Ultrasonic parking sensor (transducer)


You might be probably thinking that this question has been answered a thousand of times, but I think this case is different.

I bought a couple of days ago a ultrasonic sensor from Conrad with the following reference:

ULTRASONIC SENSOR K-14WP10 http://shop.conrad-uk.com/components/sensors/ultrasound-sensors/182271.html

I was expecting this sensor to be same as the rest of the ultrasonic sensor examples I've found but this is not the case, this sensor has only two wires, while the rest of the examples three wire sensors which confuses me a bit.

The spec data sheet does not have many details si I'm a bit without much ideas from where to start from.


Maybe you guys are able to provide me some guidance on where to start from. I swear I've googled but most probably I'm not issuing the correct words.

Thanks in advance.


I forgot to say that the reason that confuses me is that this is supossed to be a transducer.. not an emitter or receiver.

this sensor has only two wires,

Isn't that just a bare transducer?

Why not buy a Devantech or a Ping? If you're having to ask these questions, you're probably not going to be able to build a working solution from scratch.

Sorry I cant be of much help except to say all the US parking sensors I have seen ( and thats a lot) have been two wire ones.

I forgot to say that the reason that confuses me is that this is supossed to be a transducer… not an emitter or receiver.

A transducer is “any electronic device that changes one form of energy into another, such as a microphone, which changes sound waves into electrical signals”.

A transceiver is “a device that has both a transmitter and a receiver which are combined and share common circuitry or a single housing. If no circuitry is common between transmit and receive functions, the device is a transmitter-receiver”.

An ultrasonic transmitter is a “transducer” it converts electrical energy into ultrasound.
An ultrasonic receiver is a “transducer” it converts ultrasound into electrical energy.

Are you sure the “sensor” device you purchased is not just a “detector” or “receiver” i.e. you also need a transmitter.

The “ping” unit mentioned by AWOL is an ultrasonic range finder it has both a transmitter and a receiver, its range is 2cm to 3m.
Before you purchase anything you might want to consider the environment it will work in e.g. if on a vehicle will it survive a car wash.

This one is just like a microphone. There is no IC in it to detect distance. It seems to go on a car rear bumper cover. Look at newer cars they have up to 4 of these on their rear bumper covers. You need driving circuit to send waves out and receive them and amplify them before you can detect distance.

The 'sensor' you linked to is just a simple raw ultrasonic element (or resonator). It is neither a sensor, nor detector, nor emitter without proper electronics wired to it.

Just as a 2 wire crystal resonator is not a crystal oscillator, without first being wired up to a amplifier circuit with proper feedback. The ultrasonic element is of such a size and thickness as to be designed to operate at 40khz, just as a crystal resonator has physical size properties that determine it's operating frequency.


Thankyou all! Your messages actually clarified a bit the whole thing. Now that I know what is this, could someone point me to some “sample” circuit? Of course I need to understand the princople behing these devices but it would help if I had a sample circuit I could try to learn from.

Any help?

Thanks in advance!

The Devantech SRF04 schematics are online somewhere, if you look for them