The Timex/Sinclair as an Intelligent Lab Station Terminal

Imagine a science laboratory with up to 16 stations, each containing a computer capable of instrument control as well as analog and digital data collection. Each lab station computer could either display the data as they are being received or store the data. The stored data could then be sent to a larger computer for storage on disk and later analysis and display. The incoming data at the lab station could be sampled at selectable time intervals or, alternatively, sampled at the request of an external signal. In addition, the lab station could generate digital or analog signals for control of stepper motors or voltage-controlled instrumentation used in experiments. A nice thought, you say … but, oh, the expense!

Now suppose that each lab station costs no more than $300 (including the computer, computer memory, interfacing hardware, and CRT monitor); and the large host computer with which the lab station communicates was an unmodified Apple computer. Interested?

During the past few months at Technical Education Research Centers (TERC), while on sabbatical leave from the Physics Department of Hiram College, I have been developing the hardware and software which will turn the Timex/Sinclair microcomputer into the intelligent lab station described above. The T/S 1000 with 16 K memory pack can be purchased for under $100. A small black and white television costs less than $100. The interface hardware which allows the above capabilities has been built and thoroughly tested. And an initial software capability has been developed. The hardware and user-friendly software should not cost more than $100. A $300 lab station is feasible.

The prototype interfacing board (see figure 1) measures 7-1/2 by 5-1/2 inches. It should be possible to reduce the size to about 4 by 5 inches. Consequently, not only will the cost be low, but also the size will be such as to take up very little space at the lab station. The television monitor will be the biggest part of the system.

Preliminary software includes four programs. The first program displays the voltage levels on two of the eight analog input channels of the interface board (see figure 2). A marker on the voltage line for each channel moves back and forth as the level is changed. A program such as this would be helpful during experiment set-up to determine if the voltage levels from the equipment are within the 0 to 5 volt range needed for the interface circuitry.

The second program samples the input voltages and plots the values on a time axis while the voltage is varying. For example, it generates a sine curve on the monitor as a potentiometer is rotated by a swinging pendulum. In its present form, the program plots the curve with 32 large squares. Double this resolution is possible. A curve made up of 64 data points, however, is still much too coarse for most experiments. Therefore, this program would be used in setting up the experiment, not in collecting the actual data.

A third program allows the collection of 500 data points at sampling time intervals of multiples of 100 microseconds. Once the data have been stored in the Timex/Sinclair, the communications portion of the program, together with a receive/send program in the Apple, can transfer the 500 data points to the Apple in one half of one second. The transfer rate is 20,000 bits per second. The connection to the Apple is through the paddle port. Consequently, the transfer of data can be made to an Apple II, and Apple II+, and an Apple Ile with no hardware modification. Once the data have been transferred to the Apple, a high resolution graphics program can be run to plot the data. Figure 3 shows the display which was obtained after a 10 second collection period (500 data points) for a swinging pendulum.

A fourth program has been written which allows the Timex/Sinclair to receive data from the Apple, again at 20,000 baud. In the planning stage is software which will load programs from the Apple into the Timex/Sinclair. With this 160 Press return for receive menu capability, a cassette tape recorder will not be needed at each station. When all is completed, the system with up to 16 lab stations networked to the Apple, will be controlled by the Apple. Each Timex/Sinclair will have the capability to request programs from the Apple. The programs will include those for specific experiments (e.g., the swinging pendulum) and general-use programs.

Since the software is still in the development stage, I would appreciate suggestions concerning types of programs you would find useful in your labs (or any other environments you envision for the low cost networking system). I left TERC to return to Hiram College at the end of March. However, I am continuing work on the project. I hope that general user-friendly software can become a reality by the end of the summer.