Circuit for PWM dimmable LED lamp using two 5W bulbs

Other Hardware LEDs and Multiplexing
1

Hello,
I'm a newbie slowly learning arduino and looking for some general advice on how to wire a PWM dimmable lamp using two 12V 5W MR16 cob leds. Bulb specifications:
• Item: 5W COB LED Light Bulb
• Base Type: MR16
• Input Voltage: MR16(DC/AC 12V)
• Power: 5W (1x5W)
• Power consumption: 4-4.6W
• Dimmable: Non-dimmable

It will be controlled by using the arduino to decode pulses from a rotary phone dial and then setting the brightness at different levels based on which number was dialed. I have the dial decoding pulses but still have a few questions about driving the leds.

I'm guessing I'll need a 12V 2A DC power supply with a splitter; one end powering the arduino jack, and the other going to the LEDs.

  1. Would 12V --> mosfet --> 5W LED for each bulb using two separate PWM pins be a good idea?

  2. Is it overkill to use a mosfet? I figured other transistors might be more likely to overheat. Was thinking this one: N-Channel MOSFET 60V 30A - COM-10213 - SparkFun Electronics

  3. Do I need to use any resistors? Or could I basically use this guide without changing anything? http://bildr.org/2012/03/rfp30n06le-arduino/

Any help is much appreciated!

arduino power led-1.png
arduino power led-1.png1175×643 53 KB

2

rileybubbs:
• Dimmable: Non-dimmable

You can't dim this bulb! It was not designed to support that. PWM-ing it with a transistor/MOSFET won't work. It will either not light, or flicker like crazy if you try. You may damage it.

rfp30n06le-arduino-lightbulb.png
rfp30n06le-arduino-lightbulb.png1175×643 53 KB

3

Oh, ok thanks. I must have misunderstood a related post. I thought that it was possible to use the arduino for pwm dimming with non-dimmable bulbs only because the extra electronics in dimmable leds would interfere with the arduino pwm. If that's the case, I'll have to order some new ones!

4

Any advice for how to wire up the circuit?

5

What circuit?

6

The circuit from my original post in the thread lol. I'm just not quite sure how to power two 12v DC 5w bulbs (assuming I order the right kind). Are mosfets overkill? Should I control one bulb per pwm pin? Any resistors? And is it possible to do this all from one 12v power supply? Sorry for all the questions and thanks in advance for helping a newbie!

7

P = I x V

So if driving two bulbs with one pwm pin

I = P / V = (2 x 5) / 12 = 0.83A

That's too much for most small transistors, so a MOSFET is appropriate. Make sure to use a MOSFET with a logic level gate, like the one you posted the link to (read the forum rules to find out how to post links correctly). It is a good idea to put a low value (eg. 220R) between the gate and the pwm pin. The 10K pull-down you show is a good idea. It should be connected on the pwm pin side of the 220R.

But for a single 5W bulb per pwm pin, a smaller transistor such as bc337 should be OK but keep an eye on the temperature, it might get quite warm. Use a 470R or 510R between the pwm pin and the transistor base.

When you find a suitable bulb, post a link here before you buy and we can check it for you.