Parking sensor sonar?

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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Parking sensor sonar?

Post by bigbadbob »

Well I was bored "working from home" today so got to thinking about using a car parking sensor as a crude sonar.
I have a cheap set that I was planning on fitting to my van but thought I'd play with it first.
The sensors are at least semi waterproof so I rigged it up to a battery with one sensor fitted and did a few measurements in air,
It seems quite accurate over it's measurment range from 0.3 to 1.9m considering it's 0.1m resolution.
Next I put my thumb over it and it didn't beep or give a distance reading so that seemed positive.
Dipping it in my water tank was another matter though...
It beeped continuously and gave a 0.0m reading when facing down towards the bottom of the tank. (0.7m deep)
thinking about it, the speed of sound in water is abt 1500m/s compared to abt 343m/s in air.
so over four times as fast and the signal is probably returning too quickly at that range for the system to handle.
Maybe it'll work better in deeper water. by my calculations that should be 1.3 to 8.3m which would be handy for collision avoidance for a rov. :D

The chips on the board are-
SM8P2501 microprocessor.
CD4052B 4ch multiplexer. the board takes up to 4 sensors so that makes sense.
4558D op amp. fair enough, nothing fancy there,
LM2903 voltage comparator, hmmmm.... not sure what that's doing.

next time I'm bored I'll investigate the microprocessor data output stream.
I'm away to walk the dog and think about this...
Anyone else played with these things before?

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asesorplaza1
Posts: 187
Joined: Mar 4th, 2018, 6:11 pm
Location: Valverde de Júcar, Cuenca, España

Re: Parking sensor sonar?

Post by asesorplaza1 »

Buenas tardes.

Esos sensores son hermanos del sensor de ultrasonidos JSN-SR04T, se pueden usar en exterior, porque tienen la electrónica "protegida", y son iguales que el sensor de ultrasonidos HCSR04, pero no aguantaran la presión al ser sumergidos, si quieres usarlos en la camioneta, yo primero probaría con un sensor JSN-SR04T, es mas barato que tu sensor de aparcamiento, y si se rompe, no se fastidiara la posibilidad de ponerlo en tu camioneta.

Un saludo.



Good afternoon.

These sensors are brothers of the JSN-SR04T ultrasonic sensor, they can be used outdoors, because they have the electronics "protected", and they are the same as the HCSR04 ultrasonic sensor, but they will not withstand the pressure when submerged, if you want to use them in the van, I would first try with a JSN-SR04T sensor, it is cheaper than your parking sensor, and if it breaks , the possibility of putting it in your truck won't be disturbed.

Greetings.
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bigbadbob
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Joined: Nov 28th, 2011, 10:24 am

Re: Parking sensor sonar?

Post by bigbadbob »

Thanks AP1. that's good to know.
the breakout board that comes with the JSN-SR04T will make life easier as will the ping library.
I'll order one and play with that and pot the sensor in oil.

I have been poking my sensor board data output with a logic analyser and it is putting out what look like strange data signals but it all makes sense now, it's putting out timing signals. I'll poke it with my oscilloscope.
Thanks again. :D
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bigbadbob
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Joined: Nov 28th, 2011, 10:24 am

Re: Parking sensor sonar?

Post by bigbadbob »

I had another go at this today thinking that using all four sensors (two front, one port, one stbd) would be interesting as they are mutiplexed together and the data from all four is transmitted on a single data line from the control board to the receiver/display board.
using my logic analyser showed it is putting out some sort of manchester coding or similar at 1kbps but my analyser didn't recognise the protocol and I lost motivation to take it any further.
asesorplaza1
Posts: 187
Joined: Mar 4th, 2018, 6:11 pm
Location: Valverde de Júcar, Cuenca, España

Re: Parking sensor sonar?

Post by asesorplaza1 »

Buenas noches.

Es que, como pasa siempre, una cosa es la teoría y otra muy distinta, la práctica.

Cada marca de este tipo de sensores, utiliza un protocolo de codificación, como bien has dicho, y averiguar cuál es el de tu equipo, es bastante complicado, por no decirte imposible.

Entre otras cosas, porque en el libro de instrucciones, como máximo, te dirá que cumple la normativa para poder venderse en USA, junto con unas fotos del proceso de montaje, y que no lo tires a la basura, y lo lleves a reciclar, y poco más.

Si tú buscas la marca en Internet, no aparecerá, como mucho la distribuidora para USA, UE, ASIA, y ya está, que será la misma tienda donde lo has comprado.

Por lo tanto, volvemos a la casilla de salida.

La teoría es que tiene un controlador, vaya usted a saber cual, normalmente algo parecido a un Arduino Nano, pero aunque abras la caja, cosa que dudo que puedas hacer, porque estará termo sellada, no atornillada, por lo que para abrirla tu tendrás que romperla, y lo que tu verás será un montón de componentes electrónicos, cuya distribución no tiene nada que ver con lo que conocemos como algún Arduino.

Y aunque puedas utilizar la ingeniería inversa, llegar al procesador interno de tu equipo, y sacarle el programa, traducir el código binario a código ascii, lo normal es que este en algún idioma Asiático, y lo máximo que puedes conseguir es llenarte la pantalla de símbolos ilegibles


Este controlador, recibe la señal de los cuatro sensores, que tienen su posición para saber cuál es, normalmente están numerados, para pincharlos en el mismo orden en su puerto del controlador, y lo que hace es procesar esos datos, y en función de los dos sensores que mas señal de rebote o eco reciban, marca en la pantalla el lado de la proximidad del objeto.

La teoría es así de sencilla, y seguro que no te he dicho nada nuevo, pero la realidad es así de cruda, tú no vas a poder averiguar cómo se hace el proceso internamente en tu equipo.

Con las mismas, si compras cuatro sensores JSN-SR04T, un Arduino del modelo que quieras, un zumbador, y una pantalla, tienes los mismos componentes, pero te toca a ti hacerte el programa. Solo así, tu podrás saber cómo funciona de verdad

Un saludo



Good night.

It's just that, as always happens, one thing is theory and another very different, practice.

Every brand of this type of sensors, uses a coding protocol, as you have said, and find out what your computer is, is quite complicated, because you do not know impossible.

Among other things, because in the instruction book, at most, it will tell you that it complies with the regulations to be sold in the USA, along with some photos of the assembly process, and that you do not throw it away, and take it to recycle, and little else.

If you search for the brand on the Internet, it will not appear, at most the distributor for USA, EU, ASIA, and that's it, it will be the same store where you bought it.

Therefore, we return to the exit box.

The theory is that it has a controller, go you know which, usually something like an Arduino Nano, but even if you open the box, which I doubt you can do, because it will be thermo sealed, not screwed, so to open it you will have to break it, and what you will see will be a lot of electronic components, whose distribution has nothing to do with what we know as some Arduino.

And even if you can reverse engineer, reach your computer's internal processor, and take the program out, translate the binary code into ascii code, it's usually in some Asian language, and the most you can get is to fill the screen with unreadable symbols

This controller, receives the signal of the four sensors, which have their position to know what is, usually numbered, to click them in the same order on their controller port, and what it does is process that data, and depending on the two sensors that receive the most rebound or echo signal, mark on the screen the proximity side of the object.

The theory is that simple, and I'm sure I haven't told you anything new, but the reality is that raw, you're not going to be able to figure out how the process is done internally on your team.

With them, if you buy four JSN-SR04T sensors, an Arduino of the model you want, a buzzer, and a screen, you have the same components, but it's up to you to play the program. Only then, you'll know how it really works

A greeting
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bigbadbob
Posts: 272
Joined: Nov 28th, 2011, 10:24 am

Re: Parking sensor sonar?

Post by bigbadbob »

I did some more to this but found it wasn't sending all the sensor data every time so I gave up on it and fitted it to the van.
I'll play with the JSN-SR04T when it arrives.
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