Yard lamp power

[Sweet pea]

Hi I received a couple of yard lamps from layouts4u with the resistor already fitted. I'm wanting to put one of the lamps on a photo plank I am building. What I want to know is can I power this using something simple like a battery or not. Any advice will be great as I'm no expert with electrics.

[Lemmy282]

A quick look on their website for the 13cm one says "12 volt (resistor fitted) Warm White LED (remove the resistor if you want to use a 3 volt supply)".

I would check the website for the one you have.

 

Nigel L

[johnb]

Yes subject to the voltage as Lemmy says a battery will work fine.

[Brian]

IMO its very poor advice to remove a series resistor on any voltage! The resistor is there to reduce current to the LED.    

I would run the lamps off of a 9 volt PP3 battery supply with the series resistor supplied in circuit. Ensure the LED lamp is connected the correct way around.  

If you really want to use a lower voltage, then I personally would not go below 4.5volts (e.g. 3 x 1.5v AA cells in series) then use a 100R series resistor.

[Stubby47]

If you connect all the red leads and all the black leads, then connect each bunch to one of the battery terminals, all the LEDs will be the same brightness.

 

However, if you string the LEDs, so red of one to black of the next, then the two ends to the battery,  the brightness will diminish the more LEDs there are in the string.

[DCB]

 Historically heritage LEDs lit at around 2 volts and burned at around 3.5 volts. Then we got blue/ white which lit around 3.5 volts and burned around 5 volts. Now   2020, the common white LEDs from Home Bargains, like christmas lights run off a single AAA cell around 1.5 volts.  You can only blow up an LED by excess current and only get excess current by increasing the voltage.

Little test, connect a standard LED with 6 rechargable AA cells in parallel, nothing happens, doesn't light, take out the LED and short the cells, impressive pop bang and smoke, loads of amps but the LED won't pass them at 1.5 volts..  Put them in series with the LED and Pop, an ex LED

People run 2 volt LEDs off nominal 12 volt, supplies because it's easier to fine tune the brightness with common resistors like 1K than to use low value resistors down in the tens of ohms range, This is especially important when balancing Red with Green brightness for colour light signals, its ridiculously wasteful of energy, dissipating 80% as heat in the resistor, but the actual power used is miniscule.

If you want the lights to be seen in daylight you probably need a "12 volt" controller like nearer 20 volt off load. I run my yard lamps so they can't be seen in daylight but give a decent 1940s sort of glow in the dark.