![]() ![]() Several one clock tick operations per sample, but not killer at least with 16B PIC running at 7 MHz. If the immediate sample is below the accumulated average, the difference is multiplied by the release time constant coefficient and subtracted from the running average. If the immediate sample is above the accumulated average, I multiply this difference by the attack time constant factor or coefficient that simulates the charging current in the R of an RC and add this charge current to the running average. I model a one pole time constant by calculating the difference between the immediate sample and the accumulated average. There are enough spare A/D inputs that the log output could be programmed to accept different step sizes for multiple zones, or notĬlick to expand.Relatively simple. PS: I haven't come up with a good way to cover fully custom random scales, but I'm open for suggestions. This would obviously take a back burner to my more pressing projects I have going.Īny interest? I think I have asked about this before to mostly silence. Note: I haven't generated the specific code to read step size but it is not very heavy lifting for a micro. I actually owned a kit business back in the 70-80 and lost faith in the business model (due to automation and lower cost manufacturing). I would be willing to work with somebody on this, but I am really not interested in getting back into the kit business after a few decades. I don't know if the better LED drivers even come in TH, so perhaps the play is to make a small PCB with PIC and LED drivers already populated, that the user connects the led output lines to his custom display application. OTOH, for a simpler modest number of LEDs meter, it is possible to use one older 8 bit PIC family that could drive LEDs directly, but I am not enthusiastic about the only 10 bit A/D, or dealing with 8 bit math (i hate 8 bit after getting used to 16 bit), or multiplexing the LEDs to use less drive lines, but perhaps making more noise inside an audio product. However I fear the economy of scale means there would be a premium to buy PICs in small quantity and program them independently. The two chip solution, PIC and LED driver could be close to the cost of the LM3915/15 but far more powerful. There it may be worth standardizing on 8 or 16 evenly spaced linear thresholds, and scale with your input divider. ![]() In the linear scale the number of outputs would not go on forever and depend on the step size. Sending serial data to the LED drivers with smallest threshold first, means you could push out 32 or more bits of data, and string multiple LED drivers in series, then just use a x8 or x16 latch to grab the top 8 or 16 data thresholds. That will be interpreted as a - 3dB ratio between each step reading down from full scale. For example to make a log meter with -3dB steps, send a voltage equal to. Further with all the spare A/D inputs some of those spare inputs could be used to program a user customized linear step size, or a custom dB step size for the log scale. It would be reasonably simple with programming pins to select between dot or bar, peak or ave (or both, my favorite), linear or log meter scales. it might make a bigger difference for metering individual instruments in say a large console. ![]() The cheaper low voltage family of PIC is not comfortable directly driving LEDs, but there are nice dedicated LED driver ICs (available in x8 or x16 LED capability, or more cascaded in series) that accept serial communication and are also modest cost.ĭetecting both peak and average are relatively simple inside a microprocessor, and it is even possible (but not as easy) to compute RMS, while I haven't found that justified yet for metering complex audio. The commercial meter I did easily handled 6 audio streams but i would probably standardize on a x2 meter chip set. There are modern low cost PIC families with multiple 10 or 12 bit A/D convertors built in. I have given this a lot of thought and will share my thinking on how something like this "could" work. ![]() I did one commercial design based on a PIC and I own the software so I have though about the possibility of perhaps offering pre-programmed PICs that could be customized with option pins and glue circuitry. ![]()
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