LCD's and Sleeping Pics

[andybarrett1]

Hello

Thank you for the quick read…. Posted this elsewhere by mistake :-)

Is it deemed correct to drive a 16x20 LCD and back light direct from a single output Pin.

Don't worry, when I say direct I "DO" mean via a Transistor or Darlington buffer….

I am using an interrupt routine which will put the PIC to sleep…but the LCD is hung on the supply rails, The LCD will stay on, so was thinking if I hang it on a spare output port it can be shutdown before the PIC goes to sleep.

Or is there a more elegant way of doing it??

Thank you again

Andy

[tekart]

Andy,
I *almost* always drive the back light with a separate pin via a MOSFET to have the option of PWM dimming of the light. If you have 2 pins to spare - 1 for LCD and 1 for BL. Many LCDs draw so little power that you can direct drive the LCD from an I/O pin. Check the power specs of your particular LCD or just use a MOSFET. My preferred MOSFET is the 2N7000 for up to 200mA or the BS170 for up to 500mA.