Have you found a resistor with only a black band in a printed circuit board (PCB) before? Did you immediately search on google to find what kind of resistor was? Chances are that was a zero-ohm resistor.
Zero-ohm resistors are resistors with an insignificant resistance value, almost no resistance at all, used as a jumper cable that connects circuits in a PCB. The usage of zero-ohm resistors seems unnecessary at first as they restrict in small values the electric current of a circuit if barely anything. Hence, the definition of zero-ohm resistors.
Zero-ohm resistors are uncommon for those who create electronic circuits as a hobby and even for some professionals. In this article, we are going to explain the different types of zero-own resistors, the reasons why they are used, the benefits of using them along with answering other frequently asked questions.
Table of Contents
Types of Zero-Ohm Resistors
There are two types of zero-ohm resistors. Wire-wound and surface-mounted resistors. Let’s take a look at each of them.
Wire Wound Zero-Ohm Resistors
A wire-wound resistor is a wire wrapped around insolation, usually, ceramic, plastic, or fiberglass core with each end of the wire soldered to the core. Wire wound resistors are the most common resistors, especially for those starting to learn about electronics.
Wire-wound resistors typically have color code bands that help people to read the resistance value of the resistors without the need of using a multimeter. This kind of resistor typically has three to six-color bands. However, zero-ohm resistors are different as they only have one black color band.
Surface Mount (SMD) Zero-Ohm Resistor
Surface-mounted resistors are typically smaller than traditional wire-wound resistors. They take less space on a circuit and are primarily used in professional manufactured PCBs.
Unlike wire-wound resistors, SMD resistors don’t use a color band system to determine the resistance value. SMD resistors instead use a three and a four-digit system using the IEC 60062:2016 standard.
SMD zero-ohm resistors are easy to determine as they are labeled with one zero (0) or 3 zeros (000) on the surface.
Reasons Why Zero-Ohm Resistors are Used
Flexibility
When building circuit prototypes using a breadboard, you use jumper wires to connect all the electric components of a circuit. Once you decide to take the prototype circuit into a professional circuit, some of those jumper wires could be changed with the usage of zero-ohm resistors.
Creating a professional PCB requires an initial schematic design of a circuit. However, there are often unknowns when creating these circuits as not all the time it is possible to know how to configure the circuits until there is proper testing and experimentation. This means changes could be required at any point and there needs to be some level of flexibility in the circuit for modifications.
Due to the nature of PCBs, these boards tend to have a printed copper circuit that maps the connecting points between all electronic components.
Let’s say after testing a PCB, you found out you need to add a resistor, a capacitor, or any other component to take care of an edge case. One way is to make changes to a printed copper circuit. However, think about how difficult this process could be: time-consuming and manual.
By designing a circuit to use zero-ohm resistors, it allows the circuit to be flexible to modifications. It is easier to change a resistor than make changes to the circuit once it is printed on the board.
This flexibility also allows configuring the same circuit board for different products. From a cost point of view, it can be more affordable to replace the materials than make changes in an existing PCB. In this way, zero-ohm resistors can work as placeholders for resistors, capacitors, and inductors.
Cheaper than Inserting Jumper Wires
If the idea behind using zero-ohm resistors is to have flexibility in the circuit in case of requiring changes, the zero-ohm resistors act as jumper wires.
You might wonder why not use jumper wires instead of zero-ohm resistors?
One of the most common reasons why zero-ohm resistors are used is because whenever the circuit goes from the prototyping phase to the production phase, automated insertion machines are used to mass-produce the circuits.
Unfortunately, if we were to use jumper wires in the circuit, this would require using a different machine and even manual labor to get the wires cut, bent, and inserted into the circuits, which is a more expensive process without mentioning how time-consuming it could be. The cost of buying zero-ohm resistors and inserting them using automated insertion machines is lower than installing jumper wires.
Testing and Calibration
Having zero-ohm resistors also gives the flexibility to test currents on circuits connected series to power supplies. Hence, it is easy to desolder one end of the resistor to measure the current, and then solder it back to the circuit than attempting to cut tracks of the circuit and attempt to connect them back after gathering current measurements.
In ideal situations, this is not always applicable since professionals should have measured the current before creating a final PCB.
Another case of using zero-ohm resistors is whenever there are circuits using a resistors-capacitor (RC) low-pass filters, but after testing professionals realize the filters are not necessary. Hence, zero-ohm resistors are installed to replace the resistor in the RC filter and then leave the capacitor off.
Frequently Asked Questions
Should I use a zero-ohm resistor when prototyping circuits?
If you are using the breadboard to build circuit prototypes or spending some time working with electronics as a hobby, most likely you won’t need to use zero-resistors. It is more practical to use jumper wires as they usually come when purchasing electronic kits, or easy to cut and bend in case you need to connect electronic components without the need of buying new components such as a zero-ohm resistor.
What is the resistance of a zero-ohm resistor?
Saying zero-ohm resistors’ resistance value is zero would be incorrect as they do have a small resistance value. The fact that it is made up of material shows it has some internal resistance. It is possible to find zero-ohm resistors with a power rating of 1/4W and 1/8W. For example, the actual resistance of a 1/4W zero-ohm resistor is approximately 0.003Ω, and 0.004Ω in 1/8W zero resistors.
Can a zero-ohm Resistor Restrict Current Flow?
Since there is an actual resistance in the zero-ohm resistors, like any other resistors, they can restrict current flow. However, it barely restricts the electric current due to resistance values being insignificant.
Difference between a zero-ohm resistor and a direct (jumper) wire
There is no functional difference between using zero-ohm resistors and a direct wire in a PCB if they are both intended to connect the circuit or electronic components. The main difference relies on how flexibly and cheaper is to use zero-ohm resistors during the production of PCBs.
Can I replace a zero-ohm resistor?
If you have a zero-ohm resistor blown and you don’t have another zero-ohm resistor with the same specification to replace it, you can use a jumper wire in replacement. Remember, zero-ohm resistors are typically used during the fabrication of PCB as placeholders of resistors or capacitors, acting as a jumper wire.
