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This Instructable demonstrates a method of increasing the measuring range of the popular HC-SR04 ultrasonic distance sensor.

The enhancement in range is based on reducing the 'field of view' (FOV) of the basic sensor by using it as a feed element for a parabolic dish.

No changes have been made in the electronics of the basic HC-SR04 sensor. However, a blanking circuit has been added externally so as to ignore the first reflection/distance from the feed element to the parabolic dish.

The HC-SR04 is connected to an Arduino uno which displays the measured distance on a standard PC1602 16X2 LCD display. The distance is also sent on the serial link through the USB connector.

For outdoor experiments the system was powered through the USB connector using mobile power bank.

A maximum distance of 9.24 meters was achieved in the experimentation as compared to the 4 meters specified for the basic sensor.

I wish to acknowledge useful inputs from Emil's Project Blog where he has provided an excellent tear-down of the HC-SR04 ultrasonic distance sensor:

http://uglyduck.ath.cx/ep/archive/2014/01/Making_a...

Step 1: The Parabolic Reflector

The specifications of the HC-SR04 ultrasonic sensor indicate a measuring angle of 15 deg. When used as feed element for a parabolic dish, so that the dish is fully illuminated it needs to be placed at a sufficient distance from the dish. A shallow dish is required so that the focal length matches this requirement.

An old frying pan with a diameter of 250 mm and a depth of 16 mm is chosen as the parabolic dish. Standard calculations for sound in air at 40 kHz indicate a focal length of 24.4 cm and a FOV/ beam width of 2.31 deg.

The reduction in measurement angle/FOV from 15 deg to ~ 2.3 deg will be used to provide the increased measurement range.

The pan handle-arrangement is modified and a aluminum tube suitably bent is taped to the handle bracket to form the feed support beam. The HC-SR04 sensor is fixed along the center line of the parabolic dish at a distance of ~ 24 cm.

<p>Thank you for unveiling how to blanking the HC-SR04!<br>I thinking of doing it for another project with a false echo.<br>I don't have any Schmidt-inverter gates in stock.<br>Is it possible to connect the blanking pin direct to a output pin on the arduino, and do the timing with software?<br>What do you suggest for component in between? Is a diode enough?</p>
<p>A negative going blanking pulse with the diode and 6.8 k Ohm worked for me. You may need to experiment on the resistor value for the particular build of the HC-SR04. Yes you could synchronize the blanking with the trigger using the arduino and software based on an ISR. I found it easy with the Schmidt gates.</p>
<p>The pan you used does not look like one you can get easily around here (I guess it's used to make chapati or the like?). Would an old Sat receiver dish work too? I guess so.</p>
<p>nice work !!!</p>
<p>Great mod to a popular item. I love the frying pan!</p>
<p>Very cool instructable! I learned a lot from this. Thanks for posting!</p>
<p>your designs are always simple and effective. This is another addition to awesome designs, Thank you for sharing, sir!</p>
<p>Can't you simply ignore the first echo instead of making an hardware filter ? Or do I miss something ?</p>
<p>The way the HC-SR04 operates is that the Echo goes High shortly after the trigger and then comes Low for the first reflection/return which crosses the detection threshold. When using the reflector the first return would normally be from the reflector itself. The blanking signal moves the detection threshold to a large value for ~2.5 msec/ 40 cm and then restores the threshold back to the old value so that the sensitivity is maintained. The High-to-Low would then be from an object in front of the dish. The Arduino Sketch measures the Low-High-Low time of the echo signal and works out the distance based on this.</p>
That looks awesome! How accurate is it at distance?<br><br>Have a great day! :-)
<p>I was basically checking out the scheme. Need to work on the accuracy.</p>
Excellent!
<p>This project is ideal to use my unused 90cm satellite dish with the HC-SR04. Some day I will try too this experiment, thanks!</p>

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Bio: I am a retired Electronic Systems Engineer now pursuing my hobbies full time. I share what I do especially with the world wide student community.
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