digital pots ?

can anyone suggest or know if a digital pot is available that is rated to handle up to 13 watts of led lights .
i know this is a general question since i cant supply the specs for the lights i want to control but if someone can tell me yes or no if they capable of doing this and maybe make some suggestions as to what i would need would be greatly appreciated
thanks james

can anyone suggest or know if a digital pot is available that is rated to handle up to 13 watts of led lights .

No you can not get such a thing.

To control lights you can use PWM for DC lights with a FET, or phase control with an SSR for AC lights.

Digital potentiometers are only designed for a very small amount of current.

Typical approach for controlling one or more LEDs in series: http://www.ledsee.com/index.php/led-accessories/led-driver-9-26v-3507001000ma-with-dim-function-detail

You don't want to resistively dim LEDs anyway, its not linear, its very wasteful of power
and you can't even turn them off!

jc286006:
can anyone suggest or know if a digital pot is available that is rated to handle up to 13 watts of led lights .
i know this is a general question since i cant supply the specs for the lights i want to control but if someone can tell me yes or no if they capable of doing this and maybe make some suggestions as to what i would need would be greatly appreciated
thanks james

Can't you just use PWM like everybody else?

jc286006:
can anyone suggest or know if a digital pot is available that is rated to handle up to 13 watts of led lights .
i know this is a general question since i cant supply the specs for the lights i want to control but if someone can tell me yes or no if they capable of doing this and maybe make some suggestions as to what i would need would be greatly appreciated
thanks james

A digital pot, no, a regular pot yes (with a nice price tag) they're called rehostats.

Using pwm and transistors however.

i have a set of these lights
http://elivepet.com/fish/lighting/led-module-track-light/
and was thinking they might be modified to be dimmed by an arduino there is a manual dimmer on 1 channel and i would like to dim both channels with my arduino i am waiting for a reply from them as to voltage wattage specs i guess once i get those and post them you guys will be better able to suggest a proper way of doing it if it`s even possible.
thanks for the replies
James

It is hard to say if it is possible but it looks like it.
That is an AC to DC power supply. It should say on it what voltage and current it can supply.
Have you got one can you read it.
You then need to connect it to a logic level power FET to switch the led strip on and off very rapidly using one of the PWM outputs of the arduino.

However the problem will come if that blue dimmer control actually has some electronics behind it. Then you might have to hack into the electronics to remove it and use three FETs.

hi grumpy mike
removing the blue dimmer is exactly what i planned on doing that way my arduino could control each channel of lights
when i get home i will look at the power supply and open up one of my light fixtures to see what is connected too the blue dimmer
thanks for your reply
james

hello all

The power supply is 20 volts 1.5 amps.

Inside the fixture is a small PCB with a D882M transistor , a SS14 diode , R1 is marked 68A R2 is marked 221 R3 is marked 223 , then it has the dimmer slide which i am assuming is a adjustable pot or reihostat Im no electrical engineer LOL just a curious DIYer that probably gets myself in over my head alot!

i have tried to attach a picture of the PCB but can not get it to attach.

hopefully the list of parts above can give you and idea of what it does and how it works if you can PM me at
jc286006@yahoo.com i can send you the picture of the PCB
thanks james

"D882M" means its a 2SD882, medium power NPN, "221" means 220 ohm, "223" means
22k, SS14 is a schottky diode (40V 1A).

If those are all the components then its likely a linear circuit controlling the current,
cheap and nasty.

[ to be complete, the numbering scheme for resistors uses the last digit as a multiplier
(ie the number of zeroes to add after the other digits, hence 223 = 22000, 221 = 220.

Japanese transistors: 2Sxnnn = 3 terminal silicon transistor (you add one to the
first digit to get the lead-count, the first letter is the semiconductor material). The
second letter says whether NPN or PNP (or FET) and whether high frequency or
not. D means audio frequency NPN. Typically devices are marked without
the 2S being printed as this can be assumed.
http://en.wikipedia.org/wiki/JIS_semiconductor_designation ]

jc286006:
i have tried to attach a picture of the PCB but can not get it to attach.

Use the Additional options triangle at the bottom of the reply box.
Make sure your photo is no more than 1000 pixels wide.

here is a picture of the PCB

any ideas on whether or not these lights can be modified

I am sure they can be modified, but it might be a bit of work. Basically it would be a good idea if you could trace that circuit along with how the LEDs are wired. Then I would compleatly remove that circuit board and replace it with something you can drive directly from the arduino.
By knowing the original circuit you can design a proper replacement.