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  #1  
Old 06-13-2012, 10:30 AM
Dawud Beale Dawud Beale is offline
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Default How to practice with digital electronics

Hi hi everyone

I was hoping to get a bit of practice in at home with the digital electronics we are studying at Uni, seeing as I have 4 months off

We have learned combinational and sequential logic

Any recommendations on cheap and effective equipment taht I can purchase that will enable me to have a practice at home?
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Old 06-13-2012, 10:36 AM
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Bill_Marsden Bill_Marsden is offline
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Basic breadboard, wire, a small set of chips. I'd use CMOS, due to wide voltage range and flexability. They can be powered by a 9V battery.

To display a logic level this would work well...

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Old 06-13-2012, 11:15 AM
Dawud Beale Dawud Beale is offline
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what about logic trainers? Is it quite difficult to set up large logic circuits using CMOS on a breadboard? I havent tried it before but wouldnt I need to power up each individual CMOS chip?
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Old 06-13-2012, 11:29 AM
Dawud Beale Dawud Beale is offline
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Do you think I could just purchase some of these:

http://www.maplin.co.uk/cmos-logic-h...0-series-31820

and use them?

I would prefer to get one of the logic trainers we used at uni first as it seems a bit intimidating trying to set up large logic circuits using IC chips. If I jumped straight in, can you recommend any "getting started projects"?
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Old 06-13-2012, 11:53 AM
absf absf is offline
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Those are CMOS logic chips. Of course it would be nice if you can start with a logic trainer. The trainer would take care of making your own power supply, debounced input switches, LED output indicators, function generators. Some even have decoded 7 segments displays built-in.

If the prices are good, try to get a new one with documents and tutorials bundled. Failing that you can also get used ones by reputable manufacturers like Elenco from eBay. You still need to buy the logic chips from maplin as they are probably not supplied with the trainers.

http://www.ebay.com/itm/Elenco-Analo...#ht_500wt_1032

http://www.ebay.com/itm/Analog-digit...item2a1e8b8dee

2 of them from eBay for your reference......

Allen
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Old 06-13-2012, 12:31 PM
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Bill_Marsden Bill_Marsden is offline
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All a matter of what you want to do. If you go the breadboard route, you will need to pick the chips for the job, not the other way around.

Here is a website I have found useful over the years.

http://users.otenet.gr/~athsam/database.htm

It is good for looking up specific chips.

My PaintCAD selection also has drawing templates for drawing logic.

Introduction and PaintCAD
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Old 06-13-2012, 03:14 PM
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Simulators are a good way to go, too. I've been spending a bit of time with Multisim (there's a student version available) and you can learn things a lot faster than constantly plugging/unplugging. I'm not saying it's a substitute for the real thing, but it works works well for me.
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Old 06-13-2012, 03:17 PM
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Quote:
Originally Posted by Dawud Beale View Post
what about logic trainers? Is it quite difficult to set up large logic circuits using CMOS on a breadboard? I havent tried it before but wouldnt I need to power up each individual CMOS chip?
It's not particularly difficult to set up large logic circuits, just somewhat tedious and time consuming. A plug-in breadboard, such as on the logic trainers, avoids having to solder, thus simplifying the wiring. I would highly recommend one of those trainers since they also usually include a power supply and signal generator. And certainly you need power (and ground) to each chip but that is easy to do since there are typically power and ground buses on the breadboard.

Edit: And a simulator, such as vpoko mentioned, is also an easy way to experiment with different logic circuits.

As a start for experimenting, I would suggest setting up some different types of counter and flip-flop circuits to learn about sequential circuits. Making a counter with an LED readout is an interesting project.
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Old 06-13-2012, 10:07 PM
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The most important thing is to do projects that are interesting to you. Taking someone else's project suggestion and doing it is on limited utility if you are just going through the motions. What you do doesn't have to be anything fantastic - just taking a line of LEDs and figuring out how to get different "Knight Rider" effects can be a hugely educational experience.

What will be most valuable to you is to start with an idea from you where YOU are the customer with a vague notion of what you really want. It could be a simple digital clock or perhaps one with some common features such as an alarm, a stopwatch, and a countdown timer. Then try to design a circuit that does what YOU would like it to do. What you will find is that you probably didn't have a good enough idea and have to make a lot of decisions such as how so I set the time? Should display in AM/PM or 24HR format? Should the stopwatch include hours? What about the countdown? Should there be a snooze on the alarm? If so, how long? Adjustable? Since you are the customer, you can make these decisions quickly and move on, but it begins to expose you to the fact that most engineering jobs are poorly specified and require back-and-forth with the customer. You will also likely find that some things you want are more complicated than they appeared at first blush. That's fine, you're the customer, so change the requirements to keep the project deliverable and within the scope of your engineer (which is also you), but push those abilities in order to expand them.

I'd vote for making your own trainer as you go.

Get some solderless breadboards and build up little modules that do a simple, specific thing and then, once they are working, rebuild them onto either a cheap PCB that you make or have made or just use solder-type protoboards to make more permanent versions.

You can start out with a 9V battery for the supply and later add a module that provides a regulated 5V and 3.3V outputs. Then, when you get tired of replacing batteries, add a module that takes wall power and steps it down to 6V or so (depending on what regulator you're using in the first module).

You can make a module that has a bunch of switches and LEDs on it and you can debounce some or all of them.

You can make a module that has several 7-segment displays that includes the encoders and multiplexers so that you can interface it easily to your other projects.

You can make a module that is a voltage and/or current meter, either analog or digital.

You can make a module that is a clock source, either centered on a crystal oscillator or even use a 555 timer.

You can make a pulse generator module that takes an input and produces a pulse output of defined (and adjustable) width.

Each module you build will give you experience at working with hands-on electronics. You can sit down and make a list of capabilities you would like your trainer to have (both stuff the trainers at school have and stuff that you wish they had) and use those as the basis for many of your projects.

You can keep going for a long time this way. Modules to work with a keypad or switch array, an LED array, an event counter, a low-frequency function generator, a simple LCD display, a multiline or graphic display, static memory, dynamic memory. Keep adding modules as you find a need for new capabilities for your trainer. You can keep right on going and eventually have modules for an MCU or and FPGA or whatever.

You can be as kludgy or as elegant as you want. You can start out kludgy and then polish things and make them more elegant as you go and decide what is and what isn't really useful.
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