transistor as a switch

ponsakthi said:

eric in port b if microcontroller, o/p current is 25 ma. lcd backlight is 50ma. how do i drive

Click to expand...

Look at the transistor circuit I posted earlier.

470R > BC547 base > lcd backlight to collector> high side of lcd backlight to +5V. [ it may have to be +7V.!, but try +5V first]

For a quick first test of the transistor, dont connect the base resistor to the PIC, just connect it to the +3.3V. The backlight should go on/off as you touch the base resistor to +3.3V and 0V alternately.

Once that test works OK, then think about using the PIC pin to drive the 470R.

OK.?

Transistor for driving motor with MCU

I have a similar question where i need to understand how to drive a motor circuit rated at 250ma from my PIC MCU.

First of all I cannot make out how much is the output current from the PIC.

The datasheet mentions that
Maximum output current sunk by any I/O pin........... 25 mA.

If I am driving the PIC using 3.3 V and need to drive the motor which transistor should I use to switch the motor. Also what would be the typical values for the circuit.

BEst REgards,
Sumit