I'm using a HD44780 controlled LCD, but the display is almost invisible. I'm using a 10k pot from +5 to ground with the wiper to VL to control contrast as the data sheet suggested. If I go from +5 to -5 the contrast is great. Has anyone had similar problems or any suggestions to avoid the dual supply?
I'm using a HD44780 controlled LCD, but the display is almost invisible. I'm using a 10k pot from +5 to ground with the wiper to VL to control contrast as the data sheet suggested. If I go from +5 to -5 the contrast is great. Has anyone had similar problems or any suggestions to avoid the dual supply?
Please check the naming of the LCD power connections in your pix, above.
The Hitachi manual for the HD44780 says:
pin#1 Vss, signal ground.[0V]
pin#2 Vdd, power supply for logic.[+5v]
pin#3 Vo, power supply for LCD driving voltage.[Vo=> +1.5V]
The recommended variable resistor is 10K0 thru 20K0
Please check the naming of the LCD power connections in your pix, above.
The Hitachi manual for the HD44780 says:
pin#1 Vss, signal ground.[0V]
pin#2 Vdd, power supply for logic.[+5v]
pin#3 Vo, power supply for LCD driving voltage.[Vo=> +1.5V]
The recommended variable resistor is 10K0 thru 20K0
you must have an 'extended temperature' lcd, which requires negative voltage for contrast.
stealing a little -V from a max232 is an awesome and easy idea, you can also generate some using a charge-pump consisting of two capacitors and two diodes driven by a sq. wave from your microcontroller.
another option is a dedicated charge pump controller - Microchip has an easy to use SO8 verison that works with inexpensive ceramic caps.
you must have an 'extended temperature' lcd, which requires negative voltage for contrast.
stealing a little -V from a max232 is an awesome and easy idea, you can also generate some using a charge-pump consisting of two capacitors and two diodes driven by a sq. wave from your microcontroller.
another option is a dedicated charge pump controller - Microchip has an easy to use SO8 verison that works with inexpensive ceramic caps.
Hi,
I use the -V from the max for graphic displays.
You can steal upto 10mA from the +/- lines of the MAX232, I usually make the MAX caps 4.7uF or 10uF, when I do that.
Use the +/- 9v thru 78/79L05 for opa supplies.