Model Railway Forum

I refer back to it every time I have to use LEDs - not clever enough to remember like some on the forum.

The taxi lights - between flashes Now to unwire and start again.

IMG_0766 by Barry Clayton, on Flickr

How infuriating - slightly funny though. R-

Steve M wrote: ↑Sat Oct 17, 2020 9:16 pm Barry it’s one or the other.

Try this:

http://led.linear1.org/led.wiz

Thanks Steve - good find now saved to my favourites. All I've got to do now is remember at some future date that I have done that and find it! R-

RogerB wrote: ↑Sun Oct 18, 2020 12:12 pm How infuriating - slightly funny though. R-

I thought about putting the "flashing" to music.

Hi Barry
The 3 volt power supply you're using, can you advise what its output current is? This should be stated on its label/rating plate. Its the Secondary or Output current.
BTW why 3 volts?

Hi Brian - I was cheating - no resistors - naughty I am now putting in a 12v supply with appropriate resistors. I did try a 9v supply, with the resistors that came with the beacons - they stayed on - no flash. Now have to get hold of a 12v psu. Barry

In answer to you question - it was a 9v 500ma psu running through a voltage reducer(?) that I bought from Kytes Lights - anything up to 35v In and 3v Out - output guaranteed.

Barry

It might be useful posting a schematic of how you wired your original circuit. If they were wired in series then one flashing LED would have the same effect on the rest, a bit like old Christmas lights where you had one bulb that would flash but so would the rest wired in series.

The LEDs in the Belisha beacons are they the type that have an inbuilt flasher circuit as these examples?

https://www.rapidonline.com/Catalogue/S ... ing%20leds

Or are you using an external circuit to cause the flashing? When first introduced flashing LEDs tended to work off 12V with a flash rate of 0.5Hz but as you can see nowadays you can get a whole range of forward voltages. Again some details regards the specifications of the Belisha beacons would help. It is a little worrying that you say at 9V they stay ON, it might be the higher voltage has affected the frequency and they are flashing so fast you cannot discern it. As Brian has said we need more info to help you, in the meantime I would take your Belisha beacons out of circuit before they come to any harm.

Richard

bulleidboy wrote: ↑Sun Oct 18, 2020 4:38 pm <SNIP>
it was a 9v 500ma psu running through a voltage reducer(?) that I bought from Kytes Lights - anything up to 35v In and 3v Out - output guaranteed.

9 volts DC at 1/2 amp (500ma) should be able to run around 50 or more LEDs with suitable series resistors to reduce each LEDs current to 10milliamp or less.

OK Barry. Just had a look at Kytes Lights and your voltage adaptor. There is not a great deal of information but it looks like the device can produce 3V at up to 2A. There in might be your problem. You need to understand that the main function of resistors in LED circuits is to control the current - the Amps. Yes the voltage is a function but only so far as Ohm’s Law relates voltage, current and resistance. LEDs are current driven devices but have a very limited current range that is why the resistors are important.

I am assuming the Belisha beacons are the Kytes supplied, which reading between the lines are flashing LEDs as there is no mention of a driver circuit. They say they supply resistors for use with 12V supplies. Do they provide ones for the voltage adaptor? Despite matching voltages of the adaptor and the Belisha beacons you still need to exercise current control ie a resistor unless there is one already built into the lamp assembly?

Richard