TIP31 feeding about 25 leds (audiorhytm circuit)

[betwixt]

For amazing light displays for almost zero cost, there is a simple alternative. Use one or more laser LEDs, the pen things that cost a dollar each. On top of your loudspeaker cabinet mount one small loudspeaker, facing upward and glue one mirror per Laser to it's cone. The mirrors should be as small as possible so they don't restrict the cone flexure too much, 1/4" square should be big enough. If you use more than one, position them at different distances from the cone center so they move slightly differently to each other. Shine the lasers at close range on the mirror and as the cone moves in time with the music it will draw patterns on the ceiling!

There are lots of variations on this theme, for example using more than one loudspeaker and reflecting the light via two mirrors or if you really want to impress your friends, get hold of a multi-faceted mirror ( a tube with say 8 flat mirrors around it's circumference ) and spin it with a motor. When you shine a laser on it you get a straight line drawn as the reflected light sweeps from side to side. Then use the loudspeaker trick to reflect the laser before it hits the spinning mirror and you get an oscilloscope trace of the waveform on your ceiling!

You can combine it with the comparator circuit to make the laser flash on and off at the same time.

I did an experiment a number of years ago using two spinning mirrors, one to deflect the light left to right and one at slower speed to deflect it top to bottom. I used a focussed LED as lasers have limited brightness adjustment and fed a video waveform to the LED through a power driver. The result was a giant TV picture on the wall! The principle isn't new and the quality was horrible so it isn't marketable but as an experiment it was quite entertaining.

Brian.

 

[Audioguru]

A laser drawing patterns is great!
But IF you shine a laser on your ceiling and IF you have a skylight and IF an airplane flies over then you will be in big trouble if it blinds the pilot.

 

[c_mitra]

But IF you shine a laser on your ceiling and IF you have a skylight and IF an airplane flies over then you will be in big trouble if it blinds the pilot.

If the pilot were not sleeping! Unless he is about to land in a few minutes, there is no direct line of sight from the eye to a vertical line from ground.

The common laser pointers have very short coherence length; after a few meters they are no more lasers.

The common laser pointers have lots of divergence; at 1000m, the spot will be several meters in diameter and practically harmless.

Has it every happened that the light from a common laser pointer of 5mW power has blinded a pilot (or anyone for that matter)? The airport searchlights are far more powerful.

 

[Audioguru]

Have you noticed that Chrysler/Fiat Jeeps have full brightness high beams for daytime running lights? Chrysler ordinary cars too and now Kia and VW cars are copycats. At dusk they blind everybody.

 

[c_mitra]

Have you noticed that Chrysler/Fiat Jeeps have full brightness high beams for daytime running lights? Chrysler ordinary cars too and now Kia and VW cars are copycats. At dusk they blind everybody.

I do not understand the comparison or reference. The reasons are:

1. A laser pointer (typically) outputs only 5 mW of energy. A car headlamp has more than 50W (10,000 times) of power beamed (I do not know the exact power)

2. Nothing happens unless you are directly in the path of the head lamp beam (perhaps as close as 10-20m from it; not at 1000m) and staring into the head lamp.

3. I cannot imagine how a vertical narrow beam coming out of the skylight can be in the line of sight of a airline pilot several km away. If it is within a distance of 100m or so, better be careful yourself.

4. There are warnings supplied with all laser pointers not to aim the beam towards pets or humans at close range; but I have often difficulty to see it even on the screen. It gets lost so often.

5. I do not understand how Chrysler/Fiat Jeeps have full brightness high beams for daytime running lights helps the driver or others- do they shut them off (full brightness high beams) at night?

6. Aircrafts too have headlights but I do not know whether anyone has ever come on the line of sight of the beam.

 

[Audioguru]

5. I do not understand how Chrysler/Fiat Jeeps have full brightness high beams for daytime running lights helps the driver or others- do they shut them off (full brightness high beams) at night?

Modern smart cars automatically turn on normal low beam headlights when it is getting dark like a $1.00 solar garden light. But stupid old cars (and some stupid new cars like Lexus) and stupid drivers do not turn on low beam headlights (and rear lights) at night. You know why? I asked a driver why aren't her headlights turned on? She said they were on but I showed her that the rear lights were off. So she turned on the headlights and said how is this? I said that now the high beams are on. She said that the high beams are always on when the headlights are on (she did not know how to select high beams or not). Most stupid drivers do not know how to turn on the normal headlights and do not know how to select high beams or not. Because most drivers are stupid. End of rant.

In the daylight and at dusk you can see these blinding bull brightness high beams daytime running lights on Chrysler and other cars that are MUCH brighter than the other cars miles away. I think the engineers know the daytime running lights are too bright because they turn off that side when its turn signal light is flashing.

 

[betwixt]

Conclusions:

1. do not stand in front of cars when they are travelling with high beam turned on. (you are blinded....but only for a moment before being hit)
2. for safety, if you have a skylight window, keep the volume high to disperse the light beams.
3. aircraft in Canada should not land on peoples roofs.

Just to satisfy my curiosity, has anyone ever seen an aircraft with a window in the pilots floor, maybe with the exception of a helicopter?

Brian.

 

[Audioguru]

My uncle owned a helicopter business. He gave me a ride and the dome of glass (acrylic?) curved under my seat so I saw the ground below me going past and coming closer when landing. Luckily nobody beneath was pointing a laser upwards. That was before disco lights.

 

[betwixt]

I've flown over your city many times Audioguru (flight path between London and Chicago) in 747s but never seen a laser pointing upwards toward me, or disco lights for that matter. Looks like a nice place from above.

Brian.

 

[Johanx2]

@betwixt, hey buddy, final thing, are you sure this circuit can be connected directly into the speaker terminals? is there a limit in watts? I am considering connecting this into the output amp, which would receive about 100w, supposing I test the sub on 2ohm with that amplifier I mentioned before, and maybe on hundreds of watts in the future, who knows, that maybe would require modifying something or otherwise will be burned the IC? bought things are on their way, still can not practice with that.

 

[betwixt]

We are 111 mesages into this thread and I've lost track of which circuit you are planning to use !

Basically, if it has a resistor with a value more than about 1K in series with the input it should be safe. That value is high enough that it isolates the amplifier from damage and also prevents enough current reaching your circuit to harm it. The value could be several times higher without changing performance.

Brian.

 

[Audioguru]

I looked at the ebay ad for the no-name-brand Chinese amplifier again and it does not say the speaker impedance for 100 Whats. 100 real Watts into 2 ohms is 14.2V RMS which has a peak voltage of 20V. Then a single-ended amplifier needs a supply of about 48V. But the supply is only 24V for this amplifier and the amplifier is not single-ended, it is paralleled and bridged so it produces 100 real watts into 2 ohms if it uses genuine Texas Instruments ICs.

The peak voltage from one of its active speaker wires is only 10V so the LM311 schematic input is fine. But the LM311 will oscillate like mad at times since it has no hysteresis (I think it is shown on another thread). Note that there is only one subwoofer speaker output that is not stereo.

EDIT: Here is a graph of the Whats and Watts power output on the Texas Instruments datasheet:

 

[Johanx2]

Good thing is that the less affected frequency by distortion, is the 20hz, so a subwoofer may be not affected so badly. does not it?

By the way, that graph refers to PBTL, which not sure, but I think PBTL means that two chips are linked and on bridge mode each one. The Chinese amplifier has only one chip in bridge mode.

 

[Audioguru]

Good thing is that the less affected frequency by distortion, is the 20hz, so a subwoofer may be not affected so badly. does not it?

No. Clipping distortion produces many odd numbered harmonics that aree not musical. Odd harmonics of 20Hz are 60Hz, 100hz, 140Hz, 180Hz, 220Hz, 260Hz, 300Hz ands more. You can hear all of them and a filter will not stop them. They cause a buzzer sound.

By the way, that graph refers to PBTL, which not sure, but I think PBTL means that two chips are linked and on bridge mode each one. The Chinese amplifier has only one chip in bridge mode.

ebay says that the amplifier uses TPA3116 chips but does not say who made them. Look in Google to get the Texas Instruments sales sheet and datasheet. One chip has two bridged amplifiers. P is Parallel so the subwoofer amplifier uses both amplifiers in the chip in parallel. BTL is Bridge Tied Load where both wires of the speaker are fed signals with opposite phase which doubles the voltage and doubles the current across a speaker.

 

[Johanx2]

No. Clipping distortion produces many odd numbered harmonics that aree not musical. Odd harmonics of 20Hz are 60Hz, 100hz, 140Hz, 180Hz, 220Hz, 260Hz, 300Hz ands more. You can hear all of them and a filter will not stop them. They cause a buzzer sound.

ebay says that the amplifier uses TPA3116 chips but does not say who made them. Look in Google to get the Texas Instruments sales sheet and datasheet. One chip has two bridged amplifiers. P is Parallel so the subwoofer amplifier uses both amplifiers in the chip in parallel. BTL is Bridge Tied Load where both wires of the speaker are fed signals with opposite phase which doubles the voltage and doubles the current across a speaker.

It seems the board has arrived! its at uncles house, hope to test it soon. Will take some pictures with a magnifier attached to galaxy S4, I have used it as a microscope even with a laser pointer lense, of course I wont use that, I dont want to see the atoms of a tiny resistor.

 

[Johanx2]

Finally the TPA3116 50wx2+100w amp has arrived. I took the pictures with a magnifier app for android, I think they are pretty good. So here they come. Hope you can tell me if my idea of adding aux RCA after the Bluetooth module its possible.

 

[Audioguru]

The amplifier looks well made. It is too bad there is no schematic, parts list or parts layout available.

 

[D.A.(Tony)Stewart]

TI Design docs
https://www.ti.com/lit/ds/symlink/tpa3118d2.pdf

 

[Audioguru]

TI Design docs
https://www.ti.com/lit/ds/symlink/tpa3118d2.pdf

I agree that the Texas Instruments circuit would be nice to have but here is a very inexpensive Chinese amplifier with hardly any spec's and no schematic. Maybe they used the Texas Instruments circuit but their Chinese to Engrish translation does not say so. It might be a cheapened circuit instead and might even use Chinese copies of the TI ICs.

When I quoted spec's from the Texas Instruments datasheet I always said the amplifiers spec's "might be" or "maybe is " the same.

My reliable bicycle was made in Canada but it got old and needed replacement. My kids gave me gift certificates for Father's Day gifts so I used them and bought the same bicycle, same manufacturer and same model number. I rode it only 1 block but returned it with a problem in its crankcase so the bicycle was replaced. The replacement also developed exactly the same problem in its crankcase so they investigated but did not fix it. As I rode it home a steel brake cable snapped.

It was made in China. Too much rice in the crankcase and the steel cable was steal instead. I got my money back.

 

[betwixt]

Just a word of caution: if the output of the amplifier is connected as a bridge, it means both speaker wires are driven. The schematic I gave will still work if driven from the pre-amplifier stages but if you drive it from the loudspeaker wires, make sure the ground of the power source is isolated. If you do not, it would short one of the speaker wires to ground and possibly damage the amplifier. It is doubly important if you try to drive it from the loudspeaker wires from two channels.

The alternative is to use a small audio isolating transformer at the signal input so the loudspeaker wires have no direct connection to anything else.

As I stated, if you connect it to the pre-amplifier output (before the volume control) it will still work as it is.

Brian.