Automatic fan controller problem

[hantu lipas]

I cant make this auto fan controller to work
circuit ,i even used hair dryer to heat the termistor
https://www.coolcircuit.com/circuit/fan_controller/automatic__fan_controller.GIF
is something wrong?

 

[Reloadron]

I believe the LM311 is open collector output and you should have a pull up resistor at the output to V+. Check out this link and note the use of Rl in the comparator circuits.

Ron

 

[ericgibbs]

hi,
As Ron states, in that configuration a load resistor is required on pin 7 to +V, try a 2k2 thru 4k7.

 

[hantu lipas]

hmm okay i switch the connections without the pull up, its on all the time without heating the thermisor is it because without the resistor pull?
i dun have any resistor rite now

 

[ericgibbs]

hmm okay i switch the connections without the pull up, its on all the time without heating the thermisor is it because without the resistor pull?
i dun have any resistor rite now

hi,
Why have you switched 'which' connections.??

You need the resistor...

EDIT:
This is your circuit in simulation, it works OK.
The 2k2 is the pin 7 resistor.
What is the resistance of the thermistor when cold and hot..??

 

[Boncuk]

The LM311 should even work properly with a 240Ω resistor connected to +UB (12V).

According to the data sheet it can source 50mA.

Anyway, you need a resistor.

Boncuk

 

[hantu lipas]

hi,
Why have you switched 'which' connections.??

You need the resistor...

EDIT:
This is your circuit in simulation, it works OK.
The 2k2 is the pin 7 resistor.
What is the resistance of the thermistor when cold and hot..??

sorry i meant, when i switch pin 7 to 12V, pin 1 to R2,
the fan goes on without heating the thermistor
and the thermistor is NTC
sorry for bad english

https://www.coolcircuit.com/circuit/fan_controller/automatic__fan_

opps sorry
https://www.coolcircuit.com/circuit/fan_controller/automatic__fan_controller.GIF

 

[4pyros]

"http://www.coolcircuit.com/circuit/fan_controller/automatic__fan_" Bad link, looks like it got cut off. Andy

 

[hantu lipas]

thanks it works! with the pullup!
i love you all

 

[ericgibbs]

thanks it works! with the pullup!
i love you all

hi,
Good news.
You should contact the author of the original drawing from where you copied the circuit diagram and tell him about the missing resistor.
It could prevent others from repeating your work..............

 

[hantu lipas]

hi,
Why have you switched 'which' connections.??

You need the resistor...

EDIT:
This is your circuit in simulation, it works OK.
The 2k2 is the pin 7 resistor.
What is the resistance of the thermistor when cold and hot..??

what program sim your using sir?