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LCD contrast controlled by LCD

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togarha

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lcd contrast pwm

Hi!!!

What is the frequency (through Low Pass Filter) recomended for the contrast of a LCD?

I want to control the contrast of a LCD with the PWM of a PIC microcontroller, but I don't know what is the best frequency for it.

I want to use a Low Pass Filter (with a resistor and a capacitor) to convert to DC the output of the PWM, but if it is possible I want to use a smd capacitor, then the capacitor may be as long as 470nF (personal stock). It is enough value for the LPF or I must to put a larger electrolitic capacitor? In theory it is possible, but I want to know the practical experience of people...

Thanks in advance...

Regards,
 

lcd contrast control

Hi,

I just found following circuit with the code to generate -3V ... +1V:

h**p://www.piclist.com/techref/microchip/pwmvee.htm

hope it helps
 

pwm contrast lcd display

why don't you use a digital pot,that what they use on cellphones
 

pwm lcd contrast

It can also be done using pwm...

Added after 3 minutes:

togarha said:
Hi!!!
I want to control the contrast of a LCD with the PWM of a PIC microcontroller, but I don't know what is the best frequency for it.

It's the duty cycle which matters
 

lcd pwm contrast

LCD contrast is a bit vague. If you are using hitachi compliant alphanumeric module, have a 5V supply available, and don't want to mess with it more than once then you can try connecting the Vcon pin to ground. That's what I do with mine. Readable, no extra parts, good down to about 4V5.

For other LCDs, you've got different rules to play by.
 

lcd pwm contrast control

please see the following circuit diagram use to control the Graphical LCD

45_1172410489.GIF
 

avr pwm lcd contrast

Most probably the LCD had LED Backlighting... that can be easily controlled using PWM.

If it's VFD.. it should have it's own contrast adjusting circuit...
 

lcd contrast voltage adjust digital potentiometer

Hi
I used AVR PWM for DAC later, therefor cause LCD contrast adjust with a voltage from 0 to about 5 v , you can use this dac for do this.
the frequency is not important but use fast pwm mode.
for covert the pulse to analog voltage, use low past filter. for better result use more than 3 LPF.
 

avr contrast lcd

the PWM is a good idea, but if the contrast voltage is negative used a diode doubler circuit for negative voltage
 

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