Posteado por: josefd8 | julio 19, 2009

HDB3 Coder Circuit

HDB3 is a code that allows us to transform a sequence of 1’s and 0’s into an alternate sequence of positive and negatives voltage pulses.

An HDB3 coder can be easily programmed in a computer language. For coding a binary signal, a couple of rules must be followed, like the amount of straight zeros for example, keeping in mind that this 0’s sequence will be replaced with positive and negative voltages.

A very interesting college project in my days was: how to build a simple HDB3 coder, using only electric and electronic devices?

With only electronic devices, the story is a bit different. One of the solutions is through a microcontroller, this one will “read” the bits sequences and with analogic devices at the very end of the circuit, output signals will be transformed into a 3 voltage signal. This is a valid solution, but still needs some programming underneath (the microcontroller program). At that moment, my teacher considered that it was a “to easy solution”, and why don’t make it more complicated doing it with only simple electronic devices???

Anyway, after a while, we came up with a solution to the problem. We present a complete functional HDB3 circuit coder (High Density Bipolar of order 3 code), designed in Electronics Workbench 5.12. Before we hear any complains, yes, we know that the ewb version is a bit old, but the circuit itself its based on very simple electronics devices, and can be used for demonstration purposes of how the HDB3 coding works, or why not, for coding  a given bits sequence and see the output. In there are a lot of leds, showing the state of the bits (1 or 0) throughout the circuit, helping to identify violations or valid bits sequences.

Below, some pics of how the HDB3 coder looks, and its output for a sample bits sequence:

Besides the *.ewb file with the circuit, an instructions manual is included, explaining every part and detail, and a copy of Electronics Workbench 5.12, where it was originally created. Maybe in the future we can include a post with the circuit working on a more recent version of ewb.

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