LED peak meter with fastest transient detection (clipping indication meter)

[moamps]

12v!? I you have to increase input to ref!?

Yes. The reference voltage should be very stable and arbitrary on level. Higher ref. voltage is better, IMO. 

 

[seva]

what is the voltage of v+ and v- of the trident high res meter. Also 12v? same psu?

can i leave comarator legs open when i need less then 4 in any stage?

 

[abbey road d enfer]

Is VR1 to increase the rectified input signal to the 24v ref?

Or is VR1 to decrease ref V to rectified input signal?

VR1 is the input adjustment. The reference is not 24V, it's about 4V. The resistor string is about 10k and the voltage divider with the 47k (R32) gives about 4V.

what is a good value for the hole ladder R? I choose 51k for the calculation attached. Is it OK? 

Typically I would use about 10k.

Why do you use 24v for your power supply?

Because that's what I had available! The LED's are in series, so they need about 16V, to which you have to add about 2V for the CCS.

What is the minimum for 30 LED´s with 40dB range?

You can't put 30 LED's in series; that would require about 60V, which the comparators cannot handle. You have to arrange them in strings of 8 or 10. So you would need about 20V for strings of 8 or 24V for strings of 10. I would use strings of 8 because the comparators come in quad packs.

 

[abbey road d enfer]

what is the voltage of v+ and v- of the trident high res meter. Also 12v? same psu?

I believe they are +/-17V, the audio rails.
A string of 12 LED's plus the CCS requires about 26-28V.

 

[moamps]

what is the voltage of v+ and v- of the trident high res meter. Also 12v? same psu?

It's D&R Triton. Power supply gives +/-18V, at strips it drops to +/- 17,5V.

can i leave comarator legs open when i need less then 4 in any stage?

It depends of the used opamp/comparator.
For opamps, usually +in goes to gnd, -in goes to output.
For comparator LM339, unused inputs and outputs should go to pin 12 (gnd or -V), IIRC.

 

[seva]

thanks for the explantation!

I am on the right way. I am tuning the scale right now. I found a calculator form Elma and did a new calc.  Are my values ok for the ladder resistors?

 

[seva]

I found

LM 239 DIL

is that the right comparator?

 

[seva]

@ Abbey

what is the value of R31 in your meter schemo? why is it na?

 

[abbey road d enfer]

I found

LM 239 DIL

is that the right comparator?

LM139/239/339 are all the same beast except guaranteed temperature range. I use LM339 in PDIP14, but you may want to use an SMD version that would take less real estate.

 

[abbey road d enfer]

what is the value of R31 in your meter schemo? why is it na?

R31 is a dirty trick that reinjects a fraction of the input voltage into the reference. The result is the response is in the form (ax+b)/cx+d), which is an hyperbolic.
Within a carefully chosen range, an hyperbolic is close enough to a logarithmic, so that makes a reasonable dB scale with a linear resistor string.
It's NA in the level meter because the resistor string is specific, but for the GR meter, it's used to increase resolution around 0dB, but still allows displaying high GR (about 40dB).

 

[seva]

I looked to the 3 schem´s for comparison. there are 3 different ways of connecting positive comparator inputs +

1. the trident has this section on ground
2. ruffrecords schemo shows no connection to ground
3. Abbeys schemo shows connection to the input back.

Could you please explane it or link me to the basics

 

[seva]

I see -2. goes also back but is not grounded

 

[abbey road d enfer]

3. Abbeys schemo shows connection to the input back.

Input is at the top of VR1. The signal is rectified elsewhere.

 

[seva]

still not understand why the trident goes to ground.

I did a first schemo- attached. I hope that I understood everything right so far. When it looks good, i plan to go over to the math tasks. 18Vsupply V+ and V-

 

[abbey road d enfer]

still not understand why the trident goes to ground.

Not "trident", it's Triton, from dutch manufacturer D+R.
See pins 8, 9 & 10 of connector 2, and pin 3 of connector 1 ? They go to this kind of slash symbol. That's ground, and you see many instances of it all around the schemo, particularly at the bottom of the resistor strings (R60).

 

[seva]

OK- Now, I see it thanks Abbey!

But I mean R1 - 100k goes to ground. I don´t know why. Other circuits don´t have it (or not?)

 

[abbey road d enfer]

OK- Now, I see it thanks Abbey!

But I mean R1 - 100k goes to ground. I don´t know why. Other circuits don´t have it (or not?)

R1 is there to ensure DC path to ground when the TL074 is missing. Just there for troubleshooting purpose.

 

[seva]

OK

Do you think V+ V-, gounding and combining stages is ok- How i did it?

 

[abbey road d enfer]

OK

Do you think V+ V-, gounding and combining stages is ok- How i did it?

Seems ok, but your pic is hard to read, not enough resolution.

 

[seva]

Many thanks to looking over! Here is the high Res