UPDATE: The site linked has disappeared but someone in Korea has captured the heart beat schematic I think?
Here’s a cool DIY circuit that you can make.
It’s a heart rate monitor that you can use for your next golf outing or jogging.
One day whilst walking through the town centre in Manchester (probably on the way to Maplin!), I came upon a heartbeat measuring machine – here, you had to place a finger into a “thimble”-like sensor, and hey presto, your hearbeat was measured and shown on a large LED display! Back then, I only had a very vague idea as to how something like that actually worked, but after looking in magazines, and tinkering around, I came up with a small circuit.