Need Help adjusting the hysteresis on my Schmitt trigger with two transistors.

[andemand80]

I need help to which resistors that i should change to make the hysteresis Smaller in my schmitt trigger(Se picture). i use this as a temperature controller in my garage but now the hysteresis is equivalent about eight degrees celcius, which is Too much, i was hoping to get it to around half a degree... Best hopes from here

View attachment 40708

 

[Hero999]

I don't like that circuit myself, I prefer using a PNP and NPN transistor because the output voltage swing is greater.

Look at the circuit where's the positive feedback?

Try changing some of the component values.

Why not use an IC comparator such as the LM311?
http://www.silicontronics.com/index.php?action=ezportal;sa=page;p=17

 

[desolatordan]

http://www.play-hookey.com/digital/experiments/rtl_schmitt.html

Raise RC2? Lower R2?

 

[andemand80]

Thanks a lot- desolatordan- for the link
Apparently i can control the hysteresis by raising the resistance of RE- wupti! And it worked!!!

Yei!