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12v relay driven by 5V

Oops. You're right, the green power indicator LED is the one at lower left.  The middle red LED turns on when the relay is successfully triggered (relay clicks on).

Well, this is quite the pickle!

Above shows my experiment.  Again, I don't have a FT turnout and am proposing a method that turns on the relay with +5V DC and turns off the relay with -5V DC.  As shown in the photo I was able to reliably trigger the relay with as low as 2.5V DC.  And at 5V DC the current required from the yellow wire was only 1.5 mA which I'd think the FT turnout can supply; but this is an assumption.

If you have not abandoned ship (yet),

1. confirm the silver band on the diode is oriented as shown.  btw, what diode are you using?

2. disconnect the yellow wire and touch the left side of the diode (without the silver band) to DC+.  This applies 12V to the IN trigger and should fire the relay for sure! 

3. can you read the white markings on the component I call R5 - should be 3 digits like "222".

4. do you have a voltmeter?

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  • 12v relay driven by 5V
@stan2004 posted:

12v relay driven by 5V

Oops. You're right, the green power indicator LED is the one at lower left.  The middle red LED turns on when the relay is successfully triggered (relay clicks on).

Well, this is quite the pickle!

Above shows my experiment.  Again, I don't have a FT turnout and am proposing a method that turns on the relay with +5V DC and turns off the relay with -5V DC.  As shown in the photo I was able to reliably trigger the relay with as low as 2.5V DC.  And at 5V DC the current required from the yellow wire was only 1.5 mA which I'd think the FT turnout can supply; but this is an assumption.

If you have not abandoned ship (yet),

1. confirm the silver band on the diode is oriented as shown.  btw, what diode are you using?

2. disconnect the yellow wire and touch the left side of the diode (without the silver band) to DC+.  This applies 12V to the IN trigger and should fire the relay for sure!

3. can you read the white markings on the component I call R5 - should be 3 digits like "222".

4. do you have a voltmeter?

Hi Stan,

My diode I think if I am reading the marking right are 1N400. Diode is connected correctly.  When I touch the left side of the diode to DC+ I get an almost imperceptible flash from the middle LED .  I think my R5 resistor is 302.

So Since I bought a pack of these relays I took out another one and YAY, I got it to work.  The relay LED turns on when I touch the diode to DC+.  But when I connected the diode to the yellow wire, I got just an imperceptible flash from the relay but no click.  Oops! I forgot to touch run a wire from the AC GND to DC-.  So NOW the light switches color BUT flipping the turnout switch does not change the color. Should I be connecting the diode to the switch or to the turnout itself? So it seem that the yellow wire does not go on or off.  It seems to be in a steady state.

I do have a voltmeter.  

...

Should I be connecting the diode to the switch or to the turnout itself? So it seem that the yellow wire does not go on or off.  It seems to be in a steady state.

I do have a voltmeter.  

The left side of the diode (the side without the silver band) goes to the yellow wire.  As I understand it, there is a 4-wire color-code cable that connects to 4 screw-terminals on the controller as shown in a previous photo.  The other end of this 4-wire cable comes from the guts of the turnout electronics itself.  If I understand your question, the answer is you can connect the diode to either end of the cable but I'm not sure how accessible the yellow wire is underneath the turnout.  I'd think the yellow wire is easier to access at the controller but I understand how that might be physically located for the convenience of the operator and no where near your signal light.

If you have a voltmeter, measure the DC voltage at the yellow wire.  The + meter lead (typically red probe) goes to the yellow wire.  The - meter lead (typically black probe) goes to DC-.  From what others report this voltage should be either +5V or -5V depending on the turnout position.  I suggest you make this measurement in two steps.  Confirm you have that connection between AC common and DC-.

First, make the measurement without the diode connected to the yellow wire.  You want to see the yellow wire voltage alternate between +5 and -5 depending on turnout position.

Then, connect the diode to the yellow wire and confirm the voltage still alternates between +5V and -5V depending on turnout position.

@stan2004 posted:

The left side of the diode (the side without the silver band) goes to the yellow wire.  As I understand it, there is a 4-wire color-code cable that connects to 4 screw-terminals on the controller as shown in a previous photo.  The other end of this 4-wire cable comes from the guts of the turnout electronics itself.  If I understand your question, the answer is you can connect the diode to either end of the cable but I'm not sure how accessible the yellow wire is underneath the turnout.  I'd think the yellow wire is easier to access at the controller but I understand how that might be physically located for the convenience of the operator and no where near your signal light.

If you have a voltmeter, measure the DC voltage at the yellow wire.  The + meter lead (typically red probe) goes to the yellow wire.  The - meter lead (typically black probe) goes to DC-.  From what others report this voltage should be either +5V or -5V depending on the turnout position.  I suggest you make this measurement in two steps.  Confirm you have that connection between AC common and DC-.

First, make the measurement without the diode connected to the yellow wire.  You want to see the yellow wire voltage alternate between +5 and -5 depending on turnout position.

Then, connect the diode to the yellow wire and confirm the voltage still alternates between +5V and -5V depending on turnout position.

Hi Stan

I measured the AC voltage at the turnout where the yellow, red, green and black wires go in and the AC voltage I got was .86. I do get 5V in DC. I do get a negative voltage when I switch the turnout.  

So I tried wiring the circuit again and it WORKS!  Thanks for your help! I think I may have had the polarity reversed somewhere, perhaps the power supply .

Cheers

Roger

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