5mm 120 led flashlight driver idea needed
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bshanahan14rulz
Flashlight Enthusiast
a series-parallel build might just be your best option. One thing I did when I built an array of 5mms was to regulate the voltage of the entire array, and then using a resistor on each series string. It's not the most efficient solution, but it works pretty well. I was using cheap ebay LEDs, though, so I can't say for certain that each LED was seeing the same current, but since yours seem to be all from the same manufacturer and probably from the same bin, there hopefully won't be much variation from LED to LED in your situation.
Also, I'm sure you've seen this already, but just so you have a link handy, check this out: http://led.linear1.org/led.wiz
.
Edit: just ran your numbers through that and found that you will be needing like, 40x180 ohm resistors, and that total, the resistors alone would be dissipating 3W of heat. Sorry, this was a bad suggestion...
Also, I'm sure you've seen this already, but just so you have a link handy, check this out: http://led.linear1.org/led.wiz
.
Edit: just ran your numbers through that and found that you will be needing like, 40x180 ohm resistors, and that total, the resistors alone would be dissipating 3W of heat. Sorry, this was a bad suggestion...
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The_bad_Frag
Enlightened
You could get a buck driver that can be set to 2400mA. Then wire all leds in parallel.
...why dont you use just 1 high power led? I would make it a lot easier to build!
...why dont you use just 1 high power led? I would make it a lot easier to build!
arek98
Enlightened
You could try Hyperboost from TaskLed. It works from 8V to 50V input and can boost output to 80V
You could make 10 strings, 20 LEDs each, set trimpot to 200mA output current. You could even make it dimmable by adding external pot.
Boost limit for Hyperboost is related to input current. It cannot be higher than 5A but with your low output current of only 200mA you are good even with such high boost. Efficiency will not be great but it should work.
Problem is that current will not be well balanced between strings. You could add balancing resistors but it does not help much in reality. Current monitor (mirror) may be used to balance two strings but I don't know if it is possible for so many strings (and if yes than probably will be complex).
Other option would be to boost battery battery voltage to higher constant one and use bunch of regulators like Supertex CL2 (Mouser has them in stock, less than $0.5 a piece). How many you need, will depend how high you can/want boost voltage.
You could make 10 strings, 20 LEDs each, set trimpot to 200mA output current. You could even make it dimmable by adding external pot.
Boost limit for Hyperboost is related to input current. It cannot be higher than 5A but with your low output current of only 200mA you are good even with such high boost. Efficiency will not be great but it should work.
Problem is that current will not be well balanced between strings. You could add balancing resistors but it does not help much in reality. Current monitor (mirror) may be used to balance two strings but I don't know if it is possible for so many strings (and if yes than probably will be complex).
Other option would be to boost battery battery voltage to higher constant one and use bunch of regulators like Supertex CL2 (Mouser has them in stock, less than $0.5 a piece). How many you need, will depend how high you can/want boost voltage.
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Luxeon star (website name) sells cyan rebels on MCPCBs already, they are 505 nm, but the overal bandwidth is 490-520nm. Is this acceptable? If so that makes driving the LED somewhat easier.
For a showerhead arrangement, youre going to have to have parallel strings, and since Vf can vary, youre going to have to add resistors in series to make them share load and behave nicely with each other. Cheap chinese LED lights dont use resistors for paralleling because they buy X0,000 LEDs at a time and can sort them by voltage. (someone here had a decent citaiton for that too, cant find it atm.)
For a showerhead arrangement, youre going to have to have parallel strings, and since Vf can vary, youre going to have to add resistors in series to make them share load and behave nicely with each other. Cheap chinese LED lights dont use resistors for paralleling because they buy X0,000 LEDs at a time and can sort them by voltage. (someone here had a decent citaiton for that too, cant find it atm.)
arek98
Enlightened
I don't know. It is unclear for me too. I sent a question to their support. Let see if they answer and what they say.
EDIT: that was fast, I got an answer that it needs 5V overhead to maintain 20mA, so Vf + 5V. Higher difference supposed to be ok as long as total power disipation by CL2 is within limits. According to spec with TO-92 it will be 30V (0.6W / 20mA), other two packages can go even higher. 30V is plenty of headroom for different Vf of strings.
Actually I may try these drivers myself. Given a price and simplicity they may be worth a try.
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alpg88
Flashlight Enthusiast
- Joined
- Apr 19, 2005
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- 5,331
most sites that sell cyan leds show wavelength is 505nm, 490 is aqua color.
led supply has them.
the best practical way to wire 120leds to be powered from li ion, is to wire all cells in paralel, and wire leds individually, same as paralel but with each led has it's own resistor, its value will be small since you only have only 1 li ion cell voltage vise, but you need few of them in parallel so drain of 3+a (120leds +resistors) wont drop the voltage too much.
there is no need for boost drivers, strings, kiss.
led supply has them.
the best practical way to wire 120leds to be powered from li ion, is to wire all cells in paralel, and wire leds individually, same as paralel but with each led has it's own resistor, its value will be small since you only have only 1 li ion cell voltage vise, but you need few of them in parallel so drain of 3+a (120leds +resistors) wont drop the voltage too much.
there is no need for boost drivers, strings, kiss.
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Illum
Flashaholic
heh, This might be a stretch, and yes if you blow an LED its going to be a real PITA to resolve, but have you considered a nixie tube power supply?
Something like this: http://www.ledsales.com.au/kits/nixie_supply.pdf
Last I recall my circuit pumped out about 255VDC at 18ma+/- connected to a 9V battery. 255V across 120 LEDs makes about 2V per LED. I suppose you could connect the same circuit to a 12V battery and you might get higher voltages, but just make sure your output cap is rated for 500V or more.
Something like this: http://www.ledsales.com.au/kits/nixie_supply.pdf
Last I recall my circuit pumped out about 255VDC at 18ma+/- connected to a 9V battery. 255V across 120 LEDs makes about 2V per LED. I suppose you could connect the same circuit to a 12V battery and you might get higher voltages, but just make sure your output cap is rated for 500V or more.
