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Input panel assembly

A project log for The Cardboard Computer

My goal is a 4-bit cpu using discrete transistors. I am learning from scratch as I have never worked with hardware at the gate level.

Mark Nesselhaus 01/05/2017 at 09:246 Comments

Well, I have started the layout for the switch input section for this machine. As with my 4-bit adder, I am using household power switches found at the local thrift store. Just a little bit oversized but then again this project is a tad odd anyway :-) The bank of four on the left is address input. The middle bank of four is data input and the right side bank of six is for control functions ( Step, Run, Stop, Reset, Deposit and Examine ).

Here is closer look at the switch modules. Again using cardboard as the base material.

01/09/17 - I have decided on a simple basic RC debounce circuit for the six function switches. So I am laying out a strip with the debouncers and Not gates to be placed between the switches and the lower display led circuits. I am using the Not gates as the led inputs need a solid 0 or 1 to function and the switches are spst and going to ground. I lack a scope to see what my signals look like so my debounce resistor and cap value will be trial and error. Hopefully less error :-) I will post the circuit shortly.

Discussions

Ted Yapo wrote 01/05/2017 at 18:09 point

Now you have me looking around my house at how many light switches we rarely use.  I'm wondering if anyone would miss a few :-)

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esot.eric wrote 01/06/2017 at 01:45 point

seconded.

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David H Haffner Sr wrote 01/05/2017 at 12:36 point

I knew you were!

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Mark Nesselhaus wrote 01/05/2017 at 17:56 point

Can't resist a good deal and these switches were only 25 cents each.

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David H Haffner Sr wrote 01/05/2017 at 12:12 point

Hey Mark! Maybe put some switch debouncers on those "switch" modules!

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Mark Nesselhaus wrote 01/05/2017 at 12:35 point

I am ahead of you on that , they will be in there :-)

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