hc sr04 tester.

[dwood]

I am trying to get this ultrasonic module test circuit to work but the 555 chip overheats in 10 sec. even if the ultrasonic module is not connected. Whats wrong with it? I have gone over the circuit a hundred times and everything seems to be right. The module I have only has 4 pins. Will this make a difference in the overall operation?

 

[audioguru]

Your circuit is missing the very important supply bypass capacitor mentioned in the datasheet of the LM555.
The datasheet shows a minimum timing capacitor value of 1000pF but your 22pF is 46 times less.

The HC SR04 module needs a 10us positive pulse input for it to send 8 waves of 40kHz out. You never feed 40khz to it.
Why are you connecting a multimeter to its echo output? The echo pulse is much too short for a multimeter to sense it. An Arduino is usually used to test it.
https://docs.google.com/document/d/1Y-yZnNhMYy7rwhAgyL_pfa39RsB-x2qR4vP8saG73rE/edit

 

[alec_t]

As AG says ^^. Try 220nF instead of 22pF.

 

[Nigel Goodwin]

As AG also says there seems nothing in that 'circuit' to make it work, you need to measure the time until the echo pulse is detected, and while you could do it with a handful of chips it makes FAR more sense to use a microcontroller.

 

[dwood]

I don't know enough about electronics to do other than the schematic tells me. For now anyway. I connected the multimeter because that is what the guy demonstrated on the video. I would much prefer to have a buzzer to tell me if something is getting closer or farther away. I want to avoid using arduino and am hoping I can find a good circuit with a 555 to make it work. I will change the cap.

 

[dwood]

It shows in the video that it works. That is what I based my assumption on.

 

[alec_t]

am hoping I can find a good circuit with a 555 to make it work

If you don't go the Arduino route the circuit will need much more than a 555 to sense if an object is getting closer or further away. Would you be able to build it?

 

[audioguru]

The datasheet for the sonar range detector says that its input is a single positive pulse of 10μs that a 555 IC can produce if it is wired as a monostable and its output is a single pulse with a width from 150μs to 25ms depending on the range. Why bother testing it to maybe hear a tiny click? You need to test that its pulse width is correct for the distance.

 

[Nigel Goodwin]

It shows in the video that it works. That is what I based my assumption on.

The video uses a completely different sensor, one that provides a DC output voltage related to distance. The HC SR04 doesn't work in that way, you have to measure the time for the echo to return, you need a micro-controller to do that, an Arduino would be one way of doing, or a PIC, or anything else.

 

[alec_t]

Here's a relatively simple circuit which should give you an output voltage approximately proportional to target range. Not a 555 in sight .

 

[dwood]

The actual project is for a Theremin type device. Actual distance measurement was not important. I was hoping to do away with a microprocessor. Seems like it won't work that way.

 

[Musicmanager]

Hi Dwood

For a Theremin, I think you'd be better off with one of these .. ..

I built this using one of them last year, works well.

It's a Sharp GP2Y0A41SK0F Optical Sensor RS Pt No 666-6568

S

 

[dwood]

The attachment didn't work. Is that another ultrasonic sensor? If it is IR will it work in bright light? To what distance?What is required to make it work.? I want a 1 handed theremin which is why I went with ultrasonics. True, it is not a "real" Theremin but it works for my purposes. I have an arduino minipro that should work.

 

[alec_t]

The attachment didn't work

If you're referring to the attachment in post #10, that's a simulation file for LTspice.

 

[Musicmanager]

The Sharp GP2Y0A41SK0F is an optical sensor, that is it works using IR light and is good for a distance of approx. 30cm.

The Theremin in the picture uses the opto sensor to control volume and telescopic mast to control frequency and therefore pitch, according to the position of your right hand.
There's no microcontroller onboard, it uses 2 or 3 ferrite coils and a small amplifier (Lm386, I think ) I can't find the schematics at the moment ! It was a project published in EPE magazine in Sept 2015.

I have to say, I'm very much an EE novice and although the project was eventually successful it was not before a great deal of angst and even more help from the guys on here.

I'm intrigue to know how you would effectively use a 'one handed theremin' ?

S

 

[dwood]

One hand moving through the scales and the other controlling different sounds and effects. I think I will go with the arduino minipro and ultrasonics. That seems to be the simplest way.

 

[audioguru]

The circuit in post #10 will detect the pulse width from your ultrasonic range finder and produce a DC voltage dependant on the distance of your hand. The datasheet of an LM358 dual opamp has a schematic of a circuit that is a voltage controlled oscillator. Put them together and you can control the pitch of a continuous buzz or whine with the distance of your hand. To make it into a theremin you need something to turn the oscillator on and off and perhaps adjust its attack, volume and release.