Auto Dimming LEDs

[Graham]

Hey guys,

I'm after some advice on the best way to automatically pulse LEDs whilst dimming them at the same time (if that makes sense?)

Sort of like having the LED at full brightness and then slowly dimming it until it's at 10% brightness, then slowly increasing it back to full brightness then slowly dimming to 10% again etc etc..

I've searched and searched for a (cheap ) controller to do this but there doesn't seem to be much at all.. Theres cheap modules out there to increase and decrease brightness, but I want it to do it automatically not me having to manually do it.

If anyone can recommend a specific product/circut to do this it'd be much appreciated!

Thanks



EDIT:
This page seems to have good info on what I want [/url]

[Blakey]

Hey guys,

I'm after some advice on the best way to automatically pulse LEDs whilst dimming them at the same time (if that makes sense?)

Sort of like having the LED at full brightness and then slowly dimming it until it's at 10% brightness, then slowly increasing it back to full brightness then slowly dimming to 10% again etc etc..

I've searched and searched for a (cheap ) controller to do this but there doesn't seem to be much at all.. Theres cheap modules out there to increase and decrease brightness, but I want it to do it automatically not me having to manually do it.

If anyone can recommend a specific product/circut to do this it'd be much appreciated!

Thanks



EDIT:
This page seems to have good info on what I want [/url]

why do you want it to be automatic? whats it for. and do you mean you want it to fad in and out?.

the easiest way to dim a led is with a variable resistor(drop the current, but then you get to big a voltage drop. and then when the voltage gets to low, the LED's turns off or flickers.

other then that make a PWM circuit,

Pulse Width Modulation,
it turn's the LED on and off very quickly. longer the pulse the brighter the LED is, shorter pulses the duller the LED is.

just look up how to create a PWM circuit,

[Graham]

cool cheers,

I may need to look at making one, do you know of anywhere that sell these 'premade'?

[smithsy]

Gonna need to look at an AVR or PIC micro-controller with a built-in PWM output if you want to have an easily and completely adaptable automated PWM circuit.

You won't exactly get one pre-made, you'll need to buy the micro-processor and then design your circuit and write the C or Assembler code for a program to do what you want.

Really though it depends what you are trying to accomplish. Maybe it can be acheived simply using a variable voltage regulator (LM317T) or a 555 timer based PWM circuit.

Might help if you say what it is you want to do....

[Blakey]

you might be lucky if jaycar sells a PWM circuit. if not go out and buy a solderless breadboard, look at an online PWM LED dimming circuit, buy parts from jaycar. or have a look at using a voltage regulator like smithsy said.

using a regulator you can get the fading effect you want, but I'm not to sure on its dimming capability, as from smooth dimming. but you will get that affect i think you are after.

[davmax]

The request was for auto dimming both up and down. This is best achieved witha small 8 pin micro processor such as the AVR Tiny 25. Whilst this method has been mentioned above it can be achieved more simply than using a C compiler etc. The AVR code can be writtem in simpler Basic and then auto compiled. The software to do this is free for small projects and can be downloaded from http://www.mcselec.com/
If you cannot find any Tiny 25 I have plenty at $2.00 + post.

[smithsy]

There's nothing hard about using a "C compiler, etc" to program Atmel AVR chips and the software tools are provided free of charge. Firstly you need AVR Studio which is a very powerful and good piece of development software which enables you to write in not only Assembler but by downloading the WinAVR package you can use C. WinAVR employs the GCC compiler which has a proven track history of being a solid piece of gear that does its job well.

In fact if you write in BASIC it's still going to use a compiler (namely BASCOM in your exaple) in order to convert the code, difference just is that BASIC is a higher level and less-versatile language compared to C for the AVR chips.

Also need to remember that whilst the chip is only cheap, you will need a programmer (cheapies on eBay for ~$30-40 IIRC, althought I cant confirm how these work for the ATtiny25) or development board (such as the STK500 @ ~$150) in order to write the code onto the microprocessor.

It really would help though if you'd specify exactly what you want to do with your dimming circuit....