Arduino heart rate monitor

[Wolf] had a Polar brand exercise watch that wirelessly monitored a chest strap that sends it heart rate data. It sounds like there’s some way to transfer data from the watch to a computer, but it’s only meant for use with Polar’s website. He wanted to do a little more with the equipment so he ditched the watch and built an Arduino-based heart rate monitor.

He’s still using the chest strap and was happy to find that SparkFun sells an OEM receiver for it. Just add a 32.768 kHz clock crystal and an optional antenna wire and you’re up and running. Once the receiver finds a transmitting chest strap, it will pulse an output pin with each beat of the heart. [Wolf] used the D2 pin of an Arduino Uno to connect to the receiver because this pin corresponds to one of the ATmega’s external interrupts. A rolling average of five inputs are used to help smooth the display data, which is shown on the 2.8″ LCD screen seen above.

Controlling a CGA Monitor with an Arduino

CGA monitors may not be an amazing technological advance these days, but they can generally be found very cheaply. Additionally, they have a DB-9 connector and work off of TTL ranges (0-5VDC) making them ripe for experimentation. This hack takes advantage of all of these aspects to bring you an Arduino controlled CGA monitor.

One problem with experimenting with one of these monitors is that they are not that well documented. Fortunately, the detailed write up for this hack goes over some of the timing and frequency issues that one may encounter with this particular monitor. The article gives an Arduino pinout and the program used to drive the monitor with very detailed comments.

Although this hack is by no means a finished product, the now blurry test pattern seen above gives a pretty good proof of concept. It will be exciting to see if this hack inspires any other microcontroller-based projects. For some further information about CGA monitors, Wikipedia also has a fairly in-depth write-up about the technology.

Motion activated monitor wakeup

This hardware is used to keep a computer monitor awake when there is motion in the room. The monitor displays important information for firefighter in the vehicle bay, but only needs to be on when they are getting ready to go out on a call. The solution is a simple one, a PIR sensor combines with a mouse for motion sensitive input. When the PIR sensor detects motion it causes a mouse button click via a 2N3904 transistor. Now the monitor will not waste power or have burn-in over the long term, but whenever someone is in the room it will be displaying the information that the emergency workers need to know.

[Thanks Andy]

Apple Studio Display connector ports

[Warrior_Rocker] pulled off his own Apple Studio Display hack by removing the cable and adding ports. As we saw in Wednesday’s post, these displays use a cable with a proprietary connector that combines DVI, USB and Power. Instead of altering the cable, [Warrior_Rocker] removed it completely. By wiring up a standard barrel jack for power, a USB type-B socket, and a DVI port, he can now use standard video, power, and USB cables to connect to the monitor.

This project was actually submitted to us on May 25th and we missed it. It’s sad that sometimes tips fall through the cracks, and we’re sorry that we missed this particularly well-executed hack. [Warrior_Rocker] wrote in asking why his project didn’t qualify after seeing the similar post on Wednesday. So please don’t take it personally if your project doesn’t get posted. If you think it fits right in here at Hackaday and haven’t heard anything after two weeks or so, consider sending to us again.

Normal connectors for Apple Studio Display

[Sherry Wu] sent in a link to her Apple Studio Display hack. She got her hands on the 17″ display which has a proprietary Apple Display Connector that rolls signals for DVI, USB, and 25V power into one plug. Convenient right? Not if you want to use it on a machine that has standard video connections. No problem, she got out her meter and figured out which wires belong to each signal. After some soldering she now has a DVI connector for the video, and a 24V bench supply is standing in for power until a dedicated unit arrives. No luck so far at getting the USB and hotplug detection to work but she plans to keep going until that’s accomplished.

Looks like you can pick these displays up refurbished for as low as $75. Might not be a bad addition to your home setup if you’re willing to do some soldering.

Save a baby, nursery temperature monitor

Yes, you could argue this Nursery Room Temperature Monitor is simply an LED and an Arduino with a temperature sensor, but [Jay] really did put more thought into the process. For instance he stuck with AVR, built a wooden base and sanded globe, and even included schematics and source code. Plus, SIDS is no laughing matter and the more you know, the more it can be prevented. Back on point, one thing we would add is PWM for a more gradual change in color. What would you add?

Continue reading “Save a baby, nursery temperature monitor”

Whole house current monitoring

[Debraj Deb] put together a current monitoring device that interfaces with the circuit box at his house. The system is controlled by a PIC 18F4520 and uses an LM358 Op-Amp to rectify the AC signal, as well as an MCP6S21 for range adjustments for detecting both high or low current loads. The data displayed on a character LCD includes average, RMS, and peak current. For now the data is saved to an EEPROM and can be dumped using a serial connection but [Debraj] plans to add a GSM modem so he can send energy use data to his cell phone.

[Thanks Ganesh]