How does a digital pregnancy test work?


Digital pregnancy tests are curious electronic devices that are equipped with high-end hardware – at least, several decades ago. Twitter users @foone and @xtoff started an investigation into how these devices work and found them to be as powerful as the original 1981 IBM computer.

Currently, digital pregnancy tests are easily found in major retail stores and pharmacies in the United States, for a measly $ 5 each. Inside them, according to the curious, are a processor, RAM memory, a memory cell and a small LCD display to present the result.

The processor is an 8-bit Holtek microcontroller, accompanied by 64 bytes of RAM, reaching frequencies of 4 MHz or 8 MHz, varying according to the capacity of the battery. The numbers may seem simple, but it is “probably faster than the IBM PC in processing numbers and inputting and outputting data,” according to foone.

On the back of the test, the battery, the other side of the PCB and a paper tape that chemically reacts with urine are visible, just as there is in the conventional test. The presence of this tape reiterates that the digital test does not offer greater precision or more information than a simple pregnancy test.

As soon as it gets wet, the paper activates the battery and the device is turned on. The device uses three photosensitive LEDs and light sensors to read on the paper and take this result to the LCD display. The sensor data passes through memory, is analyzed by the processor and is then demonstrated.

In practice, the only difference between digital and conventional exams is the clarity of the information. While the conventional exam shows results in bands – which can eventually be confused – the display shows the result in a more readable way.

Doom wheel?

The profiles also asked this classic questioning, and found that it is not possible. The system that makes up the exam is not programmable; therefore, it is not possible to enter game data for it to run.

Finally, the conclusion of this investigation is that digital tests are, in fact, a beautiful waste of plastic and electronic components. As it is a disposable and single-use product, once the result is demonstrated, the device is thrown in the trash and, in most cases, the components are not reused.


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