Beating Heart Exhibit

The Junior Museum of Bay County (www.jrmuseum.org) is a children's museum located in Panama City, Florida. The Museum was created in 1967, and moved into its current facility in 1981. The Museum's outdoor exhibits include a Boardwalk and Nature Trail, a Homestead Village, and a retired Bay Line (Atlanta and St. Andrews Bay) locomotive. The permanent indoor exhibits include the Imagine Me area, the Discovery Depot, the Nature Corner, Hands-On Science, and most recently opened, the Body Works Room.

The Body Works Room includes large airbrushed paintings of a human heart and of a set of lungs in a ribcage. Located in front of the heart painting is a large metal kids-type exercise machine, consisting of a lever arm attached to a damping piston to provide resistance. I came up with the idea of using the lever arm to animate the heart painting. The idea was to use a BASIC Stamp to sense the movement of the lever arm, then to flash two pairs of rope lights mounted behind slots cut on the heart picture, outlining the four chambers of the heart. Blue lights form the left heart chambers (venous blood to the lungs), and red lights mark the right chambers (arterial blood from the lungs). The upper heart chambers would flash first, followed by the lower chambers, with speakers providing a thump-THUMP sound at the same time.

To sense the movement of the lever, I mounted a MEMSIC 2125 dual-axis accelerometer inside a small project box, to serve as a tilt sensor. The box is mounted on the end of the lever arm right next to the pivot point of the lever. Behind the panel with the heart picture I mounted the control box. The controller is a BASIC Stamp BS2-IC mounted on a BASIC Stamp 2 Carrier Board, with a Sound Module AppMod (with speaker removed) attached on the edge opposite the serial port. The two boards together are installed inside a SERPAC (www.serpac.com) A-42 enclosure with DB-9 cutouts on both ends. The programming port for the BASIC Stamp Carrier Board is brought out through one end, and the connector to the sensor box cable is located in the other. Mini phone jacks provide the connections for audio input (for loading sounds into the Sound Module), audio output (to drive an external set of powered speakers), and two control outputs. The control outputs are routed to a pair of solid-state relays mounted in small plastic boxes. The relays' AC terminals are wired inline with the two halves of a Y-style extension cord, allowing the two 3-socket heads to be turned on and off individually. The rope lights are plugged into the extension cord heads, two ropes per circuit. The audio output from the control box feeds into the battery-pack/amplifier for the speakers. Both the controller and the amplifier module are powered by a Radio Shack 9V 1300mA mini AC-to-DC adapter (with a 5V DC regulator for the amplifier's power input).
I preloaded a short audio sample of a single heartbeat into the Sound Module before loading the Beating Heart software. Once the rope lights and other hardware were mounted onto the plywood panel with the heart painted on it. I was able to calibrate the tilt sensor and adjust the timings and angle settings in the software. The beauty of using the BASIC Stamp as the core of this design is that the Beating Heart exhibit can be adjusted, or even completely reconfigured, entirely through software. Having installed the new exhibit in the Body Works Room, the next step is to spend several hours on a few consecutive Saturdays watching museum visitors interact with the exhibit, then making any needed tweaks to the PBASIC code.

I expect that in the future we'll have additional opportunities to create interactive displays for the Museum, many of them built around the BASIC Stamp architecture.

Beating Heart Exhibit (.pdf)
Beating Heart source (.bs2)

About the Author:
I am a research scientist working for the Department of the Navy in Panama City, Florida, and have been doing so for the past 20+ years. I've spent most of that time working in real-time and embedded software design and development. I got started with BASIC Stamps in late summer 2004 when I bought a "What's a Microcontroller?" kit at a local Radio Shack. I already knew what a microcontroller was, but it looked like a cool little gadget to play with, so I took one home to try out. I had so much fun with my little Homework Board that when I came up with the idea for the Beating Heart project, I quickly discarded my original idea of using discrete 555 timers and IR emitter/detector pairs and decided to make it a BASIC Stamp project.