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An external bar-graph or VU meter display for HW?

Building organ consoles for use with Hauptwerk, adding MIDI to existing consoles, obtaining parts, ...

An external bar-graph or VU meter display for HW?

Postby ludu » Thu Jan 30, 2014 10:03 am

The level of a swellbox or a general crescendo can be sent to a mini LCD screen and displayed as a percentage. However, in my opinion, this is not as comfortable as a bar-graph or a VU meter. On a wristwatch, some people prefer a digital display, other people prefer hour hands. The problem is the same with the level displays of an organ. Is there a way to send this kind of information trough an external midi accessory to integrate in a console?

Otherwise, I hope the next version of HW will allow to show a little bar-graph on a mini LCD display...
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Re: An external bar-graph or VU meter display for HW?

Postby jkinkennon » Thu Jan 30, 2014 11:01 am

This looks like the perfect project for an Arduino Teensy 3.1 and a 10-segment bar graph LED display. The Teensy's MIDI (on USB) capability makes this a "low hanging fruit" sort of project. Any volunteers?
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Re: An external bar-graph or VU meter display for HW?

Postby timhowarduk » Thu Jan 30, 2014 7:37 pm

It really isn't a hard project, the hardest bit is deciding how to display the 'answer'..

Would something like this work:
Image

It's small, but could show two or three bars in red / green or yellow, with 10 segments per bar....
and very cheap. Or even just a set of normal LEDs in a line....
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Re: An external bar-graph or VU meter display for HW?

Postby jkinkennon » Fri Jan 31, 2014 12:45 am

I like the idea of using the 8x8 matrix. I'd been thinking about the older 10 segment displays, but the matrix could display three sets of double rows for three pedals. A little more work to set up and pulse the columns, but not so bad either.

I don't have any Arduino hardware laying around and don't want to load yet another IDE on my computer, but I'd be happy to put together a little example program in C as I've got the SysEx parsing part done for my other encoders. It looks like the values from 0 to 100 are readily available for the expression pedals and it looks like they run from 0 to 31 for the crescendo. There would be just one type (and length) SysEx msg to watch for and you would have the luxury of dumping any MIDI data that didn't match that message type. Unless, of course, the Teensy was performing other functions.

And it's a good project. I think a number of people would want to give it a try since the hardware is so affordable and there's no need to purchase extras like programmers and software licenses. Sweet!
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Re: An external bar-graph or VU meter display for HW?

Postby ludu » Fri Jan 31, 2014 7:42 am

timhowarduk wrote:It really isn't a hard project, the hardest bit is deciding how to display the 'answer'.

However, I'm wondering if HW allows the control of a material other than mini LCD displays. All the dialogue boxes for outputs signals only refer to mini LCD display...
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Re: An external bar-graph or VU meter display for HW?

Postby jkinkennon » Fri Jan 31, 2014 11:49 am

The setting to enable MIDI status output is under General Settings -> General preferences where there is a tab which brings up this option. The status messages are documented in the Hauptwerk User Guide. I've used a number of these features which provide some of the raw data that is used to create the more familiar LCD messages.

Enabling the status output does result in lots of data. That's one of the reasons I'd prefer to use a device like the Teensy 3.1 that receives this traffic via a USB connection which will be a few hundred times faster than conventional MIDI. With 8-bit devices or with conventional MIDI there would at least be the potential for speed and/or buffering issues. The Teensy uses a fast 32-bit MCU with USB.
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Re: An external bar-graph or VU meter display for HW?

Postby TheOrganDoc » Fri Jan 31, 2014 2:19 pm

If anyone is interested in a simple inexpensive, analog to bargraph display device,
please search, LM 3914 along with COM 09935, or one of many other available Bargraph displays ! :D
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Re: An external bar-graph or VU meter display for HW?

Postby jkinkennon » Fri Jan 31, 2014 2:44 pm

Thanks, Mel, for the info for doing a VU meter display. I'd been avoiding that topic and concentration on expression pedals because I didn't think that updating a VU meter via MIDI would be practical. Well, maybe to display peak readings, but in any case I don't think HW provides that data. I'm thinking that the VU meter would need to track audio levels being output by the chosen audio interface as opposed to any levels within HW itself.
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Re: An external bar-graph or VU meter display for HW?

Postby ludu » Sat Feb 01, 2014 6:15 am

It seems to be perfect. Many thanks for this information.
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Re: An external bar-graph or VU meter display for HW?

Postby engrssc » Sat Feb 01, 2014 10:55 am

BTW, LM3914 is used for linear response while LM3915 is used for logarithmic (VU meter) applications. Relatively few parts needed. In place of the one piece bar graph that is available, I plan to use the http://www.ebay.com/itm/10-LED-bargraph-display-meter-PCB-panel-VU-audio-voltage-current-level-indictor-/330930748217?pt=LH_DefaultDomain_2&hash=item4d0d027b39 board which can be "remoted" and a "custom" set of LED's installed. Maybe connector-izing with a ribbon cable between the (remoted) display board and the driver board. Maybe I could install a flashing red LED at the top end. Several possibilities here. :wink:

Looking for a piece of "smoke coloured" see thru plastic (plexiglas) that I can mount in front of 3 (one for each expression pedal) displays. This for the church organ that has "surprised" :roll: one or more organists who didn't realize the position of an expression pedal (or the crescendo). Woke everyone up a few times. 8)

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Re: An external bar-graph or VU meter display for HW?

Postby jkinkennon » Sat Feb 01, 2014 1:27 pm

To offer some clarification, Ed is proposing building the VU PCB from eBay using a linear driver IC. This device would then be calibrated to track and display the physical position of an expression or crescendo pedal.

The earlier discussion was about creating a device to display the Hauptwerk interpretation of the pedal position which is a provided as an integer between 1 and 100. This is after auto-detecting the pedals and applying any ranging and/or offset to the raw values.

In an ideal world the two approaches would produce the same LED display. I'm just trying to make it clear why there are two very different approaches.
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Re: An external bar-graph or VU meter display for HW?

Postby jkinkennon » Sat Feb 01, 2014 2:09 pm

This is only semi-relevant for this thread, but Ed mentioned the surprise when an organist didn't realize the position of the pedals. One of the joys of programming my own encoder is that I can do things like monitor the OrganReady signal and send the current pedal positions when an organ is loaded. That way a sudden static glitch or other power supply fluctuation won't cause the virtual pedal to suddenly match up with the real pedal and surprise me. I was having a problem with this because I map a master volume control to the HW slider and it would suddenly pop from say 70% to 100%.
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Re: An external bar-graph or VU meter display for HW?

Postby engrssc » Sat Feb 01, 2014 2:53 pm

OTOH, H/W can be programmed to set the expr pedals to closed at startup. The "problem" I mentioned occurs after H/W is running. Since the basic LED display circuits are voltage dependent, they show the pedal position at all times.

Nick Nelson's 10 segment LED bar graph circuit ( which I have on the home organ) works quite well and is very simple to build. http://forum.hauptwerk.com/viewtopic.php?f=15&t=5285&p=36534&hilit=expression+bar+graph#p36652

I have been looking for a way to decade 2 displays to increase the resolution to 20 segments. I see some ways to do this, but of course the cost goes up along with the resolution. :o

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Re: An external bar-graph or VU meter display for HW?

Postby TheOrganDoc » Sun Feb 02, 2014 2:44 pm

Hello Ed,
As I recall the Spec sheet for the Led Bargraph driver LM3914 and its Log. partner LM 3915, are stackable and their specsheet showed how to accomplish it ! :roll:

I installed many of these, years ago when doing Musical Equipment repairs.
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