building a ceramic mic? - Page 1
Forum section: electronics / beginners

author: Deactivated-1
author_rank: Frequent Contributor
timestamp: October 21, 2022, 05:38:58 pm
content: My idea was to put some clip leads on a salt crystal and amplify ithaven't found any info on how these mics are actually constructed, on the types of crystals or ceramics that are used.

author: TimFox
author_rank: Super Contributor
timestamp: October 21, 2022, 06:04:01 pm
content: The usual source for such lists:https://en.wikipedia.org/wiki/List_of_piezoelectric_materials

author: jonpaul
author_rank: Super Contributor
timestamp: October 21, 2022, 07:23:11 pm
content: $0.50 from mic element mfgj

author: jonpaul
author_rank: Super Contributor
timestamp: October 21, 2022, 08:55:32 pm
content: Tim: Most mics nowadays re ECM with integrated FET buffer.Some are MEMS.The old ceramic mics were lead zirconate titanate, PZThttps://en.wikipedia.org/wiki/Lead_zirconate_titanateThin ceramic disc is plated with an electrode on either side.Easily damaged by stress or heat.Most elements are already plated and leads attached.We bought ECM elements from Primo in 1980s. possible they still have PZT.https://primomic.com/products/Jon

author: TimFox
author_rank: Super Contributor
timestamp: October 21, 2022, 09:27:54 pm
content: Quote from: ELS122 on October 21, 2022, 08:41:15 pmLiterally: "haven't found any info on how these mics are actually constructed, on the types of crystals or ceramics that are used."Be careful with commas.I suspect that the old-fashioned ceramic slabs were metallized with silver paint, fine silver powder suspended in a volatile binder.

author: jonpaul
author_rank: Super Contributor
timestamp: October 22, 2022, 05:59:13 am
content: Tim, the electrodes are as mentioned metallized silver paint, or vacuum deposition/sputtering.The electrode thickness and uniformity will affect sensitivity and freq resp.The PZT are still used in ultrasonic transducers (TX and RX) nowadays.The PZT microphone is obsolete as ECM are cheaper, high V out and smallerJon

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: October 24, 2022, 01:08:26 pm
content: Ceramic mics are still used in many less expensive radios, like CBs.The "Ceramic" element took over from Rochelle Salts, You can get Rochelle Salt today.Then you have to put the salt into a substrate and attach leads. That is the hard part.The ceramic manufactured is the equivalent of Rochelle Salts in a substrate. Cheaper and more stable. Different materials but works the same.Most "Crystal Mics" today are the Ceramic variety where the disc of ceramic is attached to a diaphragm to pick up sound waves and then two leads to take the resulting electric signal to an amp.There are also crystal (or ceramic) headphones. These obviously work in reverse. A crystal mic or a dynamic mice can work as a small speaker. But not well.Almost all microphones today are Electret mikes, they require a little power and are very small and have really good frequency response. All cell phones use electret. They are really a miniaturized capacitor mic. A FET amplifier is in the electret "package".If you wish to experiment, you can get an old ceramic mic with a built in amp and look at the output on a scope.If you have a CB shop around, you can get a broken mike for free and take it apart.Currently the brand "Super Star" is cheap and really good "Crystal" mic. (really Ceramic)Look at this:https://www.shure.com/en-US/performance-production/louder/the-history-of-crystal-microphones-and-artifacts-from-the-shure-archives

author: wraper
author_rank: Unknown
timestamp: October 24, 2022, 01:33:38 pm
content: Quote from: Wallace Gasiewicz on October 24, 2022, 01:08:26 pmBasically all modern phones use MEMS microphones. Even 10 years ago finding electret microphone is a phone was not that common.

author: Wallace Gasiewicz
author_rank: Super Contributor
timestamp: October 24, 2022, 02:12:32 pm
content: Sorry, I deeply apologize, I was including MEMS with electret mics.

author: TimFox
author_rank: Super Contributor
timestamp: October 24, 2022, 02:23:54 pm
content: Going back, ceramic piezo elements replaced crystal elements since many of the crystals are hygroscopic.However, here is an interesting project to make Rochelle salt crystals at home:https://rimstar.org/materials/piezo/how_to_make_rochelle_salt_piezoelectric_crystal.htm

author: wraper
author_rank: Unknown
timestamp: October 24, 2022, 03:21:29 pm
content: Quote from: Wallace Gasiewicz on October 24, 2022, 02:12:32 pmMEMS have nothing to do with electret, they are either capacitive or piezoelectric.