audioguru

The coil ratings and the contacts ratings of a relay are completely different. You show the 12V adapter powering the coil of the relay. The current is low but you do not say the coil's current. The contacts of your relay are not connected to anything so they have no current. Each contact can conduct 5A and there are three contacts so the maximum allowed contacts current is 15A. You do not say the voltage rating of the contacts so we cannot calculate the maximum power the relay can switch.

Yes, your heatsink is much too small.

If the speaker part is 8 ohms and the siren circuit gives it a squarewave of plus and minus 5.5V over and over then the power in the speaker is (11V squared)/8 ohms= 15.1W for half the time which is an average power of only 7.5W. Maybe the siren's power rating is its (fake) peak power of 15.1W.

I am glad that increasing the value of R17 fixed your problem and it is wonderful that you received samples of the opamps.

I do not see why the U1 voltage reference would cause a voltage spike when powered or shutdown. If it did then it would be attenuated by R8 and C4 on my schematic. You can use a 12V linear regulator IC instead if you want.

Picmaster's pcb is perfect.

The solution is to make the project properly using a 28VAC or 30VAC transformer then the rectified and filtered unregulated voltage with no load is 31VAC x 1.414= 43.8VDC - 1.4V= +42.4VDC. With a 3A load on the project then the rectified and filtered unregulated voltage will be +40.4VDC. It is silly to use a transformer with an output voltage too high because then the output and driver transistors will get much too hot.

You must properly disable the opamps you will not be using. Even though they are not used their idle current causes heating in opamp U2 which might be too high. The opamps in an MC34074 have a maximum input offset voltage of 5mV so when the voltage setting pot of this project is set to zero volts, the gain of opamp U2 will cause the output to be from -15.4mV to +15.4mV.

The corrected and improved circuit used MC34071 or uses TLE2141 SINGLE opamps. They have a case that has 8 pins. The single opamps have 2 of the pins for the input offset voltage adjustment trimpot used on opamp U2. The MC34071 single opamp is not available anymore as a through holes type and is now only available as a surface-mount type. If you use the MC34074 QUAD opamp (it has 4 opamps in its 14 pins case) then all the pins numbers must be changed on the schematic, a different pcb must be designed and it will probably overheat. Its opamps do not have input offset voltage adjustment pins.

I have never seen a power audio amplifier that needs a regulated dual-polarity supply. They use a center-tapped transformer, bridge rectifier and two big filter capacitors. If you build two of this project and power them from a center-tapped transformer, joining the projects at the tap then I think the negative supply in each project will not work properly.

When you make two completely separate supplies, one can be 0V to +30V and the other can be 0V to -30V. If one or both outputs are shorted to 0v then that supply will safely regulate its output current to the amount of current that is set at. The supplies have no protection from an output voltage or current of the wrong polarity so if +30V is shorted to -30V then one or both supplies might blow up.

The LME2141 is not available anywhere because nobody makes it. You have the wrong letters. The TLE2141 is made by the world's largest semiconductor manufacturer, Texas Instruments, and should be available everywhere. It was selected because its maximum supply is 44V, its inputs work at 0V without a negative supply and its output goes down to almost 0V. The NE5532 also has a maximum 44V supply but its inputs do not work below 3V and its output does not go below 2V so the circuit and spec's for the project must be changed for it to be used.

Its is a kit. They supply all the parts and you simply solder them on the circuit board. You do not learn electronics.

Your schematic looks fine. I do not know what error Proteus is giving but maybe it knows nothing about the opamps.

Very few people use your Proteus program. For us to see if there is something wrong with your schematic then please post it as a normal PNG file type that everybody can see. Maybe you can "copy screen" then paste the schematic into a picture viewer like Paint program then save it as a PNG file type.

The circuit might work with CA3140 opamps if the supply voltage is reduced by using a custom made 22V AC transformer but then the maximum output will be only about +22.5V DC at 3A if you are lucky. You might need to re-calculate a lower value many of its resistors so that the currents in the circuit are adequate.

The original circuit used TL081 opamps. Its maximum supply voltage is only 36V and it needs a negative supply so it cannot produce +30V without risking damaging it with a supply voltage too high for it. It also has a problem called Opamp Phase Inversion that causes its output to go high when its negative supply voltage drops too low when the power is turned off. So transistor Q1 was added to short its output to ground when the power was turned off. The MC34071 is not available anymore in a DIP package. It and the TLE2141 have a maximum supply of 44V and they do not need a negative supply so they work fine producing an output of +30V. If you use TL081 opamps then they need a -5.6V negative supply as shown in the original circuit. But the positive supply in the original circuit was too high for them since it used a 24V AC transformer and without a load the positive supply was about +34V or more, then the opamps are powered with a total of 40V or more. If the transformer is 20V then without a load the positive supply will be about +28 but then the maximum output from the project will be only about +20V if you are lucky.

I have one small very cheap Chinese AC/DC adapter that has no safety certification markings and is rated at 9VDC/100mA. It produces a little more than 18VDC with no load and gets hot. With a load of 100mA its output is 8V with a lot of AC ripple and it is dangerously hot so I do not use it. An overloaded transformer gets hot. A transformer with safe ratings gets pretty warm but not hot. Simply find a safe name-brand transformer with the ratings you need and compare its size with the unknown transformer. If the unknown transformer is smaller then it might be overloaded at its rating. A 2A load on a 30VAC transformer is resistance that is 30V/2A= 15 ohms at 30V x 2A= 60W. If you find this resistor then load it on the transformer and feel if the transformer gets hot.

A 30A/5A transformer is overloaded when the output of this power supply is 5A because the rectifiers charge the main filter capacitor to almost the peak voltage of 42.4V. The circuit draws about 0.1A. Then the power from the transformer is 42.4V x 5.1A= 216VA. A 30VAC/7.2A transformer is needed to provide 216VA. We use two 2N3055 power transistors for a 3A output and they get pretty hot when the output voltage is low. THREE of them are needed for an output of 5A. Here is a fairly old parts list for a 5A power supply:

Your 30V transformer supplies a voltage of 30V and its rated current is 4.17A. Then its maximum allowed power output is 30V x 4.17A= 125.1VA. The power supply constantly charges its main filter capacitor to the peak voltage 30V x 1.414= 42.4V. The rated output of the power supply is 3.0A plus maybe 0.1A for its circuitry so it uses a maximum power of 42.4V x 3.1A= 131.4VA. Then your transformer will be a little overloaded but probably not enough to smoke or to catch on fire.

That is how the circuit works. A forward biased silicon diode limits the voltage to about 0.7V across it at your fairly low current. When the current is much higher then the diode limits the voltage to about 1V. You can add an opamp circuit to limit the rectifier error to almost nothing but the output current is low. This opamp does not show its positive and negative power supply. Reverse the diodes for a negative output voltage.

The waveform at the output is normal. The negative is not clipping, instead the positive is normally clipping.

Like you were told on the other website, your signal generator is not real, it is a simulation with ZERO output impedance. Its voltage is shown as normal even when its output is shorted for each positive half-cycle by the diode. In real life the signal generator output impedance will be 50 ohms or more and the diode will cause the positive part of the waveform to be clipped.

The Soundlaser uses 39 small but high power ultrasonic transducers. They operate at a very high frequency that cannot be heard and are in an array so that they produce a very directional beam. When the beam reflects off a person's head or an object then the original beam and the reflection produce interference and normal audio that seems to come from the person's head or from the object. Ordinary speakers must be much larger to produce normal low frequency audio and they are not directional. They need a lot of power to be loud. Their sound obviously seems to come from the speakers.