I am looking for motors that can vibrate with frequencies from an audio source. They should work like contact speakers. I think LRA motors could work.
I have experimented with some vibration motors that I got from old smartphones, and I also bought several models since.
What I have found out is that the typical DC (1027, 1030, etc) don’t work well with audio signal. I think AC motors have a more similar mechanism to speakers.
My question is what should I consider? Does any LRA vibration motor would work for me?
Thank you in advance
Hello alanahued,
Thank you for contacting Digi-Key TechForum. I don’t believe any of the LRA vibration motors are able to emit sound nor are they designed for that, although I have never actually tried.
You may want to take a look at below alternative options:
Click here for speakers
-Notice there is some piezo technology in this category also
Hello @alanahued, You may want to look at audio exciters. PUI Audio has an article that goes into more detail at The Invisible Speaker – PUI Audio eXciters.
Hi Scott! Thanks for your response. I’ve worked with exciters as well, but for this project they are too big, even the smallest one… I will check again the models, maybe I missed something. 
Hi Ryan, thank you for your reply. I have worked and experimented with them. I got a couple from old smartphones and they transmit audio perfectly fine for my project. Nevertheless, I don’t know how to identify the model of the ones that work. All the other models I bought didn’t work but I later realized that they were all DC, so hence my question
Hi alanahued,
Thank you for your reply. Since a speaker can only operate on an AC voltage, yes this makes sense that you would need an AC motor.
You may want to take a look at below options, these are the AC powered LRA motors, which you may already have found:
https://www.digikey.com/en/products/filter/motors-ac-dc/178?s=N4IgjCBcpgHAzFUBjKAzAhgGwM4FMAaEAeygG0R4AGAdgCYwIBdIgBwBcoQBldgJwCWAOwDmIAL5EAtHSQhUkfgFdCJciACsIJpJBSAnHIXLVpSBWbjds8yABuAgEZ8M7AcSEgiWF9vFA
I’d look at something like VG0825001D
Otherwise there would be methods you could bias an AC voltage to turn it into DC, possibly using a comparator or a transistor, or just use an operational amplifier to boost up the voltage into something high enough to half wave rectify with schottky diodes.
If it were me I’d use an op amp to drive an Analog to Digital (ADC) converter on a microcontroller and then use the micro PWM signal to drive a transistor connected to the motor but it sounds like you’re not trying to go embedded microcontroller with this project.
Thanks Kristof, I will give it a shot with this model. I am unfortunately not trained in electronics, but I can tell you it should only be able to play the frequencies from an (3W amplified) audio player. I have done it it without microcontrollers or any other component except for the player itself.
I guess I will buy 2 or 3 different models and see how they react.
Thank you all for your input!