Tuesday 20 August 2013

Circuit Board Mystery

Think I've just made a discovery....

I previously commented about my circuit board not looking anything like what's covered in the manual....

The manual describes the interface circuitry using TTL logic chips (7400 series), and all seems relatively simple.

My Armdroid on the other hand uses CMOS (4000 series), includes a 555 timer, has completely different high power drives, and appears overly complicated in comparison.

I happened by chance to read the original Armdroid article published in ETI magazine, Sept 1981 at Alex Zivanovic's excellent website  - and it would appear my circuit board is in fact a "prototype" model

My upper and lower interface boards (click to see full size) pictured when base was opened earlier :



Compare to these pictured (dusty,but still recognisable) :

http://www.senster.com/alex_zivanovic/armdroid/UpperBoard.JPG
http://www.senster.com/alex_zivanovic/armdroid/LowerBoard.JPG

Alex then mentions he has no other information on this variant.

The article refers to this Armdroid as a prototype and the circuit diagrams accurately reflect my layout and components:

Motor driver interface (see figure 8)

Interface board (see figure 4)


Just how many prototype verses production models exists, or other variants - I don't know!   Doesn't seem to be any other information on the internet about the prototype.

At least I finally have a circuit diagram - will make life a lot easier identifying and repairing that broken track, which is another mystery.

Found this picture of what I think is "standard production" and matches the layout in the manual and blueprints:

http://robosoc.blogspot.com/2011/09/armdroid-part-1.html

This is starting to make a great deal of sense...  I was puzzled for hours trying to figure this out!

You can see there's a big difference between the prototype and production boards.  The power regulator on my model is bolted to the chassis, whereas it's mounted directly on the PCB here.  The 555 timer that provides a manual (not computer controlled) clock pulse, is simply not present on these models.


If you have anything different, please let me know, I would be very interested to see what other revisions are out there!  Better still...  If you have a broken or unwanted production board, I'd be very interested in it!

I also wonder if this makes my Armdroid a little rarer ?


WARNING:  If you open up your Armdroid and have one of these prototype boards do take precautions for handling the static-sensitive devices.  The CMOS ICs are particularly sensitive and easily damaged !

4 comments:

  1. i have the clone robotic type and unfortantely it was burned so i build a new board using pic18F microcontroller and stepper driver. anyway, after having issue with timing belt, right now it works fine without any problem....i'm waiting to see your armdroid works. goodluck

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    1. Added a link to your YouTube video you mailed me to the Resources Page - see Armdroid Connections

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  2. i just got the arm with controls but can't it to work i need help to update system if anyone can help.
    thanks Don

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    1. Hi Donald,

      Many thanks for dropping past... I'm sure we'll be able to help... The general idea of this site is to prevent these poor little Armdroids going to land fill.

      Anyway, first thing to check is the driving mode - it's possible to direct drive the steppers (which means the onboard driver logic is not used). I'll post details in the resources page later this week to confirm this. If the board is configured as direct drive, then the manual controller will not function. Meaning, you'll have to use computer control.

      Another give away to direct drive is any missing ICs - when direct drive is configured, the chips are redundant and can be removed.

      If you have computer control only, then you'll have to wait a few weeks until I'm at that stage to write about it, and what to do exactly. Drop me a message (see contact me to the right) what sort of drive type you, and i'm sure we can work from there....

      cheers,
      Richard

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