New makers are often eager to get their idea onto a PCB and tested as soon as possible. However, there are many mistakes that new makers make, which result in non-functioning prototypes and wasted components. In this blog post, we will look at a number of common mistakes that these new makers face!
Mistakes made by new makers will, more times than not, fit into one of the following categories
All circuits start off with a circuit diagram called a schematic, and this diagram shows how different parts connect together. While schematics may be abstract and seem very distant from the final project, they are critical for a number of reasons. Firstly, schematics contain the electrical connection information of the circuit, and this is needed to make a PCB. Secondly, schematics show all the electrical components needed for the project, and they can be used to make BOMs (bill of materials). Of course, new makers are quick to place the key components into their schematic and run straight into PCB design. This typically leads to missing bypass capacitors, missing pull up/down resistors, missing inductors for filtering, and incorrect component values.
While schematics can contain mistakes, PCBs are usually the worst culprit in failed projects. PCBs are printed circuit boards that translate a schematic into a real-world device with tracks, vias, and contacts.
One common mistake that new makers make is not checking the capabilities of the fabrication house that is going to make the PCB. Just because a piece of software can make tracks 7 mm wide does not mean that all PCB manufacturers can. Other problems include holes that are too small or too large, routing areas that do not consider the width of the routing bit, and parts/tracks that are too close to the edge of the board.
Mistakes are also made in the mechanical realm. PCBs will often be mounted in some kind of enclosure, which typically means screws, bolts, and fittings. Designing screw mountings on a PCB is easy, but making sure that they line up with the enclosures can be tricky without a CAD drawing. One workaround, albeit crude, is to make a 1:1 printout of your PCB, glue the printout to thick cardboard, and then cut out the design. This can then be physically handled and even mounted in the final enclosure to ensure that the PCB matches.
Component mistakes are also very common with new makers. The silkscreen (also called the component legend) is the white text and drawings found on the top layer of PCBs, and it is helpful for identifying where components go as well as their orientation. If this layer contains mistakes, it is almost guaranteed that the final project will fail. One typical mistake is the incorrect placement of pin 1 identifiers, incorrect orientation of electrolytic capacitors and diodes, and incorrect labeling of power inputs.
Simulations are a good tool for determining if a circuit will function, but just because something works in a simulation does not mean that it will work in real life. The physical world can prevent many challenges that may go unforeseen by new makers, as they won’t have come across such problems.
One of the biggest mistakes made by new makers is heat dissipation and heat management. To start, it's amazing how many new makers do not consider heat dissipation of components and how that will have a knock-on effect on the rest of the circuit. Even if a new maker includes a heatsink, there are still other heat issues which include trapped air and poor circulation. For example, a small heatsink on a TO-220 package may be suitable, but if the component is inside a sealed unit, the air inside the unit can heat up, and the result is overheating.
Other environmental factors that get ignored include ambient temperature, humidity, chemical presence, and mechanical vibrations. The ambient temperature will directly affect the current capabilities of current-carrying wires in a negative way, such that the hotter the environment, the lower the current capacity of a wire or trace. Humidity can seriously affect certain ICs and components that may need to be kept in dryer environments, and the presence of chemicals (such as alcohol) can irreversibly damage components such as sensors.
New makers often make many mistakes that could otherwise be easily avoided. Having said that, everyone starts off learning in some way, and the best way to increase one’s capabilities is to learn from past mistakes!