Distribution buses are a convenient breadboard feature. These “power rails” run the length of the breadboard so that power and ground for your circuit elements are always close at hand. In this short post we will explore the difference between the 2-bus and the 4-bus breadboard.
When viewed side by side, the 2-bus and 4-bus breadboards look almost identical as shown in this picture. However, close examination shows a break in the blue and red rail markings.
As implied by the blue and red silkscreen, a continuity test will show a break in the middle of the 4-bus breadboard while the 2-bus option extends the entire length of the breadboard.
One recommendation is shown below. Simply insert a 0.3 inch (7.62 mm) jumper into the breadboard so that the 4-rail effectively becomes a two-rail. This allows your logic circuits to be surrounded by ground and 3.3 or 5.0 VDC as appropriate.
Tech Tip: Don’t forget to include bypass capacitors to improve circuit performance as described in this post regarding breadboard stability.
We could stop here, but there is an unanswered question about the rationale behind the 4-bus breadboard.
The term “mixed” may be used to describe a circuit featuring a mixture of analog and digital components. Using the 4-rail design we can use the technique shown below featuring a microcontroller on one side of the breadboard with analog circuitry on the other. The rails are adapted to the needs of the circuit. The analog side features +/- 12 VDC for the op amps while the digital side includes 3.3 or 5.0 VDC for the digital circuitry.
In addition to providing a clean way to power your circuits it has the potential to improve circuit performance. The physical distance between sections may provide some noise immunity. The power supply rails are generally easier to decouple. Also, the single ground connection may help reduce noise.
Tech Tip : A regulator may be used to provide power to the digital logic from the +12 VDC rail. A classic solution is to use the 7805 regulator for 5.0 VDC logic. For greater efficiency consider using a switching DC-to-DC converter. Devices are available as drop-in replacement for the 7805 regulator.
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