Connecting multiple 3v vibration motors to Uno.

Using Arduino Motors, Mechanics, Power and CNC
1

Hi, another newbie here, would be grateful for help please.

I need to connect a number of vibration motors to the Uno so that only one vibrates at any time, under control of the sketch. The motor spec is on http://www.robotshop.com/eu/PDF/solarbotics-vpm2-vibrating-motor-specs.pdf. I'm not sure which specs are relevant, but it's 3vdc, 80mA and 12000 rpm.

I've worked through the introductory projects in the kit I bought, including one to control a single motor, and one to control 8 LEDs (via a register) in the way I want to work (ie send a digit from 0 to 9 to tell it which LED to light up). The breadboard diagrams for these are at http://oomlout.com/products/ARDX/ARDX-circuit-sheets.pdf, circuits 03 and 05. I can't see any spec for the motor on the oomlout website.

I've browsed through a number of previous queries on controlling motors, but haven't been able to pin down exactly what I need, mainly because I think I'm still too unfamilar with the terminology.

My questions are:

1: I've tried connecting the vibrating motor to the same circuit and sketch as Circ03, but get no response. From the other queries I've read I think that must be because the motor is a different spec, but not knowing the original spec means I don't know what's different. Can anyone advise if I need a different diode, transistor and/or resister for this motor please? Should I run it from the 3.3v pin rather than the 5v? Is there anything else I should change.

2: Some of the query threads suggest that a motor needs to be powered separately from the Arduino - can you advise please how I do this? (ie how would the additional power supply fit into the circuit?)

3: I'm hoping that, once I get the motor circuit right, I can replicate {transistor, resistor, motor, diode} combination in place of each {resistor, LED} in the 8 LEDs circuit (Circ05). Is there any reason why this might not work? Again, advice on how an additional power supply would fit into the bigger circuit would be very welcome.

Many thanks

2

famulus:
2: Some of the query threads suggest that a motor needs to be powered separately from the Arduino - can you advise please how I do this? (ie how would the additional power supply fit into the circuit?)

An Arduino running off USB has about 400 mA of 5V power to spare. That should be plenty for your tiny motor.

3

Using ULN2003 darlington array or similar (with clamp diodes) would both provide sufficient current and lose perhaps 1V (so you'd need about 4V supply or a 12 ohm resistor in series from the 5V rail). Ensure generous decoupling to control any spikes from these motors (they are very small so decoupling ought to be able to handle this well, perhaps 100uF electrolytic + 0.1uF ceramic).

With larger motors you'd normally avoid running from the same supply, but I think these motors are too tiny to need that precaution.

If you wanted to use fewer output pins then a shift register like the 74HC595 could be used to drive the inputs of the ULN2003