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Another pest device needed

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I have never used an awful-sounding cheap piezo tweeter. Motorola invented it many years ago then other companies made the same looking thing.
The sales sheet I have has a smoothed frequency response curve but I know that the peaks and nulls are actually much higher and lower. Its capacitance is rated at 0.13uF.

Now that you want to use two tweeters and a 14V supply then the entire circuit can be properly re-calculated.
The power in the tweeters and transistors is highest at high frequencies. I can't remember what is the highest frequency so I will assume 30kHz.
Then two paralleled tweeters have a reactance of 20.5 ohms.
With a voltage swing of 13.6V then the peak current is 663mA. TIP power transistors should be used.

The base current of the output transistors should be 66mA so they saturate well.
The base current of the driver transistors should be 6.6mA so they saturate well.
The base current of the inverter transistor should be 0.7mA so it saturates well.
 

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I see you have 1 watt resistors for the base of TIP32. hopefully we don't have an overheating problem?
any recommendations on the larger transistors or will the tip31 / tip32 pairs switch fast enough to prevent overheating?
Will try and locate a source for the KSN 1001A tweeters.
Ordering parts for two units today, just have to finalize design.
One minor issue with PCBoards = may not be able to purchase liquid tin to coat the PCboards.
IF and when I get actual orders for this CRIDDER RIDDER I plan on having PCboards done professionaly.
 
Back to a one transistor output
The present application does not need amplification so thinking of using this schematic https://www.electro-tech-online.com/attachments/bat-repellent-png.43050/ then insert an 8 ohm or ? resistor in series with the piezo tweeter to act as a load on the transistor.
The same circuit works using an 8 ohm speaker. But the piezo tweeter shouldn't put much of a load on the PIC output anyway.
Should work both ways but one better than the other?
 
Back to a one transistor output
The present application does not need amplification so thinking of using this schematic https://www.electro-tech-online.com/attachments/bat-repellent-png.43050/ then insert an 8 ohm or ? resistor in series with the piezo tweeter to act as a load on the transistor.
The same circuit works using an 8 ohm speaker.
The circuit will not work with an 8 ohm speaker or resistor. The 8 ohm speaker or resistor will draw a peak current of 9V/8 ohms= 1.1A but the 2N2222 transistor blows up with a current over only 0.8A.
The transistor would need a base current of 110mA to saturate but the 10k base resistor limits its base current to only 0.43mA. The max allowed current from a PIC output is only 25mA so a single 2N2222 cannot drive an 8 ohm speaker with a 9v supply and a PIC as its input.

But the piezo tweeter shouldn't put much of a load on the PIC output anyway.

On an earlier post I calculated the reactance of one 0.13uF piezo tweeter at 30kHz to be 41 ohms. Then the output current from the PIC will be 4.5V/41 ohms= 110mA which will blow up the PIC.
At 20kHz the tweeter's reactance is 61.5 ohms then its current from the PIC is still too high at 73mA.
 
A slightly warm transistor is not cause for concern. A heat sink would mean you have another piece of metal hanging around that you have to prevent everything from shorting.
 
There are two Tip-32's and two Tip-31s
seems like only one of the Tip 32 transistors got warm. At least warmer than the other one.
All the resistors are 1/2 watt except the 180 ohm which I could only get as a 3 watt. None got warm.
Tonight when I go out looking for deer I wil run unit longer than a few minutes.
Now you ask-does it work?
It appears to work. At least I get the deers ATTENTION!
It affects goats more than cows and horses. The few deer I have tested have STOPPED EATING and either ran away or walked very fast in retreat. This depended on how close I am to them. Last night I had one deer eating someones bushes about 50 feet away from the road. I parked, the deer looked at me, then continued eating.
I pluged in the unit, the deer looked up then walked at a fast pace away from me and the road.
Thanks again to Audio Guru for the amp design.
QUESTION? will the amp design using MOSFETS work better or more efficiently?
It may cost more? but maybe a better product?
I don't believe in selling something that can be built better at a small increase in price.
 
They cannot make transistors the same. Some have high gain and others have low gain. The high gain one is cool (because its saturation voltage loss is lower) and the low gain one is warm (guess why).

You will hardly notice a tiny improvement when Mosfets are used. But maybe fewer parts will cost less.

I worked for many years as a Sound Systems contractor. Customers were bank head offices, stock market trading companies, theaters, stadiums and other places with LOTS of money. Our salesmen talked to their consultants and suggested features that I designed easily but competitors couldn't so we always got the contracts at very high prices.

Everything I designed worked perfectly and my prototypes were the finished products that were sold and installed.
But most circuits were made only once.
The 5-frequencies audio equalizer circuit I designed for an unusual PA speaker was mass produced and tens of thousands were sold.
The background music with muting circuit that I designed for a huge intercom system had bass-boost and sounded great.
The treble frequencies boost circuit that i designed made telephone conference calls sound crisp and clear.
Every one I demo'd was sold. Hundreds were sold.

The cost and price of all the things I designed for work didn't matter.
 
I thank you again for your amp design.
Not really worried about the heat, just wish I didn't have any warm components.
Still contemplating adding heat sinks just for good measure. Maybe make the unit last longer?
 
The silicon chip in a transistor has a max operating temperature that is way higher than just warm so yours will last forever.
Add a heatsink to a hot transistor that is hot enough to burn you or melt plastic.

Maybe your warm transistor is a counterfeit one with failed spec's (bought at RadioShack?).
 
All the parts on this proto type are NEW from Mouser.
It just gets slightly warm, almost un-noticiable unless one is LOOKING for a warm component
Going out again tonight even though it is raining..
 
I noticed tonight
The unit SCARES the HELL outta sheep
The amp dosn't seem as loud. Wounder if the mosfet unit would be louder. Not that I want to make it louder but maybe
Oh yea I chased about 4 deer outta a yard then found about 6 bucks in a field adjecent to the road. I got video of all.
The bucks stared at me while the unit was on.
I noticed that after I went down the street, turned around and came back with the unit ON the deer, ALL OF THEM started running away in all directions..
I then left for about 5 miniutes, came back and redid the same experiment.
If the vehicle is only moving a few feet the deer scatter Not just walk but run
 
You need a complete redesign to change it to MOSFETs. Right now the amplifier is allowing both top and bottom transistors on both sides to turn on briefly at the crossover time. The BJTs forgive you because their beta (current gain) is not infinite and the current stays reasonable.

If you allow this to happen with MOSFETs they will cheerfully turn on to their Rdson which will probably be milli ohms. Current will be very high for extremely short pulses. It won't blow the fuse and the transistors might last for several days. Your radio reception might get... interesting.
 
If the pins on your transistors are the correct way around then a Mosfet amplifier will be only slightly louder. You and the critters will not notice the slight increase in loudness.
 
will leave it as it is
The 5 bucks I saw I think are on Viagra (studdies show a hearing loss)--lol
I will post a video on youtube as soon as I download etc.
If anyone is interested?
Oh yea I also saw a wanted poster for Audioguru as he designed the amp!
 
Heating of transistors

Am still concerned about one transistor getting very warm Going to add a piece of aluminum bar stock for heat sink BUT would the Mosfet circuit you posted (this is a copy of but I inserted the Mosfets backwards but will correct) prevent any chance of heating of components? In your opinion?
The circuit board will be enclosed in a weather proof enclosure so heat is not wanted.
would post revised copy but somehow I deleted PAINT. Need to reinstall or do a restore.
 
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