# What's the hobbyist way to build a digital circuit?

#### Shishka

Joined Feb 4, 2019
7
Hello everyone!

I need some help finding a way to build a project I have in mind. The problem is that the project is complicated enough that building it with off-shelf components is really unfeasible. The only other option that I know of are FPGAs.

I have a FPGA at home but using that seems wasteful, mostly because it's actually a development board - which, on top of everything, makes it bulkier than it needs to be -, and I wouldn't like to use it for something permanent. I'm having a hard time finding something on the web that's not either a FPGA in BGA package (how should I solder and, more importantly, program it?) or a very expensive development board.
What should I do? Is there some cheap way to design a one-time programmed digital circuit?

#### BobTPH

Joined Jun 5, 2013
2,602
For slow digital circuits, emulating them with firmware in a microcontroller would be the way to go. What kind of speed do ypu need?

Bob

#### WBahn

Joined Mar 31, 2012
26,326
Hello everyone!

I need some help finding a way to build a project I have in mind. The problem is that the project is complicated enough that building it with off-shelf components is really unfeasible. The only other option that I know of are FPGAs.

I have a FPGA at home but using that seems wasteful, mostly because it's actually a development board - which, on top of everything, makes it bulkier than it needs to be -, and I wouldn't like to use it for something permanent. I'm having a hard time finding something on the web that's not either a FPGA in BGA package (how should I solder and, more importantly, program it?) or a very expensive development board.
What should I do? Is there some cheap way to design a one-time programmed digital circuit?

We need a LOT more information. This is like asking someone what kind of car they should get without telling them whether your goal is to beat the punk kids at the next stop light or move your parents and all their belongs across the country.

What is this project you have in mind? What are its NEEDS?

#### atferrari

Joined Jan 6, 2004
4,122
I have a FPGA at home but using that seems wasteful, mostly because it's actually a development board - which, on top of everything, makes it bulkier than it needs to be -, and I wouldn't like to use it for something permanent.
Development boards are exactly for that: develop. Once you have your design tested and accepted, you decide if you will produce a full PCB.

#### Shishka

Joined Feb 4, 2019
7
For slow digital circuits, emulating them with firmware in a microcontroller would be the way to go. What kind of speed do ypu need?

Bob
I thought about this but I don't like this solution, but I don't really want to do it this way because it's too simple, I want the thrill of making it hardware

#### Shishka

Joined Feb 4, 2019
7
We need a LOT more information. This is like asking someone what kind of car they should get without telling them whether your goal is to beat the punk kids at the next stop light or move your parents and all their belongs across the country.

What is this project you have in mind? What are its NEEDS?
Ahahah you are right!
I want to build a complete alarm clock. Nothing too complicated, it surely doesn't need high-speed hardware, nothing special. But building it with off-shelf components would make it very hard to make it well, so that it blinks when you are setting it, it would be hard to let you set alarms, to ring the alarm and all those features that a normal clock has.

#### bertus

Joined Apr 5, 2008
20,893

#### Shishka

Joined Feb 4, 2019
7
This CPLD board is cheap - https://hobbycomponents.com/featured/274-lc-maxii-altera-epm240-cpld-development-board

Or this FPGA board - https://hobbycomponents.com/altera/819-altera-cyclone-ii-es2c5t144-fpga-dev-board

Edit: you will need to buy the programmer to go with either of these, and learning to program these will take a long time if you don't already know VHDL/Verilog well
Isn't the programmer included in the CPLD? If so, that is extremely cool and exactly what I need!

By the way yes, I know VHDL!

Joined Apr 16, 2011
464
The programmer is separate and costs £6.49 https://hobbycomponents.com/featured/273-altera-fpga-cpld-usb-programmer-usb-blaster-compatible

It will program either the CPLD or the FPGA.

The site seems to be running desperately slowly right now

... and yes, the FPGA is cool. There is a free project available to make a UK101 using the FPGA board, 4 resistors, a PS2 socket for 3.3Volt compatible PS2 keyboard and a phono socket for composite monochrome output to TV. Pointless but impressive.

I find the CPLD board less impressive, but at that price, who cares.

#### WBahn

Joined Mar 31, 2012
26,326
Ahahah you are right!
I want to build a complete alarm clock. Nothing too complicated, it surely doesn't need high-speed hardware, nothing special. But building it with off-shelf components would make it very hard to make it well, so that it blinks when you are setting it, it would be hard to let you set alarms, to ring the alarm and all those features that a normal clock has.
Not necessarily. Building an alarm clock was a very common course project for a sophomore or junior digital logic course back in the days when 7400 series chips where what you had to work with and they were more than fast enough to add all the bells and whistles -- blinking the display while it's being set is actually quite a trivial feature to implement.

#### AnalogKid

Joined Aug 1, 2013
8,708
A six, or even four digit alarm clock with all of the convenience features runs up a surprisingly large body count. Nothing will be less effort than a PIC, PicAxe, Arduino, whatever - if you know a language, have a compiler, have a programmer, etc. I love CPLD's, and the project would be relatively easy for someone who thinks in hardware. $15-20 for a board with the device already mounted is going to be hard to beat. ak #### WBahn Joined Mar 31, 2012 26,326 A lot depends on what the point is. Clearly it isn't just get an alarm clock (there was a time when people DID do a project like this because digital alarm clocks were rare and expensive). So the clock has to be secondary to some other purpose. What's that purpose? Some people might do something like this specifically because they want to design a moderately complex circuit using basic components. That doesn't sound like it's the case here. Others would do it as a means of learning a new technology (CPLD, FPGA, MCU, whatever). A bit more info about way you want to do this in the first place might help us provide more useful feedback. #### danadak Joined Mar 10, 2018 4,057 PSOC is a quick way. You drag and drop components, a component is an onchip resource (catalog attached), right click config), wire it up internal and to pin(s). Analog and digital. Tool is free, key boards$ 6 to \$ 25.

Some designs can be codeless.

Regards, Dana.

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#### Wolframore

Joined Jan 21, 2019
1,994

#### djsfantasi

Joined Apr 11, 2010
6,981
We need a LOT more information. This is like asking someone what kind of car they should get without telling them whether your goal is to beat the punk kids at the next stop light or move your parents and all their belongs across the country.

What is this project you have in mind? What are its NEEDS?
In total agreement with WBahn. I can immediately think of several ways to accomplish this.

All require different skill sets. So, why are you doing it and what are the project needs?

#### shivk56

Joined Jun 13, 2019
2
Everyday electronic items are not just molded from plastic and metal and then shipped to the store for you to buy. Electronics include a huge array of circuits, transistors, resistors, capacitors, etc all arranged perfectly to work together. This specific field of electrical engineering allows devices like the cell phone to work for you when you need to make or receive a call, let you watch tv, or even know what time it is on your digital watch. Electrical Engineering also involves a study of various machines such as AC DC motors.