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[on:]

I found a knight rider project here that I want to build:

http://fritzing.org/projects/arduino-knight-rider-with-8-blue-12v-led-modules/

I want to replace the LED modules with 1 watt LEDs like these:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350668699726

or these:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=370725075035

and it will be powered with a battery similiar to this:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=350585953725

Are there any other parts that I will need so I can run the 1 watt LEDs, or can I just hook them up to where the LED modules are hooked up?  Meaning, will they drain the battery too quickly, or will they run at all?  Thank you.

[Reply #1 on:]

The example is not correct.
A led needs a constant current.
So you can't feed a 12V led with a 12V battery. The current will be a lot too much or a lot too less.
I assume that there are specific power supplies for those 12V leds.

Normally a led with a resistor is switched on and off.

[Reply #2 on:]

The example is not correct.
A led needs a constant current.
So you can't feed a 12V led with a 12V battery. The current will be a lot too much or a lot too less.
I assume that there are specific power supplies for those 12V leds.

Normally a led with a resistor is switched on and off.

It's quite obvious that the LED's used in the example are LED's sold with pre-mounted resistors for 12V operation, that's why it says 12V LED's

The high power LED's OP has found are meany for Halogen light replacement, so they have built-in power regulation and are fine for 12V operation.

To control the LED's with the arduino, do like on this diagram:



The M is the load, place the LED-module here.

The mosfet can be replaced with a NPN transistor.

// Per.

[Reply #3 on:]

Zapro, you could be wrong.
Led modules often consist of a few leds parallel and serial. Sometimes 16 'leds' are used inside the module with 4 rows and 4 columns. So the result would be 4 leds of 3V is 12V.

af77, you have to find more specifications for those leds. Do they have some current limiting inside. If they can be used as replacement for halogen lights, they could have.

[Reply #4 on:]

Zapro, you could be wrong.
Led modules often consist of a few leds parallel and serial. Sometimes 16 'leds' are used inside the module with 4 rows and 4 columns. So the result would be 4 leds of 3V is 12V.

Yes - I COULD be wrong, but the LED's OP have found are MR11/G4 LED replacements, they are constructed so they can run on 12V DC or 12V AC from a standard Halogen lighting transformer. I work in an electronics store and sell these kinds of things on a daily basis, so I actually know what I am talking about.

// Per.

[Reply #5 on:]

Zapros cct is fine ...

I'm not so sure. If the MR16 LEDs are halogen replacements, they almost certainly contain a switching regulator and a large input capacitor. This will give rise to large current pulses when the mosfet switches on. Preferably you should tap into the switching regulator PWM control signal in the built-in regulator. See this thread: http://arduino.cc/forum/index.php/topic,139792.0.html.

[Reply #6 on:]

I'm also going to be using 2 TLC5940's.  If I ran the LEDs through a ULN2803 and then through the TLC5940, would that work instead of using the NPN transistors?  In my project, I will be using 6 LED strips like in the example in my first post, and 24 of the 1 watt LEDs.  If what I suggested won't work, what would?

[Reply #7 on:]

http://www.ebay.com/itm/1x-5x-MR11-G4-Warm-White-LED-Bulb-Spot-Light-Lamp-Downlight-1W-DC-12V-/350668699726?


you're not going to use those things are you?



http://www.ebay.com/itm/5pcs-New-1-Watt-1W-RED-Super-Bright-50-Lumen-LED-Lamp-Light-Panel-PCB-MOUNT-RL1-/120901084245?pt=LH_DefaultDomain_0&hash=item1c26442455

or

http://www.ebay.com/itm/5pcs-New-1-Watt-1W-RED-Super-Bright-50-Lumen-LED-Lamp-Light-Panel-PCB-MOUNT-RL1-/120901084245?pt=LH_DefaultDomain_0&hash=item1c26442455


I was thinking of doing the same thing, I had my circuit setup to use 5mm LED's...  which left me with a dilemma, space/pins - So i used the ULNxxxx whatever number as a darlington
transistor array supplying up to 500ma ...



That's my Greenie in Action, but like you I wanted something more Powerful.. like the 1watt LED's.


Use 1 watt LED's with a bunch of 2222a transistors and create a monster bright knite rider kit, that or go buy 12v automotive lamps for the car and paint them all red

[Reply #8 on:]

Would I need the 2222a transistors if I used the ULN2803 darlington (since that has transistors inside)?

[Reply #9 on:]

1. 2222's are cheap and each can handle up to 1 amp.
2. unl can't supply more than ?00ma... per pon

But if you're using low brightness leds below ?00ma whatever the datasheet says ...go for it.. i thought you were using high power led's...

[Reply #10 on:]

Yeah, I am going to use high power 1 watt LEDs.  Is there a diagram on how to hook up the LEDs to the transistors?  I don't understand schematics.