Friends, from what I can gather from all your excellent posts and PM's I searched and found a company in Yorkshire named LED Essentials.

Their website gives me more information which might be of use to my advisers?

The LED's that they supply are or have a Forward Current of 20Ma? and a forward voltage of 12 Volt with a maximum voltage of 14 volts.

Would they be a good buy or am I likely to waste even more money?

This is the plug-in transformer that I have been using and would use in future if it is OK in your eyes?

http://www.ebay.co.uk/itm/121175495914?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

Regards, Peter.

Peter, I don't think it matters too much where you get your led's from. No led has a forward voltage of 12v. Most are 2 to 4volts. It looks like the ones you have found have a resistor in series and the operating voltage is 12to 14 volts - that's my guess anyway.
Your power supply looks fine in my opinion.
Regards

Quote from: austinbob on July 04, 2015, 06:38:56 PM
Peter, I don't think it matters too much where you get your led's from. No led has a forward voltage of 12v. Most are 2 to 4volts. It looks like the ones you have found have a resistor in series and the operating voltage is 12to 14 volts - that's my guess anyway.
Your power supply looks fine in my opinion.
Regards

Bob, thank you!

Does this mean that their sales blurb is incorrect?

http://www.switchelectronics.co.uk/leds/prewired-leds/blue-prewired-3mm-led.html

For the lay person, like myself, I have to believe what they write is correct?

Regards, Peter.

It's sort of right but it would be better if they just said "series resistor fitted for operation on 12 to 14 volts".

When a forward voltage is quoted with regards to LEDs, I would expect it to be for the LED itself, not the combination of resistor AND the LED.

Quote from: petercharlesfagg on July 04, 2015, 06:56:26 PM

Quote from: austinbob on July 04, 2015, 06:38:56 PM
Peter, I don't think it matters too much where you get your led's from. No led has a forward voltage of 12v. Most are 2 to 4volts. It looks like the ones you have found have a resistor in series and the operating voltage is 12to 14 volts - that's my guess anyway.
Your power supply looks fine in my opinion.
Regards

Bob, thank you!

Does this mean that their sales blurb is incorrect?

http://www.switchelectronics.co.uk/leds/prewired-leds/blue-prewired-3mm-led.html

For the lay person, like myself, I have to believe what they write is correct?

Regards, Peter.

Peter - I've looked at your link and you can see there is a resistor in the top lead.
So what they mean is that the voltage range is 12 to 14volts to give a current of about 20mA. Not a good spec description from them in my opinion - wrong terminology.

One other possibility for the apparent failures is that Peter is using blue LEDs which have a higher forward voltage than green and red ones which the PPI unit instructions refer to.

All the more reason to get test kit suggested above.... troubleshoot from the top down

Quote from: Bealman on July 05, 2015, 10:03:43 AM
All the more reason to get test kit suggested above.... troubleshoot from the top down

George, if you are suggesting the test rig that you suggested in the other thread, how do you know which LED to stick into which hole?  I have no idea about the Ma's on each LED?

Or do you stick each leg in each hole in turn?

Surely it is easier to pass a current across the terminals as a test?

All these references to Ma, voltage, resistors, forward voltage etc. gets VERY confusing!

Warmest regards Peter

Quote from: petercharlesfagg on July 05, 2015, 10:18:05 AM
All these references to Ma, voltage, resistors, forward voltage etc. gets VERY confusing!

You're not alone there Peter, don't understand a word of it meself


Paul

I dunno either (but secretly I  sorta do..... I  say sorta)

In answer to your  quesrtion, you don't have to worry!

That's the beauty of it..... you  just start at the lowest mA current stick it in the holes, and work across until you have desired  brightness, read off the mA!