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How to wire and power LEDS with a constant current driver? Answered

I want to light up 6 leds, one each of red, orange, yellow, green, blue, purple.  

The specs for red, orange, and yellow are: 20 mA, 2 V.  Green, blue purple are 20 mA, 3 V.

I ordered these constant current drivers http://lighthouseleds.com/20ma-led-current-limiter-driver.html
20mA (+/- 3) Constant Current
Output Voltage Varied (constant current)
Input Voltage 2-45V Across Limiter

Now, how do I wire the leds and what type of battery do I use?  On the current driver website it shows 3 leds in series with the driver and battery.  I was thinking of using a 9 volt battery.  But placing my 6 leds in series would add up to a total of 15 volts, and wouldn't work, correct? 

So, do I need to wire 2 or 3 leds in series, then put those groups in parallel?  Do I need another current driver?

Thanks in advance.



4 years ago

Simple resistors are best for a draw that small.

If you are worried about doing the calculations here's a web page that will do it for you ! http://led.linear1.org/1led.wiz

but if you really want to use the driver you mentioned. Yes you would hook up similar voltages in series, R-O-Y and G-B-P, then wire the two groups in series with your driver on each channel. if you mix the "Forward Voltage" of the led's your controller will over or under drive some lights in the string.

also you may need more then 9V. 3 * (3v led) = 9v forward voltage. your driver may not like that.

I'd stick with resistors, Check out the pic.


Answer 4 years ago

I did make one like the second picture with through hole leds, but my project is under fabric and the wires, leds and resistors are too bulky. So now I'm using surface mount leds with conductive thread on fabric, so I thought I could use the driver to have less "bulk" on the fabric.

Would using a small 12 volt battery like this be a good idea with the drivers? http://www.amazon.com/Energizer-A23-Battery-12-Volt/dp/B00004YK10


Answer 4 years ago

Yeah SMD is the way to go then. That current limiter you linked to will work nicely with conductive thread. You can still use SMD resistors, but unless you already have them handy it's probably not worth the shipping.

For the A23, According to wiki it has a 55mah rating. That would give you (Maybe) 45-60min. that long enough ?

After that you could replace the batt or even with two in parallel !

other options are two 9V wired in series, 8 AA's, or use a li-po battery and a "Boost Converter" to up the voltage from 3.7 to 12V. You could also use a single 9V and buy that same boost converter.

Really depends on how long you need to use it for and if this will be a Functional project or more like a one-two time use Halloween costume.


4 years ago

Yes. The simplest way is two current limiters. Battery life from a 9V cell can be quite limited at 40mA draw. An Alkaline might give you 7 hours, a zinc/carbon, just over an hour.