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I'm creating a simple vibration mat for a child which will be triggered by a force sensor. I'm not trying to do anything complex (like changing frequency of vibration) - simply an on/off circuit. What I'd love to get some advice on, is suggestions for wiring up and powering what will be a large group of motors...

I've picked up a bunch of generic iPhone vibration motors from eBay that happily run on a 1.5v battery on their own. However, I would like to run them in groups of 9. Because I'd like to run the group at the same speed, I assume that wiring them in parallel would be the way to go, but do I need to be wary of how much current is being drawn, or other tricks when grouping multiple motors?

Finally, if I can I would like to have the mat run on battery power if possible - particularly as it will be used by a small child. Is this realistic for so many (albeit small) motors?

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It is definitely realistic. Regular DC motors work as follows

1) Speed is roughly proportional to input voltage

2) Torque follows the input current. A higher current gets a higher torque.

1) and 2) are should be under operating limits.

As long as they all have the same behavior with regards to speed and torque, it doesnt really matter if you put them in series or parallel.For above,I recommend in parallel.

Make sure that the battery can source as much current as each motor X 9 safely.Since its for a toy for a kid, I definitely will not suggest a li-po battery, choose a lithium ion battery for that voltage and power combination.

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  • \$\begingroup\$ Thanks for your advice, Rupin. Unfortunately, I haven't been able to find any specs for those generic motors, but I did see that the iPhone 3G uses a 3.7V Li-ion battery, so would it be safe to assume these motors are happy in the region of 3V? Current I'm a bit lost on though - I did see a replacement iPhone battery which is 1600mAh, but I'm not really sure how that's spread across the phone. \$\endgroup\$ – kodamapixel Oct 26 '11 at 11:20
  • \$\begingroup\$ Wiring motors in series generally doesn't work well unless the motors are connected mechanically. Otherwise, if one motor is turning at the other not, the one which isn't turning won't have much torque. \$\endgroup\$ – supercat Oct 26 '11 at 22:55

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