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Backlight Adjust for CFAH2004A-TMI-JP


New member
What is the best way to Dim the backlight on this beautiful LCD readout? Its too bright to use at night. I see the examples in the PDF file but the PINS are not shown and I don't want to damage the unit. I have the Blue 4 line x 20 character module and use the 16 I/O pins for control and power.

I have a tiny 3 position slide switch to short out parallel resistors to vary the backlight intensity once the correct pins are identified. I can also PWM with a PICAXE 08M but cabinet space is very very tight.

Thanks, sorry for such a stupid question. Billacj
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The connections for the backlight are on the rear, labelled "A" and "K". These connections are also duplicated on pins 15 and 16. Pin 15 (A) goes to +5 through a 25 ohm, 1/4 watt, resistor (that will give 60 mA). Pin 16 (K) goes to ground, or to a transistor for PWM control.

PWM is the best method for brightness control, but keep the PWM frequency above 200 Hz to avoid aliasing effects with the LCD scan rate. The simplest transistor to use is a n-channel FET; you can find them in a TO-92 package or surface mount.

If you use a switch to short out resistors, do not let the total resistance become less than the 25 ohms mentioned above.