adjustable timing circuit

I'm trying to put together a timing circuit which will allow me to operate a linear solenoid actuator for a predetermined amount of time and then deenergize it. Do such timer relays exist that will allow me to adjust the power-on time to between 5 and 15 seconds AND allow for fine adjustments of 0.1 seconds or so?

You can do this with a 555 timer chip in a "one shot" configuration. The 1% accuracy adjustments will require something fancy, like a 10 turn potentiometer. I think they are available as 25 turns from end to end.

You could go digital if you're willing to spend a lot more time and money. Ve haf vays of dealing mit this.

You're asking not only for accurate timer function, but accurate setting and indication. Not a simple request. We're talking a pretty sophisticated system, or a industrial control. Why do you need setting accuracy of .7% of full scale?

ok, so here's the deal. My friend owns a number of those annoying toy vending machines that you see in the malls. You know, the ones like the claw catchers that are supposed to pick up a stuffed animals? Except these are a bit different...They operate by first pushing a button to control the lateral position, and then another button to control the height, of a plunger that then moves forward through a slot to push the toy off the back of a shelf. I'd love to see my friend's face when he sees that his entire machine has been wiped out in one day! That's where the precision timing control comes in. I'm building a box that I can put over the height adjustment button to hold it down exactly long enough so that the plunger ends up in the right place to pass through the slot and push the goods off the shelf. I figured a linear actuator (to push the button) on a timing circuit should do the trick...as long as I can fine tune the timing over a few trials. What do you think?

I think the 555 timer will work because you did not ask for "real time" accuracy (traceable to national standards) or an indicator, and you'll be right there adjusting things from minute to minute, so the timer doesn't have to be repeatable for months or years. Get it close, give it a twiddle, and risk another 25 cents, right?

mecheng said:

What do you think?

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I think you have too much time on your hands.

Why not just disable the alarm, pick the lock, empty it and hide the toys somewhere?

thanks

bychon said:

You can do this with a 555 timer chip in a "one shot" configuration. The 1% accuracy adjustments will require something fancy, like a 10 turn potentiometer. I think they are available as 25 turns from end to end.

You could go digital if you're willing to spend a lot more time and money. Ve haf vays of dealing mit this.

Click to expand...

Thanks for being with the digital people.