An old robotic arm that I built 20yrs ago

Winner of the 2003 National Scientific Communications contest (Romania)

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This is an old project I never had the chance to publicize. Yet, my mindset is always set to enrich others with what I know, therefore I take the time and energy to post it up here. Maybe it finds new homes and the information shared here helps someone learn something new.

The beginnings of an era

   It was the winter of 2003, pretty much this time of year, 20 years ago. I was in my last year of technical high school. I was learning lots of electronic tips and tricks and I was also experimenting with programming in Borland Pascal 7.1. I was having a new 900MHz computer with a 6.4GB HDD and about 256MB of RAM. 

I stumbled upon a magazine 

   I was fascinated about the idea of having some electronic device driven by the computer as this was something you could only see in the SF movies back then. One day I cam across a technical Romanian electronics magazine which was having an article on how to drive some LEDs using the parallel port of the PC in order to make a vu meter for Windows 98.

(Credit: Conex Club magazine, year 2000, no 6. Romania)  

It gave the schematic and it gave me the Borland code. In it was a line which taught me how to send information to the parallel port of the PC. I remember that, once I discovered this thing I was so excited, I couldn't sleep that night. I kept thinking that this was just the beginning of endless possibilities for me. I had the knowledge on how to build analog amplifiers, on how to use relays, on how to switch on grid lines by using logical signals and many more. Having them all submitted now to this new idea of owning up to 8 bits and 255 channels to drive all of them from the computer was just amazing. I was thinking that I could even build a robot. I was saying to myself: "wow, Marius, you could even build yourself a computer driven house system. Operate the blinds, turn on the light..." And that was long before the modern day notion of smart houses.

   The next day I frankensteined together a small pcb with LEDs. Then I connected optocouplers to those LED lines and then I used the optocouplers to drive relays. I was at the peak of my happiness. I was telling my parents that I was building a robot arm to connect to my computer, but they didn't believe me. I remember now, judging the teenager memories through the mind of an adult, that they had nodded their heads, but they thought that I was exaggerating or day dreaming. Back then I wasn't even having access to materials. The only bits of hardware I was having were scrapped components from cassette tape players and telephone relays. I even had to build my own optocouplers by trimming off the heads of some metal BC107 transistors. 

   The fingertips were made of cassette tape pressure rollers, the plastic gears belonged to some old toys, the finger actuator motor came from a Walkman (if people still remember those) and the hand was made of refurbished Fr4 from old PCBs. The trickiest part of all was the forearm’s actuator which needed to be strong enough to lift the entire assembly. I had found an old actuator from a dismantled boiler.

It was a Honeywell 3-way valve motor. Those familiar with the model might remember that it was having an attached gearbox with a high gear ratio. It was only having a small problem: the motor was burned. I had to stick a rubber pad on the rotor’s case and to use an external motor with a shaft to drive it, but that worked... eventually. 

Where dreams might take me

   A few days later I went to my Digital Electronics teacher and told him that I wanted to participate to the National Scientific Communications contest. For those of you who are familiar with the Romanian context, and stumble upon this article, that was also known as the Stefan Procopiu contest.

   The Pascal code was pretty simple. It would trigger the relays one by one and it would loop the movements of the arm in a repetitive cycle. The robotic arm would reach down, close its moving thumb, move up, move to the left, move to the right, move down again and release its grab. That day I brought my project to school for the first time and showed it to my teacher, everything worked perfectly....

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Code sample 1

pas - 736.00 bytes - 01/31/2023 at 12:56



Code sample 2

pas - 706.00 bytes - 01/31/2023 at 12:56


  • Schematic

    Marius Taciuc02/01/2023 at 09:24 0 comments

    This is a recent reconstruction of the schematic. The original plans and sketches were nowhere to be found. Plus that I took the liberty to improve a few things that I got wrong 20yrs ago. 

  • Example of Pascal code

    Marius Taciuc01/31/2023 at 12:54 0 comments

       This is pretty much what I found in my archives when searching for the source code. It looks like a clear experimentation phase since it's obviously not optimized. It also has a lot of repetition in it, but by the looks of it, it should still work. 

       About working... Some people might ask what it takes to restart this robotic arm today and if this code can still run on some machine. The answer is simple: I don't know. Maybe Pascal can still be installed on some machines in compatibility mode. Maybe there are some desktop units out there still having LPT ports. Maybe one can run this in a Windows98 virtual machine? I never tried usb to LPT cable adapters, but maybe they work. Anyway... here's the code:

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Elliot Williams wrote 02/15/2023 at 20:56 point

This is soooo beautiful.  :)

  Are you sure? yes | no

Marius Taciuc wrote 02/16/2023 at 06:59 point

Thanks. So glad to see people like this. 

  Are you sure? yes | no

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