Finding a strong vibration motor for a watch

[gregweber]

Hi everyone!

I am having a hard time looking for vibration motors as an electronic part.
My goal is to find the most powerful vibration motor I can that could comfortably be worn in a watch.
The goal is to be able to wake a deep sleeper.
I would be considering a watch form factor that would be somewhat larger and heavier than normal.

My biggest problem is that most vibration motor parts I come across don't seem to actually specify the amount of vibration force produced.
I am hoping to prototype with the motors now and eventually buy in larger quantities at a low price.
I also come across custom vibration motor design companies but am hoping to find something off the shelf.

Do you have any advice for finding a good vibration motor for my use case?

 

[ClydeCrashKop]

Vibrator Motor, Flat, 3VDC
Item #: 32115 MD
Sale: $1.95

3VDC Pager Vibration Motor
Item #: 35958 MD
Sale: $1.25

1.3VDC Vibrating Phone/Pager Motor
Item #: 36040 MD
Sale: $1.25

 

[gregweber]

Thanks for those leads! None of those part descriptions actually state the force that the motor generates

 

[KMoffett]

For prototyping , you will probably have to purchase a bunch of different ones and try them. One-offs are pretty cheap.

 

[DrG]

Thanks for those leads! None of those part descriptions actually state the force that the motor generates

May not be easily found for those little wearables, but a few do:

https://www.murata.com/~/media/webrenewal/products/mechatronics/actuator/pjfv/datasheet_pjfv.ashx - called "vibration quantity" but the 1.2 G makes me think it is what you are looking for.

https://media.digikey.com/pdf/Data Sheets/NMB-MAT/PNN7RB55PW.pdf - same here - see the graph

https://www.tdk-electronics.tdk.com/inf/20/10/ds/2626H023V120.pdf - this one has what you are looking for but it is a much higher voltage device.


You may just want to search through the data sheets at Digikey and the like.

Of course, you could just use one of these https://www.clevelandvibrator.com/Product/33/1015/1900-SI-Kit I'm quite certain it will awaken even the most stubborn sleeper, but it is a bear to wear on the wrist

 

[unclejed613]

Thanks for those leads! None of those part descriptions actually state the force that the motor generates

that depends on the actual RPM the motor is run at. if you noticed the motor RPM numbers were "ballparked". if you can calculate the circumference of the weight's center of gravity, and know the mass of the weight, you then measure the RPM and divide by 60 (so now you have rounds per second). then multiply the RPS by the circumference to get meters per second (or millimeters or centimeters per second) then the formula E=(1/2)MV^2 giving the answer in joules. you could go to all that trouble, but in the end your goal is "can the motion be felt?"

if i were designing something in a watch, i wouldn't worry too much about the amount of force, as long as it's enough to be felt.

this reminds me of a movie called "Our Man Flint"
Flint, ( James Coburn ) had a gadget in his watch that would extend a small lever that would tap him on the wrist and "wake" him up from meditation.

 

[ClydeCrashKop]

https://www.murata.com/~/media/webrenewal/products/mechatronics/actuator/pjfv/datasheet_pjfv.ashx - called "vibration quantity" but the 1.2 G makes me think it is what you are looking for.

I like that one at 240 Hz https://www.bing.com/videos/search?...A3A4F2967B33745B5D05A3A4F2967B33745&FORM=VIRE

 

[DrG]

you could go to all that trouble, but in the end your goal is "can the motion be felt?"

Yes, but....

There are now a number of wearable devices designed to awaken a sleeping driver - or actually one who is getting sleepy.

STEER: Wearable Device That Will Not Let You Fall Asleep

At any sign of drowsiness, Steer will warn you with vibration and gentle electric impulse, so you do not fall asleep while driving.

www.kickstarter.com

Amazon.com: Anti Sleep Alarm for Drivers. Warns up to 5 Minutes Before Drowsiness. Beep and Vibration Doze Alert. Car Truck Safety Driving Warning Device. Stay Awake Nap Detector Technology Alertness System: Automotive

Buy Anti Sleep Alarm for Drivers. Warns up to 5 Minutes Before Drowsiness. Beep and Vibration Doze Alert. Car Truck Safety Driving Warning Device. Stay Awake Nap Detector Technology Alertness System: Multitools - Amazon.com ✓ FREE DELIVERY possible on eligible purchases

www.amazon.com

Amazon.com

Anti Sleep Device for Drivers - Stay Awake! | TBOTECH

Driver Alarm keeps drowsy drivers from falling asleep. This simple anti sleep device for drivers attaches to your ear and sounds an alarm if your head should nod.

www.tbotech.com

If the OP is designing such a device, the specification would be important I would think. If it is for research, the specifications are even more important.

Of course, the awakening stimulus is one thing, the detection of drowsiness/sleepiness is another. There is a good amount of research going on in this area and I would expect to see such devices integrated into the suite of enhancements in modern automobiles.

 

[gregweber]

I am just trying to make a better vibrating alarm watch for normal sleeping at night. I have been frustrated with trying to buy existing products for this purpose.

An energy formula is a good idea to sanity check a published force number. But I think an enclosed vibration motor in particular would be unlikely to give the specifications needed to do the calculation.

Thanks for the links to specs that specify force. I haven't come across those particular motors yet.
The Piezo Haptic form factor looks really great, and I haven't seen this type of part before, but yeah the voltage seems like an AC outlet rather than a watch.

 

[Pommie]

I would imagine that the efficiency of all vibrator motors would be pretty similar, if so, the power usage (V x A) could be a good indication of power (force).

Mike.

 

[DrG]

Thanks for the links to specs that specify force. I haven't come across those particular motors yet.

Just to be clear, the data sheets came from the Digikey products sear https://www.digikey.com/products/en...+motors&pageSize=25&pkeyword=vibration+motors They have 94 different ones according to that search.

Intuitively, I would think that using two vibrators, spaced as far apart as you could manage on a wristband, and alternating their operations might provide or more salient cue, but I have no data to support that.

 

[gregweber]

I read that using multiple vibration motors can be tricky: they can dampen each other and alter the resonant frequency, etc. It is possible if care is taken, but the recommendation was that it is easier to get one strong motor.

Thanks for the Digikey search, I think I wasn't doing my searches right. You can probably see though how many of these don't actually state the force they generate.

 

[unclejed613]

you could also use some kind of spring loaded solenoid. the solenoid actuator could be easily weighed, and you would have a known throw distance and velocity, and you could tailor the drive current amplitude and frequency to get the amount of force you want.

 

[atferrari]

The best I have seen:

A classic alarm clock

Sitting on a tray full of coins.

It works marvels.