards will cost € 0,75 each.
Complete set price, GCA179 with or without 8 sensor boards will contain all electronic parts and connectors, but no cable.

If you are interested, please send mail to, or put your remarks in this forum.

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