# Simple timing circuits

#### briscoe

Joined Jun 1, 2013
3
Hey everyone, I've got an assignment at school which uses timing circuits and as a class we have done absolutely nothing on timing circuits and I have no idea how to make one, how they work or anything like that. Essentially, the assignment involves designing a mechanical timing device (a Rube Goldberg machine) and then creating an electrical timing circuit that will give off an output of some kind at the same time the Rube Goldberg machine finishes.

To summarize, I'm looking for an easy to construct timing circuit which can be adjusted easily and the theory of how it works.

I tried researching myself but didn't understand anything. I'm not too savvy with the circuitry lingo so please be easy on me.

Thanks.

#### Dodgydave

Joined Jun 22, 2012
11,151
For the electrical timing use a 555 timer chip, as for the 'Rube Goldberg' look on You-tube.

#### Shagas

Joined May 13, 2013
804
Timing? as in you press a button and the circuit goes from state A to state B for an adjustable period of time and then back to A?

If so , then you can make it using a multivibrator . Basically when you input a signal it latches to a state and when you input another signal then it goes back into it's original state. Or you can make it that you input a signal , or push a button and after a certain amount of time the circuit reverts back to it's original state (monostable multivibrator)

I've got a few tutorials on those on youtube if you want to check them out .
I think what you want is the monostable one (that is if I correctly understood what you are asking )

the intro:

And the monostable one (press button and circuit switches on for an adjustable period of time) :

#### briscoe

Joined Jun 1, 2013
3
I only have one question, how do you change the time the circuit takes? This is important because I don't know how long the Rube Goldberg Machine will take and I need to be able to change it easily. Dodgydave, could I replace resistor Rt with a variable resistor?

#### absf

Joined Dec 29, 2010
1,968
Sure, the bigger the Rt, the longer the time delayed. You can also increase Ct, if Rt becomes too large (>10M)

Allen