Punched Card Reader for RC2014 Z80 Computer

Description

As a fun little computer to mess around on, the RC2014 is great. It does have a couple of drawbacks though, and one of those is a lack of storage device. Typing in programs or data is fine in small doses, but for anything substantial, higher volume storage is needed. Several people have pointed this out, and I have considered a few different options, including;
* SD Cards
* Compact Flash
* Cassette Tapes
* EPROMS
* Paper Tape
However, they all lack the authentic feel. Punched cards, however, fit the bill just nicely!

In order to make this a viable option, I am going to try to use off the shelf through-hole components combined with a laser cutter, some simple software scripts and a pile of regular cardboard.

Files

punch1.dxf

First test DXF for punch card

AutoCAD DXF - 174.31 kB - 05/21/2016 at 20:37

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Test punch card punched
spencer • 05/21/2016 at 21:16 • 3 comments

So, a punch card reader isn't really going to be that great without some punched cards to read.
However, I don't have any punched cards.
So, off I head to Lasery McLaserface* to make some!
Now, of course I didn't just click the "cut punch card" button on the laser cutter. Things are a bit more involved with that, although one of the main goals of this project is to automate the the process of turning a text file in to a bunch of laser cutter ready .dxf files.
What I actually did was go to http://www.masswerk.at/keypunch/ and typed a message. From there I could download a .png file of a punch card
All of the cutouts are transparent, so from there, I used Imagemagick to convert it to a black image that retains the transparent sections.
Potrace should be able to trace the edges of the image and create a dxf - however, it doesn't like .png files and even as a bitmap I couldn't get the output right. So I used Inkscape (which has Potrace built in) to do this bit.
The .dxf looked good, and came out pretty well - although some of the holes had just the tiniest whisker of card holding the chad on. At 97mm x 255mm it is bigger than 83mm x 187 of a standard size card, but at least it gives me something to get started on.
As mentioned earlier, automating this side of things is will be key to this project. I don't consider myself fluent in Linux command line syntax, but I know it *should* be able to read a text file, convert it to hexadecimal strings, send that to a web page in an appropriate amount of chunks, download the resulting images, modify them and produce a single dxf file containing all the cards needed to be made. All I have to do is teach myself how to do that :-)
* Lasery McLaserface is the name of the laser cutter at Nottingham Hackspace

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Discussions

matseng wrote 05/22/2016 at 13:56

I wonder if one of those bill (money) counting machines could be coaxed into dragging the cards one-by-one across a sensor at high speed. That would then make an awesome reader...

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spencer wrote 05/22/2016 at 14:00

Hmmm... maybe... Initially, I'll be happy enough with hand feeding the cards, but have thought about customising an old inkjet printer. Maybe I should just go and find myself an ATM (Even better if it's full!)

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matseng wrote 05/22/2016 at 14:10

I just checked the prices for cheap machines. They are as low as $50 and upwards. And they actually seem to be passing the bills across some inside surface. I will definitely get one and try to hack one into a reader when I get my lab back in a few months. The problem would be that the holes will be read in the wrong direction so 80 sensors would be required for a standard 80 column card instead of just 10'ish.

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spencer wrote 05/22/2016 at 14:33

The width of a standard punch card (187mm) is quite a bit wider than a £50 note (156mm), so they're unlikely to fit. Also, I'm not sure how much the machine relies on how bendy paper money is compared with thin card. Still worth investigating though :-)

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Yann Guidon / YGDES wrote 05/22/2016 at 17:59

I love this idea........ it's a hack !!!

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matseng wrote 05/22/2016 at 14:44

Right, the standard cards would probably not be a good fit for a machine like this, but using a more suitable paper thickness and size it might be close enough to a real oldskool reader. Since paper tape punches and card punches/readers are basically unobtanium today so having a midi-sized card reader would be ok with me.

Ahh... so many project ideas - so little time. ;-)

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Yann Guidon / YGDES wrote 05/20/2016 at 01:41

Card-memory is coming back apparently :-)

#Low-resolution scanner for cheap data input

#Binary Punched Card Reader

and another I forgot...

Let's create a club ;-)

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spencer wrote 05/21/2016 at 21:29

Cool! Those are both very different approaches, but still have a lot in common. Thanks for the links!

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Punched Card Reader for RC2014 Z80 Computer

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punch1.dxf

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Test punch card punched

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