Which bar graph driver would make the most visually appealing audio analyzer?  - Page 1
Forum section: electronics / projects

author: buck converter
author_rank: Regular Contributor
timestamp: August 29, 2017, 02:43:39 pm
content: I want to add a mini audio analyzer display to the Bluetooth speaker I am making. These chips are very popular for making VU meters and such. LM3914 seams to be the most popular for VU meters, even though LM3916 is for VU applications, according to the datasheet.Heres what I know so farLM3914 - linearhttp://www.ti.com/lit/ds/symlink/lm3914.pdfLM3915 - 3dB logarithmichttp://tronixstuff.com/wp-content/uploads/2013/12/LM3915-data-sheet.pdfLM3916 - Audio levelhttps://cdn.sparkfun.com/datasheets/Components/General%20IC/lm3916.pdfThanks in advance

author: Kjelt
author_rank: Super Contributor
timestamp: August 29, 2017, 02:53:28 pm
content: If I am not mistaken some of these are discontinued, if it is a single unit for yourself you probably can get some NOS.

author: drussell
author_rank: Super Contributor
timestamp: August 29, 2017, 02:57:43 pm
content: I don't know about "visually appealing" but the only ones that make sense for audio signals are the '16 and the '15. The '16 is a real VU meter, and is certainly the best from a technical perspective if you're actually using it for a level meter. If you are just going for useless-but-pretty-blinky-lights and the signal is always right around the same level, use the '15 so that it will bounce around more at the level you pick.If you're actually going to use it for anything useful, like the level meters on a mixer, for example, then the '16 is really the only logical choice to see the whole typical dynamic range. Main level meters you could expand it out a bit by cascading a '16 and a '15. (See the data sheets, they have many examples.)

author: drussell
author_rank: Super Contributor
timestamp: August 29, 2017, 03:00:41 pm
content: Quote from: Kjelt on August 29, 2017, 02:53:28 pmYeah, unfortunately TI recently discontinued them. Hopefully some Asian manufacturer will pick them up, I still use them all the time. I'm out of '16s but still have a couple tubes of '14s and '15s. I should stock up, I suppose. They are very handy.

author: macboy
author_rank: Super Contributor
timestamp: August 29, 2017, 03:16:37 pm
content: drussell's answer for which 391X is spot on.Look into the MSGEQ7 chip. It is a 7-band filter and peak detector that is designed for this type of thing, and greatly simplifies the analog side.You can sample the (multiplexed, "DC") output of this with an Arduino or other micro of choice, and drive the LEDs from that in a multiplexed fashion. Or if you want to do things without a micro, you could run the multiplexed output of the MSGEQ7 into a single LM391X, and use the output of that to drive a set of multiplexed LED bar graphs. (The response of the LM391X is plenty fast enough to multiplex). You'd need resettable counter for multiplexing, and a few other bits.If you want 14 bands instead of 7, run another MSGEQ7 with a lower oscillator frequency (about 60% of normal) so that its bands fall in between those of the other one. There will be a fair bit of overlap but for simple visualization rather than precise RTA measurement, it works.

author: buck converter
author_rank: Regular Contributor
timestamp: August 29, 2017, 05:41:52 pm
content: Quote from: macboy on August 29, 2017, 03:16:37 pmI did know MSGEQ7 could be used without a Micro. Thank you for the advice!I will try the 15 and the 16, see which one looks better

author: Monkeh
author_rank: Super Contributor
timestamp: August 29, 2017, 05:47:51 pm
content: Quote from: buck converter on August 29, 2017, 05:41:52 pmThey are no longer manufactured.

author: buck converter
author_rank: Regular Contributor
timestamp: August 29, 2017, 05:49:33 pm
content: Quote from: Monkeh on August 29, 2017, 05:47:51 pmThey are on eBaythis is a one-off project

author: M4trix
author_rank: Frequent Contributor
timestamp: August 29, 2017, 06:12:40 pm
content: Quote from: buck converter on August 29, 2017, 05:49:33 pmThey are probably fake or pulled out and 'refurbished'.

author: drussell
author_rank: Super Contributor
timestamp: August 29, 2017, 06:24:09 pm
content: Quote from: M4trix on August 29, 2017, 06:12:40 pmUnlikely at this point. They were available new from TI until the past year or so and they've produced millions and millions of them. There should still be plenty available here and there which are NOS.I just pulled out a tube of mine here and the LM3914s have 9606 date codes on them... Apparently I haven't had to stock up for over 20 years...Makes sense considering that was the pre-Digikey era and it was WAY cheaper to custom order bulk quantities of stuff from the local Electron Hut than try to buy a chip or two at a time.Last time I looked there were still readily available new from places like Digikey but that was several years ago so I was rather dismayed to notice recently that they had discontinued them, otherwise I would have picked up a swack more. I use them all the time for things like temperature gauges, oxygen sensor displays, etc.. (the '14)

author: DaJMasta
author_rank: Super Contributor
timestamp: August 29, 2017, 06:27:49 pm
content: While I'd disagree that all or most of the stock of a given part available is fake or pulls from equipment being sold as new, does it matter? If it's a one-off project for yourself in a non mission-critical setting where you're not pushing the performance limits fo the chip, there's a very high likelihood that even a cheap knock-off will last more than a decade performing well.Maybe you don't want to buy a stock and stash them without marking their source, but buying them for a project like this comes with near zero risk and most of that little remainder is just that the circuit won't work and it will be tricky to debug.

author: Monkeh
author_rank: Super Contributor
timestamp: August 29, 2017, 06:28:02 pm
content: Quote from: drussell on August 29, 2017, 06:24:09 pmThe LM3914 is still manufactured and readily available - the LM3915 and LM3916 were discontinued with the shutdown of GFAB6.

author: M4trix
author_rank: Frequent Contributor
timestamp: August 29, 2017, 07:02:19 pm
content: Well, if it's not fake or pulled out, then how the heck a chip which is discontinued, 5 pcs. costs only $1,22 USD ?LM3915

author: DaJMasta
author_rank: Super Contributor
timestamp: August 29, 2017, 07:30:01 pm
content: Because it was discontinued because of low demand and someone has a couple thousand sitting in a warehouse with no use in sight?Just because it's not made anymore and it's in good shape doesn't mean it's automatically worth as much as it originally sold for, or even close to that. While I wouldn't suspect a pull (there would be visible evidence), even if it was faked... does that matter for the project? If you want to take a stand against fake parts, that's fine.... but just writing off a cheap one as a fake with no other evidence seems a little hasty, right?

author: buck converter
author_rank: Regular Contributor
timestamp: August 29, 2017, 07:41:57 pm
content: Stock is not my worry. I do not care if it is pulled, and for less than $5, who cares if it is fake.This multiplexing idea sounds good, would need 4 ICs? (I think, let me know if this is wrong!)555 clock4017 decade counterlm3915/67 channel darlington array or discrete transistors (One that could supply current since the lm3915/6 sinks)

author: M4trix
author_rank: Frequent Contributor
timestamp: August 29, 2017, 07:44:36 pm
content: Quote from: DaJMasta on August 29, 2017, 07:30:01 pmThere's only one way to find out.... @buck converter should buy from that seller, test them and report here the results.

author: buck converter
author_rank: Regular Contributor
timestamp: August 29, 2017, 07:52:11 pm
content: Quote from: M4trix on August 29, 2017, 07:44:36 pmI will!