I am considering to use about 20 mini LED flash lights for an art installation. They will be running off a power supplies (probably 3V) and DMX to dim their brightness. It should be a very simply flash light with a super-narrow zoom, only one mode (full power) and if possible under $10 each.
I've tried the brightness control with DMX on a test flashlight and it seems to work perfectly. Since those flashlights have a built-in circuitry that brings up the 1.5 V from the battery to above the forward voltage of the Cree Q5 LED (3.3+ V) I was wondering if dimming with DMX could do any harm to the circuitry and what the ideal power supply voltage would be.
I found the "7W 300LM Mini CREE LED Flashlight Torch Adjustable Focus Zoom Light" on Amazon. Any other recommendations?
I have no idea what the "flashlight" is, or what's inside it ... so this is a guess:
I've tried the brightness control with DMX on a test flashlight and it seems to work perfectly. Since those flashlights have a built-in circuitry that brings up the 1.5 V from the battery to above the forward voltage of the Cree Q5 LED (3.3+ V) I was wondering if dimming with DMX could do any harm to the circuitry and what the ideal power supply voltage would be.
The flashlights probably have a voltage booster circuit in them. Applying PWM to their inputs will confuse the hell out of them.
You say it works? I'm surprised.
Will it damage them? Who knows...
If you're only going to switch them on/off (not fade them up/down) then the simple solution is to put a capacitor across their input voltage to filter the PWM to DC. Don't make them too big or they'll take ages to turn off. Ideally you need to look at the voltage with an oscilloscope and find the minimum capacitor value that works.
If you put a capacitor after the PWM circuit, you have to include an inductor as well, then you have to have a flyback diode.
Otherwise the PWM device will be trying to charge the capacitor instantly each time it switches on - and it isn't going to like that - similar problem as to whether the 1.5 to 3.3V power converter will cope with superimposed PWM.
You really need purpose-designed drivers which perform controllable current drive from whatever power supply you use, direct to the LED.
By the way, I haven't seen a seven watt mini flashlight powered by a 1.5V battery. I bought a "3W Mini flashlight" with an AA battery but it is perfectly evident that the description was missing the preceding decimal point (because I measured it!), so I can confidently assure you that a "seven watt" torch with a 1.5V battery (smaller than a telephone cell at least) is in fact no more than 0.7W.
Before you start, measure the current from the 1.5V battery (generally, just measure from the battery to case with the switch cap removed) and tell me how many watts it really is?
Need of course to use the 10A multimeter range and verify that the torch does light in order to make the measurement.
