Virtual wishing well

Virtual wishing well

Permanent installation at Zeum, San Francisco

In some ways, this is like a real wishing well: it is a real container into which visitors drop money; only the water, and its inhabitants, are virtual. Unlike a real wishing well, this provides a small reward for each donation.

This was a fun and rewarding project which allowed me to work with various skilled people, some of whom I’d worked with before, some I hadn’t. The goal was to create a new donation box for the museum, with some type of media element. I was awarded the project by Zeum, and brought in the above folks for specialized tasks. I managed the project, and as usual created an administrative web site to help coordinate people separated by time and space. This was a low-budget project with a short time frame.

Initial concepts

Red Egg Labs provided exhibit and graphic design, and acted as a base of operations and staging area. We quickly agreed on the concept of a virtual wishing well, and they generated the following concept sketches (images link to PDF files).

fountain01 drawing

fountain02 drawing

Concept development


Design development

Concept 1 was chosen, and this model was created:


From here, we began to work out fabrication, hardware and software. The dimensions of the box were designed around the size of the monitor and CPU that were donated by Zeum, a 17″ CRT monitor and a Macintosh G3 desktop. We found a local artist, Steve Chesney, to build the box (thanks to Sasha Harris-Cronin). Red Egg generated these fabrication drawings:

side1   side3   top3

Meanwhile, I tapped Joey Stein to do the electronics to detect when money is inserted. The general idea was for the box to accept both coins and bills. Since the budget did not allow for a bill reader, simple alternatives were explored, and we weighed a single slot against slots for coins or bills only. His innovative solution was a simple and inexpensive set of sensors which would fit into a single slot and distinguish between coins or bills.

 electronix schematic

The sensor is a Hamamatsu digital phoyoreflector, a tiny infrared emitter on a chip with a detector, all in a compact 4mm package. It is the type used for paper detection in copiers, and both coins and bills are able to reflect the IR light back to the chip, albeit at short distances. Six sensors are arranged on a circuit board to span the height of a bill, and are wired to a PIC microcontroller, which in turn feeds the input into the Mac’s serial port. They are spaced so that coins as small as a dime will be seen by at least one sensor. This method does not detect denomination, only a rudimentary distinction between coins and bills, all that is required for this box: coins trigger one type of animation, and bills another.

board_front board_back

The completed board is about the height of a bill, contains all of the electronics, and fits directly into the money slot. It must be positioned precisely so that the sensors are just out of sight and something as thin as a bill will trip them; the opposite wall of the slot is lined with flat black paper, to minimize any stray reflections. Below shows a top view of the unfinished box, with board in the slot; the monitor goes in the large open space directly to the right.


The hardware all sits snugly in the case, the monitor on a shelf above the CPU. The CPU is oriented so that the CDROM drive is accessible, for updating of software or animations. Two Sony SRSZ500 speakers fit beside the monitor, and a keyboard and mouse also fit inside, for maintenance purposes.

In initial testing, heat buildup caused the monitor to shut off, so additional venting was added on the side of the enclosure. Two small ventilation fans were installed, but only one is needed. There remains just enough room for a small container beside the monitor to catch the money.


Steve Chesney did a fantastic job building the box on a shoestring budget. It is constructed of plywood, with aluminum trim. Find out more about Steve’s construction of the box here.

The finished box is located near the entrance to the museum, and oriented so that visitors will encounter it upon exiting.


Graphics, designed by Red Egg Labs, are printed onto heavy card stock and mounted under acrylic. The monitor is visible through an elliptical cutout in the center. (Zeum placed actual currency under the acrylic atop the graphic.)


An attract loop of rippling water plays on the monitor. When money is inserted into the slot, one of the following animations plays:





The software is designed to be easily updated. It consists of a simple application (created in Macromedia Director) which looks in local directories on the computer for Quicktime movies. The program waits for input from the sensors, and when money is inserted, it plays them in order. There are separate folders on the Mac for bill animations and coin animations.

Concept/Software/Integration: Kevin Walker
Box Design: Red Egg Labs
Box Fabrication: Steve Chesney
Electronics: Joseph Stein
Animation: Kevin Walker, Molly Lenore
Zeum coordinator: Audrey Yamamoto