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I am looking to create a simple circuit that utilizes a very small vibrating motor such as the one here: http://www.adafruit.com/products/1201#Distributors. I would like the small motor to be powered by a small battery and to be controlled to vibrate once every 30 minutes or so. For more advanced versions, I'd like it to be able to vibrate at either every 30 minutes, 15 minutes, or at random times (at least once every half hour). Ideally, all the parts would be no bigger than a wristband.

Any help that can be offered would be much appreciated. The main area I need help with is the interval timing of the vibrating motor using some type of controller.

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  • \$\begingroup\$ Do you envision a 3-position switch (30m, 15m, random) to select the interval mode? How precise does it need to be? What is the voltage you plan on using? Are you experienced with microcontrollers? Have you looked at basic 555 timer circuits? This question is too broad to answer without knowing more about the project as well as your abilities and experience (i.e. what have you tried?). \$\endgroup\$ – JYelton Oct 22 '13 at 4:37
  • \$\begingroup\$ Duplicate? electronics.stackexchange.com/questions/23536/… \$\endgroup\$ – jwygralak67 Oct 22 '13 at 17:42
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Microcontrollers

The canonical answer for this type of question seems to be that you should look into using a small microcontroller. You can get PIC and AVR microcontrollers that are no bigger than a 555 timer.

As a hobbyist with a low level of knowledge and skill, I find an easy way to find example circuits to use as inspirations is to, for example, google "avr led blinker" - because blinking LEDs is popular and not too far removed from driving a small pager motor.

That leads to interesting stuff like

I might start with an Arduino and shrinkify it to a 8-pin DIL AVR ATtiny before using SMT ATtiny. Other people would prefer to use PICs (some PICs are really tiny and ideal for wristband products)

I'd maybe have one pushbutton that cycles through the interval settings and maybe an extra LED for feedback e.g. 1 blink when set to 15m 2 blink when set to 20m 3 blinks when set to random. I'd try driving the pager motor via a BJT or FET. That means you need a microcontroller with one input and two output pins. Or you could use that pager motor for feedback instead of the LED.

555s

The "traditional" answer :-) is to use a 555. I'd use the same technique of looking for existing examples and adapting them. I'd start at somewhere like

Any circuit I concocted with a 555 would be likely to use a lot more components and a more complex circuit diagram and PCB layout than a microcontroller based solution. However you avoid the need to write software (I don't see this as much of an advantage).

BJTs

In principle, anything you can do with 555s you can do with small-signal generic jellybean BJTs (Google TUP TUN DUG DUS)

Valves

You're on your own.

Next

I would try concoct a circuit based on ideas like that and come back here when I hit specific problems with the circuit

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  • \$\begingroup\$ +1 for 555 timer, -1 for microcntroller \$\endgroup\$ – John U Oct 22 '13 at 9:22
  • \$\begingroup\$ @John. Harsh, I have more 555s than uCs in my parts box. OK I'll 555ify my answer a little. \$\endgroup\$ – RedGrittyBrick Oct 22 '13 at 9:25
  • \$\begingroup\$ Only a personal preference for not throwing CPU cycles at things when it's more interesting to solve it in analogue. \$\endgroup\$ – John U Oct 22 '13 at 9:27
  • \$\begingroup\$ Interesting does not necessarily mean practical. That said, I do have a soft spot in my heart for a clever 555 circuit. \$\endgroup\$ – jwygralak67 Oct 22 '13 at 17:36

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