I Need Help With My 555 Monostable Circuit Please

[toh liu wang]

I am using monostable circuit to switch off my motor after a specific period of time. But the motor doesn't stay on when i press the button switch! When i remove the motor and relay and replace it with a led, the led stays on for a while before switching off. Can it be the relay? Or is it the circuit that is wrong? PLEASE HELP!

 

[KMoffett]

Do you have a schematic of what you are trying to wire on the breadboard?

Ken

 

[toh liu wang]

Do you have a schematic of what you are trying to wire on the breadboard?

Ken

This is the schematic diagram for the monostable circuit. This works for me, but when i try to put the relay and motor into this circuit, the motor wont stay on. Can i just connect the motor to pin 3 and let it run?

 

[duke37]

Show us the schematic and data on the load. You seem to have a transistor lurking there.

 

[Audioguru]

The 9V battery and the 555 timer have low output currents. The motor might use a high current that will burn them out.
The motor is not supposed to stay on, it turns off when the 555 timer tomes out.

 

[toh liu wang]

The 9V battery and the 555 timer have low output currents. The motor might use a high current that will burn them out.
The motor is not supposed to stay on, it turns off when the 555 timer tomes out.

So there's no chance for the motor to stay on?

 

[toh liu wang]

Show us the schematic and data on the load. You seem to have a transistor lurking there.

I removed the transistor and resistor that are connected to the relay. I used a bare wire to connect the 555 to the relay.

 

[Audioguru]

So there's no chance for the motor to stay on?

The monostable is a timer. It turns on when It is triggered then it turns off when it times out.
If you want the motor to stay turned on after you momentarily push the button then remove C1.

 

[Alec_t]

I used a bare wire to connect the 555 to the relay.

I hope you remembered to keep the reverse-biased diode across the relay coil? Without that the 555 probably won't survive.

 

[toh liu wang]

The monostable is a timer. It turns on when It is triggered then it turns off when it times out.
If you want the motor to stay turned on after you momentarily push the button then remove C1.

I need my motor to switch off after a period of time. But for now, the motor won't even stay on for a few seconds before turning off.

 

[duke37]

Remove the motor and replace with a led and resistor i series to check the time of the 555 pulse.

 

[Audioguru]

The values of R1 and C1 set the timing but your schematic does not say what they are.
A 51k resistor with a 100μF capacitor produces about 5.6 seconds of timing.

You say that you want timing to be "a period of time" but you do not say how much time.

I think your weak little battery drops its voltage when trying to drive the motor then the 555 timer has a heart attack.

 

[Audioguru]

On the other forum he said the timing capacitor is 470μF. Then the 51k timing resistor will cause the 555 to timeout in about 26 seconds If the battery voltage has not dropped too low.