Dimmer backlight on dark room.

[mikkokh]

Hi.

It would be nice if backlight of my LCD would go dimmer when room is really dark. Is LDR sensor and some transistor right choices for this, or is there some other and better way to do this? Has anybody in there done this kind LCD backlight control before?

Thanks!

[caesar]

You can try and match a LDR sensor with a transistor, help yourself with a variable resistor to to set the threshold.
Can't help you further with a simple setup, I know some stuff only in the digital area, so I'd use thr A/D converter pin of a microcontroller to read the LDR.

[mikkokh]

...I know some stuff only in the digital area, so I'd use thr A/D converter pin of a microcontroller to read the LDR.

Hi.

Thank's about answer, caesar!

I own a PIC programmer, but I have very little experience about it, and even less experience to writing and compiling code for it. If I would use microcontroller to do this job, it would also give me also better functions to enable/disable backlight with LCD Smartie, because it's output voltage is known... Are I right about this?

I think also that dimming of screen could be done good with PWM signal controlled transistor, so dimming would be very accurate. Bad thing would be that I would need more components to do same thing than without microcontroller and complex circuit board. What you think about this?

[caesar]

Using a microcontroller is the best way to go, it takes the burden from the computer CPU, you can connect it serially or directly by USB with a PIC 18F2550 and you can also use some buttons on it. You can shut it down together with the computer, program a startup screen.
The winamp spectrum analyzer looks best on a USB connected PIC, you can achieve more than 25fps...

If you start the project you will realize that you can do a whole lot of new things with it. LDR for backlight, fan controll, temperature sensors, etc.

It's faster and cheaper to use a transistor with LDR and 1-2 variable resistors to set the minimum and maximum screen brightness...

[mikkokh]

Using a microcontroller is the best way to go, it takes the burden from the computer CPU, you can connect it serially or directly by USB with a PIC 18F2550 and you can also use some buttons on it. You can shut it down together with the computer, program a startup screen.
The winamp spectrum analyzer looks best on a USB connected PIC, you can achieve more than 25fps...

If you start the project you will realize that you can do a whole lot of new things with it. LDR for backlight, fan controll, temperature sensors, etc.

It's faster and cheaper to use a transistor with LDR and 1-2 variable resistors to set the minimum and maximum screen brightness...

Hi.

I should think this more... USB connection instead of LPT connection would be really nice and useful, but I don't know would this PIC project to be too much for me or not. Also, I don't know can this PIC Flasher program those 28pin PIC 18F2550 microcontrollers, and can I even get those controllers from my country.

Thanks about good idea, caesar!