Mechanical potentiometers have been around for decades. In addition to being used in ruggedized joysticks, they have been used in everything from circuit trimming to volume control. While they have been around the longest, they have limitations. The main issue is the wipers wear out the sensors over time. The sensors are also prone to moisture ingress and they can be moved off their set position leading to inaccuracies. It is these drawbacks that have seen the birth of more reliable sensors. Top on the list is the digital potentiometer.
The digital potentiometer is also called a digital pot. It was created to overcome the flaws that traditional potentiometers have. The sensor solves these issues by bridging the digital domain and the analog resistor world. Since it is an all-electronic component, the digital potentiometer allows a process and software to control, vary, and set their voltage divider ratio or resistance value.
As an upgrade to the traditional precision potentiometer, a digital pot offers more features and functions that mechanic devices are incapable of providing. These sensors are also more rugged and reliable thus the reason they are more popular in ruggedized joysticks. They have no moving wiper which means they will last longer due to the reduced wear that is common in traditional potentiometers. Moreover, these sensors cannot be tweaked deliberately or adjusted inadvertently. This eliminates the issues of inexplicable performance problems.
Digital potentiometers have many uses. They are mainly used in such applications as:
- LED dimming
- LED thermal stabilization
- Closed-loop gain control
- Audio volume adjustment
- Wheatstone bridge trims for sensors
- Tuning programmable analog filters
- Controlling current sources
Specifications of digital pots
Just like all other sensors used in desktop controllers, there are top-tier parameters and secondary parameters to consider when choosing a digital potentiometer. Top rank issues are the resolution, nominal resistance, and the type of digital interface. Second considerations include voltage range, tolerance and error sources, distortion, and bandwidth.
- Resistance value
The resistance value is determined by the design considerations of the circuit. In a 1/2/5 sequence, most manufacturers offer resistance of 5 kilo-ohms to 100 kilo-ohms. There are some range units that go as low as 1 kilo-ohm or as high as 1 mega-ohm.
This refers to the number of discrete tap or step settings that a digital potentiometer has. The resolution ranges from 32 to 1024 steps. The higher the resolution is, the more precise a ruggedized joystick will be. You should note that a mid-range digital pot with a resolution of 256 has a higher resolution than a traditional potentiometer.
A lot has to be considered when choosing a sensor. Understanding what you need ruggedized joysticks for will simplify decision-making. Always be clear on what you need before you go shopping for a computer controller.