Adding a motor to a USB Memory Stick

Hi there,

I've got this idea for adding a small motor to a USB thumb drive, for decorative purposes, but I have some concerns.  I'm considering adding a very small motor such as this one: secure.precisionmicrodrives.com/product_info.php  but I'm weary about the effects of having a motor drawing from the same power as the memory stick.  Might this cause problems during read/write sessions?  Also, I'm not the most electrically savvy person, so I just wanted a second opinion on whether the 5V from the USB (and 100mA?) should be enough to run the motor. (In my case, torque and speed are not huge issues)

I've also noticed that the motor is listed as requiring 3V, and I'm sure since this is such a small and delicate motor, it would probably be damaged by the 5V supply.  Could anybody help me with the circuit elements that would allow for safely operating the motor?


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Neebio (author) 7 years ago
Just thought I'd update this.

I've gone ahead and attempted this. The power from the LED couldn't even turn the motor over, so I've had to pull power straight from the power and ground pins of the USB connector. Also, for the record, a USB memory stick does not require the LED in the circuit to operate. Found that out when I burned the connection pads off the board...

Also, based on simple observation, it would seem that any magnetic or electric field interference that a motor generates has no effect on the memory stick itself, so should be safe without any shielding, assuming of course your not inadvertently creating connections with the motor or its wiring.

I've been keeping photo records of my progress with this project, and this will probably turn into an instructible later...
Neebio (author) 7 years ago
Thanks for all the input!

I've gotten another possible idea for this, however I'm not sure if its viable.  On the USB memory stick, like most, it has an LED installed, that depending on the usage of the stick, will flash or just stay steady.  My idea is to possibly replace the LED with a small motor.

This is a motor I had in mind: secure.precisionmicrodrives.com/product_info.php

Now this motor will not have to run anything too strenuous.  At most, it will be frivolously turning some small brass watch gears most likely with a worm gear attached to the shaft.  That being said, torque and speed aren't a huge issue. 

I've measured the voltage from the power leg of the LED to the ground port of the USB to get an idea of how much voltage is available, as well as the current at the LED.  Here is what I've found:

Voltage going into LED:  1.823 Volts
Current at LED:  6.21 mA

So my question now becomes:

Would this be enough voltage and current to drive that motor with a worm gear, with the goal of simply spinning some brass watch gears?
(My guess is that it would be, but I'd like a second opinion =)    )
Punkguyta7 years ago
As far as being worried about the possibility of read/write corruption, if it is a decent quality thumb drive, I would imagine it MIGHT have the sufficient circuitry to "filter" out the noise. However, the motor itself/and/or it's power leads could "radiate" EMF and cause interference that way, which is unavoidable unless some kind of shielding is accounted for.

5v @100mA is certainly enough to power that motor, they make usb fans and other accessories that have larger motors than that. 

>I've also noticed that the motor is listed as requiring 3V, and I'm sure since this is such a small and delicate motor, it would probably be damaged by the 5V supply.

Not as likely as you'd think, the motor may spin a little bit faster than you'd like for your application, but I believe it would operate okay on 5 volts. If you were worried, a simple resistor in-line of the positive line would fix that issue. As to what value of resistor, I have no clue.
Neebio (author)  Punkguyta7 years ago
Thanks for the input!

I've given the emf problem some thought...

Any thoughts on whether a simple sleeve of metal foil between the motor and the drive's memory, grounded to the usb's ground pin, would work at mitigating any of the possibly damaging EMF?
.  The foil shield will help but you will probably need a filter on the power to the fan (just a capacitor will probably do the job). Keep the power leads as short as possible (less antenna to radiate RF). Using shielded cable for the power leads may help.
.  Instead of dropping the voltage with a resistor, I'd use a 3V voltage regulator. YMMV.
.
.  BTW: that's a gear motor and may be very noisy.
Also might add a diode clamp across the motor, to help absorb any inductive spiking...
.  Great idea. Cheap insurance.
 Also, Read: RF Chokes. I have a whole drawer of small wire bobbins for soldering onto pcb's and they serve as rf filters.