Another aspect of breadboarding is modularization. This is a major theme in electronics and is the entire basis of using ICs. An IC is nothing more than a circuit which arises in practice so often that it is worth packaging in a small unit and treating as a black box with inputs and outputs that can interface with other parts of the circuit. So why not use this approach to breadboarding? One of the fundamental axioms of hacking is to never solve the same problem twice, so rather than rebuilding repeated sections of a circuit over and over in your experiments it is much smarter to build a reusable module!
In this tutorial I will show how I address many of these issues to make a regular breadboard much more useful for development and rapid prototyping. I will cover some techniques I have developed for hacking your board that have made my life much easier and hopefully they will do the same for you. Although I will show a few specific examples, these techniques can be used for any project that you are working with. Now, on to the good stuff!
Step 1: Adding a Breadboard Battery
In the picture you will see a couple of holes that are marked with black permanent marker. Breadboards inevitably wear out through use and end up with a couple of rows that may stop connecting well. MARK THE BAD ROWS!!! It is frustrating to try to debug a circuit just to eventually find out that one of you breadboard rows is not working. It is exponentially worse to let it happen again on the same board. Just use a permanent marker to indicate bad row so you don't end up pulling out your hair!
Now, get yourself a 9V battery clip. Align it in a convenient location on your board and use your marker to track a hole on the breadboard base where you will need to drill your holes. Pick a drill bit that just slips through the screw holes on the battery clip and use it to drill holes in your base plate at the marked locations. Next, tap the holes you drilled. Use the appropriate size screws to mount your battery clip to the board. Alternatively, if you don't have a tap you can just drill the hole a bit oversized and use nuts on the back side of the board with your screws.
Once you have your clip mounted on your base plate all you need to do is insert a 9V battery and use the appropriate wired terminal to connect it to your binding posts. Now the posts will be able to powered by your battery or by an external power supply using a banana cable.
Step 2: Adding an On/Off Switch
Lead wires connect the switch module to the binding posts. I have shown the module I built for my board which connects to the middle power rails. Along with I use some jumper wires at the opposite end of the board to bring power to the outside rails. You could integrate these jumpers into your module but since I sometimes like to use the outside rails to connect select components in series I have left this mod off of mine.
Headers are used to plug the module into the board. Soldering these onto your module is really the trickiest part of making this part. However, after some practice I have come up with a reliable way of doing it that keeps the long end of the header on the bottom and keeps the pins straight. In the next step I'll show you how I do it.
Step 3: Adding Headers to Your Modules for Connection to the Breadboard
The trick is to use a breadboard. First take your perfboard and lay it on your breadboard with the copper pad side facing up. Use some jumper wires to pin the board in place. Next, cut your headers to the desired length. For most of the module I will shown in the following steps you will need a 2 pin and a 4 (or more) pin header. The switch module I showed in the last step used two 2 pin headers. It will depend on the module and hopefully this will make sense as you read on.
Place your headers in your board so that the longer part of the pin coming out of the plastic piece is inserted through the board and just sitting on the breadboard hole. This will make a gap between the perfboard and the plastic piece on the header. For the module in the following steps it is important of arrange the header pins as I have shown with two holes between the short (2 pin) and long (4+ pin header). In the end the 2 pin header will fit into the power rails to energize our module and the long header will be used to act as inputs and outputs for the module to the rows of the breadboard.
Now solder each pin to its respective copper pad. Once all of your pins are soldered into place you can remove your jumper wire that was holding the board in place. Eventually you will use a pair of pliers to pull off the plastic piece and leave only nice, straight pins on the underside of your module as I have shown. However, since you will often be doing more soldering in the vicinity of these pins as you build your module circuit, I recommend leaving the plastic spacer on until you entire module is finished. This will keep pins from becoming crooked if you need to melt the solder of a single pin as you make solder bridges.
The number of pins you use on the long header will depend on the number of ins and outs you need to the module. However, I recommend using at least 3 pins to make sure you have a nice, stable connection to your board. If you don't need all three that is fine. They will just be present to keep the module affixed to the breadboard.
Step 4: A Few Modules to Get You Started
LED Light Sensor Module
This is a simple sensor module that I use in my solar tracker project. It has three header pins that connect to rows in the breadboard but only one of them is used as a module output. Other parts of your circuit can be connected to this output using a jumper wire tied to the same row as the output pin. The other two pins on this part of the module are just there to keep the module in place and prevent twisting. The other two pins are connected to the power rail. In this case only the ground connection is used within the module.
This module is a huge space and time saver. Normally you would need to connect each output of the LM3915 IC to the bar graph LED and then make a ton of other connections to the positive power rail. By putting this all into a module, it can be rapidly added to any circuit and takes up very little room on the board. Here only one of the long header pins is used and it serves as the input. The 2 pin header provides connection to the positive and negative power rails to power the module.
This module is distinct from the other two just because I decided to try something different. In this case the board straddles the breadboard rows. Two sets of short headers connect the module to the power rails and two single pins connect the inputs of the module to rows on the board. Input can be provided to the H-Bridge using jumper wires fed directly through the labeled holes on the module and the output to a DC motor is sent through wires integrated into the module which had headers soldered to their opposite end. This entire module could be redesigned to work like the other two I have shown (and will be as soon as I bother to do so) and would probably be better for the effort. However, this was one of my earlier attempts at a modular design so I am showing it for contrast.
Step 5: A Few More Useful Breadboard Parts
To make that addition of a motor a bit cleaner I made a DC motor unit as shown. I affixed header pins to each terminal of the motor as well as lead wires. The pin terminals can be used to plug the motor directly into the board. If the rows used for mounting the motor are not linked to an input signal, the lead wires can be used to connect the motor terminals to remote parts of the board where the signal is.
Step 6: Putting It All Together
In addition, one of the inputs of the H-Bridge is connected to the same row as the VU meter input to read the incoming audio signal. The other input the the H-Bridge is connected to ground. The outputs of the H-Bridge are connected to the terminals of the DC motor module. In this arrangement, the motor will run at a speed proportional to the level of the incoming audio signal. As you can see in the video, the motor will spin when a large audio signal is provided.
This type of circuit could be used for any number of cool audio/visual projects. However, the concepts established here can be extended to all kinds of applications and as you build more and more modules you will find tons of cool ways to link them together. Now, start hacking and let me know what you come up with!