Protect Your Breadboard by Twisting the Legs of TO-220 Devices

Solderless breadboards have developed a poor reputation when it comes to reliability.

Fair enough.

I’ve damaged my share of breadboards. As an educator, I’ve encountered dozens of damaged breadboards. Most have internal damage due to a variety of abuse the most significant of which is the use of excessively sized wire.

You can prolong your breadboard’s life and improve reliability

In this engineering brief we will explore the internal workings of a solderless breadboard and then present a helpful tip for the use of larger components such as TO-220 packaged MOSFETs, transistors, and voltage regulators. Our conversation is focused on the breadboard finger springs and the flat blade of the TO-220 device as pictured in Figure 1.

Figure 1: The solderless breadboard spring finger is overstretched by the flat blade of a TO-220 device.

What is a solderless breadboard?

The solderless breadboard is a prototyping tool designed for quick assembly of electronic circuits. The term breadboard is a holdover from the earliest days of vacuum tube electronics when circuits were constructed on a block of wood (a breadboard) with screws and nails to hold the various assemblies in place.

Today, the term breadboard refers to devices such as the one pictured in Figure 2. The breadboard is “solderless” as it allows quick temporary electrical connection without the need to solder. It is also convenient as the components simply push into the board. Hand tools such as screwdriver and pliers are not generally required.

Figure 2 presents the wide range of devices that may be connected using the breadboard including through-hole components and Surface Mount devices (SMD) with the assistance of an adapter board.

Figure 2: An under construction solderless breadboard circuit featuring a surface mount adapter for the microcontroller, an LCD, and a switching voltage regulator.

What is inside a solderless breadboard?

A solderless breadboard consists of a series of spring fingers, as shown in Figure 3. A full-sized breadboard will have over 120 of these 5-position fingers are arranged the row / column matrix shown in Figure 2. For example, pin zero of the microcontroller is connected to the spring finger located at position 35.

Note that longer spring finger assemblies run the length of the breadboard (horizontal in Figure 2). Collectively, these are known as “rails” and are used to distribute power and ground to the circuit.

Figure 3: Spring fingers provide a convenient connection for small through-hole electrical components.

How is the breadboard damaged?

The solderless spring fingers are delicate. They are easily damaged by:

  • oversized wire
  • excessive force such as when a pair of pliers is used to push a component into the breadboard
  • flat-blade electrical components forced into the breadboard
  • on a related note, the breadboard plastic may be melted by excessive current

Together these actions deform or outright crush the spring rendering that portion of the breadboard unusable. It’s even worse when the damage results in intermittent faults. This can be very frustrating with significant time lost to troubleshooting. It leads to the opening comments about the poor reliability of breadboards.

How can damage be prevented?

For long breadboard life and reliability, be conservative with your breadboard expectations. Use 22 AWG solid core wire. This statement applies to connecting wire as well as wire terminal for components such as resistors. For example, the wire for a 1 W resistor will stress the breadboard. For larger components consider a hybrid approach using industrial terminal blocks such as demonstrated in this article involving precision voltage measurements with an Arduino microcontroller.

Prevent damage by twisting flat-blade connections such as the TO-220

Figure 1 shows the pin of a resistor and the pin of TO-220-packaged device held by the 5-position spring terminal. By comparison, the springs are more distorted by the TO-220 regulator. This distortion may be easier to see in Figure 4 which presents the blade as typically inserted into the breadboard (left) and then again when the blade is rotated 90 degrees (right).

Figure 4: Flat blade of a TO-220 device showing spring distortion (left) with reduced stress with a 90-degree rotation (right).

Obviously, we can’t reposition the TO-220 package with that orientation. However, we can twist the pins as shown in Figure 5 and video 1. This simple change – the twisting of pins – allows the TO-220 devices to easily slide into the breadboard.

Figure 5: Twisted leads (left) and original (right). Tool markings can be seen on the twisted leads.

Video 1: Short video showing how the LEDs may be twisted.

Conclusion

The solderless breadboard is a delicate device. The spring fingers are easily damaged by excessive force and oversized wire including the flat blade connections of TO-220 device. Take care to protect your investment by considering simple ideas such as twisting the leads of a TO-220 device. It’s a quick tip that can prolong the life of your breadboard. More importantly, it can save you hours of troubleshooting time.

For more tips like this be sure to visit DigiKey’s breadboard guide

Best Wishes,

APDahlen

About the author

Aaron Dahlen, LCDR USCG (Ret.), serves as an application engineer at DigiKey. He has a unique electronics and automation foundation built over a 27-year military career as a technician and engineer which was further enhanced by 12 years of teaching (interwoven). With an MSEE degree from Minnesota State University, Mankato, Dahlen has taught in an ABET accredited EE program, served as the program coordinator for an EET program, and taught component-level repair to military electronics technicians. Dahlen has returned to his Northern Minnesota home and thoroughly enjoys researching and writing articles such as this. LinkedIn | Aaron Dahlen - Application Engineer - DigiKey