This Handheld Tape Reader Can Extract Data From Paper Tape
Although paper tape is now a very outdated technology, this device allows for it to be easily read over USB.
Paper tape
Back in the day before the internet, hard disk drives, or even rasterized displays existed, programs and other data was fed into a computer through punch cards and/or tape. Each row would represent or column, depending on the layout, would hold the value of a single word, and this data could be extracted by running the card through an electromechanical reader. Jürgen Müller, who runs the site e-bastein, sought out to miniaturize the process by building a tiny tape reader that can accept inputs up to a single byte wide (eight bits) and at a feed rate of one meter per second.
Components
Because paper tape relies on using a series of holes and non-holes to denote either a 1 or 0, Müller's first task was to figure out how to compactly read them. His idea involved placing a line of nine LEDs that would emit light in a single direction, and then have a mirrored lineup of detectors that output an analog value in proportion to the amount of light the receive. Essentially, a higher value on a detector indicates a hole in the paper tape, whereas a lower one indicates no hole is present.
To read these signals, Müller added an Arduino Pro Micro that continually checks the analog value of each photodetector and, if the value is above a preset threshold, outputs a 1, otherwise, a 0 is outputted.
Constructing the reader
The vast majority of projects like this would have a pair of PCBs that are inlaid within a 3D-printed enclosure. But instead of going this more traditional route, Müller decided to make his out of eight individual PCBs that each have a special purpose. The top layer carries the Arduino Pro Micro and photodetectors, whereas the bottom layer contains the LED array. At the very center are two mask PCBs held together with double-sided tape that direct the light in a single, outer direction. And lastly, four thinner PCBs act as spacers in order to raise the through-hole components far enough away from the center.
Feeding in some tape
Once built, the reader can easily be connected to a host PC over USB, after which a calibration process begins to ensure that the difference between a '1' and a '0' on the tape can be accurately measured. There are also three jumpers on the top PCB that set how many bits are on the tape. To start seeing the on the serial monitor, the user must manually pull the tape through the reader at a rate that does not exceed 1m/s. You can read about this project in more detail by going to Müller's website here.