Strobe light

Projects General Guidance
1

Hi everyone!

As my title says, i am looking for guidance in making the strobe light.

I have already got the code and the circuit built using a bread board, however was having some trouble...

First off, i want to place a cluster of LEDs symmetrically in a square inside a box i built and was curious of convenient ways to connect all the LEDs?

Secondly, using the breadboard i noticed that if i add multiple LEDs in series, the more lights i add, the dimmer they get (obviously?), i am using 1 240 Ohm resistor for all LEDs (is this wrong?), also, how should i connect the LEDs to have all running at full power?

If you haven't noticed from what i am talking about, i am a newbie, so please use appropriate language with your assistance :slight_smile:

Cheers,

Phil.

2

Does your circuit include a relay or transistor? The arduino can only supply 200ma, which will supply a handfull of 5mm leds but not some high power ones available. a relay will control an external powersupply (battery, wallwart etc) to power the LED's, to the tune of the arduino
If you want them at full power you will wire them in parallel.
the resistance needed depends on the number of led's, their voltage and the source voltage. there are online tools for calculating "voltage drop" and "resistance calculators" available if you search.
Goodluck!
-kl3vr

3

The LEDs are all to come on at once?
I would wire them as strings of LED/Resistor in parallel, 5V to LED to resistor. Connect all the resistor at the collector of an NPN transistor, emitter to ground.
Connect arduino output pin to 150 ohm resistor, other end to transistor base.
Then High from arduino will turn all LEDs on. Can use a PWM pin to control brightness too, fade them in & out of you want to.

4

http://www.kpsec.freeuk.com/projects/flashl.htm
Change the value of the capacitor (.1mF would work well) to make it pulse faster for a more strobe like effect.

5

Thaanks for the replies guys! :slight_smile:

I am still a bit lost with all of this, but hope to get acquainted with all this terminology and theory.

Does this look like parallel?

http://www.filedump.net/index.php?pic=img20120105002491325774921.jpg

If so, here is the case, the first light is very bright, the rest are at the same intensity, however lower than the first one.

BTW, these lights were classified as "Very bright" and did cost more than the standard LED:

http://www.filedump.net/index.php?pic=img20120105002501325775092.jpg

Finally, for future purposes, what TYPE of transistors should i order ahead of time (which are most commonly used), so i don't have to waste free time waiting for equipment?

6


http://arduino.cc/playground/Main/InterfacingWithHardware#Output

7

Cheap resistors rated for 2x the power they will see.
Say 3V across the resistor, 20mA per LED string:
P=IV, 3V * .02 = 60mW, so 125mW (1/8W) resistors will do.

8

Thanks for the links Magician and the help CrossRoads :slight_smile:

I will be using the 5V arduino output, so...

5 * .02 = 0.1mW *2 = 0.2mW ? (i believe i saw 1/4W &1/8W, not 1/5W lol)

Did i not account of the resistance?

Also, i noticed in some tutorials that the resistor was wired from the cathode to the ground rather than voltage to anode, is this fine? (i am assuming that the resistor is only there to protect the Arduino in this case)

Cheers!

9

5 * .02 = 0.1mW

No - 5 * 0.02 = 0.1W