I have just had another look at the circuit in post 5. Very strange!
Q1 (near the centre of the diagram) has no base drive, so can be deleted.
The other Q1 (on the right) seems to be a cap multiplier, although perhaps with one resistor in the wrong place. Probably unnecessary, unless a very noisy PSU is used. Remember, we are talking about control here, not signal.
All the other BJTs appear to be wired as diodes, and may have some effect in current steering, or may just be due to the OP's obsession with adding diodes into circuits.
The opamp outputs are all paralleled together (bad idea?) and then simply feeds the input
of a 5V regulator. The output goes (via another diode!) to a 317 wired as a CCS. This current is then fed via the pot to the LEDs. The pot steers the current one way or the other.
At this point I will give up. The circuit appears to have been drawn by a 6-year-old with an ECAD program, with random wire connections. It could be that this circuit is meant to confuse us, and the real device is quite different.
I am very calm, but I don't like to see nonsense put forward as 'progress'. So far, as last time, the OP's explanations just demonstrate more and more clearly that he simply does not understand what he is doing, but appears to be blissfully unaware of just how far from reality he is. For the avoidance of doubt, this is not an argument between experts about some disputable matter (as happens in some threads) with people taking sides, but simply nonsense being identified as nonsense - you don't even need to be an expert to do that, just know some elementary circuit theory.
PS TL072 is a JFET input amp - it is not intended that people take a current from an input gate!! Any non-tirvial current here can only come from the input protection diodes.
Q1 (near the centre of the diagram) has no base drive, so can be deleted.
The other Q1 (on the right) seems to be a cap multiplier, although perhaps with one resistor in the wrong place. Probably unnecessary, unless a very noisy PSU is used. Remember, we are talking about control here, not signal.
All the other BJTs appear to be wired as diodes, and may have some effect in current steering, or may just be due to the OP's obsession with adding diodes into circuits.
The opamp outputs are all paralleled together (bad idea?) and then simply feeds the input
of a 5V regulator. The output goes (via another diode!) to a 317 wired as a CCS. This current is then fed via the pot to the LEDs. The pot steers the current one way or the other.
At this point I will give up. The circuit appears to have been drawn by a 6-year-old with an ECAD program, with random wire connections. It could be that this circuit is meant to confuse us, and the real device is quite different.
I am very calm, but I don't like to see nonsense put forward as 'progress'. So far, as last time, the OP's explanations just demonstrate more and more clearly that he simply does not understand what he is doing, but appears to be blissfully unaware of just how far from reality he is. For the avoidance of doubt, this is not an argument between experts about some disputable matter (as happens in some threads) with people taking sides, but simply nonsense being identified as nonsense - you don't even need to be an expert to do that, just know some elementary circuit theory.
PS TL072 is a JFET input amp - it is not intended that people take a current from an input gate!! Any non-tirvial current here can only come from the input protection diodes.
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You mean wire it up as shown below and then measure Vout and the current through the resistor?
Attachments
Hi DF96
My circuits are drawn on Oregano Linux, so apologies they do not comply with your needs, it is the best program that my present resources extend to. BJT's are indeed wired as current steering diodes.
No it is not intended to normally take current from a inverting input, yet it works very successfully. Yes the pot steers current one way or the other to work very well as an attenuator, and the circuit I designed maintains voltage to the anode of LDR at all volume settings.
This thread attempts, and simply suggests to address better control of LDR's, other than cheap ohmic pots and a fixed voltage, may be it cannot be done, and it is better we all go on holiday but,your contribution particularly if you have a good design is most welcome. 🙂
Cheers / Chris
My circuits are drawn on Oregano Linux, so apologies they do not comply with your needs, it is the best program that my present resources extend to. BJT's are indeed wired as current steering diodes.
No it is not intended to normally take current from a inverting input, yet it works very successfully. Yes the pot steers current one way or the other to work very well as an attenuator, and the circuit I designed maintains voltage to the anode of LDR at all volume settings.
This thread attempts, and simply suggests to address better control of LDR's, other than cheap ohmic pots and a fixed voltage, may be it cannot be done, and it is better we all go on holiday but,your contribution particularly if you have a good design is most welcome. 🙂
Cheers / Chris
Perhaps if, before selling the circuit, if you had determined what the limitations of "cheap ohmic pots" were and demonstrated how your circuit overcame those, you may not have taken so much flak.
It is not the style I am concerned about but the substance. A BJT with no base bias, opamps used back to front etc. This might be what you could get if a 6-year-old child was given an ECAD program and asked to draw a circuit.
I assume you meant LED, not LDR. As I said, this is quite pointless.
Here is how you can simplify the circuit:
- scrap the opamps
- scrap the all the BJTs
- use a CCS to feed a current to the pot wiper, as at present
- then the pot simply steers the current between shunt and series arm LEDs (guess what - LEDs are diodes! They can steer themselves)
This will retain the unnecessary requirement that the LED does not switch off.
Of course, such a simple circuit will need a much better story to sell it to the unsuspecting. There will be less 'science' to blind people with.
Hi DF96
Great, I look forward to your schematic, and confirmation using NSL32SR2 or similar that it functions as an attenuator in an actual audio system,🙂
Cheers / Chris
Great, I look forward to your schematic, and confirmation using NSL32SR2 or similar that it functions as an attenuator in an actual audio system,🙂
Cheers / Chris
Thanks for that well needed overview here.
One more point about improvement - as drawn, the LEDs are in parallel. This means one can hog more current than the other if they (or the transistor as diode before it) are not precisely matched.
A better approach as shown by others, is to eliminate the diode before it and put the LED in series, so each gets the same current. Have a peek at the Nelson Pass design posted here.
If you use this improved design and sell it, be sure to give full credit to where it came from. 😎
If I did that I would require a royalty on every one you sell!Chris Daly said:
I personally don't believe that LDR volume controls are a good idea. However, my concern with this particular design in not that it uses LDRs, but that the LED driving circuit is daft and it doesn't achieve the stated aim of good channel balance. The daft idea then has to be bolstered by an imaginative story. I still don't know whether Chris believes his own story. Of course, if he really wants to sell expensive tat to ignorant audiofools he ought to include a couple of valves to do the current control.
Yes, of course, I should have said that. Then you are absolutely guaranteed to have identical currents in the LEDs. It will, of course, then show even more clearly that it is LDR matching which really matters.BFNY said:
Where is the Nelson Pass schematic? I did a search but could not find it. BFNY, thank you.
First off should be figuring out whether the circuit works as advertised, before attempting to sell it for $450.00 on eBay.
$450? Really? For something that *may* work almost as well as a $5 potentiometer? Holy cow, you just can't make this stuff up.
Green, your LDRs are broken.
An LDR with no light input goes beyond a few 100k.
An LED with zero current transmits no light.
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It does come in a lovely shiny box!SY said:
I guess after selling his daft opamp supply idea for only $19 each he decided that this time he wanted to join the big boys. I'm puzzled why he wants to discuss the circuit on here as he should have known that we would (ahem) point out some of its weaknesses. Maybe he really does think that it works?
Every time my wife looks at the forum, she shakes her head sadly and asks, "Just what is WRONG with these people?"
Some toxic combination of extreme male brain combined with a modern content-free education? The result is people who believe passionately in technology but don't understand it.
450?!
OK. That's it. I'm calling Shenanigans!! (a la Kyle at the carnival, on South Park)
This thread has become quite an embarrassment and the sale of the circuit is either outright fraudulent or right on the edge of fraudulent-by-ignorance.
If I had to guess, I might think that the OP is trying to play us, and is mining for free re-designs for the original nonsense-circuit, and/or for circuits that actually work well, so he can sell them.
OK. That's it. I'm calling Shenanigans!! (a la Kyle at the carnival, on South Park)
This thread has become quite an embarrassment and the sale of the circuit is either outright fraudulent or right on the edge of fraudulent-by-ignorance.
If I had to guess, I might think that the OP is trying to play us, and is mining for free re-designs for the original nonsense-circuit, and/or for circuits that actually work well, so he can sell them.
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Drew, I am not in disagreement other than your claim my "LDR's are broken". Reread my post. My comment was in response to the claim that voltage after the 100K pot in my schematic is 0V. It is not 0V, if it were 0V then resistance of the optocoupler would be over 1M.
In addition, out of desire to separate myself from the rest of this thread, my schematic functions adequately. If it sounds better than a $5 pot is between you and your ears. Nothing I said should be construed as an endorsement of Chris Daly's circuit.
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It is true to say, that to date the only real advancement with LDR design has been marketing of devices containing a potentiometer with a fixed voltage.... that do sell, and people buy in various marketplaces at high prices. There has been no advancement away from nothing more than that marketing, and like a whirlwind of product adoration of a fixed voltage and potentiometer, no one has found time to contribute to any thing else that I am aware of.
You will note I have not mentioned where my product is sold, there has been no image, or website link. I have fully complied with forum rules concerning advertising, and I pay monthly fees for the right to advertise at that different location.
Comments way off focus like I am mining ideas, are totally wrong. I do not copy other persons contributions, and never will.... rather I enjoy finding and creating electronics ideas myself that are different, that perform well and that no one has approached before.
I am proud of the original product I have designed and created, it performs very well as an attenuator, providing excellent audio reproduction 🙂
Cheers / Chris
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