PWM controller for LEDs

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Could anyone point me in the direction to get more information on a PWM controller for some LEDs? How do you control it to control the output? Also, where can I find plans on how to build one? I can hold my own soldering and stuff, but never got much into the theory on designing circuits. Is it really that much more effective than a plain potentiometer, assuming that I could find one in the correct value?

On a slightly different note, I've ordered a lot of cheap LEDs off of ebay. Assuming that they are what I want, I'm a little concerned about the viewing angle. I know that the more rounded the LED tip, the narrower the beam. These MAY have a 10 degree viewing angle (it was listed as "VIEWING ANGLE:± 10°"). If that's the case, I'll need to widen that out for my use. Would sanding down the end help with that? How much can I sand it before causing a problem with the LED that keeps it from working?

edit: oh yeah. in regards to the last question, is it possible to sand the LED so that instead of projecting a cone, it does more of a flat beam.
._______
(_______)

Something shaped like that sort of.
 

INRETECH

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It would be better if you used external optics than to sand the plastic

You could use a LM555, although the voltage control input is not very linear

Another way would be build using 3 of the 4 Op-Amps in a LM324

Setup 2 of them into a Triangle WaveOsc, and then take the control-voltage of a pot to compare to the output of the triangle wave - works great
 

Avatar28

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It would be except for two problems. 1) I need the ability to dim it. 2) I will be powering the LEDs off my power supply. 5v is the lowest CONVENIENT voltage. I could, I suppose, open up the PSU and run a wire from the 3.3v rail and power it from that. Even then it will be overvolted by 10%.
 

INRETECH

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The 3/4 LM324 Circuit works VERY well for this application, you can have a linear control voltage that will PWM the LED and you would use a output resistor to limit the current since the PWM would be running at 5v
 

Avatar28

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[ QUOTE ]
The 3/4 LM324 Circuit works VERY well for this application, you can have a linear control voltage that will PWM the LED and you would use a output resistor to limit the current since the PWM would be running at 5v

[/ QUOTE ]

Know where I can find plans for one of those? Also, does anybody know a way to easily create a long string of LEDs without tediously soldering short pieces of wire to each leg of the LEDs? I'm thinking something along the lines of a string of christmas tree lights, but with LEDs.

My plan is to run a long string of them around my case. It has windows on both sides and the top, so my plan is to have lights going around both sides of the case, plus a couple more mounted so that they make the acrylic front of my case glow.
Linkage here
That's what it looks like if anyone's got any ideas. I have my LEDs now and I'm itching to use them.
 

INRETECH

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Checkout the circuit at

http://home.kabelfoon.nl/~bertrik/bat/osc.htm

To run it on a single supply, change the ground pins (2 and 3) on the Omp-Amps to 1/2 Supply voltage

Then take the output triangle wave and run it into the 3/4 Op-Amp of the same chip with the other input being the control voltage, you will be able to control the PWM output by varying the input voltage

This is a VERY simple and VERY reliable Voltage Controlled PWM circuit
 

UK Owl

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build an astable mulitvibrator circuit, but instead of connecting the two transistor base's to the +v, attach them to either end of a Pot. attach the tapping of the pot to the +v {where the resistor would be} you now have a way of adjusting the bias on either side of the circuit, so you have a crude PWM circuit.
 

UK Owl

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OOPS,

where I said "connecting the two transistor base's to the +v, attach them to either end of a Pot" I should have said "connecting the two transistor base's to the +v via a resistor, attach the transistor bases to either end of a Pot".

p.s. if you file the rounded bit on the end of the led flat you will no longer have a beam, you will have a diffused light source. This can be handy if you want a light to inspect a map, or read a book when camping etc..

Sorry if I caused any confusion.
 

Avatar28

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Or light up a computer case? :) Diffuse light is exactly what I want in this case. I don't want lots of pools of light.

I appreciate the help on the controller, but, unfortuantely, it was all greek to me pretty much. I'm wondering if my best bet might not be to try to find a kit for one, or get some schematics and have someone build it for me.
 
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