Old Timers quiz: identify this circuit


Red Oak & Western

Red Oak & Western

Active Member
This is for the old timers out there. About 30 years ago, I was building a garage sized layout, since taken down due to a cross country move. As part of that project, I made up 24 parts kits for a circuit to be used with the layout. Now here's the problem: in going through my parts box, looking for the components to build a crossing signal detector/driver, I came across the kits. But I have no idea where the associated schematic/circuit diagram is. I don't even remember the purpose or where the design came from. I checked in the following books, but didn't find any circuit using the kitted components: CTC-16e System (Gutierrez), Practical Electronic Projects (Thorne), Easy-to-Build Electronic Projects (Thorne), 34 More Electronic Projects (Thorne), Basic Electricity and Electronics (Fiehmann), and Electrical Handbook for Model Railroads Vol. 2 (Mallery).

So here are the components:

1 – LM339N Quad comparator
2 – 1N5401 Diode 100PIV 3A
4 – 1N4001 Diode 50PIV 1A
1 – 2N3904 General purpose NPN transistor
1 – 5mm Infrared LED
1 – 0.1uf ceramic disc capacitor
1 – 0.5uf 35V electrolytic capacitor
1 – 10k trim pot
1 – 35k ohm 1/2w resistor
1 – 2.2k ohm 1/2w resistor
2 – 2.2k ohm 1/4w resistor
2 – 220k ohm 1/4w resistor
4 – 10k ohm 1/4w resistor
1 – 10 ohm 1/4w resistor
1 – ? ? ? 1/4w resistor (I dropped it and can't find it and didn't want to go dig out another kit)

Does anyone recognize the circuit and know where it came from?
 
I kind of thought it might be an occupancy detector, since the kits include an IR emitter. But there is no IR receiver in the kit, nor were there any separate "receiver" kits. I guess I'll break the kits apart, put the parts in the "junk" box, and figure somewhere else to use then. On the current layout, I'm using DCC for switch (turnout) control and the associated position signals. I'm designing and building the crossing detector/ crossing signal driver circuit from scratch. I haven't yet decided what I'm going to use to drive the block signals. I'll be using ABC/TO, I don't want to add a CTC panel and dispatcher.
 
The quad comparator is a giveaway, the key to the circuit, compares 2 voltages and gives you a result that you can use for detection, the rest of the parts are more support parts to make the IC work.

Bruce Chubb had a detector in a Model Railroader series for computerized model railroads. He had other circuits for signals, the computer, etc.

http://www.jlcenterprises.net/Support.htm#Parts

scan this for possibilities, he has an updated OD on that list, might be differrent than the MR article, plus a detector for DCC, if your going DCC thats the way to go, forget this circuit.
I have chubbs articles stocked into a notebook for reference.

I visited Chubbs layout years ago with my club.
 
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