 Joined: 08/04/2023(UTC) Posts: 6 Location: Skåne
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I recently purchased a big lot of C rails and among them were a couple of what I think is train detectors. Someone has drilled out a section between two of the ties and inserted something that looks like a detector (magnetic sensor perhaps). The sensor is then connected to a home made PCB populated with a couple of digital IC's. Does anyone have more information as to what it is and how to connect it to something ? Below are couple of pictures of the units.  
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 Joined: 28/03/2007(UTC) Posts: 303 Location: Torino,
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I would say there is a glass tube in the slot, likely a reed relay. A closer picture of the other side of both rail and pcb could help
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 Joined: 15/12/2005(UTC) Posts: 3,594 Location: Spain
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Could they be Hall sensors? |
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Joined: 08/04/2023(UTC) Posts: 6 Location: Skåne
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Mystery solved, kinda.
The sensor is a photo resistor connected to what looks to be a serial shift register. From what I can see it most likely has a master unit (that I do not have) that sits in the start of a number of these units connected in a chain using 10 pole flat cables. Each connector has 4 signals in total: 1-power, 2-clock, 3-data, 4-Ground, and one of the connectors is an input and the other is an output that feeds the next unit in the chain.
So, when the train runs over the sensor it signals this in a bit in the shift register that the master can read out. The board I have played around with seem to work and I can see the sensor data in the generated bit stream.
Date codes on the chips indicates that it was assembled sometime 1998. It does require that you have a significant amount of light right above the sensor so night sceneries are not possible here.
I will not use these at all so if anyone wants them I can send them if you pay shipping.
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 Joined: 23/07/2014(UTC) Posts: 8,475 Location: ENGLAND, Didcot
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Originally Posted by: 3030guy  Mystery solved, kinda.
The sensor is a photo resistor connected to what looks to be a serial shift register. From what I can see it most likely has a master unit (that I do not have) that sits in the start of a number of these units connected in a chain using 10 pole flat cables. Each connector has 4 signals in total: 1-power, 2-clock, 3-data, 4-Ground, and one of the connectors is an input and the other is an output that feeds the next unit in the chain.
So, when the train runs over the sensor it signals this in a bit in the shift register that the master can read out. The board I have played around with seem to work and I can see the sensor data in the generated bit stream.
Date codes on the chips indicates that it was assembled sometime 1998. It does require that you have a significant amount of light right above the sensor so night sceneries are not possible here.
I will not use these at all so if anyone wants them I can send them if you pay shipping. I would expect to find the electronics emulates an s88 sensor, and would probably quite happily work in an s88 string.
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 Joined: 04/02/2021(UTC) Posts: 482 Location: USA
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That's pretty fancy electronics for location sensing. Ground sensing or reed switch seem a lot simpler solution (and cheaper).
Ben |
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Joined: 08/04/2023(UTC) Posts: 6 Location: Skåne
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I did a little digging into the S88 stuff but these boards do not comply with this standard. There is for one no PS (load) signal on the connectors. From what I can determine the master unit resets the string of boards by holding the clock signal low for a fixed period of time. When the clock starts each board generates a load signal to the shift register that loads the sensor state but also a few bits from a ripple counter. Not sure what this is for.
However, i have gotten really curious right now so I will connect two of these boards to an arduino and see what I get from it.
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 2 users liked this useful post by 3030guy
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