Figure 1: Collision avoidance
Advanced driver-assistance systems (ADAS) like park assist, object detection and collision avoidance are the next big thing in the automotive sector. These systems are all made possible thanks to the use of ultrasonic sensors.
However, there are lots of applications for ultrasonic sensors outside of the automotive industry. Adding ultrasonic sensors to ATMs can save power by introducing a down cycle. Or you could add ultrasonic sensors to lights and alarm systems to increase safety and security. With the right artificial intelligence software and ultrasonic sensors, you can even make an autonomous robot for cleaning or industrial purposes.
Figure 2: PGA450-Q1
Traditionally, working with ultrasonic sensors has been too challenging in terms of complexity and cost to include them in typical industrial designs.
However, Texas Instruments (TI) has developed the PGA450-Q1 , an SOC with everything you need to manageably add ultrasonic sensors to your project.
The system includes a microcontroller and internal memory for storage and processing of data. These will help designers determine an object's distance or motion with respect to their product.
The PGA450-Q1 features:
- NMOS Low-Side drivers
- Configurable burst generator
- 12 bit-SAR (Successive Approximation Register) ADC (Analog to Digital Convertor)
- Configurable Digital Band-Pass Filter
- Built in 8-bit Microprocessor
- Adjustable LNA (Low-Noise Amplifier)
Figure 3: Low Noise Amplifier (LNA)
The PGA450-Q1 works in the 40MHz-70MHz range and can detect objects up to 6m away.
It does this through echo location - the same method bats use to fly and submarines use to traverse the ocean. By sending out an Ultrasonic signal and detecting the echo, the sensor can determine the distance and motion of an object using Doppler calculations. With two or more sensors, triangulation can be used to determine the location of the object.
As seen in Figure 3, a Low Noise Amplifier (LNA) and a capacitor are used to amplify the echo's analog signal and eliminate any DC offset. The gain is then adjusted using a couple of control bits and a register.
Next the amplified analog signal is passed to a dedicated 12 bit SAR ADC (Successive Approximation Register) and ADC (Analog to Digital Convertor) where it is converted into a digital signal.
Figure 4 shows that the Digital signal moves to a programmable band-pass filter, a rectifier, a peak extractor, a programmable down-sample and a selectable low-pass filter. These elements will extract the echo's signal peak and then store the data in FIFO RAM (First-In, First-Out RAM).
Figure 4 - Digital Data Path
To save memory, the data output format can be controlled so that either all 12 bits can be stored in 2 bytes; or the upper, lower, or middle 8 bits can be stored as one byte.
The data is finally fed to the 8051 WARP core microcontroller to calculate the distance. The calculation requires only 2 clocks per machine cycle, decreasing the amount of time required to process the data. TI's datasheet shows that the core can be clocked by an internal 18MHz oscillator or by an externally applied crystal oscillator.
Watch as Clancy Soehren, Applications Engineer for MSA, describes the PGA450-Q1 :
Implementing Ultrasonic Sensors into your Designs
Whether you are designing an automated vacuum, passenger assistance, or object detection device; TI supplies the programmability, tools, and documentation you will need to implement their
PGA450-Q1 ultrasonic sensor
into your designs.
For instance, TI offers a PGA450-Q1EVM (evaluation module) and USB Interface Board. These tools are designed to help assess software configurations for distance measuring and proximity detection. TI also offers documentation, ready to use firmware samples, and an easy to use GUI for program testing.
Figure 5 - PGA450-Q1 EVM setup and GUI
If you are having difficulty with alleviating low level noise and peak signal detection, read TI's white paper . Alternatively, if you would like to learn more about TI's High-Performance Analog Products check out their Analog Applications Journal .
Texas Instruments has sponsored promotion of their ultrasonic sensor interface solutions on ENGINEERING.com. They have no editorial input to this post - all opinions are mine. Christine Halsey