Light voltages

[55F]

I have an assortment of yard lights, platform lights etc.  In the absence of labelled packaging, how can I ascertain the voltage of each lamp so that I know how to wire them?  Any help appreciated, especially simple advice!!  Thank you.

[5BarVT]

Are they lamps or LEDs? (Or a mixture of both?). Advice will vary, depending.

And, do you have a means of measuring voltage e.g. a meter?
Paul.

Edited December 26, 2023 by 5BarVT
Extra Q

[55F]

Mixture of lamps and LEDs and yes I have a voltmeter.  Thanks for your  response.

[MartinRS]

I take it these are grain-of-wheat type bulbs, without anywhere for the manufacturer to write any specifications about voltage? My advice would be to test them using a resistance mat type controller. (Newer controllers might kick out maximum voltage, but in short pulses, which could pop the elements). Set the controller to zero and slowly increase the voltage. If you exceed the operating voltage you will burn out the element so stop turning the control knob when you get a reasonable level of illumination.

 

How about posting photos of the bulbs. Someone might recognise them and know their voltages.

 

As a slight aside; when I was in the S&T, when dual filament bulbs were still in use, I remember adjusting the voltage of bulbs in signal heads. They were rated at 12v but an instruction had been issued to run them at between 11.5v and 11.8v IIRC. It increased the operating life of the bulbs with no appreciable loss of illumination.

[Michael Hodgson]

The simple approach with filament bulbs is to try them on a very low voltage (1.5v battery) and if that's not enough, try two batteries etc.

 

LEDs only work on DC of the right polarity (or half of the cycle of AC) because as the name implies, they are diodes and only pass current in one direction.  Most don't like more than about 1.5v and will also burn out if subject to overvoltage, though more modern ones depending on colour have a higher "forward voltage".  If they are built into a yard lamp or similar they might well be connected in series with a resistor hidden inside the lamp and intended for a voltage such as 5v or 12v.

 

It is standard practice to include a resistor in series with each LED to limit current to say 20mA, so you should add a resistor if your lamp doesn't have one provided.   Commonly 1000 ohms.  Similar approach if you don't know electrical details of the LED - Start with a high resistance, and if its too dim, decrease the resistance till you're happy.  Separate resistor for each LED, resistors are dirt cheap.

[55F]

Thanks for the help and advice.  That will keep me busy for a few hours.