ex-Gooserider wrote:If you have a variable voltage supply (a Shirley supply works great for this) try hooking up and turning on at zero volts. Slowly increase the voltage and see what voltage the LED's start turning on at... You will probably just start seeing them light up around 7-8V.
Then note how bright they are at about 13-14V (the actual voltage put out by a '12V' car battery) and see if they get significantly brighter as you increase to 24V... (or really 26-28V)
If they do, then back down the voltage, if they don't, then feel around on the circuit board (especially any non-LED components) and see if anything is getting warm after a few minutes.... If any part is more than warm, I'd worry about operating at 24V
There may be a current limiter as Lenny said, or it may be a case of the LED's being wired with parts that let them work optimally at 12V and not blow at 24V, but be 'stressed'....
LED's need to be wired with a 'current limiting resistor' to keep the amount of current flowing through them at the appropriate value which is chosen to give as much light as possible while lasting the manufacturer specified life... The value of the resistor is calculated based on the diode specs and the intended operating voltage... For any given resistor, at some voltage they will start putting out light which will gradually get brighter as the voltage increases - and they will keep getting brighter until they blow.... If you set the voltage at something above 'optimum' for that resistor, but less than the 'blow' value, the LED will work and be very bright, but have a much shorter life than it should... If the voltage is less, you won't get as much light, but the LED will just about last forever...
If I was trying to make a 'dual voltage' light, I might pick a resistor value that is 'optimal' for around 18V knowing that I'd get an OK amount of light at 12V, and be stressed but last long enough to have the warranty expire before crapping out at 24V....
I tend to be on the conservative side about this, especially in something safety critical like a tail light, so unless I either had explicit promises (and could see signs of designing to do it) about dual voltage, or saw no signs of 'stress' at 24V, I would either stick with running at 12V or add an additional resistor as mentioned earlier...
ex-Gooserider
Hi, thank you for your detailed reply, it was very informative
The light seems to running off 24v okay and hasn't blown/burnt out yet (fingers crossed).
I'm actually getting one of Shirley's power supplies, they look really good, much better than the 24v power supply I have that blew up at the weekend and it was only supplying 18A 24V and it was supposed to rated over 1100 watts. But it's still going even though it went bang and a load of smoke poured out of it. I wonder if I might fix it, or just chuck it in the bin?
Back on the subject of auxiliary lights on my scooter. I now have 3 if you included the trailer taillight. A front CREE, rear red LED bar, and the trailer LED block.
At the moment I switch them on/off using a rocker switch mounted on the scooter tiller. But it would be nice if they all came on with the OEM tiller dashboard lights on/off button. That way it would be better and I wouldn't forget to switch them on/off.
This is the same as tiller dashboard panel on my scooter. It's a PCB board with 'Pad' buttons.
https://www.ebay.co.uk/itm/Sunrise-Ster ... :rk:1:pf:0The top right button is the lights.
I would like to wire the auxiliary lights (via an inline fuse) to the same switch wire as the OEM scooter lights, but not sure if the PCB would be able to withstand the additional load?
The 3 aux lights I fitted draw about 400-500mA in total. I have thought of wiring them via a 24v relay to as to reduced the load on the PCB switch/electronic component, but the only relays I can find I 24v automotive 30A-40A ones which seem a bit overkill
Is there a simple electronic switch that will cope with 1A or more?