Decimal to Binary LED Converter Circuit

binary-digital converter_close-up

Using the diodes I salvaged from an old electronic organ, as well as a 1980s Forrest Mims III Radio Shack Engineer’s Mini-Notebook on semiconductor circuits, I made a circuit that converts the digits 0 – 9 (each digit with its own pushbutton) to binary using a four LED readout. I did it quickly, not expecting it to work because I hadn’t tested all the diodes out and because there was so many places to misplace a wire. But it worked on the first try, and I was excited about that!

This isn’t exactly the cutting edge of electronics, considering both diodes made in the 80’s as well as a book printed in the 80’s were utilized for this project, but it’s just fun to make bigger circuits that don’t need computer programming. Check out my photo and explanation. Note that I was pressed for functionality and organized aesthetics, this is rather bad prototyping because as you can see I crossed wires and used all different colors. It’s almost impossible to troubleshoot should you need to.

binary-digital converter_with lights copy


Tech Tear Down: Old Long-Buried 1980s Electronic Organ Guts

This is one of my strangest Tech Tear Downs yet… My dad, my brother, and I cleaned up our backyard, filling up a Bagster all the way to the top. We went through an old junk pile, and buried underneath everything and covered up with leaves and dirt was the electronic guts of an old electronic organ that we trashed sometime around 2007. I was of course extremely curious, and despite the dirt, I salvaged the bulk of the electronics to see what they we’re made of or course to see if there was anything useful.

TTD_organ_all four PCBs apart

Basically, there was four large PCBs stacked and bolted on top of each other. They consisted of diodes, transistors, resistors, and capacitors, as well as a few op amp ICs. Other than on the top layer, there was little corrosion on the components, and I wondered as to how useful they would be, considering that they’re from the 80s and they’ve been subject to very extreme temperatures, as well as water.

TTD_organ_the diodes

I was excited to see that there was loads and loads of diodes (the image above shows a section of one PCB after I removed a bunch of the diodes; they were easy to get to). I would estimate there was close to 80 silicon diodes that I could have used in a breadboard. I set a table and got out all my tools and spent a while removing the diodes and a few of the resistors, using mainly a small flat-head screw driver and needle-nosed pliers. I was able to get maybe 50 diodes, a few resistors, and a few transistors, as well as a few useless souvenir ICs.

TTD_organ_curvy copper connections

I tested a few of the diodes out, and they worked great. The transistors were junk, and most of the resistors had leads that were too short. But now I have enough diodes to make a decimal-to-binary converter!


Above is where I was working.

There’s a few differences I noted between these four giant PCBs and modern day ones. First, the etched copper connections were very curvy, instead of rectangular and crammed together as you see on modern machine-made PCBs. Secondly, the wires coming off the PCBs weren’t directly soldered onto the board. Instead, a little metal spike pokes out of the board and the wire wraps tightly around the spike, so the joint is more mechanical, as you can see in the picture below.

TTD_organ_wire spikes

Quite frankly, I don’t really know how these PCBs work inside the organ. They were labeled in a few spots as having something to do with ‘rhythm’ and there was a large mass of wires exiting the PCBs, so my guess is these boards were responsible for generating the different tones on the organ.

About Resistor Value Color Banding

Here’s a little background on electrical resistors and their color banding.resistors

Resistors are measured in ohms (the symbol is Ω). The more a resistor is able to resist electrical current, the higher it’s ohm value. As they are small, a system of colored bands marked are marked onto every resistor to help people identify it’s value without having to test it. A typical 0.5 watt resistor, commonly used for small electronic prototyping, has four color bands. The first two colors represent the first two digits of the value, the third value is the multiplier, and the fourth value is the tolerance, or how much the actual resistance varies from the specified resistance. Usually the tolerance is ± 5%, so a 1000Ω resistor could have an actual value between 950 and 1050Ω.

Color First Digit (1st Band) Second Digit (2nd Band) Multiplier (3rd Band) Tolerance (4th Band)
Black 0 1
Brown 1 1 10 ±1%
Red 2 2 102 ±2%
Orange 3 3 103 ±3%
Yellow 4 4 104 ±4%
Green 5 5 105 ±0.5%
Blue 6 6 106 ±0.25%
Violet 7 7 107 ±0.1%
Grey 8 8 108
White 9 9 109
Gold   ±5%
Silver ±10%
None ±20%

To find the colors for a specific value:

  • Identify the value you want. Let’s say you want a 470Ω resistor.
  • Find the first color band based off of the first digit. The first digit of a 470Ω value is the 4. Looking at the chart under the first color band, the value of 4 is represented by yellow.
  • The second digit is 7. Again looking at the chart for the second digit, the next band is violet.
  • The third value is multiplier. You multiply the first to band values together (47) by this one to get the final value. In this case 47 * 10 = 470, so looking at the chart, the third band is brown.
  • The fourth value is the tolerance. With most resistors, used by hobbyists, this value is ±5% or ±10%, gold or silver.
  • So the final color banding for a 470 Ω resistor with a ±5% tolerance is yellow-violet-brown-gold.

To find the resistor value based off of the color bands :

  • Using the chart look at the first two colors and match them up to the first and second digits. For example, say you had a resistor with colors red-red-brown-gold. This would mean that the first two digits are 2 and 2.
  • For the third band, find the equivalent multiplier amount and multiply that by the first two digits. Since brown is representative of 10, I multiply the first two digits, 22, by 10 to get a value of 220Ω.
  • The final band shows the tolerance. Referring to the chart for the value, the gold tolerance band means that the 220Ω resistor has a tolerance of ±5%.

The Zen of Python

I was absent mindedly looking through the the Python 3 function library documentation after looking for a specific function, and I came across an interesting Python poem called the Zen of Python. If you want to read it, type import this into the Python IDLE or go into a Codecademy Python lesson and type it. It’s sort of an interesting way to think about coding.

Tools of the Amateur Electronic Maker

tools of the electromaker_4-2-15I’d like to consider myself an amateur electrical and design maker, and here’s a list of the tools I use regularly for my breadboard prototyping and reverse engineering.

  • needle-nosed pliers
  • standard pliers
  • wire cutters
  • toenail clippers (they actually work better than wire cutters for trimming smaller gauge component leads)
  • large phillips screwdriver
  • small phillips screwdriver (this is the green one I use for all my Tech Tear Downs)
  • small plastic bead organizer (for organizing components)
  • knife (for quick wire stripping used with the wire cutters, otherwise I have to borrow my dad’s wire strippers)
  • graph paper (for drawing schematics and writing ideas down, regular paper would work fine, but graph paper is waaaay cooler)
  • a blue pen that leaks ink
  • calculator (faster than calculating in Google or on the computer calculator)

The pliers are best suited for reverse engineering things, and for removing or placing wires in tight places on a breadboard. I haven’t gotten into soldering things yet, but I’m perfectly happy with breadboarding for now.

Simple Quadratic Calculator Made With Python

quad formula pic courtesy Wolfram Alpha

Here’s a simple Python 3 program that I made a while back, to help me with algebra. It’s a quadratic calculator that uses the quadratic formula to compute solutions based on inputs for a, b, and c. I made two versions of it, one with more condensed code. It’s rather simple, and it doesn’t handle complex solutions (It’ll give an error message). Feel free to make changes to the code if you like.

Quadratic Calculator

Condensed Quadratic Calculator

Here’s a screenshot of the program running in commandline.