RoGeorge Attacks a Pulse Meter

The “Crivit Sports” is an inexpensive chest-strap monitor that displays your current pulse rate on a dedicated wristwatch. This would be much more useful, and presumably more expensive, if it had a logging option, or any way to export your pulse data to a more capable device. So [RoGeorge] got to work. Each post of the (so-far) three-part series is worth a read, not the least because of the cool techniques used.

In part one, [RoGeorge] starts out by intercepting the signals. His RF sniffer? An oscilloscope probe shorted out in a loop around the heart monitor. Being able to read the signals, it was time to decode them. Doing pushups and decoding on-off keyed RF signals sounds like the ideal hacker training regimen, but instead [RoGeorge] used a signal generator, clipped to the chest monitor, to generate nice steady “heartbeats” and then read the codes off the scope without breaking a sweat.

With the encoding in hand, and some help from the Internet, he tested out his hypothesis in part two. Using an Arduino to generate the pulses logged in part one, he pulsed a coil and managed to get the heart rates displayed on the watch.

Which brings us to part three. What if there were other secrets to be discovered? Brute-forcing every possible RF signal and looking at the watch to see the result would be useful, but doing so for 8,192 possible codes would drive anyone insane. So [RoGeorge] taught himself OpenCV in Python and pointed a webcam at the watch. He wrote a routine that detected the heart icon blinking, a sign that the watch received a valid code, and then transmitted all possible codes to see which ones were valid. Besides discovering a few redundant codes, he didn’t learn much new from this exercise, but it’s a great technique.

We’re not sure what’s left to do on the Crivit. [RoGeorge] has already figured out the heart-rate data protocol, and could easily make his own logger. We are sure that we liked his thorough and automated approach to testing it all, from signal-generator-as-heartbeat to OpenCV as feedback in a brute-force routine. We can’t wait to see what’s up next.

Hackaday Prize Entry: HeartyPatch

[Ashwin K Whitchurch] and [Venkatesh Bhat] Have not missed a beat entering this year’s Hackaday Prize with their possibly lifesaving gadget HeartyPatch. The project is a portable single wire ECG machine in a small footprint sporting Bluetooth Low Energy so you can use your phone or another device as an output display.

Projects like this are what the Hackaday Prize is all about, Changing the world for the better. Medical devices cost an arm and a leg so it’s always great to see medical hardware brought to the Open Source and Open Hardware scene. We can already see many uses for this project hopefully if it does what’s claimed we will be seeing these in hospitals around the world sometime soon. The project is designed around the MAX30003 single-lead ECG monitoring chip along with an ESP32 WiFi/BLE SoC to handle the wireless data transmission side of things.

We really look forward to seeing how this one turns out. Even if this doesn’t win a prize, It’s still a winner in our books even if it only goes on to help one person.

Wearing a Homemade EKG Whilst Base Jumping!


[Andrew Wilson] is a pretty extreme guy. He base jumps for fun, and is also a hacker. And while you can try to explain the awesome adrenaline rush that comes with this kind of extreme hobby, it’d be nice if you could show it off, you know, quantitatively. So, he decided to make his own EKG, pair it with his GoPro, and go for a jump!

An EKG is an electrocardiogram — a fancy term for a heart rate monitor — and [Andrew’s] has built his own using a small instrument amplifier circuit. This circuit amplifies the differential signal put out by your heart. The data are fed through an ADC on an Arduino Uno, and then saved to a SD card. He also added a piezo buzzer to try to help sync the data to the video — unfortunately it was too quiet for the GoPro to pick up. So for now he’s stuck with pressing record and start on his EKG at the same time.

Once he was satisfied with a few safe tests, he decided to take it for a base jump. For our viewing pleasure, he’s taken the data collected from the EKG and post-processed it into a nice scrolling graph overlay for the video.

We guarantee your hands will get sweaty as his heart rate goes up as he prepares to make the plunge.

Continue reading “Wearing a Homemade EKG Whilst Base Jumping!”

Build your own ECG heart monitor

Our own Hack-A-Day emeritus took some time out from his showgirl pursuits to pass this along. The ECG was built to pad a resume, but it doesn’t make it less useful. Be warned, too much power could stop your heart. If you build one, triple check everything before wiring yourself up. Basically, an electrical differential is generated by the contraction of muscles in the heart. This slight signal is amplified by an op-amp and sampled with an A/D converter.