Electronic – Novice LED questions

ledresistors

I'm hoping that you friendly and knowledgeable folk can help me finally figure out how I should be wiring up my LEDs in my panels.

Just a short history…

Many years ago I took over a panel building department which was in a dire state. I have managed to turn it around now having correct wiring diagrams, CE conformity, etc, etc.

I build 3 phase panels for use in the chain hoist industry and each panel has a 'handset' which controls the hoists. Each 'channel' on the handset has a toggle switch and bi-colour LED to show the direction chosen, green for up and red for down. Now ever since the dawn of time, we have fitted an AC transformer in the panel which sends 24v AC and a 0v down to the handset which goes to the toggle switches and also the LEDs.

On each toggle switch, we solder a resistor which then feeds both legs of the LED.

Now my question….

As far as I am aware it's unusual to power LEDs with an AC supply. Primarily they prefer DC. I am assuming the use of the AC power supply was because of the very long distances these handsets have been used in (some over 100 meters) and thus the AC works better.

I wish to ditch the AC transformer and fit a DIN mounted 5amp DC unit.

My question is though, will I still have to fit the resistors? I know they should be needed to smooth out the current going to each LED but just wanted to check.

Below are links to the LEDs and resistors I use in case anyone wants to check the specs.

LEDs

Resistors

I hope you can help me gain more of an understanding of LEDs.

Best Answer

Now ever since the dawn of time, we have fitted an AC transformer in the panel which sends 24v AC and a 0v down to the handset which goes to the toggle switches and also the LEDS.

This is probably because when the system was designed at the dawn of time,

  1. They might have used 24 V incandescent lamps instead of LEDs.

  2. A 24 V transformer was probably lower cost than a DC supply.

I wish to ditch the AC transformer and fit a din mounted 5amp DC unit. My question is though, will I still have to fit the resistors? I know they should be needed to smooth out the current going to each LED but just wanted to check.

You will still need to fit the resistors. These limit the current through the LED so it doesn't blow up. You will probably need a different resistor value to get the same brightness from your lamps, when you switch from 24 V AC to some other DC voltage.

You can also buy LEDs or LED lamps with the resistors built in, which could save you having to assemble the resistors yourself.

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