Ultra sonic sensor selection

I am designing a proof of concept product that needs to have an ultra sonic sensor placed inside a small dome 70mm w x 35mm deep

The purpose of the sensor is to detect movement that occurs over the dome at close range eg no more than 10-15mm proximity

You have a rang of sensors I am wondering which is the simplest and cheapest solution given my above application

The sensor will need to be connected to an arduino mini so that each time the sensor detects object within proximity ( passing over front of dome ) it will activate a 5v push solenoid ( unless it’s possibly to connect sensor, solinoid and 5v battery together to activate solinoid each time it detects proximity

Please note the ultra sonic sensor simply needs to detect proximity of object it does not need to measure distance

I welcome your advise

Hey Claude,

That sounds like a great project!

Before we continue forward into potential designs, have you thought about using PIR (Passive Infrared) Sensors.

They are used in most motion detector circuits e.g. automated lighting, motion triggered alarms etc.
The one I just linked above has both a variable sensitivity and time delay before switching.

Take a look at them because I think they will be your best option!

Hi

My application is outdoors and I have researched that after dark or bright sunlight can influence the effectiveness of ir sensors so that’s why I am focusing on ultra sonic instead

Given above my initial question I posted remains.

Claude Raiola

0414 228 948

Hey Claude,

No worries then. Ultrasonic sensor will likely be your nest best bet then, however unlike the PIR Sensor they don’t really work within a dome setup as they detect in an area in front of them as shown in the picture below.

image

There may be a workaround though, we’ll leave this post open ended for now and someone may come up with an answer!

Some only have 1 sensor not 2 ???

How do u know which will be sufficient as your site has many at differing prices

All I need is to detect movement ie proximity no need to based on distance as the object will only ever be 10-20mm from surface of dome

What about temperature ir sensor as the object waved over the front will always have a temperature eg a humans hand

Claude Raiola

0414 228 948

Hi

Just read about pir it advises it will work equally well in sunlight as it will at night.

So would the pir solution be ably to be mounted under my own dome and therefore able to remove the pir sensor dome ???

Claude Raiola

0414 228 948

I found a PIR however the details in the specs advise

The human body sensor module can only work indoors and the work environment should avoid the sun, a strong direct light exposure, if the work environment has a strong RF interference, you can use shielding measures. In case of strong air interference, close the doors and windows or prevent convection. The induction area to avoid facing heating appliances and objects as well as easy to wind debris and clothing.

So this brings me back full circle

I still want the motion / proximity sensor to work in direct sunlight as well as dark but it needs to be mounted inside a small opaque dome

I welcome your advise

Regards

Claude Raiola

0414 228 948

I have used an ultrasonic sensor with Arduino. My device monitors an empty beehive to detect when a colony of bees move in (for biosecurity). It is designed to measure hourly and run for about a year, reporting to the Internet via either LoRa or GPRS. So low power consumption is important.

In my case, it was the RCWL-1601 (Ultrasonic Distance Sensor - 3V or 5V - HC-SR04 compatible). The HC-SR04 itself is 5V (this may be important, depending on your Arduino). These ultrasonic sensors are specced to measure down to about 2cm, so may not be quite right for your application. One thing I found was that the sensor continued to draw current even when the Arduino was sleeping, so I had to add a MOSFET into the circuit to act as a switch in order to prolong battery life.

I did try a IR Distance Interrupter (RFR-359F photoreflector) but found this was very much affected by sunlight.

I can send you more details or a copy of the code if this would be helpful.

Hi yes please do send all assistance appreciated

The 2cm would be ok but it would need to be limited to about 5-10 cm

I do not want a person walking past to trigger the sensor so only close proximity between 5-10 cm

Claude Raiola

0414 228 948

Also my project needs to have the sensor place inside a Perspex dome as it is placed outdoors in public areas exposed to the weather.

Are their any ultra sonic sensors that will still work when covered by a dome

As always I thank you for any advise / assistance

Claude Raiola

0414 228 948

you could easily limit the range in software - only send trigger 2-10cm and ignore any readings greater than 10cm

I don’t imagine that the ultrasonic sensor would work with a perspex dome. You probably need to either use a different technology or come up with a different way of shielding from weather. Having said that, I think the parking sensors on the back of your car are ultrasonic!

Hi again Claude,

Yep, Andrew was right on that last one. Ultrasonic sensors will work only in gas environments or through materials which are transparent to ultrasound. I think polyurethane may work or like Andrew the material that covers the reverse sensors in cars.

Sound will travel within hard plastic or perspex for some distance. The majority of incident energy reflects off, and only a small amount transfers through.

As a possible middle-ground sensor, I’m gonna suggest looking into LiDar. It is the light-using equivalent of Ultrasonic Sensors and works using very similar principles.

Hi I had a look at your suggested alter erode however it seems to measure objects from 30cm and above when I need to sense objects between 20mm to 50mm from the sensor and ignore all objects further away than that.

As always I welcome any advice

Claude Raiola

0414 228 948