Arduino with LCD 20x4 Display

[MatthewB]

I've wired up an LCD 20x4 display to my arduino but have only now realised that I require some method of diming to be able to actually read the screen, supposedly. Instead of a variable dimmer, could I possibly use a resistor to keep it at a constant level so that it is backlit but I can also read the text, if so, what resistance would accomplish an acceptable level of readability?

[Divvi]

Yes, just replace the potentiality with a fixed-value voltage divider:

[AlxDroidDev]

I've wired up an LCD 20x4 display to my arduino but have only now realised that I require some method of diming to be able to actually read the screen, supposedly. Instead of a variable dimmer, could I possibly use a resistor to keep it at a constant level so that it is backlit but I can also read the text, if so, what resistance would accomplish an acceptable level of readability?

Use an RC filter to set the voltage of the backlight, and control the filter through a PWM pin. This way you can programatically set whatever voltage you want on the backlight (from 0 to 5V) simply by using "AnalogWrite(Dn, val)" where Dn is the digital PWM pin and val is a value from 0 to 255 (meaning 0V to 5V).

This is a kind of "poor man's DAC", but it is good enough for these applications where a precise output voltage is not needed.

http://provideyourown.com/2011/analogwrite-convert-pwm-to-voltage/

[NivagSwerdna]

Push the boat out

http://www.ebay.co.uk/itm/10PCS-10k-103-Ohm-3296W-Potentiometer-Trim-Pot-Trimmer-Variable-Resistor-25-Turn-/281465009320?hash=item41889f34a8:g:0C0AAOSwR0JUOOKE

[dannyf]

Without knowing exactly what LCD you are talking about and what dimming you are attempting to achieve, there really ia no answer to your question.

[collingtech]

yep put a model /brand , will help a lot

[danadak]

If the display is transmissive you need the B/L on.

If transflective one or the other or both, ambient light, B/L.

If reflective you need ambient light.

If B/L is LED best way to control brightness is a PWM driving a pin switching power
to the LED chain.

If pin is the contrast pin, a simple pot to Vdd, wiper to pin, other side grounded.


Regards, Dana.