A question of POWER. How do I make this project's lamp BIGGER/BRIGHTER?

Hi Forum,

I am new to Arduino and just finished doing this project successfully: http://itp.nyu.edu/physcomp/Tutorials/HighCurrentLoads

Now, I want to use a BIGGER, BRIGHTER LIGHT. The DC adapter that I'm currently using is 12volts/1A and I'm wondering how to figure out what is the brightest light bulb I can light up with that kind of adapter.

Or put another way, let's say I have a 15W/120V light bulb. What kind of power would I need to light that bulb up?

THANK YOU for helping me!

You've already answered your own question. A 15watt 120 volt bulb needs 120 volts and will produce 15 watts (which will be rather dim)

The maximum a 12 volt 1A power unit can supply is 12 watts - so you are limited to 12 watts after which you eventually get a release of smoke and smell.

If you want bright at low voltage go for something like a 12 volt 50watt halogen lamp. This will draw in excess of 4 amps so your power supply needs to be suitably rated. If you want brighter then couple several in parallel, but you then need to look at bigger power supplies.

You can switch this on using a suitable transistor or better still an FET (lower ON resistance), operated via a resistor from an arduino output pin. In fact if you use a PWM output you can even vary its brilliance.

You can get very bright LEDs but these are less tolerant to abuse on the control side (they need constant current control) and so can end up being rather expensive if you don't know what you are doing.

Hi JackRae!

Thanks so much for answering my question. In terms of brightness do you think a 12 volt 50watt halogen lamp would be bright enough to light up a 9 foot by 8 foot room (10 foot high)?

What form does the power supply come in? Most DC adapters I see go up to 2A, so will I need to power the 12volt/50 watt bulb some way other than using a DC adapter?

For all my beginner's projects up until now I've always used a DC adapter so I don't know of any other way to power stuff up. Please advise?

If you get a 10w led it will definetly light the room up nicely, I've used them in my car and without a lens it'll throw light 30,40 feet away
it can safely be used up to 1 amp so its just right for your supply, if you heatsink it right and maybe even put a lens to help spread the light the way you want it could easily work for your situation
and they go for about 5-7$ on ebay for cool or warm white


Awesome! thanks for confirming. I want to do exactly as you describe given that I already have a 1amp DC adapter.

Can you put together a basic parts list for me and suggest what you would use for

  1. 10W LED
  2. heat sink
  3. lens

I looked at Sparkfun and thought of getting these. What are your thoughts?

  1. LED (but I can't tell if it's 10 Watts or not) - Luxeon Rebel High Power LED - Warm White - COM-09637 - SparkFun Electronics
  2. Sink - Solderless High Intensity LED Holder - Heatsink - COM-09639 - SparkFun Electronics
  3. Lens - Luxeon Rebel Triple-LED Wide Lens - COM-09732 - SparkFun Electronics

You can't just use a high power LED like a light bulb or even like a low power LED. You need an LED driver to provide it with a constant current.


You mean like this? TLC 5940 - PWM Driver - COM-10136 - SparkFun Electronics

I've been meaning to get this, along with other components I'll need (like the photocell you pointed out earlier). But I want to make sure I have a complete parts list thought out first.

If you can suggest something better please let me know!

You mean like this?

No, that is a controller for 16 LEDs, yes it is constant current but that current is only limited to a few hundred mA. You need a 1A constant current LED driver. A quick google reveled this

Ok Mike, got it. I think I still need to wrap my head around how the LED driver and PWM all connect together before buying them.

Are you trying to dim it with PWM? You need to make sure you get an LED driver that will allow external dimming. Like this BuckPuck

Although, I think that may only dim with a POT or 0-10V. You might need something more expensive, like this Mean Well:


Make sure you get the P type

Optional dimming function : 1.1~10VDC (D type) or PWM (P type) controller

Hi jvdb,

Thanks for your suggestion. Let's say I buy the BuckPuck or MeanWell. What is the brightest LED that I can buy (to light up my room with) that you would suggest I get?

Rather than trying to find the world's brightest LED, how about using several readily available identical units (say 3 watts each). Because they are identical, they all use the same current, so, by wiring them in series you can use one constant current controller and simply supply enough voltage to drive the LEDs. With a typical drive voltage of 3 volts a single current source providing say 12 volts could power 3 LEDs in series (you need some excess voltage to ensure the LEDs are fully driven)

Hi JackRae,

I thought about making an array of LEDs but my concern is whether it would be BRIGHT enough to light up my 8 foot x 9 foot room (10 feet high). Do you think that wiring three 3 volt LEDs would be bright enough?

If so, do you have any that you recommend from past experience?

I thought about making an array of LEDs but my concern is whether it would be BRIGHT enough to light up my 8 foot x 9 foot room (10 feet high). Do you think that wiring three 3 volt LEDs would be bright enough?

So basically you want to use an Arduino as a lighting controller? Their are many problems with using LEDs for general lighting, personally I would buy these:


I don't think you're going to engineer a solution yourself that will provide diffuse room quality lighting in a nice heat-sinked package like that.
You could then use an SSR to switch it. Or even one of these kits to dim it:


You misread what I wrote. I suggested 3watt LEDs, which are exactly what you linked to in one of your previous entries. Together with one of the current control units as Mike suggested you should have more than enough light to brighten your day (or night). However you need to be aware that the lens you specified produces a 40 degree beam, which is quite narrow for total room lighting purposes. You may need to use some form of diffuser to widen the beam angle.

Ok thanks for confirming JackRae.

Jvdb, I want to stick to using an Arduino so that I can do add-on stuff later like add a PIR to detect when I walk into the room. Thanks for your suggestion though.