Ultrasonic Pest Repellent

[zeitcheist]

First thing, I'm a newbie in creating electronic projects. I've just been studying the basics. I need help on this please. Anyone who can help me will be much appreciated. We need to assemble the following circuit:

**broken link removed**

Sorry, if the image is large, I don't know how to change the size in BBcode.

The circuit is freely available and I think we can build it.

The author made a note about the schematic. But I need to clarify certain points. The quoted phrases are from the author, next each of them is my question.

It is well know that pests like rats, mice etc are repelled by ultrasonic frequency in the range of 30 kHz to 50 kHz. Human beings can’t hear these high-frequency sounds.

1. Is this true? Isn't this frequency harmful to humans (even if we can't hear this)?

By using this circuit design, frequency of emission of ultrasonic sound is continuously varied step-by-step automatically. Here five steps of variation are used but the same can be extended up to 10 steps, if desired. For each clock pulse output from op-amp IC1 CA3130 (which is wired here as a low-frequency square wave oscillator), the logic 1 output of IC2 CD4017 (which is a well-known decade counter) shifts from Q0 to Q4 (or Q0 to Q9).

1. Can I replace CA3130 with UA741? I have researched and they have the same pin configuration, but different technology. Can it affect the output?
2. Can I replace CD4017 with HEF4017B?

Five presets VR2 through VR6 (one each connected at Q0 to Q4 output pins) are set for different values and connected to pin 7 of IC3 (NE555) electronically. VR1 is used to change clock pulse rate.

1. What values should we use for VR1-6.
2. We are using trimmer resistor for this. Is it correct? Should we use different var resistor?

IC3 is wired as an astable multivibrator operating at a frequency of nearly 80 kHz. Its output is not symmetrical.

1. I'm lost. Please explain. =(

IC4 is CD4013, a D-type flip-flop which delivers symmetrical 40kHz signals at its Q and Q outputs which are amplified in push-pull mode by transistors T1, T2, T3 and T4 to drive a low-cost, high-frequency piezo tweeter

1. Can we replace CD4013 with HCF4013? What effects, if any?
2. What tweeter? We have been looking for this part. All we found were piezoelectric tweeters with frequency of 5-20kHz. We didn't get it. After asking someone, he told us to use transducer. We bought it and it looked like a thin penny. Can it produce the frequency we need? And does the 5-20kHz piezoelectric tweeter can do the job of outputting 30-40kHz? <-dumb question

For frequency adjustments, you may use an oscilloscope. It can be done by trial and error also if you do not have an oscilloscope.

1. How can we do it by trial and error if we can't hear the sound?

If you want low-power output in 30-50 kHz ultrasonic frequency range then the crystal transducer may be directly connected across Q and Q outputs of IC4 (transistor amplifier is not necessary).

1. Can we buy crystal transducer? What is it like? Are there specs when it comes to transducers? Coz we bought a transducer and the seller didn't ask us about frequency output.

 

[zeitcheist]

1. By the way, we are planning to use generic power supply adapter, from 220 to 12V. The output tells 500mA. Can we use that? Can the ICs receive current as high as 500mA?

2. We would like to put LED for "power indicator". What resistor value should we use? I have read and found out that about 30-40 mA and 2V is suitable for LEDs. How can I reduce the voltage from 12v to 2v along with the current from 500mA to 33mA?

3. We would like to put a flashing LED for "gadget working indicator". How can we build that?

Thanks in advance.

 

[Hero999]

1. By the way, we are planning to use generic power supply adapter, from 220 to 12V. The output tells 500mA. Can we use that? Can the ICs receive current as high as 500mA?

2. We would like to put LED for "power indicator". What resistor value should we use? I have read and found out that about 30-40 mA and 2V is suitable for LEDs. How can I reduce the voltage from 12v to 2v along with the current from 500mA to 33mA?

Use Ohm's law to answer questions one and two.

Light Emitting Diodes (LEDs)

3. We would like to put a flashing LED for "gadget working indicator". How can we build that?

Thanks in advance.

Use a flashing LED.
**broken link removed**
flashing LED - Google Search

 

[audioguru]

The circuit was tested with a tiny telephone ceramic earpiece, not a powerful tweeter.

Where are you going to find a tweeter that produces ultrasonic frequencies and can survive high power? The piezo tweeters that were used in old PA speakers barely made it as high as 18kHz. Continuous power destroyed them nearly as quickly as normal tweeters.

A HEF4017 is exactly the same as a CD4017B but costs much more because it is a "replacement".
The lousy old 741 opamp will work fine as the low frequency oscillator opamp.

 

[Boncuk]

Hi,

to calculate for the power LED resistor use Ohm's law as already posted.

Subtract the LED forward voltage from the supply voltage to obtain the correct current limiting resistor.

The CD4017 is manufactured by many semiconductor manufacturers. For example ST Microelectronics uses the prefix HCF for the CMOS series ICs.

As long as the number '4017' is the same it should fit your needs.

To make the power LED flash use the timer circuit IC NE555 with different values for R1, R2 and C. The calculation formula is available in the data sheet.

Using 2K7, 680K and 1µF will make the LED flash at 1Hz.

Boncuk

 

[zeitcheist]

Hi! Thanks to Hero999, audioguru and Boncuk! I really appreciate your help.

Some of my questions were answered, thanks to you guys! But I still need to clarify certain points.

Okay.. So basically, here is what I understood.
1. Any replacement to ICs as long as same in part number will be okay for the circuit.
2. I should drop the voltage to 2V (typically, for LEDs) by using a resistor, and Ohm's law to compute.
3. I should definitely use crystal transducer instead of a piezo tweeter.
4. I must construct my own flashing LED.

Questions:
1.

Five presets VR2 through VR6 (one each connected at Q0 to Q4 output pins) are set for different values and connected to pin 7 of IC3 (NE555) electronically. VR1 is used to change clock pulse rate.

Q: What values should I use for trimmer resistors?

2.

IC3 is wired as an astable multivibrator operating at a frequency of nearly 80 kHz. Its output is not symmetrical.

I don't understand a thing. Please do explain.

3.

Where are you going to find a tweeter that produces ultrasonic frequencies and can survive high power? The piezo tweeters that were used in old PA speakers barely made it as high as 18kHz. Continuous power destroyed them nearly as quickly as normal tweeters.

I must use crystal transducer. Is it commercially available?

4.

Use Ohm's law to answer questions one and two.

The computation would drop the voltage. How about the current?

Plus:
I just want to confirm this thing about current. Which of the following is correct?
1. A power source delivers the amount of current 'full blast' to a component, so a resistor must be used to limit the amount.
2. A component uses only the amount of current it needs, regardless of the amount fed by the source.
If the answer is no.1, please do answer the next question:
How will I reduce the voltage AS WELL AS the current (that is, at the same time) by only using a resistor?


I know they're newbie questions, but I need technical answers. Please do help me. Thanks again in advance.

 

[audioguru]

I should drop the voltage to 2V (typically, for LEDs) by using a resistor, and Ohm's law to compute.

No.
The resistor in series with an LED limits the current to 20mA so it doesn't burn out. The LED limits its own voltage.

3. I should definitely use crystal transducer instead of a piezo tweeter.

I haven't seen a crystal transducer for about 45 years.
I don't think you will find an ultrasonic transducer that will survive the high power of this old project.

Questions:
1.Q: What values should I use for trimmer resistors?

You can look at the original project or calculate the values for the amount of frequency change you want.

2.Q:I don't understand a thing. Please do explain.

We talk in electronic terms. Please learn them.

I just want to confirm this thing about current. Which of the following is correct?
1. A power source delivers the amount of current 'full blast' to a component, so a resistor must be used to limit the amount.
2. A component uses only the amount of current it needs, regardless of the amount fed by the source.
If the answer is no.1, please do answer the next question:
How will I reduce the voltage AS WELL AS the current (that is, at the same time) by only using a resistor?

A circuit uses only as much current as it needs.
An LED is a diode and will draw an extremely high current then will burn out if its current is not limited to an allowable current with a resistor in series with it.

A red LED is 1.8V to 2.0V and an old green LED is 2.2V. A new green LED, a blue LED and a white LED is about 3.5V. The current in an LED must be limited by a series resistor or current regulator circuit. They limit their own voltage.

 

[Ubergeek63]

an electronic Pest repellent? how about a cattle prod?

 

[audioguru]

an electronic Pest repellent? how about a cattle prod?

I don't know if rats and mice run away from cattle.
I don't know if rats and mice run away from an overloaded tweeter that can't produce ultrasonic frequencies.
Look what I found:

 

[blueroomelectronics]

My dog hates the sound of a camera flash, she'll run when she hears it. Either that or she's camera shy.

 

[zeitcheist]

Hmm.. Thanks for the answers. I really do appreciate.

So you are telling me to drop this project. But we need a project that is useful at home. Can you recommend me some projects that are economically feasible to build? Please reply as I need to finish this project this sem. I will look into the forum but please advise me if you have anything to recommend. Thanks again audioguru!

 

[audioguru]

Make the old project but reduce the frequencies so that they are audible then use a normal speaker.
You can demonstrate how it produces switched frequencies and will repel humans.

Maybe you can set the frequencies into a little tune.

 

[Boncuk]

My dog hates the sound of a camera flash, she'll run when she hears it. Either that or she's camera shy.

That's why hunters in Germany use ultrasonic pipes to call their dogs in the forest. The dogs can hear the pipe, the dear can't.

 

[Boncuk]

Look what I found:

Very interesting, but not proved.

We had an airfield equipped with 'Fouga Magister' jet trainers. They had very small turbines (size of a water bucket) running at 40,000rpm. There were no rats and mice in a radius of 15km around the airfield.

 

[zeitcheist]

@Boncuk

So you are telling me to pursue this project? Can you help me with the technicalities?
Thanks again!

 

[audioguru]

Maybe rats and mice don't like the smell of jet exhaust. The roar noise is probably louder that the high pitched whine noise.

EDIT: 40,000 RPM makes a frequency of only 667Hz doesn't it? Times the number of blades in the turbine?

Can you buy a high power ultrasonic piezo transducer in The Philippines?

 

[zeitcheist]

Only ceramic transducers are available.

I am thinking of building a power saver circuit. Do you think it's feasible to construct in 3weeks?

Or, do you have any useful project to that you could recommend? Any project that you think is feasible. I have checked the project forum but I didn't find any. Please do help me on this guru. Thanks again.

 

[blueroomelectronics]

3 weeks you better start soon. How does it save power?

 

[Boncuk]

Maybe rats and mice don't like the smell of jet exhaust. The roar noise is probably louder that the high pitched whine noise.

EDIT: 40,000 RPM makes a frequency of only 667Hz doesn't it? Times the number of blades in the turbine?

results in exactly 16,008Hz + harmonics + the engines didn't roar, just were audible with a high pitch sound.

 

[zeitcheist]

Hmm.. Guys, please advise me on this.

Should I continue this project?

Or, should I try to pursue power saving circuit?

Or, do you have any project to recommend?

^^