How to test an ultrasonic toothbrush - Page 1
Forum section: electronics / beginners

author: makerman
author_rank: Regular Contributor
timestamp: July 30, 2024, 10:09:04 am
content: Hi, my friend bought an ultrasonic toothbrush for her pets and she's not sure that it's working.There are two contacts going from the body to the head, would a frequency counter be able to test it ?She lives in another country so i'll send her one of my little DDS counters if anyone can confirm that the brush can be tested like this.Thanks, Gary.

author: Phil1977
author_rank: Frequent Contributor
timestamp: July 30, 2024, 10:36:29 am
content: Sorry to say it provocative but if you need a measuring instrument to see that a toothbrush is working then it´s not necessarily an electronic problemMost of the sonic toothbrushes are just sonic, not ultrasonic. If it´s really an ultrasonic one you should anyhow see the action if you bring it in contact with some foaming agent or even just water.If you tell us the type of toothbrush, it´d be easier to propose a functional test for it.

author: Zero999
author_rank: Super Contributor
timestamp: July 30, 2024, 10:40:41 am
content: According to Wikipedia, 1.6MHz is the most common frequency used.https://en.wikipedia.org/wiki/Ultrasonic_toothbrushThe oscillator might not work when no head is fitted, so connecting a frequency counter to the contacts isn't a good test.

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2024, 10:41:08 am
content: Irrc, the standard shop demo for Philips sonic toothbrushes used to be a sachet of liquid (probably water with a little detergent) with the brush head being applied to the outside.If the brush is truly ultrasonic, the pets will hate it. They have much more extended high frequency hearing.Edit: MHz?That doesn't sound right. (1.6M oscillations per minute would make more sense... 26.6kHz)

author: Zero999
author_rank: Super Contributor
timestamp: July 30, 2024, 11:24:51 am
content: Quote from: Gyro on July 30, 2024, 10:41:08 amI know Wikipedia isn't always right, but other sources say 1.6MHz.https://www.emmi-dent.com/c/Ultrasonic-toothbrushes/https://news.google.com/newspapers?nid=2457&dat=19940216&id=JagzAAAAIBAJ&pg=1353,151368https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7175112/This is well above the frequency range of pets, so won't cause a problem.

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2024, 11:34:14 am
content: I'm just wondering how you get the far end of a toothbrush bristle to move mechanically at 1.6MHz.

author: pcprogrammer
author_rank: Super Contributor
timestamp: July 30, 2024, 11:41:30 am
content: Quote from: makerman on July 30, 2024, 10:09:04 amSlightly beside the topic, but sending something like a DDS counter from the UK to I assume an European country will cost you or the receiver import duties. Customs won't see it as something that will be returned to you and tread it as a gift for which duties have to be payed.

author: Zero999
author_rank: Super Contributor
timestamp: July 30, 2024, 11:42:11 am
content: Quote from: Gyro on July 30, 2024, 11:34:14 amSound waves are longitudinal, so I imagine it propagaes along the bristles and more through the fluids, i.e. water and saliva, than actually moving the bristles back and fourth at 1.6MHz.

author: Gyro
author_rank: Super Contributor
timestamp: July 30, 2024, 11:45:37 am
content: Oh yes, I was just going to add 'axially'. I'd just never heard of such things before.

author: pcprogrammer
author_rank: Super Contributor
timestamp: July 30, 2024, 11:50:27 am
content: Quote from: Gyro on July 30, 2024, 11:34:14 amBy the looks of it with a piezo element pushing against the but of a bristle group. Impressive.

author: makerman
author_rank: Regular Contributor
timestamp: July 31, 2024, 08:38:02 am
content: Thanks for the replies.Yes she tried water and gel but no foaming, the unit charges to green light status.It's this one :https://www.emmi-pet.com/p/emmi-pet-basic-set/0043She emailed tech support so waiting for an answer from them, but she's in RF where tech support isn't so reliable :/

author: Phil1977
author_rank: Frequent Contributor
timestamp: July 31, 2024, 08:57:53 am
content: Quote from: makerman on July 31, 2024, 08:38:02 amOkay, that thing is ultrasonic and not only sonic.Anyhow, I think it will be difficult for someone who has never used a scope before to test this thing electronically. I´m quite sure that the ultrasonic generator uses some kind of resonant circuit to reach the MHz-oscillation frequency. That means you can not test the handle with the driver for itself, you probably need to test everything in an assembled state.There would be more than one possibility to electronically detect the oscillation. But for a normal consumer it will be much easier to check the efficiency more directly.Tell her to dive the brush head into sparkling water and then switch it on! I´m serious, ultrasonic waves are often used to degas liquids, if the generator is working you should clearly see the water bubbling up as soon as the ultrasonic generator is activated. If it can't significantly degas sparkling water, then it also won't be able to remove dirt.

author: MrAl
author_rank: Super Contributor
timestamp: July 31, 2024, 09:17:59 am
content: If the frequency is less than 100kHz you can feel it on the skin by touching it. That's what ultrasonic welders use I think.However, I think the range of ultrasonic is 20kHz and above, so even 2GHz or even higher.The word ultrasonic could be taken as "above sonic" which would simply mean higher than sound, and sound we usually associate with human hearing which the range is usually taken to not exceed 20kHz (although it could be a little higher). I suppose that would include 10GHz it just depends on if anyone made anything that goes that high yet.

author: makerman
author_rank: Regular Contributor
timestamp: July 31, 2024, 10:52:16 am
content: Thanks, it failed the testTech support has arranged a call with her, hope it's not a dud, seem to be a lot of scammers in RF since the sanctions.

author: Kleinstein
author_rank: Super Contributor
timestamp: July 31, 2024, 12:34:14 pm
content: There are 2 questions: does it actually produce a significan amount of ultrasound and does this actually help cleaning.The normal ulrasonic cleaners use high amplitude at some 40 kHz (so relatively low frequency) to create cavitation and the actual cleaning action is from the cavitation. One can here them because the cavitation can happen at a lower rate. Reduce the amplitude below the threshold and the cleaning action is essentially gone.The problem for a toothbrush is that this high intensity can be damaging to tissue (AFAIK especially nerves) - so nothing one wants in the mouth without care.

author: iMo
author_rank: Super Contributor
timestamp: July 31, 2024, 02:03:36 pm
content: Quote from: Kleinstein on July 31, 2024, 12:34:14 pmThe dentists will be happy if that ultrasonic toothbrush helps with creating the cavities..

author: themadhippy
author_rank: Super Contributor
timestamp: July 31, 2024, 02:32:48 pm
content: Quotebuy the dog a bone instead

author: makerman
author_rank: Regular Contributor
timestamp: July 31, 2024, 05:23:29 pm
content: Ye if it was a dog that would be my advice, 3 cats though.

author: MrAl
author_rank: Super Contributor
timestamp: August 01, 2024, 12:01:48 pm
content: Quote from: iMo on July 31, 2024, 02:03:36 pmThey are the ones selling it

author: richnormand
author_rank: Unknown
timestamp: August 01, 2024, 05:46:42 pm
content: Quote from: Zero999 on July 30, 2024, 10:40:41 amIf the thing is actually working at 1.6MHz you might be able to pick up the electronics radiated signals with an AM radio near the end of the band?What is the AM band in the UK compared to US and Canada?

author: Zero999
author_rank: Super Contributor
timestamp: August 01, 2024, 08:18:05 pm
content: Quote from: richnormand on August 01, 2024, 05:46:42 pmIt's 1.6MHz in the UK.A radio might detect it at very close range, but it still wouldn't definitively prove it's emitting ultrasound, just the oscillator is working.

author: richnormand
author_rank: Unknown
timestamp: August 01, 2024, 09:36:53 pm
content: Agreed.One of the comments was about seeing if the electronics worked at all.That would give a partial answer.