Diode Question

[sammmm]

Hi All,

 

Excuse the rather primitive question, but the search function isn't helping me particularly.

 

I'm looking to feed my LED's from the DCC In's and Frog port on some Cobalt IP Digitals.

 

I have already some 12v 3mm Yellow LEDs with a Vmax forward of 14V so should be fine with my NCE power cab.

 

However DCC Concepts website shows a diode used to protect the LEDs from reverse voltage when the frog polarity is switched

 

I have no clue around diodes about what to get, would these be suitable ? - would i need 12v or 14/15v diodes? https://www.ebay.co.uk/itm/Zener-Diode-BZX55C-2V-to-75V-0-5W-Pack-of-10-or-20/160784709135?_trkparms=ispr%3D1&hash=item256f83f60f:m:mNmOIwFk5Oi7oFKV516xRRw&enc=AQAEAAACQBPxNw%2BVj6nta7CKEs3N0qWpsDC91MM32yNX%2BgknRS3VFMcdWQgh8rkkw4jqMk5VtEcL%2BNdiMmGKi0rA5i6wn5I32swCFlrjKpCd4hMkDXPDx9KDulYCNGWO5uLbUj180vaC47S1GzBtbTM766VTbVYze5OHK4EqYYCEeYz1HPdDk6DUKu9ExolcTPB6BnVLMfDGfs10qWdaY49TcbuttfUlXDbEutk%2Ba0JDGBx3DujnsW9HvC83Y070zP7iLL97OWMlWPgCzGJS%2F5iTTirC4Xt0fck9TKYsFMkHbw%2BbHtxnt8xs2fAvR%2FoqT2OtM%2F%2FUditjn5IzBpwdleyDq1BaVpwk0SghE2mbSsaaaopbO8WEHYRvJ%2FRpbAxZ2oxnSOulJ7VSKdSiCuUKoqqPO51%2BDN41vm76jnREqI5glXH9anN6FbBjElqSBIx7VG92nSN8Hvuz%2FBhLUORri2ye%2FHwSxA04825UU0yKjlj6%2F6B7qv0C3naPOjy4EnrwmFBJd9nuFyVuUYG1%2FeYDcLhFup%2Ff9bOGwbbdQiKJkrQoeB0%2BxEUQrUMhZhbxK5YIYkyS9LeoHYUCJeD1esSJWK%2FCtqcFO%2BRYoQI4YH4Sz3CpWm4CUdGltd0xJ50jttKn5R%2F9FIMtgKTuj5YarcF4y4VwIQRXHU0zTnFg%2BF3SwldwrQMlH8%2Fc8pz646KfL1NpvI0fLTKqOtGNs5ZKKxnKo2z2oC12cVxDPCI8cUb413XHhiU6LQlVc6aVC3EwXRtFUuAyrO6BfA%3D%3D&checksum=160784709135227cb823daf6419a94f91ba84bc23989

 

Or can someone suggest something that is more suited?

 

Thanks all in advance!

[Ian Morgan]

Taking power from the DCC supply using ordinary diodes will cause the DCC waveform to be degraded, and should be avoided. It is safer to build a bridge rectifier from 4 'fast recovery' diodes, which can then feed DC (unsmoothed) to your LED. There is no need for reverse voltage protection then.

 

This could be made from 4 BA159 diodes, or a complete bridge such as B40FD-DIO. Plenty on eBay.

 

 

[sammmm]

Thanks Ian, I'll take a look into the rectifier wouldn't know where to start with wiring them up or introducing them into the circuit.

 

Would a simpler and safer way be for me to feed the LED's from a separate 12v source and switch them from the spare switch on the cobalts (S2) as I have no plans to use this?

[DCB]

Using a separate supply sounds like a good idea, just check what the voltage is, some "12 volt" model railway controllers are 18 or 20 volt off load or under minimal load .