sink vs. source

I'm using a 555 monostable to drive a motor after a short delay. I want an LED to light when the 555 is sourcing and the motor to turn on when the 555 is sinking. My problem is that the LED does not turn off when the 555 changes from source to sink. How can I fix this?

Posted by JJR on 15/10/2007, at 04:50 GMT

Sink vs. Source

Ever thought about driving the motor via a 2.2k resistor operating a PNP driver transistor? The LED can then be linked with its limiting resistor and an extra diode in series directly to the 555 output. You have to be aware that the transistor can also be baised on by the LED circuit (hence use of the extra voltage drop of the series diode in the LED circuit) in this case.

Posted by Robert Neill (varient412@yahoo.co.uk) on 30/01/2010, at 17:14 GMT