Infrared Close Object Alert –

An Infrared close object sensor installed on an industrial vehicle detects objects or pedestrians located in a hazardous area. When it detects a problem an audio/visual indicator makes an alert, that helps drivers prevent collisions.

This is a miniature infrared close object alert device for robotic/autonomous vehicles, industrial vehicles, etc. that uses an active infrared proximity sensor for effective close object detection.

Note that an infrared (IR) sensor is an electronic device that detects/measures infrared radiation in its surrounding environment. There are two types of infrared sensors: active and passive. Active infrared sensors both emit and detect infrared light. Active infrared sensors have two parts – a light sender and a light receiver. When an object comes close to the sensor, the infrared light from light sender reflects off the object and is detected by the light receiver. Active infrared sensors act as proximity sensors and they are broadly used in obstacle detection/avoidance systems. Passive infrared (PIR) sensors, on the other hand, only detect/measure infrared radiation from objects in its field of view, but hardly respond to active infrared light. Quick Read

Circuit Diagram & Design Description

The key component in this little circuit is a cheap adjustable infrared proximity switch E18-D80NK. This particular noncontact proximity sensor switch has a comparatively long detection range (3cm-80cm) and has a normally-high (H) logic-level NPN transistor output. This TTL output goes low (L) whenever the sensor detects an obstacle. The recommended working voltage is 5V DC.

E18-D80NK Datasheet

E18-D80NK Seller (no affiliation)

The sensor is a ‘standalone’ infrared proximity sensor, so no external control/driver circuitry is needed to play with it. You can directly connect a low-current 5V electromagnetic relay or piezo-sounder at its output as depicted in the below wiring diagram. The output can sink a maximum current of 100mA at 5V DC.

However, a more sensible alarm circuit is tailored specifically to work with the E18-D80NK sensor. The complete schematic (v1) is below.

The alarm circuit revolves around the revered 14-stage ripple-carry binary counter/divider and oscillator CD4060BE (IC1) which has three oscillator terminals, ten buffered outputs and an overriding asynchronous master reset input. The oscillator configuration allows design of either RC or crystal oscillator circuits. See RC oscillator components R2-C3 in the schematic. As stated in the intersil™ CD4060B datasheet, the formula to set the RC oscillator frequency is FOSC = 1/ (2.2xRTxCT). So, in our case FOSC = 1/ (2.2 x 1 x 106 x 22×10-9) = 20.66Hz. This results in a buzzer drive frequency (Q4) nearly 1.2Hz and indicator drive frequency (Q5) circa 0.6Hz.

CD4060 Datasheet

Here, IC1’s pin 7 output drives a small active piezo-buzzer (BZ1) through a common NPN transistor S8050 (T1), while pin 5 drives a high-bright red indicator (LED1). The 1N4148 diode (D1) wired across the piezo-buzzer is optional but it should be there if you are using an electromagnetic buzzer in lieu of the active piezo-buzzer. The 100K resistor (R1) is the pull-up resistor for IC1’s master reset terminal (Pin 12) to reset the counter. Remember, a high (H) level on Pin 12 resets the counter, independent of other input conditions.

The working principle of this circuit is extremely simple and straight forward. When the infrared proximity sensor (E18-D80NK) senses an object in front, its internal NPN transistor pulls the output down (H→L), and this action enables the alarm generator (CD4066BE) by grounding its reset pin (Pin 12) linked with the output of the sensor.

Construction & Installation Hints

The entire electronics (except the infrared proximity sensor) can be assembled on a flake of standard perforated circuit board. The next steps are to build a box for it, and to prepare a mounting bracket/clamp for the infrared proximity sensor. Since the body is threaded and two knurled nuts are included, it can securely be mounted in a 19mm hole. The 45cm cable length of E18-D80NK might make interconnection between the sensor and alarm an easy job. Author’s alarm enclosure suggestion (artwork) is provided below.

It is worth noting that the entire setup needs a regulated 5V dc power supply. Therefore, a 12V to 5V dc regulator/buck converter must be included for automotive applications. Simply pick up a homemade or readymade dc-dc buck converter and go!

The sensitivity detection is adjustable using a multi-turn screw head on the back of the unit. By turning the screw head clockwise and counter clockwise we can set the detection sensitivity/range. The red indicator on the same side is lit when an object is detected.

Closing Note

To sum up then, the infrared close object alert device (simply an active infrared proximity sensor) transmits pulsed infrared light. An object within the detection area will reflect the transmitted infrared light, thus propelling the sensor alarm activation. The maximum detection range will vary depending on the ability of the object to reflect infrared light. That is all!

Here are some snaps of my quick breadboard setup.

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