Did you seriously think the power supply and signal grounds were connected?
If so, then being a unbalanced audio device, relying on signal interconnects,
do you see that as sufficient ?
Unbalanced can be better than balanced, what has that got to do with connecting PSU 0V and signal return?
Totally agree Unbalanced is great, Unplugging or plugging interconnects when powered without a 0v , can be tragic.
Figure 7 on Page 10 provides manufacturers data for output impedance vs frequency at 500ma, with Vin of 10v http://www.ti.com/lit/ds/symlink/lm340.pdf
Thanks. I take it you were not able to measure your sample, but that's ok, I will accept the data sheet. Now, what does it tell you? What is the range of the output impedance of the 7895 in the audio band? Does it ever reach anywhere near 4K79?
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Thanks. I take it you were not able to measure your sample, but that's ok, I will accept the data sheet. Now, what does it tell you? What is the range of the output impedance of the 7895 in the audio band? Does it ever reach anywhere near 4K79?
No, but does not change its implementation of output and ground which are directly in parallel with LDR anode and cathode along with capacitance and potentiometer resistance.
Politely suggest you stop defending a 7805, and instead concentrate on seeing the better way of powering LDR's using a dedicated current source for anode and current sink
for cathode, with nothing as a parallel between them.
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Do you make the error in your design of connecting 0V to signal return?
No.
I'm glad to hear it, then you can stop worrying about all the rest, it's completely irrelevant to the functioning of the LDR, since there is no electrical connection, it is not "powered" by the supply, I presume you realise that.
What type and model of LDR are you discussing by the way ?
No, but does not change its implementation of output and ground which are directly in parallel with LDR anode and cathode along with capacitance and potentiometer resistance.
Can we have that in English, please? I have no idea what you mean by all that, but your claims about the output impedance of a 78xx voltage regulator are just plain wrong. And, as DF96 has pointed out repeatedly, Light Dependent Resistors are not polar and do not have anodes or cathodes, though LEDs do.
Politely suggest you stop defending a 7805, and concentrate on seeing the better way of powering LDR's using a dedicated current source and current sink
Funnily enough Chris, I agree with you. The light output of an LED varies as a function of current, and if you want precise control of LED output, and hence LDR resistance, then a variable current source is the best way to do it. An LEDs Vf varies with current (and temperature) so varying voltage to the LED in series with a fixed resistance, will not change the current through the device in a linear way. Nothing to do with "sound quality", but a current source is the best way to control current through an LED. An LM317 is easily configured as a variable current source.
Having said that, most of what you write here is gibberish and you clearly have no understanding of the subject you write about, including your ridiculous "measurement" of a voltage regulator's output impedance.
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The type with 4 wires, 2 for the LED, 2 for the LDRWhat type and model of LDR are you discussing by the way ?
Can we have that in English, please? I have no idea what you mean by all that, but your claims about the output impedance of a 78xx voltage regulator are just plain wrong. And, as DF96 has pointed out repeatedly, Light Dependent Resistors are not polar and do not have anodes or cathodes, though LEDs do.
The figures within the graph for output impedance are from Texas Instruments data sheet,would you like to correct them if you think they are plain wrong ? Figure 7 page 10 http://www.ti.com/lit/ds/symlink/lm340.pdf
their address for contact is Dallas Texas 0800 446 934
And a Light Dependent Resistor indeed has an anode and cathode for its LED
as shown here: http://lunainc.com/wp-content/uploads/2016/06/NSL-32SR3.pdf shown on the Right hand side image as Anode lead and Cathode Lead
Funnily enough Chris, I agree with you. The light output of an LED varies as a function of current, and if you want precise control of LED output, and hence LDR resistance, then a variable current source is the best way to do it. An LEDs Vf varies with current (and temperature) so varying voltage to the LED in series with a fixed resistance, will not change the current through the device in a linear way. Nothing to do with "sound quality", but a current source is the best way to control current through an LED. An LM317 is easily configured as a variable current source.
Have you tried a current source implementation ? was it better than the
parallel arrangement shown at Post 127 across the anode and cathode being 78xx + capacitance + pot resistance.
Where the anode and cathode have no parallel components at all is what you need to try, so current source and current sink, with no parallel capacitance or resistance - (internal to devices) or external via pots.
I would rate a LM317 arranged as a Vref/r regulator for anode of the device on its own, poor to average, with resulting audio, compared to with what can actually be achieved. But compared to Post 127's schematic - quite a leap forward.
then with a dedicated current sink for the cathodes better again
Having said that, most of what you write here is gibberish and you clearly have no understanding of the subject you write about, including your ridiculous "measurement" of a voltage regulator's output impedance.
Your assertion of including ridiculous measurements argument would
need to be taken up with Texas Instruments. As shown by the measurements they did on a 78xx
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I would have thought such a measurement would tell me nothing of any use at all. It certainly will not tell me the output resistance of the regulator. Have you ever understood how a regulator works?Chris Daly said:Pretty easy I would of thought but ...
Place the Positive probe on the Out pin and the Negative probe on the Ground
pin, for a LM7805 what resistance do you measure ? Can that be answered
Yes/No
I think you will find that R20 is part of the feedback arrangements. Its exact value does not matter.That schematic fails to show the resistance from Output to ground
Even in Texas instruments latest schematic, it is vague because one
resistor called R20 has no stated value.
No. It is a regulated voltage source for the LED driver arrangements.So placing a 7805 in a LDR circuit with accompanying capacitance, could we say its really a constantly powered R/C shunt circuit between anode and cathode, and signal ground ?
There is nothing harmful to escape from. The LED just sees a voltage source and a variable resistor.If we now step forward to escape the parallel 7805 device between anode and cathode
(with accompanying capacitance , fixed internal 7805 device resistance
and potentiometer necessary to have current being adjusted to cause
LDR signal side resistance being changed ) shown in Post 127
No. On the contrary, unless you arrange for the two sources to exactly track each other (hint: this is impossible, except perhaps in Spiceworld) one will dominate and the other will hit a limit and cease to be a CCS. Poor engineering.A dedicated current source for the anode, and a dedicated current sink for the cathode
becomes apparent as far a better approach.
The 100k pot means that they are not "directly in parallel".No, but does not change its implementation of output and ground which are directly in parallel with LDR anode and cathode along with capacitance and potentiometer resistance.
I don't understand your fixation about nothing in parallel with the LED.Chris Daly said:Where the anode and cathode have no parallel components at all is what you need to try, so current source and current sink, with no parallel capacitance or resistance - (internal to devices) or external via pots.
There is absolutely no need for both current source and current sink. You simply need one, if you want current drive for the LED. The LED emits light based largely on the current; it does not know and does not care what voltage it sits at with respect to its own PSU ground or the audio signal ground. Do you understand what 'voltage' is?
The schematic at Post 127 has the cathode of the LDR at the same potential
as signal ground
In post 102 I asked about separate grounds. In post 104 you said the grounds were separated. Now which is it?
Take another look at the regulator schematic. You can clearly measure the resistance from output to ground and that is why I posted it. I measured a number of different brands out of circuit and they all measure 15K. This isn't going to make any difference after all because per your post #104 you stated the grounds were separated.
Do you even have a clue as to what your talking about?
An opto-isolator is an electronic component that transfers electrical signals between two isolated circuits by using light. Opto-isolators prevent high voltages from affecting the system receiving the signal. Commercially available opto-isolators withstand input-to-output voltages up to 10 kV and voltage transients with speeds up to 25 kV/μs. A common type of opto-isolator consists of an LED and a phototransistor in the same opaque package
The above is an explanation of the opto-isolator.
Note the "two isolated circuits" in the first sentence.
The above is an explanation of the opto-isolator.
Note the "two isolated circuits" in the first sentence.
No, not yet ?Chris, are you Garry and Glenda's lad...?
I don't understand your fixation about nothing in parallel with the LED.
There is absolutely no need for both current source and current sink. You simply need one, if you want current drive for the LED. The LED emits light based largely on the current; it does not know and does not care what voltage it sits at with respect to its own PSU ground or the audio signal ground. Do you understand what 'voltage' is?
Chris..... I'll help you out.
Voltage, electric potential difference, electric pressure or electric tension (formally denoted ∆V or ∆U, but more often simply as V or U, for instance in the context of Ohm's or Kirchhoff's laws) is the difference in electric potential energy between two points per unit electric charge.
volt·age.
.
[ˈvōltij]
NOUN
physics
.
an electromotive force or potential difference expressed in volts.
"the ratio of two voltages" ·
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