Designing a simple DC Massage device

[crowtor]

Hi there,

My last massage device that I use for my back pain has burned down and it's the 5th or 6th unit that did that so I'm trying to make something more reliable and long lasting.

The current specs I'm thinking about are:

DC Motor up to 12V (preferred 6V), max. 28mm in diameter
2-4 18650 cells

Current motor candidates :
1. https://www.pollin.de/productdownloads/D310493D.PDF
2. https://www.ebay.de/itm/173909902699

My previous devices run 2 problems, I don't know why either of these happened.

- Batterries overheating
- Motor overheating

I'm still missing a controller, I'd love to make it future proof for up to 4 motors.

If there's anyone willing to bear with me, I'd very much appreciate help with any of the issues:

- choosing proper motor
- choosing proper controller
- avoiding either the batteries or the motor overheating

Many Thanks!

 

[alec_t]

Welcome to ETO!

- Batterries overheating
- Motor overheating

You obviously need heavier duty batteries and/or a heavier duty motor. Do you have the specs (Wattage, HP, Watts, running current) for the present motor?

If there's anyone willing to bare with me

This is an electronics forum, not a nudist colony .

 

[crowtor]

Thanks for a swift reply! I do not have any specs of the current motor other then 6V , 10'000RPM. The device manufacturer doesn't specify anything beyond that. The motor itself looks like your regular cheap unbranded motor they put in everything, with cut outs at both sides, 2 wires.

Similar to this: https://p.globalsources.com/IMAGES/...Customized-Shaft-N20-Mini-Vibration-Motor.jpg

 

[DrG]

My previous devices run 2 problems, I don't know why either of these happened.

- Batterries overheating
- Motor overheating

I have never designed such a device, but FWIW, I am wondering about the devices that have gone bad.

Seems to me that if you put a lot of force on the motor (e.g., if you sit back with all your weight on one of those shiatsu devices) then the motor tries to overcome that force and heats up. Not sure about the batteries overheating but maybe it is related to drawing more current than they are happy about providing. I don't know.

So , what I am getting at (and again I have limited experience to base my opinion on) is...do the devices you have been going through have a shutoff for overheating?

For example, the first one I looked at... https://www.amazon.com/Sable-Portable-Massager-Massaging-One-Button/dp/B07HBQJKQL
explicitly states:

• Equipped with overheat protection device and programmed with 20-minute auto shut-off to ensure safety

Maybe the best solution is to buy a better device.

 

[crowtor]

Thanks for the reply. The device in question hasn't been designed for back massage specifically, I've only repurposed it, because it's the only type of device on the market that really works for me. It's small and can be operated by one person, as opposed to those big sticks that you need a second person to operate.

With the motor overheating, your idea is probably correct, as I lay on the device with my back, so its squashed between my back and the mattress. My first device kept the motor running at the same speed and the batteries were overheating. The first motor probably had more torque.

As for the hardware itself, the motor is really cheap and no writings on it are present. I assumed if I used better quality components my problem could be at least mitigated so the motor doesnt burn out after 2-3 months.

Any suggestions as to what type of controller I could use that supports up to 4 motors and is easy to program for someone who can't really write any code? Like with lots of tutorials and support?

 

[gophert]

I opened up a message chair in hopes of repairing it for a neighbor. There were 3 big motors (90VDC @ 1A) to adjust recline, leg position and back message. All motors were connected through high torque worm gears.

The unit failed because one of the steel back message shafts bent and caused misalignment at the wormgear. That 90W motor just shaved the teeth off of the gear.

I'm sure it would have lasted most people a lifetime but my neighbor is a large man (300+ pounds) and the Panasonic chair was clearly labeled "100 kg (220 pound) max."

 

[crowtor]

I actually made a mistake, This is the current motor(21mm in D) and board:

https://imgur.com/QLAE3ak

https://imgur.com/CX1bTQw

https://imgur.com/jSdzSOp

 

[dr pepper]

If you want longevity I'd suggest a brushless motor, as theres no brushes to wear out.

 

[crowtor]

If you want longevity I'd suggest a brushless motor, as theres no brushes to wear out.

That was my initial idea. I thought to use on of those motors they use in rc planes and choppers, but I didn't realise those run in thousands of kv.

What do you think of this one? https://www.ebay.com/itm/263558709233, it seems to already have a driver board inside. What type of controller would I need to run this one? How about 4 of these?

I managed to find data on it from the manufacturer,but it seems like it's not a vibration motor per se

Product Search | NIDEC CORPORATION

www.nidec.com

 

[dr pepper]

I didnt believe it was bldc from the first pic, but looking at the field coils, rotating magnet and the pcb it is.
Looks like a good price too.
Though you'll need a 555 circuit or something to provide it with the pwm signal to make it turn at various speeds.

 

[crowtor]

I didnt believe it was bldc from the first pic, but looking at the field coils, rotating magnet and the pcb it is.
Looks like a good price too.
Though you'll need a 555 circuit or something to provide it with the pwm signal to make it turn at various speeds.

Is this PWM controller going to work? I decided to delay 4 motor version, just to have a single, reliable device on hand.

I got 2x Samsung Q30 18650 cells, these ones. I can just plug these in without anything else to worry, besides not mixing + with - ?

Thanks!

 

[dr pepper]

The speed controller might not work, the motor has a built in driver and accepts a pwm signal, the signal most likely is logic level, a motor power controller isnt the right thing.
You'd probably have to build something, if thats a problem maybe its not the motor for you.

 

[crowtor]

Problems are there to be solved. I found this tutorial, here's a quick diagram from the tutorial :

I assume I don't need the L298N since the motor comes with a driver itself, right? I already ordered 10 motors so there's no avoiding it, gotta tackle this head on.

 

[gophert]

If the motor only needs two wires, then, you are correct, no need for the L298N.

 

[dr pepper]

Yes that might work.
Try pin 6 or pin 7 connected to the motor direction input.
And pin 9 to the Pwm input.
Yes you shouldnt need the L298.
I didnt know you hd technology to program an arduino.

 

[crowtor]

Allright, I got all the parts. Before I start connecting anything theres a FG (1FG) output cable in the motor. Can I leave it unconnected? What would it's use be besides determining the rpm? I couln't find any info on FG/1FG/3FG anywhere. Anyone knows where I can read more about it? That is if I even need it in the first place.

 

[dr pepper]

The yellow wire I think is the one you mean, it isnt required for your setup, a yellow is often found on computer fans, its just used to tell how fast the fan is running, and for diagnostics.
Power, direction & pwm speed command should be all you need.
Fold back & tape up the yellow, or do something so it doesnt short out, it might blow something in the control board otherwise.

 

[ronsimpson]

How about one of these massage "cars" connected to a linear actuator?

 

[gophert]

Allright, I got all the parts. Before I start connecting anything theres a FG (1FG) output cable in the motor. Can I leave it unconnected? What would it's use be besides determining the rpm? I couln't find any info on FG/1FG/3FG anywhere. Anyone knows where I can read more about it? That is if I even need it in the first place.

FG is Frequency Generator (sometimes also Feedback Generator). It gives a pulse from the motor that a system ( CPU. For example) can make sure the fan is still working before it Powers up. Make sure any motor works before actuating. You can use it to make sure a linear actuator is not at the limit (shuts down if pulses stop). Or shuts down if too much pressure is applied and it stops turning. Or you can ignore it.

 

[crowtor]

allright, I'm getting somewhere:

All that's left now is the power switch. I've found this tutorial.

Does anyone know if there are any ready-made boards that have a timed auto shut-down capability?

and how about standalone boards that won't require any signal from the arduino to cut the power after specified time? Something hardware based and analog that isn't reliant on software to execute the shut down.

Thanks!