mosfet not right?

[audioguru]

Your 2N2222 is probably destroyed by the very high flyback voltage made by the relay coil when its current is turned off. The relay coil needs a reverse-biased diode across it to eliminate the high voltage.

Most transistors show the saturation voltage loss on their datasheet when they are turned on HARD with the base current 1/10th their collector current. Their current gain is shown with plenty of collector to emitter voltage so they ARE NOT SATURATED!

hfe is AC current gain.
hFE is DC current gain when the transistor has plenty of collector to emitter voltage so IT IS NOT SATURATED.
The 2N2222 is spec'd to have high hFE when its collector to emitter voltage is 10V or more, THEN IT IS NOT SATURATED.

 

[MrDEB]

I have a diode across the relay coil (the schematic does not show it , my bad)
So can I assume all is well with my schematic circuit? or ?

 

[MrDEB]

Looking at the data sheet you posted I assume I need a smaller base resistor?

 

[audioguru]

Looking at the data sheet you posted I assume I need a smaller base resistor?

Your circuit probably has a 2N2222 transistor that is better than most typical ones so you are lucky that it saturates fairly well with low base current.
But if you make a few or more then some will not work unless you reduce the value of the base resistor so that the base current is 1/10th the collector current as shown on the datasheet.

 

[MrDEB]

I find the relay is 89 ohms so the collector current, using 12v = 130ma
130 / 10 = 13 ma I need for base current (now I know where you got the figure of 13.)
4.5 / .013 = 346 ohms. yea my calculations using a 1k is way off(duh)
Will insert a 470 as just to be sure n safe
Like I stated before, I was the last in line when it came to handing out math skills.

 

[audioguru]

My 31 years old daughter also needs to use the calculator on her cell phone to divide a number by 10.
I simply push the decimal point over.

 

[MrDEB]

I now show 9 ma draw on the base (I just put another 1k in parallel
Hopefully get this project done. Just need to tidy up my code and make some adjustments.