https://stream.echo6.co/videos/watch/7563be94-3ccd-49a3-a2bc-2ac7c5ea2529 Old smoke alarms often have piezo transducers in them. Here's some uses for them in electronic projects. Contents 0:00 Introduction 1:13 Test with audio amplifier 1:48 Test with LED connected 2:31 Use as a speaker - how good? 4:07 Use as a selective speaker for CW 4:43 Use with a crystal set 5:11 Audio oscillator 6:05 Summary PS: If you liked this video please consider supporting Amateur Radio VK3YE by: Subscribing on YouTube, Checking my books page at https://books.vk3ye.com ​​​​​​​​​​​​​​​​, Shopping on Amazon via: https://amzn.to/3iiDQXv​​​​​​​​​​​​​​​ , or, Shopping on eBay via: https://ebay.us/i9DuWP (then if you buy something I'll get a small commission at no cost to you) Sat, 13 Jun 2026 18:03:05 GMT https://validator.w3.org/feed/docs/rss2.html PeerTube - https://stream.echo6.co https://stream.echo6.co/client/assets/images/icons/icon-512x512.png https://stream.echo6.co/videos/watch/7563be94-3ccd-49a3-a2bc-2ac7c5ea2529 All rights reserved, unless otherwise specified in the terms specified at https://stream.echo6.co/about and potential licenses granted by each content's rightholder.