How would I make a (very very very) basic transistor computer

[benhc123]

I am wondering how I would create a really simple electronic calculator/computer

 

[berkeman]

I am wondering how I would create a really simple electronic calculator/computer

Welcome to the PF.

What have you read so far? What have you read at wikipedia.org and HowStuffWorks.com?

 

[sophiecentaur]

Hi and welcome.
Unless you know a lot about basic circuit design and have a lot of experience of circuit building then I would say the project would be unlikely to succeed. If only one in a hundred of your solder joints is dry or connected wrongly, the device will not work and testing it could be a nightmare.
There are many less complicated digital projects that would be fun and instructive to go for first.
Sorry to be a damper but they haven't made 'discrete' processors since the 60's - for good reason.

 

[benhc123]

Hi and welcome.
Unless you know a lot about basic circuit design and have a lot of experience of circuit building then I would say the project would be unlikely to succeed. If only one in a hundred of your solder joints is dry or connected wrongly, the device will not work and testing it could be a nightmare.
There are many less complicated digital projects that would be fun and instructive to go for first.
Sorry to be a damper but they haven't made 'discrete' processors since the 60's - for good reason.

Do you have any examples of 'more simple projects'?

 

[dlgoff]

I am wondering how I would create a really simple electronic calculator/computer

A calculator/computer doesn't necessarily mean assembling a bunch of logic chips. You could make a simple Electronic Analog Computer which uses electrical components, such as capacitors, inductors, resistors, and operational amplifiers to model physical systems of linear mechanical components.

For example, here's how you would add several inputs (in volts) to get the negative output sum (in volts).

By using an Op-amp and some resistors (d.c. power supply required). Here are other Operational amplifier applications.

 

[sophiecentaur]

@digoff
You are totally right about the analogue computer and the OP amp in that diagram could be replaced by a very few discrete transistors. That may not be what the OP intended, though; the last time I actually saw an analog computer (explicitly used as such) in use was in the late 60s - just before the advent of Digital Computers for all.

@benc123
You could start with a self-assembly kit for combinational logic systems to control lights / buzzers / motors, using simple RTL (resistor - Transistor Logic) gates. That may sound trivial but it is a way to start and can produce pleasing and reliable results for a beginner.

As Berkman says, you need to read around before you actually launch out on something. My Dad told me "that would be too difficult for you" when I told him I wanted to build something like the valve audfio amplifier he'd just completed (way back) and he was right. I started on something really really basic, first, and it worked.

 

[berkeman]

For example, here's how you would add several inputs (in volts) to get the output sum (in volts).

(Actually, the output voltage of this circuit is the negative sum of the inputs...)

 

[dlgoff]

@digoff
You are totally right about the analogue computer and the OP amp in that diagram could be replaced by a very few discrete transistors. That may not be what the OP intended, though; the last time I actually saw an analog computer (explicitly used as such) in use was in the late 60s - just before the advent of Digital Computers for all.

Well, yes late 60s for analog computers. But a good way to learn linear/analog devices. We do still use op-amps

(Actually, the output voltage of this circuit is the negative sum of the inputs...)

Well, yes.

 

[mheslep]

(Actually, the output voltage of this circuit is the negative sum of the inputs...)

minus 2 points, sign error. :tongue:

 

[dlgoff]

minus 2 points, sign error. :tongue:

Can't get away with anything here.

 

[Bobbywhy]

You can make a really simple calculator/computer project using one integrated circuit and a few external components.

For example, the AD633 integrated circuit made by Analog Devices is a low cost device that can be used as a Multiplier, for Squaring and Frequency Doubling, Generating Inverse Functions, Variable Scale Factor, Linear Amplitude Modulator, Voltage-Controlled Low-Pass and High-Pass Filters, Voltage-Controlled Quadrature Oscillators, and an Automatic Gain Control (AGC) Amplifier. You can download the pdf data sheet at:

www.analog.com/static/imported-files/data_sheets/AD633.pdf

Check out the applications section for ideas.

 

[sophiecentaur]

Can't get away with anything here.

Don'tcha just hate 'picky'?

 

[sophiecentaur]

A very simple project to start with could be to make a simple frequency divider / counter with a number of flip flops and LED indicators to show binary counting.
A single chip oscillator, followed by two Quad D types (8 stages of ÷2 would involve minimal soldering and external components yet deliver a visibly impressive result. You can't beat some flashing lights for generating satisfaction and confidence.
You need to bear in mind that beginners may have virtually no equipment for inputting or examining what their circuit is doing. It's the I/O that takes up all the effort and resources.

Do you know about or have you considered an Arduino system, to get started?