While looking for a way to make a DIY parking sensor kit for my car I came across Arduino and some cheap ultrasonic range finders such as SRF-06 and HC-SR04.
The problem is both of these use separate transmitter and receiver units (apart from the fact that mounting these on my bumper is not an option). I bought a few parking sensors off eBay and they seem to be an all-in-one design. The parking sensors are only big enough for a single transmitter/receiver, and there are only 2 wires coming from them, meaning that they must be some sort of transceiver version.
Does anyone know if these ultrasonic kits can be modified to use the parking sensors, or of another way to use them?
Do you have any link to more information about the sensors as this is too little info to give any meaningful answer.
The fact they are on E-bay or cheap says nothing about connectivity
The ultrasonic rangefinders can be mounted under a bumper sometimes (keep them dry)
Just your typical drill-a-hole-in-your-bumper style parking sensors.
Plastic housing so no grounding.
EDIT: Just pulled one apart expecting to find an ultrasonic unit, not sure if that's what I found.
After getting though a pile of plastic/glue/rubber stuff, I found the 2 wire cable connecting to a small PCB which in turn has 2 thin wires heading to the tip/front of the sensor. In between the rubber glue gunk and the tip was a cork plug of some kind with some cotton between the cork and the front. I'm not sure, but there might be a cheap speaker at the front, like those you find in cheap handheld games which are little more than a tiny cone with a thin metal backing.
...So it's just a glorified speaker?
Either way, I'm guessing it's nothing like the rx/tx units in the ultrasonic kits.
Well what you bought are raw ultrasonic 40khz resonator elements. With no support electronics these resonators are not useful as is for connecting to an Arduino board. The seller seems to also sell the support electronic assembly needed to utilize these sensors.
retrolefty:
Well what you bought are raw ultrasonic 40khz resonator elements. With no support electronics these resonators are not useful as is for connecting to an Arduino board. The seller seems to also sell the support electronic assembly needed to utilize these sensors.
If by support assembly you mean the buzzer/5 LED unit that's what I'm trying to avoid. I want precise measurements I can display in in/cm, not just some red/green LEDs.
I was hoping I could use a addon such as the HC-SR04, but with these in place of the tx/rx elements provided. Then I could use an Arduino to display the results in whatever manner I choose.
retrolefty:
Well what you bought are raw ultrasonic 40khz resonator elements. With no support electronics these resonators are not useful as is for connecting to an Arduino board. The seller seems to also sell the support electronic assembly needed to utilize these sensors.
If by support assembly you mean the buzzer/5 LED unit that's what I'm trying to avoid. I want precise measurements I can display in in/cm, not just some red/green LEDs.
I was hoping I could use a addon such as the HC-SR04, but with these in place of the tx/rx elements provided. Then I could use an Arduino to display the results in whatever manner I choose.
Might be worth a try, just unsolder the elements on the HC unit and wire to these new elements.
retrolefty:
Might be worth a try, just unsolder the elements on the HC unit and wire to these new elements.
Lefty
Yes, but the problem is those addons use separate tx/rx resonator elements, whereas these appear to be some kind of combo element.
All raw ceramic ultrasonic resonator transducers are useable as both either a radiating element or as a receiving element. Just like a loudspeaker can be used as a microphone as well as a speaker, just not at the same time.
Many of the earlier ultrasonic rangefinders just used one resonator element, and switched the internal electronics from transmitting mode to receiving mode as required.
retrolefty:
All raw ceramic ultrasonic resonator transducers are useable as both either a radiating element or as a receiving element. Just like a loudspeaker can be used as a microphone as well as a speaker, just not at the same time.
Actually, Lefty, this isn't true - there are some ultrasonic elements out there that are sold in TX/RX matched pairs - you can't use a TX as an RX, or vice-versa...
retrolefty:
Many of the earlier ultrasonic rangefinders just used one resonator element, and switched the internal electronics from transmitting mode to receiving mode as required.
Switching isn't done - based on the circuits I have seen, the transmitter outputs a pulse to the element; the element is also connected to the receiver amplifier with a back-to-back, opposite polarity diode configuration, which (IIRC) is supposed to clamp/dampen the transmitter output, but let thru the comparatively smaller return-echo (which occurs later than the transmit pulse, obviously - except for extremely close ranges, where the ringing and such overlaps with the return echo). This diode arrangement is essentially there to keep the transmitter amp from blowing the receiver amp; the pulse is sent out, then the system waits a beat (to "skip" the dampened transmitter pulse on the receiver amp - allowing it to settle to "quiet"), then the system listens for the echo from the transmitted pulse.
Actually, Lefty, this isn't true - there are some ultrasonic elements out there that are sold in TX/RX matched pairs - you can't use a TX as an RX, or vice-versa...
What I said was "All raw ceramic ultrasonic resonator transducers are useable as both either a radiating element or as a receiving element." What isn't true about that?
I wonder why that might be? Other then maybe different physical size to optimize for sending Vs receiving? 16Mhz crystal elements blanks come in many different sizes but they all can be made to resonate at their designed frequency. The very first ultrasonic resonator I came across was the Polaroid unit sold as an experimenter's kit in the very early 80s. Polaroid used the same element in some of their cameras of the time for a auto focus function. They used the single element for both sending and receiving. The complex part of the circuit was the receiver ramping automatic AGC circuit that would increase receiver gain the longer the time it took for the pulse to return, as longer distance = weaker return pulse, But a short return pulse could overload the receiver input stages if a fixed gain was used.
...So I guess I can't just by one of these kits, hook these parking sensors up in place of the receiver/transmitter (or ideally both at once) resonators, and expect it to work?
I'd love to find a ultrasonic kit that uses a single resonator, but so far I've only seen these ones that have separate rx/tx ones.
If you have separate TX and RX units then the drive electronics is easier since you don't have to switch between transmitter and receiver circuitry. Also the TX unit can be optimized for transmitting (high power handling) and the RX unit for sensitivity.
The after-market parking sensors seem to all be single units for easy of mounting (4 holes in car rather than 4 pairs of holes). The electronics is basically four resonant-transformer-based output drivers (40V output or so IIRC) and a CMOS analog switch for routing the low side of the transformer to a sensistive amplifier / level-detector circuit. An MCU cycles round the the sensors pinging each one with something like a 6 cycle square wave at 40kHz and then listening to the sense amplifier and identifying the significant echos (presumably with ADC)
I thought about trying to hack one of these units by cutting off the MCU and connecting direct to an Arduino (there's basically logic output, analog input and some logic lines to control the multplexor).
That way you get 4 distance/proximity sensors for quite a low price (I've seen the sets at about £30). I'm also hoping the board has a 5V regulator on it (I suspect its 3V3 though). One of those projects I haven't got around to yet though.
I thought about trying to hack one of these units by cutting off the MCU and connecting direct to an Arduino (there's basically logic output, analog input and some logic lines to control the multplexor).
Yes, I saw the Maxbotix single sensors, but at $25-30 each (plus shipping), I'm preferably looking for something cheaper. (I'm planning on installing sensors front, back, and ideally on each corner, hence the standard 4 reversing sensor kits aren't much use)
I use a regular car, are very simple to use.
You have 3-wire: +12 V, GND and command.
Keeping the command in gnd it does not transmit anything, put in a condition of input it sends a pulse train with the distance information. This wire must have 10K pullup.
Can you give more information about how you use them Edsoncan?
Maybe some pictures of how you do it?
My plan was to use a standard all-in-one ultrasonic sensor like Maxbotix and solder the car sensor to it instead, but if I can use a full car kit like that (and get accurate distance measurements for all 4 sensors, not just a bunch of LEDs and a single distance measurement) I would do so.
lostcaggy has posted a link to his blogpost on another topic on this forum on hooking up the control unit to the arduino and getting results in cms for each individual sensor.
