2N3055 heat sink

audioguru said:

Speakers are designed to be fed AC but your single 2N3055 is not push-pull so it feeds DC pulses. An audio amplifier produces AC. When your DC pulses feed a speaker then the power must be 1/4 the speaker's rating.

Your idea of using a 60V supply will produce 60V/8 ohms= 7.5A pulses. The average output power is (60V x 7.5A)/2= 225W! A 100W 8 ohm speaker maximum peak input voltage is only 40V. Any more voltage will cause the voice coil to smash against the magnet structure causing damage.

I wonder what is the jail sentence for somebody who is disturbing the peace with an illegal siren?

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I don't know how to build a push pull transistor circuit. I looked online and found push pull with 1 NPN and 1 PNP transistor. I have no PNP that match 2N3055 but I do have 2N345A that is PNP it is not = to 2N3055. Is there a push pull circuit that uses two 2N3055s?

I just realized I already have an 1KHz AC output from a 555 that I can use to test a voltage multiplier. Wonder if there is a formula to determine what size caps to use on a voltage multiplier with 1N4007 diodes. I can build a voltage multiplier on a PC board and mount it between the 555 and 2N3055. First build it an test it see if it works. I have lots of caps, 100uf might be too small, 470uf might work, 1000uf might work better. I wonder if 1000uf will pull more than 1a and blow the 1N4007 diodes?

But wait output of 555 is pulsing DC not AC. I drew this circuit but I don't see how it can work on pulsing DC.

Look at this. https://www.instructables.com/id/High-Voltage-Multiplier/

gary350 said:

I don't know how to build a push pull transistor circuit.

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This does not get you more voltage but it does push and pull. The large ele. cap. finds the average output voltage and with 50/50% it will make 6 volts on its own. The transistors are for more current.
Yes the voltage is lower but the speaker will push and pull. So the peak to peak sound is as loud.

Now about your voltage multiplier. If the voltage goes up by a factor of 5 then the current must go down by 5. Example: input voltage=12, output voltage=60, the gain is 5x. The current on the other hand: input current=5A, output current=1A. (power in = power out) if 100 percent efficient.

ronsimpson said:

Now about your voltage multiplier. If the voltage goes up by a factor of 5 then the current must go down by 5. Example: input voltage=12, output voltage=60, the gain is 5x. The current on the other hand: input current=5A, output current=1A. (power in = power out) if 100 percent efficient.

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Not to mention he's trying feed the multiplier from the output of a 555, so very little current available anyway.

I found some push pull circuits online. I could replace T1 with a speaker and get about 4 times more power output using 2N3904 and 2N3906 push pull to the speaker instead of one 2N3055 transistor. I could also use this circuit to make 60v for one 2N3055 or push pull 2N3055 NPN and 2N???? PNP.

I think I would like to do push pull with 2N3904 and 2N3906 that will be easy. Then make this circuit to see if I can make 60vac for a 2N3055. I have several PC board transformers I will have to test them to see what ratio they are. I might get lucky and have a transformer that will work. I have 17 mini transformers with CT on 1 winding and 8 more with no CT.

Hey big spender! https://www.jameco.com/z/MJ2955-Maj...55-TO-3-PNP-Silicon-Power-60-Volt_211502.html

My 2N3055 NPN datasheet shows the matching MJ2955 PNP transistor. It is still available. Because they are in an old metal case they are expensive.

Gary, you should read the datasheet that shows that an NE555 has a maximum allowed output current of 200mA and produces about 10V, therefore its output power to feed your voltage multiplier is only 0.2A x 10V= 2W. A push pull pair of the above transistors can amplify the current enough to feed the voltage multiplier.
A second pair of the power transistors can be biased and use a driver transistor then used with the 60VDC to drive the speaker though an output coupling capacitor for an output of about 50W into an 8 ohms speaker.

The datasheets for the little 2N3904 and 2N3906 transistors show that their maximum allowed output current is 200mA but they work poorly above 100mA.
100mA in an 8 ohm speaker is a voltage swing of only 0.1A x 8 ohms= 0.8V. If the output of the 555 feeds them plus and minus 5V then their output current will try to be 500mA each which will destroy them.

I could not resist building this to see if it works. It works on the AA batteries so I tested it on the car battery. It sounds the same volume as the 2N3055. This is not the complete drawing it is just enough for me to make the changed. VOM reads 3.43vac across the speaker.

Both of the 555s on the circuit board are NE555P is that different than NE555 with no P ?

Finally found NE555 datasheet it says 200ma. but not finding anything on NE555P

gary350 said:

I can not find a real datasheet

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Go to the manufacturers websites instead of some datasheet warehouse.

gary350 said:

It sounds the same volume as the 2N3055.

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I agree.
With one transistor the speaker moves in one direction. One of the comments way above was that the speaker may move too far and hit the magnet. (damage)
With two transistors the speaker moves in and out. (two directions) It will move "6 volts" out then "6 volts" in, giving a 12 volt travel. So the sound will be the same.
The difference is; if the speaker can only handle 8 volts with out distorting or hitting the limits, the +12 will only sound like 8V not 12V. But with a +6/-6 signal the speaker will not be at the limits. I do not know what your speaker can handle. I was responding to the comment by AudioGuru.

The "P" is the package "8 pins dual inline plastic" that is mounted "through holes" and is not one of the smaller "surface mount" packages.

You are severely overloading the small 2N3904 and 2N3906 transistors.
With the 12V supply, the output of the 555 will go high to about +10.5V and go low to about +0.3V.
The outputs of the transistors will try to go high to about +9.5V producing a collector current in the 2N3904 of 500mA and the collector current of the 2N3906 will also try to be 500mA but their maximum allowed current is only 200mA each.

At 200mA then the speaker voltage is 200mA x 8 ohms= 1.6V from each transistor then the power in the speaker will be (3.2V squared)/8 ohms= 1.3W but the overloaded little transistors will get too hot and produce maybe 0.5W before they are destroyed.

If you use 2N3055 and MJ2955 transistors then the output power with the 12V supply would be about 3.92W. Only 2W is the sounds you want and the other 2W is the squarewave harmonics that the speaker might not produce or you might not hear.

If it has a much higher supply voltage (the 555 has a maximum allowed supply of only 16V and the transistors are emitter-followers with a voltage loss of 2V p-p) then the output power will be higher. A 3 transistors amplifier could be designed to use the higher supply voltage and the 3rd transistor could amplify the voltage swing from the 555 and the emitter-followers would amplify the current.

I said that a speaker power rating is 4 times higher if it swings in and out (driven with push-pull) at its maximum allowed amount before its voice coil smashes into the magnet structure than if its voice coil moves the maximum amount one-way (driven with a single transistor). The "4 times" is because when the voltage swing is doubled then the current swing is also doubled. Power is voltage x current. 2 x 2=4.

Here is a much more simple version of a European siren using 555's. Both 555's use the symmetrical astable circuit from the LMC555 datasheet. Each oscillator makes a nearly perfect 50/50 duty cycle squarewave. The first oscillator is running at approx. 0.7 Hz. It changes the U2 frequency by switching in extra capacitance with Q1 to lower the output frequency.

For U2, R2 and C2 set the high tone, and R2, C2, and C3 set the low tone.

C4 decouples U1. C5 decouples U2.

ak

AnalogKid said:

Here is a much more simple version of a European siren using 555's.

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Note for Gary:
AK's circuit appears to be for 5V operation, with the value of the resistor driving the output transistor.
Do not try it on 12V without changing that to a buffered output.

This car radio amplifier might solve the problem it operates on 12v, output 20w into 4 ohms. I have 2 speakers 10w 8 ohms each in parallel = 4 ohms 20w.

WHAT is standby? Is that mute button?

First I thought, use LM386 to drive 2 2N3055s in push pull but that does not solve the 60vdc problem. Find a real life every day product like car radio amp that operates on 12vdc. I could kick myself in the butt I had about 30 audio amps from salvaged TVs I threw them all away last summer thinking I will never use those for anything.

gary350 said:

WHAT is standby? Is that mute button?

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Yes. Like a power down button.
A bridge amp is good in that it puts the supply voltage across the speaker in both directions. You get twice the voltage across the speaker.

rjenkinsgb said:

AK's circuit appears to be for 5V operation, with the value of the resistor driving the output transistor.

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R3 was selected to keep the U2 output current below 200 mA at Vcc = 9 V. Calculation assumes Vout = (Vcc - 0.5 V), and Vbe = 0.8 V at Ib = 0.2 A.

For 14.4 V operation, increase R3 to 68 ohms or larger.

Again, using a FET to switch the timing capacitance rather than messing with the timing resistors is smaller, cheaper, and WAY more reliable than a relay. Also, it preserves the 50/50 duty cycle.

ak

AnalogKid said:

R3 was selected to keep the U2 output current below 200 mA at Vcc = 9 V. Calculation assumes Vout = (Vcc - 0.5 V), and Vbe = 0.8 V at Ib = 0.2 A.

For 14.4 V operation, increase R3 to 68 ohms or larger.

And to be clear, using a FET to switch the timing capacitance rather than messing with the timing resistors is smaller, cheaper, and WAY more reliable than a relay. Also, it preserves the 50/50 duty cycle.

ak

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I don't know about FET?

gary350 said:

I don't know about FET?

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There is a FET on the Schematic, marked Q1.

ak

AnalogKid said:

There is a FET on the Schematic, marked Q1.

ak

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I though Q1 is a mosfet?

JFET symbol

Image: commons.wikimedia.org
The JFET symbol indicates the channel as the main line between the drain and source. Sometimes the drain and source will be marked with the letters to indicate which connection is which. The JFET symbol shows the gate as the connection from the channel.
JFET | Junction Field Effect Transistor FET | Radio ...

MOSFET symbol


MOSFET Symbol. A metal-oxide-semiconductor field-effect transistor (MOSFET) is a voltage-controlled electronic component invented by a South Korean Engineer Dawon Kahng, and his colleague Martin M. Atalla in 1959 whilst working at Bell Labs.

"FET" can be any kind of FET.

There are many different types of field effect transistors: JFET, IGFET, dual-gate FET, MOSFET, etc. with sub categories like n-channel, p-channel, enhancement mode, depletion mode, etc. The 2N7000 / 7002 is a low-power n-chanel enhancement mode MOSFET. Unlike a bpolar transistor, it passes both charging and discharging current when "on" (fully-enhanced). It acts as a voltage-controlled resistor, and its fully-on resistance (called Rdson) is around 5 ohms.

ak