Hi:

I have a 5 volt relay that requires 70mA of current in order to energize the coil.
I am trying to get a driver to work using a 2N3904 transistor, a 1N4148 diode for
the flywheel and a 1KΩ resistor on the base. The emitter is grounded. I want a 5
volt level on the base to trigger the relay. It just doesn't work. Any ideas?

Thanks

 

Then you have something not connected or mis-connected.

Is it on a breadboard or something else?
Schematic?
Photos?

 

Hi:

I have a 5 volt relay that requires 70mA of current in order to energize the coil.
I am trying to get a driver to work using a 2N3904 transistor, a 1N4148 diode for
the flywheel and a 1KΩ resistor on the base. The emitter is grounded. I want a 5
volt level on the base to trigger the relay. It just doesn't work. Any ideas?

Thanks

Sounds like it should work.
Maybe something wired incorrectly or a bad/incorrect part.

 

Then you have something not connected or mis-connected.

Is it on a breadboard or something else?
Schematic?
Photos?

Bread board. Its on a proto board.
No wiring errors. The input is a 5-volt level, ignore the "555 Output" label.

 

It just doesn't work.

Does not work; relay is open? or relay is closed all the time?
---edited----
Have you checked the pin out of the transistor? Common error.

 

Does not work; relay is open? or relay is closed all the time?

Normally open.

 

Is the relay operated all the time or never operated?
The circuit as drawn should work so it would seem it is not connected as per diagram.
Give us some photos. We may be able to see the problem.

 

 

Does it come on when you short out the transistor C/E terminals?

 

Normally open.

The base lead broke so I guess the connection was intermittent. Thanks guys!

 

The base lead broke so I guess the connection was intermittent. Works with a new xistor. Thanks guys!