555 timer to run DC motor

[osuwa]

I need help with my circuit. i am trying to design a timer circuit for a 12V Dc motor. i want it to run for 3 minutes and stop that is it. but i want to use an IR sensor in the circuit the switch 1 is the sensor only when the sensor dectects  only would the circuit run the motor for 3 minutes and stop and if sensor dectects again the it would run ansd stop. so i dnt know if its a monostable or astable connection i used a monostable in my circuit i want some one to help me urgently. and if it is monostable i would i trggger the 555 timer. thanks

[johnsold]

I cannot see your circuit because I do not have Multisim.

1. Trying to get a 3 minute timer with a 555 will result in unrealistic component values. It is marginally feasible with the the CMOS variants of a 555.

2. This would definitely be a monostable function.

3. Is it your intention that the IR sensor serve as a trigger? What happens if the trigger signal persists longer than 3 minutes? What happens if the trigger signal recurs after 2 minutes? Does the motor run for another 3 minutes, making it run for 5 minutes total, or does it ignore that trigger?

4. What kind of device are you using to control the power to the motor?

Lynn

[osuwa]

If I get 60 seconds I would be cool with me and if another 2 minutes from the trigger that's perfect and what can I use as a trigger? The IR sensor is to the dectect motion and make the Circuit run the motor.

[johnsold]

One typical way to make long timers is to run the 555 as an astable with a period of about 1 second and use a counter to determine when 2 minutes or 3 minutes have elapsed.  You should be able to use the IR sensor to trigger your timer. Depending on what kind of output is has, you may need to put a comparator between the sensor and the timing circuits.

Lynn