Intro: Building a Breadboard Prototyping Module
Many of us old timers cut our teeth on the classic Archer 200-in-1 Electronics Lab or similar kits. Think of it as an analog Arduino- an electronics Swiss army knife. They consisted of a tray with various components mounted on it with spring connectors. By slipping the ends of wires into the springs, you could connect the components to create all kinds of things. These kits made building circuits quick and easy.
Eventually, we moved on to building circuits on breadboards. Breadboards are great for building and modifying circuits. Being able to quickly switch out components helps you see how their values affect the rest of the circuit. Breadboards are an invaluable part of any electronic hobbyists education, but they have their drawbacks. For one thing, the small components used on breadboards are hard to work with. Trim pots, DIP switches and tiny momentary switches are finicky and often come loose at the worst times. I've spent lots of time trouble shooting a circuit only to discover the failure was due to a loose switch or trim pot.
The breadboard prototyping module gives you the versatility of breadboarding with the convenience and 'solidness' of the old style circuit building kits. Switches, pots and other panel mounted components can be easily connected to a breadboarded circuit with common jumper wires, making prototyping a breeze. Here's how to build your own.
Step 1: Designing the Prototype Module
When I design a breadboard prototyping module I have to keep a few things in mind. The components you want to use, the shape and size of your project box or panel and the kind of circuits you are interested in building all have an impact on the final product.
The components are very important. I use mostly recycled parts, especially when I first got started. Using recycled parts gives you access to a wide variety of options with very little investment. The best thing a new electronics hobbyist can do is to find a broken audio mixer. I took apart a 16 channel audio mixer recently and got 90 potentiometers with knobs, 50 switches, 2 dozen audio output jacks, two meters and a ton of useful internal bits. Whatever components you use, get them all together in one place before you start building to insure they will all fit the enclosure you choose.
The unit I'm building here will be used in an upcoming series of projects. It will have six pots in three different values, four switches and four posts for alligator clips, as well as two 830 hole breadboards.
The project box is also very important. It needs to have enough room to hold all of the needed components. It also needs to be small enough to be useful and easy to work with. I've used cigar boxes and other flat rectangular enclosures. You want to be sure that the material is thin enough that the components can go through with enough room for their mounting hardware.
I used 4"x4" PVC fence post material to make a 4"x14"x1" panel. This will later be mounted in a box as part of a larger series of projects.
Finally, you need to consider the kinds of circuits you are interested in so the final project meets your needs. If you want to build synthesizers and audio circuits make sure to include lots of pots and switches and maybe a speaker and small class D amp. If you want to work with a breadboardable microcontroller to work on robotics code include some motors, servos and sensors. What ever you want to make, you can build a cool custom prototyping module to design and perfect your circuits.
This project will be used to design and test simple CMOS based audio circuits. I need pots and switches for this. The circuits built with this module will be part of a modular synthesizer, where the various sub-circuits are connected with alligator clip jumper wires, so I'll also include a few machine screws to act as contact posts.
Once I determined the components and the box I would use, I used graph paper to draw a few different layouts. Once I had a design that I was happy with it was time for the next step.
Step 2: Preparing the Panel
I used the layout from the graph paper to create a template. I taped it to the front of the panel and used it to drill pilot holes for all the components. I drilled them to their final sizes with the appropriate bits and installed the components and screw posts. I cut a slot between the two holes to the side to create a slot to accept the wires from the bottom of the small breadboard in the next step.
Step 3: Installing the Breadboards
I used two different kinds of breadboards for this project- full-sized 830 hole boards and a mini 170 hole version. The 830 hole boards are where I'll be building the circuits. I removed one of the power rails from one of the boards and them snapped them together. I peeled off the adhesive backing paper and mounted the boards on the front of the PVC panel. Simple.
The 170 hole board is a bit more complicated. This board will be used to connect the panel mounted components to the circuits being built. To do this, the conductors in the board were connected to the components by wires. First I removed the adhesive pad from the bottom of the board and wiped it down with alcohol on a cloth to remove any residue. I used a stiff wire to push the conductors out of the board. I've tried to solder the wires in the past, but the shiny plating of the conductors prevents the solder from sticking well. Instead, I bared 3/4" of an 8" piece of the wire and bent a small, tight hook in the end. I slid the wire into the connector so that it hooked the bottom edge and then I pressed the conductor back into the board. I used a pair of pliers to push and crimp the conductors back in tightly, creating a good electrical contact. When all the wires were crimped in place, I added strips of two-sided tape to the bottom of the board, slid the wires into the slot in the panel and mounted it in place.
Step 4: Connecting the Components
I was very careful to keep track of the wires colors. I started with the top right conductor (from the back side) and soldered it to the first panel component, in this case it was the first screw post. I proceeded in order, connecting all four posts. Next, I connected the first switch, These are double pole, double throw, center off toggle switches, but I only wired them as single pole switches. I soldered the wire from the 5th conductor to the first lug on the switch, the 6th conductor to the second lug and the 7th conductor to the third and final lug. I continued in this manner until all the switches and pots were connected.
I installed a USB 5/3v regulated power supply into the end of the breadboard to provide power. Since the microcontrollers and CMOS chips I'll be working with like 5v, this is perfect. You could use any power source that suits your needs- a re-purposed wall wart, a battery pack or a USB connector will work just as well.
Step 5: Labeling the Components
I used some recycled vinyl adhesive and a fine-line permanent marker to make labels for the prototyping module. I marked the sides of the 170 hole breadboard 'A' and 'B'. I made a label for the middle of the board and labeled the rows 1-17. I also made labels for the components to identify them and to note which rows on the breadboard each one was connected to.
That's it- the breadboard prototyping module is ready to use. This is much better than trying to adjust tiny trim pots with a screwdriver!