relay dimming lcd backlight.....

[jit_singh_tara]

hello frnds....

I am driving a lcd with a controller pic16f77a. i am giving output from a pin to a resistor 100ohm which is connected to base of transistor,emittor is grounded,collector is connected to a relay whose other terminal is connected to 5 v supply same which is powering up the whole circuit.

when i turn on the relay . the lcd backlikght is dimmed .this is because the relay is taking more current ,please suggest a solution.


the transistor is 2n3904,resistanc is 100 ohm , relay is 5V 2 pole relay.please suggest a solution.

 

[betwixt]

Your power supply is inadequate and dropping voltage when the relay coil draws current.

Your options are:

1. a better power supply.
2. possibly powering the relay coil from before rather than after a regulator.
3. a relay with a more sensitive coil (less current).
4. replacing the relay with a different kind of switch.

There is no way to fix your problem in software or hardware except those suggestions.

Brian.