LM324 a couple of questions

[ghostman11]

we use a couple of vellemen thermostats (mk138) Velleman nv it might help if you click on the assembly manul to see the circuit. (sorry i cant do circuit diagrams or very much on here at the mo as i need to sort out pc) would i be right in thinking that in that circuit only one side of a quad comparator is being used? if thats so would it be possiable to use both sides in a simillar circuit so i can have 2 sensors and 2 relays, both would use the same pot.
this is not going to be used to control tempreture but to operate a couple of fans.
2nd question on the parts list it mentions R8 as being 0Ω, however i cant see it on the circuit diagram??? what does it do and where would it go?

3rd and final question.........i have tried to copy this circuit in both proteus and multi sim, but when i tried to run a simulation it just keep coming up with errors. i was hoping to play with the circuit on proteus so i could play with the values etc sorry if theese are stupid questions but any ideas would be appreciated!
BTW i am not hopefuly looking for someone to come up with a circuit for me just help me get over the first couple of obstacles

 

[Dragon Tamer]

I'm afraid I don't understand could you post the schematic when you find it?

But from what I think you are asking: the whole comparator would be used in the circuit, or a different comparator would be used. Multisim just gets cranky sometimes, i've made circuits in multisim and it said that it would not work but when I made the circuit in real life it worked perfectly.

 

[MikeMl]

Schematic is **broken link removed**

One stage of the LM324 is used to buffer the zener reference voltage. Another is used as a Schmitt Trigger to click the relay when the sensor resistance reaches the set point; the other two stages are dormant.

 

[ghostman11]

thanks mike so am i right to assume i could use the dorment part? oh and i am curious why the 0 ohm resister?? and where would it go on the circuit diagram??

 

[MikeMl]

Are you adding sensors, or adding additional trip points to the existing sensor?

 

[ghostman11]

i would like to add sensors that would controll another relay but i dont need the set point changing they can both use the same one if that makes sense. thanks for the help

 

[MikeMl]

I think that you will find that unless you carefully match sensors, the differences between sensors will require duplicating the pot/network that sets the trip point.

 

[ghostman11]

ahh that makes sense thanks for pointing it out. one last question if there is half dorment then would it be poss to swap out the quad for a dual ??

 

[MikeMl]

Sure, an LM358

 

[ghostman11]

cheers mike