I want to use the distance sensor HC-SR04 or US-015 to just pick up sounds around 40khz. I'm not interested in sending any sound out (just using the modual as a sound detector),
The benefit for my project is that the microphone does the frequency filtering and the whole modual is so cheap.
My question is can the transmit part of the modual be cut out so as not to use any power and can the receive part be programmed to act as a sound detector.
I'm not an electrical engineer or coding expert just an old man trying to make a project (with a lot of help)
Thanks to any one who can help.
If you have a schematic, you may be able to isolate the receive section's amplification.
Be aware that these units usually incorporate their own microcontroller, and this may affect how the receiver operates.
What are you trying to do?
HC-SR04 schematic and other info
If you remove the transmit transducer it will continue to operate, but will waste less power generating the ultrasonic pulse.
My project is to build a cheap, compact data logger. I want to log any sound around 40khz for about 12 hrs a day, for periods of about two weeks and I want it to run off batteries. My idea is to use either a US-015 which I have or a HC-SR04 which is on order. To pick up the sound. I don’t need the transmit part of these distance sensors so may be If I can just get rid I will save some power.
I plan to use the ds3231 to time stamp any signal and switch on off the system which I have.
I have sent off for a nano but if any of the experts tell me it’s not up to the job then I’ll go along with that. I have the micro sd tf card storage module spi. So what I need to do is put it all together and code it. It’s not that I’m being lazy asking for help it’s because I know I won’t be able to do it.
The first two answers seem like good advice so thanks for that.
Sleep is a great way to save on battery power - but you need a way to wake up the moment a sound comes in.
So the first step is going to be to build yourself a working sensor. The HC-SR04 is a possible starting point; but you have to study the schematics and probable reprogram it's on-board MCU to send you a signal when a 40 kHz sound is received (as that's not how it works out of the box).
Maybe it's simper to take one of the 40 kHz transducers as microphone off the HC-SR04, build an appropriate detection circuit (some kind of sound amplifier) that produces a digital signal when a sound comes in. After all, it sounds like that is what you're after. Such a signal can then wake up the Arduino, which can check the time from the RTC, log it somehow (SD card?), and go back to sleep waiting for the next signal to come in.
Circuit of a ultrasonic receiver that might help. It outputs 4khz to speaker
The distance sensor as far as I can see send out 8 pulses and receiver listens for this to make a measurement. Stops false readings. So probably won’t work for a single 40khz pulse.
suttle0577:
Circuit of a ultrasonic receiver that might help. It outputs 4khz to speaker
The distance sensor as far as I can see send out 8 pulses and receiver listens for this to make a measurement. Stops false readings.
Want to bet?
Try shaking a bunch of keys during readings and see how many false returns it eliminates.
I wrote some notes on an experiment in ultrasonic communications using a pair of HC-SR04 modules in this thread a while back: Using HCSR 04 for communication - Project Guidance - Arduino Forum
Note that there are a couple versions of HC-SR04 on the market. I've seen at least two different board layouts based on the schematic shown below and discussed in great detail at the link jremington provided in post #2 above. There is also newer version which uses a different driver for the transmit side and which will work down to 3.3 V whereas the older version was 5 V only. These are (sometimes?) advertised and marked as HC-SR04P.
As I recall, for my experiments I soldered a wire on pin 10 of the microcontroller, the "Signal" net and ran that to a digital input on an Arudino Uno board. For analog one would tap off pin 7 of the LM324.
The piezo sensor is resonant at 40 kHz so it will respond well at that frequency, but won't see much even a few kHz away from that frequency. Good for it's intended application, but it's not a good broadband receiver.
To minimize power, one could remove the microcontroller and the MAX232 chips, but the MAX232 is powered down when not actively transmitting and the microcontroller probably isn't drawing heaps of power, so one probably won't realize vast power savings.
I’ve had a thought, Get a cheap sound detector swap out the microphone for one off the distance sensor test it using another distance sensor if it picks the signal up fine. There might be some rc filtering on the sound detector but I can just swap out a couple of capacitors.
I’ll try it out see how it goes when the parts arrive then post the results.
Thanks for your help guys.