Teardown: Vehicle Backup Sensors - LEKULE BLOG


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Thursday, 13 October 2016

Teardown: Vehicle Backup Sensors

What's inside of a card backup sensor? Find out in this teardown!

May cars today come equipped from the factory with reverse sensors that warn drivers when they're about to back into something. If you want to add this functionality to a car after purchase, however, you can get a system of sensors that you can install, yourself.

The concept of backup sensors was first patented in the 1970s and re-patented in the early 90s, but have only become popular as a feature for automobiles in the last several years.
The system we are tearing apart in this Teardown Tuesday is from E-KYLIN and was purchased from Amazon for around $15.

The E-KYLIN system. Image courtesy of Amazon.

This system is comprised of a control module, a display, and four sensors. Let's take a look at the insides of all of these.

Opening it Up

First, let's open up the control module. The control module acts as a hub for the four sensors and the user interface to plug into.
Opening up the control module was a breeze! Two Phillips head screws were removed and the box was opened. Inside of the plastic box was a single circuit board.

The Control Module Opened
The control module opened up

Getting into the sensors was a bit more challenging. The back of the sensor was easy to remove with a small flat head screw driver, but the removal only revealed a relatively large amount of white and grey flexible potting compound.

The Sensor Module Opened
The inside of one of the sensors

To open the user display two Phillips head screws were removed. With the screws removed, the housing was able to be opened. Inside of this display, there was a small speaker, a circuit board, and a segmented LED display.

The Display Module Opened
The inside of display

Circuit Boards

There are two circuit boards used in this product. There is the board inside of the control module and the board inside of user displays. The board inside of the control module measures 39.5mm by 85mm and features typical green solder mask and white silkscreen on both sides. This board contains SMD components and a handful of through hole ones exclusively on a single side.

The Control Module PCB
The control module circuit board

The board inside of the user display measures 14mm by 36mm and has a matching color scheme to the other board. This board has SMD components and wires soldered directly to it. There is a three-conductor cable that terminates with a position connector that gets plugged into the control module. There is a 29-segment LED display soldered to the board.

The display pcb
The display's PCB


The Microcontroller
The unmarked microcontroller

There isn't a lot to discuss concerning these microcontrollers. Both microcontrollers—the one in the control module and the one in the user display—lack part numbers. These are in SOIC-14 packages.

Analog Signal Processing

The Mux
The HCF4052 multiplexer

This system works on ultrasonic waves. The sensors emit a high-frequency sound and the electronics look for a reflection. These reflections are typically very small and require amplification and processing in order to be useful.
On the control module, there is a multiplexer that passes the output of the sensors to the input of a low noise amplifier. The mux is in an SOP-16 package, part number HCF4052B. The amplifier, in an SOIC-8 package, is made by Texas Instruments, part number NE5532.

The TI NE5532 LNA

Power Supply

The LDO voltage regulator

This sensor system runs off of a car’s electrical system. These voltage rails aren’t perfect and can be noisy or fluctuate in value over time.
This device uses a 7805 linear power supply to regulate the 12VDC down to 5VDC. There is a diode across the power input and several caps to filter out transients.


The Sensor
One of the four sensors

This backup system relies on four sensors. These sensors are in a housing made of a stamped metal shell and plastic components. This shell is packed full of a flexible white potting compound.
After removing a lot of potting compost, a small piezoelectric transducer was revealed.

The ultrasonic transducer
The small piezoelectric transducer

This sensor system is an inexpensive way to add more safety features to your car. It's a relatively simple device, but its accessibility is a testament to how quickly technology is going from concept to consumer.

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