GSSL - LED METER QUESTION

[anythingcansoundgood]

Hello!

I initially posted this in an old thread (here: https://groupdiy.com/threads/my-gssl-variable-scale-meter-board.30057/#post-1171342), but since I didn’t get any replies, I thought I’d try again here. Please let me know if this isn’t the right place for this question!

I’m working on building a simple LED-based GR meter for a GSSL compressor. I want the scale to be fixed at 20 dB.

I came across information suggesting that the current output for the meter is negative. Is that correct?

If that’s true, I assume I’ll need an inverting op-amp configuration. My question is: with the same inverting buffer circuit, could I amplify the signal by 2.5x to bring it to a 0–5V range? If so, would I then be able to use the circuit from page 2 of the LM3914 datasheet (https://www.ti.com/lit/ds/symlink/lm3914.pdf) directly?

Here’s a schematic to clarify what I mean (the IC shown is the LM3914):



As my V+ and VLed source, I would be using the +12V output of the 78L12 voltage regulator (already in the GSSL's circuit).

Thanks!

 

[Hobbyist]

Hi ! I don't have experience with TL072 in this circuit. Tested it with TL071 based on the original thread and works perfect in my unit with 3 different settings. Trimmers are needed to tweak ! Some pictures of the pcb and the process.
Good Luck !

 

[anythingcansoundgood]

Hi ! I don't have experience with TL072 in this circuit. Tested it with TL071 based on the original thread and works perfect in my unit with 3 different settings. Trimmers are needed to tweak ! Some pictures of the pcb and the process.
Good Luck !

I'm currently searching for a schematic I could easily reproduce in Kicad, because it's not easy to understand where the traces are on the layout. But at this point I think I'll simply breadboard mine and we'll see I'll also implement a trimmer for the gain, thanks for this tip !