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chien_fu
Joined: 11 May 2008
Posts: 8
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 11 May 2008 16:32 Simple timer design looking for help |
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I'm looking for some help designing the following circuit. I've done a few hobby level circuits based on the PIC 16F877 / 84 and assume this will probably require something along those lines.
Functional goal description:
Vibrating motor that gives a quick pulse (< 1sec) every 15, 30 or 45 minutes. I'm looking for one momentary-push button that controls the circuit ON/OFF as well as the interval. IE. Push the button once, the circuit turns on and interval is set to 15 min. Push again, interval changes to 30 min. and again for 45 min interval.
It's a 3-5v dc motor and I'm assuming I can run it at line level. As you see I don't have a lot of knowledge around this yet, and would appreciate any help I can get.
Thanks a lot!
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Audioguru
Joined: 19 Jan 2008
Posts: 521
Helped: 39
Location: Canada
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| 11 May 2008 18:36 Simple timer design looking for help |
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What is "line level"?
The motor needs 3VDC to 5VDC so give it that.
Make a circuit to give the timed pulses then add a transistor or two to boost the current high enough to power the motor.
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VVV
Joined: 26 Nov 2004
Posts: 1492
Helped: 278
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| 12 May 2008 17:08 Re: Simple timer design looking for help |
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Yes, the kind of thing you are describing requires some intelligent chip.
I would think a PIC10Fxx, or 12Fxx would do the trick.
One I/O line of the PIC will be used to power the motor, through a transistor, and another I/O would be needed to sense the switch closure. From that point on, it's all software, which is relatively simple, by the way.
I can help with that.
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chien_fu
Joined: 11 May 2008
Posts: 8
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VVV
Joined: 26 Nov 2004
Posts: 1492
Helped: 278
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| 26 May 2008 17:28 Re: Simple timer design looking for help |
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| You will need two timers to do it: one that gives you the motor on time, 1s, the other that gives you the interval. Two 555 timers or a 556 will do the trick.
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chien_fu
Joined: 11 May 2008
Posts: 8
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| 26 May 2008 19:04 Re: Simple timer design looking for help |
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| Can I use a 555 or 556 to easily create a random timer interval? I'd like to time an interval between 15 and 75 minutes. Is this possible with these timers?
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sabeti_1990
Joined: 16 Nov 2007
Posts: 124
Helped: 7
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| 27 May 2008 10:56 Re: Simple timer design looking for help |
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hi chien_fu
yes u can use 555 or 556 to have long time
but it's better to us a divider after a 555 (like 4017)
see this
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blueroomelectronics
Joined: 17 Sep 2006
Posts: 1230
Helped: 61
Location: Toronto, Canada
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| 27 May 2008 14:36 Re: Simple timer design looking for help |
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| chien_fu wrote: |
| Can I use a 555 or 556 to easily create a random timer interval? I'd like to time an interval between 15 and 75 minutes. Is this possible with these timers? |
You'll need more than a 555 or 556 if you want random. One of your PICs could do it no problem.
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