Nick Pennella

Project Write-up

Description:

For this project I have chosen to implement Darrell Bishop’s Marble answering machine. This idea was first brought up in the early 90’s while Bishop was working on his graduate work. His idea was to have a tangible interface to a very standard device, an answering machine. The idea for this was fairly simple; represent each message that has been left on a simple telephone answering machine by a tangible object, in this case a marble. Once a message was left on the machine, a marble would drop out of the machine into a tray. In order to play back your message, all you had to do was simply re-insert the marble back into the machine and the marble would trigger some mechanism that would play back the message. Unfortunately, Bishop never got around to implementing his idea in any practical way. He left of the idea and concept as an exercise for a grad student to implement (someone like me). Using some basic knowledge of electronics and some help from the logochip, I hope to build the same, or similar interface that Bishop had originally perceived.

Subcomponents:

This project can be broken down into a number of subcomponents that will make up the total structure. The components for this system would include a color sensor (for detecting which marble matches which message), a Hopper system (to dispense the marbles), a digital recorder (to record the messages), and a telephone interface circuit.

One of the major sub-components to this system is a color sensor. Since color sensors are traditionally very expensive and are not all that widespread, it would be my first and most daunting task to try to come up with a design to implement one. The design I have chosen for this circuit was based on a couple of designs that used LEDs and refraction to take a measurement. The basic idea is to have a set of 3 LEDs shine on a given target, one blue, one red, and one green. Then by using a phototransistor you can take readings from the intensity the amount of light that is reflected off for each one of the colors, and deduce what color it is. The layout for each of the items would look something similar to the following:

Where R is the Red LED, B is the blue LED, G is the green LED and P is the phototransistor. Once wired up, I would simply have to apply a current to each one of the LEDs in sequence using the logochip and record each one of their measurements. Certain “calibration” may have to be done in order to get the type of response that I am looking for. One choice that I did make when making this circuit was to use a phototransistor rather than a more standard approach of using a photo resistor. I made this choice due to the fact that photo resistors need time to clear before applying power a second time, otherwise you would only be able to take approximately 2 readings in a second because of the average amount of time it would take to clear the cell.

The second component would be a drive system to get the marble from a storage location to a tray to display for the user. In order to do this I have created a new and original design that was inspired by a trip to an average vending machine. The idea is to use a spiral from a notebook to drive the marble from a marble storage location to a marble display tray, much like the way potato chips are dispensed from a vending machine. This design involves using a length of PVC pipe along with a spiral from a used notebook along with a motor. The basic design is illustrated below:

Using either a handy cricket, or a logochip I would drive the motor to pull out a marble from the funnel like hopper down the PVC tube and deposit the marble into the tray. In order to be efficient, right before the marble is deposited, I would take a measurement from the color sensor.

A piece that would be important to have would be the subcomponent that plays back the messages. This is rather easy to implement once I conquer the color sensor. This would have to be nothing more than a simple ring of PVC cut about ¼ inch long with one of my custom designed color sensors at the bottom. The PVC pipe (the diameter of which is smaller than the diameter of the marble) would be no more than a holder, which the marble can be placed on so that the message could be played back.

The most important piece to this puzzle would be digital device in which I would record messages with. This device would probably have to be some sort of purchased device, seeing I can’t really think of a way to implement a cost-effective part with my limited knowledge of electronics.

The final and most worthwhile piece is the telephone interface. Since the telephone standards are widely published, I would implement a set of code to deliver the required signals to the telephone line through the use of an RJ11 input. A cricket or logochip may be required to create this as a bus enabled device to have the extra feature of interfacing this with either a logochip or the device that will do the digital recording.

Milestones:

Goal	Date Due
Come up with a design to move the marbles from some sort of storage area into a tray.	Completed
Research a way to detect color using some sort of photo sensing or reflecting or LED device	Completed
Implement a cricket bus enabled device to perform color sensing, which will deliver a number (corresponding to a color) as it’s output.	3/22
Create the PVC tube structure that will hold and move the marbles, and hook up a notebook spiral to a motor.	3/23
Hook up the structure to a logochip, which will act as a master to drive the contraption and take sensor inputs.	3/24
Hook up a digital recording circuit that will deliver a signal to the logochip once a message is received to spit out a marble	3/26
Implement the playback feature using a piece of PVC and a color sensor and deliver its outputs to the master logochip.	Time Permitting
Implement a telephone circuit to answer a phone call and then deliver the output to the digital recorder	Time Permitting

Parts and Cost:

Part	Quantity	Cost	Description
Jameco 120221 Phototransistor	2	$1.95 each	The phototransistor needed to implement the color sensor
Ultra bright Red LED	2	$0.99 each	Color Sensor part
Ultra bright Blue LED	2	$0.99 each	Color Sensor part
Ultra bright Green LED	2	$0.99 each	Color Sensor part
Marbles	1	???	The marbles needed for the device
PVC piping	1	< $3.00	Miscellaneous PVC needed (less than a foot total)
Motor	1	$1.50	Motor needed to drive the spiral
Digital Recorder	1	???
RJ11 Telephone interface	1	???

Integration Plan:

Now that I’ve described the total design, I need to talk about what I need to do to put it together, and what I hope to achieve by the time Bot-Fest rolls around. Although this task seems a little bit daunting, I hope by the time I need to perform a demo that I have at least a working ball dispenser, and a set of color sensors. Ideally, I would like to push a little bit further ahead and get a digital recorder up and running but I don’t think there is enough time (at least for this first demo).

In order to piece the individual subcomponents together I was picturing myself using a single Cricket as a master controller. The cricket (through the use of the cricket bus) would drive each one of the color sensors as well as drive the mechanism that dispenses the marbles. The color sensors for this project are going to be no more than a simple logochip bus device that will take a reading when sent a signal and deliver a result. The result would then be sent to the Cricket who would save in an array (indexed by color) a number. For Bot-Fest, I would like to have this mechanism rigged in such a way that when the user presses a button a marble would be dispensed, and the color would be displayed or beeped so that the user knows what type of color was dispensed. This would a huge step in making the marble answering machine a reality.

The next step once the Bot-Fest portion is complete is to handle the digital recording of a telephone line. This would be a multi-step process in which I would have to buy/integrate a circuit that would either have or would have to be driven by a simple RJ11 interface (possibly through the use of a phone device as a device on the cricket bus). This functionality would have to be added time permitting.