hey guys I have made a timer with ne555 in proteus, i wanna use a variable capacitor instead of C4 my capacitor so then i can get different output as i change my input capacitance, the problem is whenever i wanna use variable capacitance it gives me an error message that i should configure my variable capacitor so i was wondering if u could please help me ?

 

Not all components in proteus can be simulated. Many are just for drawing schematics and PCB footprints.

So if you must use variable caps, you can always do in this way....

Allen

 

Not all components in proteus can be simulated. Many are just for drawing schematics and PCB footprints.

So if you must use variable caps, you can always do in this way....

Allen

Thank u so much, it is really smart, i dont know why i couldnt think of it at the first place,
cheers

 

Can't proteus use a parameter for the capacitance, so that you can sweep through the values? All spice simulators I know of can do this.

 

Yes of course, but not on a variable capacitor.

I guess what the OP wanted was an animated variable capacitor with an "UP" and "DOWN" arrow. So he could change the values of the cap on the fly while the circuit is running.

Using a fixed cap, one can put in a value for the cap, run the simulation. Then stop it and enter a new value for the cap and hit RUN again. That works too.

Allen

 

Can't proteus use a parameter for the capacitance, so that you can sweep through the values? All spice simulators I know of can do this.

i don't know much about proteus that is the problem i am using multilism it is such a great strong software but the problem the library is not as complete as proteus and it doesnt have the voltage to frequency convertor LM2917, i shall try the spice simulators then, does it have LM2917 ?
thanks for ur time and help !
Best Regards,
shayan

 

I don't know if proteus or multisim accept pspice models, but i guess they should, so look here http://forum.allaboutcircuits.com/showthread.php?t=38423
Or use Ltspice as mentioned in that thread.
http://forum.allaboutcircuits.com/showthread.php?t=38423

 

Why do you want a variable capacitor on pin 5 of the 555 oscillator? The capacitor does not adjust the oscillator frequency, it simply smooths power supply fluctuations.

R3, R4 and C3 set the frequency of the oscillator. You have the frequency set too high to blink the LED.

 

Why do you want a variable capacitor on pin 5 of the 555 oscillator? The capacitor does not adjust the oscillator frequency, it simply smooths power supply fluctuations.

R3, R4 and C3 set the frequency of the oscillator. You have the frequency set too high to blink the LED.

well i am having my semester project which i have a stretchable capacitor sensor so i should convert the capacitance to the frequency and then convert the frequency to the voltage, as i stretch my sensor i am supposed to get different output voltage, well that is the reason i use variable capacitor.
cheers

 

well i am having my semester project which i have a stretchable capacitor sensor so i should convert the capacitance to the frequency and then convert the frequency to the voltage, as i stretch my sensor i am supposed to get different output voltage, well that is the reason i use variable capacitor.
cheers

Then use the variable capacitor at pin 2 and pin 6 (C3 in your circuit) to vary the frequency of the oscillator.

 

Then use the variable capacitor at pin 2 and pin 6 (C3 in your circuit) to vary the frequency of the oscillator.

yeah sure i know that i must use a variable capacitor instead of C3 mate to vary the frequency but my problem is the software proteus offers the variable capacitor but it needs to be configured first which i dont know but it is ok i am gonna use the method suggested by our friend, several capacitors connected to the switch
anyway thanks mate,
cheers