Hello
please help how to get down voltage from 555 timer pin 3 down from 0.9v to 0v help please
input voltage is 13v

 

0 V at what load? Use 555-3 to drive a reed relay with mercury wetted contacts to give near 0 V up to relays rating. Or use power FET with inversion from 555 to give around 50 m ohms.

 

a diode maybe?

 

Are you talking about a conventional 555 or a CMOS 555?

Pin 3 on a convention 555 will reach 0V easily. If not you have something dramatically wrong with your circuit.

 

Hello,

I agree with Bill. There could be something wrong.
Post your schematic to see if there is anything wrong with it.

Bertus

 

The output saturation voltage of the 555 timer's pin 3 will increase with the amount of current you're trying to sink.

At light loads, it's nearly 0v. As you approach 200mA sink current, the saturation voltage increases. If you attempt to sink more than 200mA, the saturation voltage will become excessive.

 

I was thinking about that while driving. I suspect the OP is trying for more than 0.1A, it seems to be a common mistake. 200ma (the absolute max, you should not try for more than half that) is plenty of current for most applications, if you need more you need transistor drivers.

If you have pushed this chip too hard forcing it beyond its limits it is probably blown. They can only take so much.