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Hi all. I am trying to figure out the relay killing the power to the track. I use the trackmate board so it is easy to setup but I am trying without the board.
Here is a quick diagram of what I have tried with little success.



Wondering if any of the more electronically gifted among us here could fault what I have done!
 

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Julius Wilkko
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Hi!

Please make sure that ULN2803 is connected the following way:

pin 10 track power + (12V?)
pin 8 input from printer port and program control
pin 11 relay coil ( other end of the relay coil goes to track power + (12V?))
pin 9 track ground
NOTE!
You should connect printer port ground to same ground as ULN2803 pin 9

I think that at your diagram your relay output is connected to printer port ground pin, this is not right and may damage your printer port.

Maximum relay coil current can be 500mA and relay should be 12V model.

Relay part of the device should be easy. Place relay to cut power. If you have switch over contacts you can have power track grounded while power is off. This stops cars from coasting.

Hope this helps

Cheers!

Julius
 

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Hi, starting with the relay driver. You are using the buffer no. 8, with input on pin 8, fine. The output you should use is 11 and it seems like you do.
The COM pin (10) should be connected to +power and you seem to have done that too.
THE GND pin(9) should be connected to power gnd, ans it seems like you have done this. This is crucial.

The ULN2803 is providing GND(!) (from pin 9) on the output, not 12V and the relay thus needs +12V on the other side of the solenoid.
When the ULN is not driving the output is 'floating' like an open wire with just the diodes in revese protecting the transistor from spikes.

The solenoid of the relay is pins 85 and 86. You can keep the 86 connected to pin 11 of the ULN, and connect 85 to power+ (12V).
The switch in the relay is on pins 30 and 87. You can keep the 30 connected to + on power source but move the track+ to the 87 terminal.
The ground on the parallel port should also be connected to GND on the power source.

This setup will activate the relay when the output of the parallel port is high (5V), if this is desired?

Your circuit will never work for 2 reasons: the relay is never activated, given GND on both sides of the solenoid and one contact pin not connected (87).

Good luck.
 

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Discussion Starter · #4 ·
Thanks Lowrd and Tboy. Sorry, I forgot something on my original picture. 87 on the relay goues to the white lead on the Drivers station.

 

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I am not familiar with the drivers station. What is the purpose of the white wire?

Anyhow the basic wiring is still wrong. The relay will not work.
 

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Your diagram is improving


But your drivers station is wired wrong. The black wire should go to the track + side. The white to 87 on the relay, but the TrakMate diagram shows a relay with 87A,
which is connected to 30 in the relay when it is resting. When the solenoid is powered the 30 terminal is connected to 87, and 87A is disconnected.
The TrakMate circuit will disconnect power when the ULN is driving the relay, yours the opposite. I am not sure which you want?

The red wire can be connected to GND if you want brakes.

And the track needs GND too.
 

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Rich Dumas
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Another way to do this is to use a solid state relay that uses little power and can be switched directly by the parallel port. A KYOTTO KG1010D is an example of one that works well if you do not put a lot of amps through it. White from the driver's station is connected to pin 1, + from the power supply is connected to pin 2, pin 3 is connected to pin 2 of the parallel connector and pin 4 is connected to pin 25 of the parallel connector. For high powered tracks the electronic relay can be used to switch a conventional relay.
 

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Discussion Starter · #9 ·
QUOTE (RichD @ 20 Jan 2012, 03:14) <{POST_SNAPBACK}>Another way to do this is to use a solid state relay that uses little power and can be switched directly by the parallel port. A KYOTTO KG1010D is an example of one that works well if you do not put a lot of amps through it. White from the driver's station is connected to pin 1, + from the power supply is connected to pin 2, pin 3 is connected to pin 2 of the parallel connector and pin 4 is connected to pin 25 of the parallel connector. For high powered tracks the electronic relay can be used to switch a conventional relay.

So Rich, I can use the SSD to connect to a normal relay. But then how would I connect the pins on the SSD to the automotive relay for example?
 

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SSD is Solig State Disk, not what you want. You need Solid State Relay, SSR, which is considerably more expensive than an ULN and a relay.
Check the prices before you decide.

The SSR is meant to replace both the ULN and the relay in one unit, and you need to find a unit that can be driven from the printer port (5V).
It is a good alternative, but pricey.
 

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Rich Dumas
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You would connect pin 1 of the SSR to the conventional relay coil and connect other side of the relay coil to the negative side of your power supply. Pin 2 of the SSR would be connected to the positive side of your power supply. The SSR will only conduct in one direction, so you have to get the polarity correct. The contact terminals of the conventional relay would be wired as usual.
 
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