Uses for piezo transducers from old smoke alarms

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)