The sensor inputs are as important as the outputs. So, keeping the input voltage of the sensor at a constant level with a step-up/step-down voltage regulator is mandatory to have accurate measurements.
In another tutorial, I have shown you how to make accurate ADC readings with Arduino. In this post, I continue the series of articles about how to make accurate readings with sensors. Using a switching voltage regulator to keep a constant voltage level at the input of sensors is important for both digital and analog sensors.
A sensor is designed to return accurate measurements at a certain value of the voltage. Most of the sensors used in robotics are in the range of 3.3V and 5V. Of course, some sensors are exceptions. For example, the LIDAR-Lite v3 is designed to work with a power supply between 4.75 and 6V maximum.
For example, if the sensor requires a 5V constant power supply, it will return the most accurate readings at this value. So, we need to make all we can do to have a constant voltage at the input of the sensor. The power supply voltage value is indicated in the datasheet of every sensor.
A voltage regulator is designed to provide a fixed voltage level regardless of its input.
There are several types of voltage regulators, but in this article, I will focus on the switching regulators.
A switching regulator can work as a step-up and step-down voltage regulator. I choose to concentrate on this type of voltage regulators because it has high efficiency and is capable of providing multiple regulators.
The power dissipation of a switching regulator is low compared with other regulators. Also, it is able to carry heavy load currents at low voltages with less bulky heat sinks.
Of course, the efficiency depends on the parts designed for a specific input and output voltage. An efficiency between 85% and 95% is considered a good one for a switching regulator.
The two main types of switching supplies are called simple step-up and step-down regulators. On the market, you can find step-up voltage regulators, step-down voltage regulators or a combination of these. A step-up regulator will take a lower voltage and make it a higher voltage. For example, it can take a 3V supply and produce 5V at the output. A step-down regulator works in the opposite of a step-up regulator. This one can take a 7V input and create a 5V output. A combination of these two – a step-up/step-down regulator – has the ability to convert both higher and lower input voltages. Lastly, a step-up/step-down regulator can efficiently produce, for example, 5V from input voltages between 2.7V and 12V.
Example: Step-up/step-down voltage regulator and the HC-SR04 sensor
In this example, I use the Pololu’s 5V step-up/step-down voltage regulator S7V7F5 and the HC-SR04 ultrasonic sensor. The S7V7F5 switching regulator has an efficiency of over 90% and produces 5V from input voltages between 2.7 V and 11.8 V. When stepping down, the module can supply up to 1 A.
Find more step-up/step-down voltage regulators here.
This voltage regulator is designed with three connections:
- the input voltage (VIN);
- ground (GND);
- the output voltage (VOUT);
The input voltage VIN should be between 2.7 V and 11.8 V.
The output voltage VOUT has a fixed output of 5 V.