hello. I know there are many timer circuit in the google. but in all of them use push button.

in this circuit when we press the push button and We will not give up the push button. this capacitor is charging permanently and the circuit timer do not work correctly. I want use the simple switch instead of the push button in the above image. What changes should I make to the above circuit?
Thanks.

 

It is not clear what you are asking.
What do you think is the difference between a push button and a switch?

In the circuit above, you can replace the push button with a switch.
Simply turn the switch on and off again.

 

It's not clear what you want the circuit to do when the switch is closed.

 

hi R1000,
Is this a college assignment project?.
Moderation

 

It is not clear what you are asking.
What do you think is the difference between a push button and a switch?

In the circuit above, you can replace the push button with a switch.
Simply turn the switch on and off again.

when we turn the switch the capacitor charging permanent and it is not discharged for time operations

 

Do you want the LED to come one when power is applied to the circuit and then go off after a set amount of time ?
Les.

 

Do you want the LED to come one when power is applied to the circuit and then go off after a set amount of time ?
Les.

yes. when the switch is on forever

 

hi @rezas1000
Is this a college assignment project?.
Moderation

 

Right now that we know what you require the circuit to do can you answer the question in post #4
Tell us your understanding of how the circuit in post #1 works. From that we will probably be able to guide you into a modification of that circuit that will do what you require.
Les.

 

hi @rezas1000
Is this a college assignment project?.
Moderation

This circuit works when we press the key momentarily and not continuously. I want the switch to stay on all the time and the circuit works correctly.


Moderation: Thread moved to the Homework Forum.

 

Thatis what it does. I want you to explain how it works.
Les.

 

Thatis what it does. I want you to explain how it works.
Les.

When we press the switch, that capacitor gets charged and that resistor gets discharged and the timing operation is done. But if the switch is always on, that capacitor gets charged all the time and that circuit does not work.How can I solve this problem?

 

Resistors do not get charged or discharged. They control the current through a circuit. (And hence in that circuit it controls how long the capacitor takes to discharge.
How would you change the circut so the the LED was on during the time required to charge the capacitor ?
Les.

 

The simple solution is to put the ON/OFF toggle switch in the power circuit. When the power is off, you want a capacitor in the discharged state. Turning the power on will cause the capacitor to charge and eventually turn off the LED.

Now can you design a circuit to do that?

 

This circuit gives you about 6sec timer after switch become On:

1n4148 diode speed up discharging the capacitor after SW is turned Off.
Otherwise you would have to wait too much time for capacitor discharge.


Moderation: this is a Homework assignment

 

The simple solution is to put the ON/OFF toggle switch in the power circuit. When the power is off, you want a capacitor in the discharged state. Turning the power on will cause the capacitor to charge and eventually turn off the LED.

Now can you design a circuit to do that?

I want the LED to turn on when the switch is permanently closed and turn off after a period of time without opening the switch

If the capacitor is charging forever, the LED is always on

 

The capacitor will NOT charge forever. It will charge until the voltage accross the capacitor is the same as the voltage source. charging it. (So the charging current will have dropped to zero.)

Les.

 

I want the LED to turn on when the switch is permanently closed and turn off after a period of time without opening the switch

If the capacitor is charging forever, the LED is always on

You need to quantify “after a period of time”.
Is that 10 seconds, 10 minutes, 10 hours?

 

You need to quantify “after a period of time”.
Is that 10 seconds, 10 minutes, 10 hours?

For example 60 seconds. I want to make this circuit for a toster

 

This is possible to do. But why would you want to do this for a toaster? A toaster already has a builtin timer of some kind. The toast pops up when it is done.