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Topic: First Project: Simple Strobe/Flashing Light (Read 2577 times) previous topic - next topic

kleggy

Hey guys.

Looking at starting my first project. I have a party coming up and I want to make a strobe/flashing light. Just wondering is there anyway I could make a high powered strobe light like in clubs controlled by the adruino?

I have the Freetronics Eleven (Arduino UNO)

Any tips/code/materials that I need would be greatly appreciated

Thanks

CrossRoads

#1
Jun 04, 2011, 08:25 am Last Edit: Jun 05, 2011, 04:35 pm by CrossRoads Reason: 1
Sure, get some 15,000mCD LEDs from www.mpja.com, some current limit resistors, and write a brief sketch that will turn an  output or 3 or 4 on & off. Pretty simple.
http://www.mpja.com/prodinfo.asp?number=15415+OP
These things are super bright - do not stare at them!

Where are you located?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

kleggy


Sure, get some 15,000mCD LEDs from www.mpa.com, some current limit resistors, and write a brief sketch that will turn an  output or 3 or 4 on & off. Pretty simple.
http://www.mpja.com/prodinfo.asp?number=15415+OP
These things are super bright - do not stare at them!

Where are you located?


Hey mate, thanks for the tip. I went out and bought a 100 pack from the local distro in australia. Only cost $16 delivered. :) Just wondering now, how do I connect these up. I hooked up 1 led that I already had and used the basic tutorial of switching port 13 from high - low with a delay of 50ms and this seems to be the speed I need. Is there anyway to control as many LEDs at the same time with max brightness. I know while doing automotive electrical you can get a relay that powers high powered spotlights with minimal strain on the switch itself. Is there any such thing for LEDs?? Any input once again is welcomed. Btw I'm in Australia

Thanks

liudr

How about this?

http://www.arduino.cc/playground/Learning/TLC5940

Each TLC5940 can control 16 lights. You may need a separate power supply for this chip if you want to run 16 LEDs. The arduino power supply can probably get damaged if you try many lights together.

Chagrin

I know while doing automotive electrical you can get a relay that powers high powered spotlights with minimal strain on the switch itself. Is there any such thing for LEDs??


You could similarly use a relay but that's a bit overkill for LEDs and the constant clicky clicky of the relay would wear it out in a hurry. You would want to look into driving a mosfet with the Arduino as the mosfet would serve the purpose similarly but in a solid-state way.

The trick with LEDs is that you need to control the current they consume. As is typical for any diode -- which a LED is -- after you pass the threshold voltage every additional bit of voltage causes the LED to rapidly consume more current until the point that they burn out. This occurs within the span of just a few tenths of a volt, and when you're dealing with a bag of 100 LEDs you're never guaranteed that they'll all have perfectly identical threshold voltages. Thus, pulse-width modulation (PWM) with a transistor, mosfet, or an IC like the TLC5940 is used to rapidly chop the current to the LED to prevent the burnout.

CrossRoads

kleggy, can you give us any details on the LEDs you bought?

Liudr, totally off topic, how many pins were on that signetic 87C451 I sent you? Was it 68? More? I can't find the data sheet I had, did I send you a copy?
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

kleggy


kleggy, can you give us any details on the LEDs you bought?

Liudr, totally off topic, how many pins were on that signetic 87C451 I sent you? Was it 68? More? I can't find the data sheet I had, did I send you a copy?


Hey Guys

Here is the link to the place where I bought them:
http://www.ebay.com.au/itm/5mm-Ultra-Bright-Clear-WHITE-LED-15000mcd-50-pieces-/110658467247?pt=AU_Electronics_Wholesale_Electronics&hash=item19c3c235af#ht_1404wt_902

Thanks

CrossRoads

Nice documentation on those.
Now, since you are making a strobe, the assumption would be that you switch them at the same time?
What do you have for a power source?
If you could connect these in series from say a 30V source, then you could have 8 in a string with a 20mA current limit resistor, then make a bunch of strings.
The strings could all be connected in parallel and switched with a single N-type transistor, NPN or N-channel MOSFET.
Control Base/Gate from the arduino. Or a simple 555 timer with a potentiometer to control the frequency.
Some examples here
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

liudr


kleggy, can you give us any details on the LEDs you bought?

Liudr, totally off topic, how many pins were on that signetic 87C451 I sent you? Was it 68? More? I can't find the data sheet I had, did I send you a copy?


I counted last night. It has 64 pins. I don't think I miscounted 2 pins on one side. The spec sheet is on your website.

CrossRoads

Thanks! Didn't think to look there. Shows 64 pins.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

kleggy

#10
Jun 07, 2011, 10:39 am Last Edit: Jun 07, 2011, 02:02 pm by kleggy Reason: 1

Nice documentation on those.
Now, since you are making a strobe, the assumption would be that you switch them at the same time?
What do you have for a power source?
If you could connect these in series from say a 30V source, then you could have 8 in a string with a 20mA current limit resistor, then make a bunch of strings.
The strings could all be connected in parallel and switched with a single N-type transistor, NPN or N-channel MOSFET.
Control Base/Gate from the arduino. Or a simple 555 timer with a potentiometer to control the frequency.
Some examples here



Hey. Thanks for the drawing. I was thinking of using a downlight transformer from work as the power source. Here are the specs:

Input: 240V
Output: 11.4V
Amp Output: 3.95A
For 50W 12V lamps

Would this work and power my LED's also what resistors and MOSFET/N-Channel thingy would you suggest. I would be buying from http://www.jaycar.com.au/

Thanks again.

CrossRoads

Well, divide 11.4V by the LEDs Max Vforward, the whole number part will tell you how many can go in a string.
Then figure the current limit resistor = (11.4V - #LEDs * Minimum Vforward)/20mA, use Minimum Vforward so you can never exceed the 20mA.
Then go search Digikey for N-Channel Mosfet,
select Single FETs
then start filtering:
> In stock
> through hole
> logic level
that should narrow the list a lot
Click on View page
Click on sort by price, then browse down to find the Lowest Rds  you can find (down in the low mOhm kind of range) in a package you can work with at a price you like. At 20mA per string of LEDs, you can have a lot of strings switched by 1 really low Rds MOSFET before it starts to gets warm.
P = I*I*R.
So with your supply and 12mOhm Rds for example
P = 3.95A * 3.95 * .012 = 187mW which may not even need a heatsink since you are strobing & not on all the time.
That's assuming you have 3.95A/20mA/string = 197 strings of LEDs!  In which case you better hand out shade too 8)

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

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