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How can I use a timer module to make my circuit stop after a set amount of time?
Hi,
For a school project, I am making an electrical car, that stops by itself at a given distance (5-10 meters), and I need to be able to predict how many seconds this will take (0-45).
So I was thinking of using this timer module,
http://electronics123.net/amazon/datasheet/vm141_uk.pdf
and attach it so it cuts off the circuit for my motor in a set amount of time. How would I go about doing this?
Thanks!
*Could you please explain the steps really clearly, and make it as easy as possible?
Thanks!
That module is more than you need...
You can use a smaller and more suitable timer called a 555 as follows. The second link explains a monostable mode of this device that will do this job. This device outputs a voltage pulse for a specific time, once triggered. It will work on battery voltages from about 5 Volts to 15V. This voltage pulse is used to start and stop the car. When you press a button it starts, and then runs for the time it is set for, and stops. The actual time is very repeatable. The accuracy according to the formula is within 10%. It can be adjusted to suit. The doctronics link below has a downloadable calculator to determine the values. It also selects the nearest standard value of resistor or capacitor.
You have to make up a circuit just like the one in the diagram. Use a small piece of matrix board and a soldering iron for the connections. It is so simple you can dispense with the matrix board, and stick it together with hot glue or something like that.
Make a list of everything you need, including the calculated values for the expected time. The motor will run a bit slower with this connected, as it s voltage will be reduced a little.. It helps to get yourself a cheap digital multimeter.
If the motor uses less than 200 mA and the battery is 12V, or the motor uses less than 100mA and the battery is 6V then the timer's output is directly connected to the motor, replacing the battery connection to the motor, on the positive (+) voltage side. The negative side of the motor still goes to the battery negative. If the current is more than these figures, you will need an additional external transistor to switch the current to the motor. A useful type is the 2N2222 for up to 1 Amp. You will also need a 100 ohm resistor and a 1 Amp diode. You will need to contact me by email if you need that approach. I will need somewhere to send you diagrams of the circuit, like an email address.
The start button is a simple momentary action switch. It could be as simple as touching a pair of wires together, or shorting two pins/screws out with a coin or other piece of metal. You can buy a proper switch also. It can be very small. One side connects to the supply which is also the battery positive through a 10 thousand ohm resistor. This same side is also connected to the trigger input. The other side connects to the common or 0V line, which is also the battery negative.
Get a data sheet from the external links on the bottom of the Wiki page. Study the monostable connection.
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