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Pot LED ring idea/question


mirv

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Hey,

I'm about to start my first real from scratch project with full case design pcb board layout and such. I'm actually not going to be a midibox design (thats number 2, want to get a little better before I build my LC!!!!) but I'm thinking midibox might be perfect for a certain addition I'm planning. 

Basically I'm making the edrum from edrum.info.  I want to add LED rings for a visual display of the current pot values. I've seen the LED ring's for the LC and was thinking something like that might be possible using just normal pots.

From what I can tell the values for the rings are sent by the program on the computer but there should be a way to adapt MIOS to turn on the led's based on the pot resistance and then forward the value to the edrum inputs right?. I'm going to dig in deeper this weekend but any guidence would be awesome.. at least where I should be looking. I'm a software developer and am generally pretty new to electronics.. but I'm learning quick and generally just need a point in the right direction.

Also could anyone suggest a configuration that would give me control over 128 leds?  The edrum I'm making has 16 pots. I'm thinking if I use the MIDIO128  firmware  I should be able to support 4 DOUTX4 modules which would give me my 128 leds. Confirmation on that one would be awesome too! 

Thanks!!

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I want to add LED rings for a visual display of the current pot values. I've seen the LED ring's for the LC and was thinking something like that might be possible using just normal pots.

... no problem. I just don't see why one wants LED-rings while using pots. - The knob pointer shows position much more accurate than som LEDs do.

Greets, Roger

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If I understand the question correctly, and I might be wrong..

The EDrum has it's input pots connected from the piezo input to Gnd, with the wiper connected to the input circuit. This allows you to control the "level" of the input from the piezo, setting the sensitivity of the circuit.

Most MB pot inputs connect +5Volts across the pot, with the wiper connected to the input, so you get a constant voltage somewhere between 0 and +5 volts into the AD input.

I think the easiest way to combine these is.. a double-pot at each position. One wired to the EDrum input, and the other wired for the MIDIBox's analog input.

Not a simple solution.

But I might misunderstand completely!

LyleHaze

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... no problem. I just don't see why one wants LED-rings while using pots. - The knob pointer shows position much more accurate than som LEDs do.

Greets, Roger

I considered that but honestly I'm wasn't overly concerned about the accuracy. Really I was wanting to add a unique touch to my edrum, something visual .. and I just happen to like LED's! This was my first though of something I could actually accomplish for the edrum which would give me a better understanding of MIOS and midibox at the same time.

You comment though made me rethink my plan though. A good quote came to mind "Just because something can be done, does in no way imply it should be done".

I do think I've found a reasonable alternative which Ive started looking into.

I'm going to add velocity meters for each of the channels. I read a few posts on the edrum where someone had concidered using midibox for just that but he never seemed to follow through with it.

I haven't fully decided on how I'm going to layout the faceplate or case but I think its a much better plan and will provide a much more interesting visual feedback.

Also, if I wanted to do this for 24 Channels (I'm thinking I'll still go with 8 LEDS per) would I need 2 core's? and a total of 6 DOUT's?

If thats the case I'll likely just stick with the 16 chan version       

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Really I was wanting to add a unique touch to my edrum, something visual .. and I just happen to like LED's!

And my first though was; Then why not:

add velocity meters for each of the channels.

Hehehe. I shoulda read the post, before I bit ;)

Also, if I wanted to do this for 24 Channels (I'm thinking I'll still go with 8 LEDS per) would I need 2 core's? and a total of 6 DOUT's?       

24*8 = 192 = Too many leds to run direct off the DOUT chain... but you'd be mad not to do a matrix for this. You could easily use some existing code and possibly even enhance it to update the columns individually per-channel.

I assume you mean drum channels  though, as midi tops out at 16... so how will the edrum send the velocity data to the midibox? Lyle touched on this earlier, but you haven't responded to him yet... How you plan on the boxes communicating is not clear... this is your big obstacle, do this one first...

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Velocity information is available in the MIDI output of the EDrum. Perhaps you could just set up a MIDIBox with a hardware MIDI-THRU jack, and monitor the data coming in.

I know that software MIDI-THRU is available, but doing it in hardware is not too hard, and it reduces the delay to near nothing.

That way you get the "peak" value of each hit from the velocity of the NOTE-ON message.

Most drum controllers (I'm not sure about the E-Drum) never send NOTE-OFF messages, so just set up a rapid decay for each ring that has something lit.

It would make setting your input gain pots a lot easier, if you could see how big your signal is.

Sounds like fun!

LyleHaze

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Velocity information is available in the MIDI output of the EDrum. Perhaps you could just set up a MIDIBox with a hardware MIDI-THRU jack, and monitor the data coming in.

I know that software MIDI-THRU is available, but doing it in hardware is not too hard, and it reduces the delay to near nothing.

That way you get the "peak" value of each hit from the velocity of the NOTE-ON message.

Most drum controllers (I'm not sure about the E-Drum) never send NOTE-OFF messages, so just set up a rapid decay for each ring that has something lit.

It would make setting your input gain pots a lot easier, if you could see how big your signal is.

Sounds like fun!

LyleHaze

That was pretty much exactly the same though I landed on. 

It would seem however the NOTE-OFF's are sent (well, you can enable and disable them). Heres a comment from the creator  "Note-off messages are automatically sent after a short period of time.

To confirm what exactly midi-thru does is it sends the unchanged midi signal directly to midiout (for processing elsewhere) meanwhile giving the core a copy of it to work with?

24*8 = 192 = Too many leds to run direct off the DOUT chain... but you'd be mad not to do a matrix for this. You could easily use some existing code and possibly even enhance it to update the columns individually per-channel.

Am I incorrect in thinking you can still only have 64 LED's per DOUT? I had planned on using the MAX7219 which I seen some people have success using (ordered some samples a few days ago!).

It would be nice to do it to the 24 channel version (which hasn't even really been realeased yet) as its set to have USB and moving to a better processor (the 4650 I do believe) very soon.

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I have not worked with DOUTs or LED Matrices yet, so I'll avoid those questions.

Whether you use the NOTE-OFF messages or just do a rapid decay from NOTE-ON is your choice. Since it's a software change you can easily try it both ways after it's built.

I will _suggest_ a change in terminology. The word "channel" has very specific meanings in MIDI terms. Perhaps it would be less confusing if we described it as 24 NOTES on a given channel (priobably channel 10, if I recall).

Your assumption on MIDI-THRU is exactly correct. It's an exact copy of MIDI-IN for the "next device in the chain".

If you do it in hardware there is no software issues and almost no delay (let's call it less delay than measurable)

Have Fun,

LyleHaze

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I will _suggest_ a change in terminology. The word "channel" has very specific meanings in MIDI terms. Perhaps it would be less confusing if we described it as 24 NOTES on a given channel (priobably channel 10, if I recall).

Never really thought about it but now I understand the confusion. I came from an edrum to midibox world and midi was a completely new thing to me when I started researching. The edrum site refers to each piezo input as a "channel" thus a 24 channel edrum.

When I say channel to people who are from a midi world they assume I'm refering to the 16 possible midi channels (yes, 10 is the midi chan edrum is on).

From now on I will refer to the edrum "channels" as peizo inputs!  :)

So, from what I can tell from http://www.ucapps.de/midibox/midi_thru.gif all I need to make midi-thru is connect that schematic to pin 26 of the PIC on the CORE module and apply +5V's to pin 14 on the chip and the midi connector (not sure what pin that is off the top of my head, I always have to refer to documentation!) .. and connect grounds of course as well.

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Ahhhh... So how does the midibox know which note to show on which LED meter?

I'm not  sure I completely understand your question.   Do you mean how midibox would know how to route the peizo input to the proper LED meter? 

I had assumed I would have the midi notes or at the least the numerical values of incomming midi notes from the edrum along with velocity information in MIOS. Am I incorrect in my assumption?   

As long as I can access those values in MIOS I didn't think it would be that hard to program it.

edit:

and after a short read at  http://www.ucapps.de/mios_c_set_dout.html and the midi spec page it links too it seems I can.

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Yes indeed.

Every "NOTE_ON" message includes:

A channel number (usually 10 for drum kits)

A note number    (For drums, which drum got hit)

A Velocity number(For drums, how hard it got hit)

Bonus question: Why are drums usually on channel 10?

LyleHaze

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That's the GM spec :)

mirv: how does the midibox know which note# to monitor?

I'm was thinking I could run the incomming note# through a switch statement.

You're right though, I would need to know what the incomming midi notes are going to be for that to work and if I changed the incomming notes  I would have to change the firmware.   

I could likely get around that and do remaping  (aka, change the expected note the notes on the fly) but it would take a 2nd lcd in my mind which I would rather not have.

Its likely not he best solution as it would be a pain in the a$$ to change the note's around, but it should work.    

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The switch statement is one thing but my point was the other part... I'm glad you're with me now! (only took like 5 posts hahahah)

Yeh it's far from elegant... I'm not sure why you can't build the meters into the edrum?

How about a learn mode, so you put a channel on the midibox into learn mode, hit the pad you want it to react to, and from then on, it monitors velocity for that note?

I'd still build into the edrum if possible.

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Takes me a little time to catch up sometimes... but once I'm there!!! look out  :P

I'm not sure why you can't build the meters into the edrum?

I think one of the largest reason's is the closed source status of the firmware for edrum. If I had access to the firmware it might be possible but its likely still over my head electronically. 

Unless of course I'm missing something, which is entirely possible.. but I'd think I'd need direct access to the firmware to be able to add it in as part of the edrum. Or the creator willing to write it for me, but I'm sure thats very low on his priority list.

I do like the idea of a learn mode. Hadn't considered it.  thanks for the idea!

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The eDrum already has velocity meters on the main LCD display, for the purpose of setting the gain controls.

Yes, but can you think of a way to tap into that information without the PIC firmware?

I realize that my idea really has no practical usefulness, but like I mentioned earlier, I want to add something visual to the edrum. Velocity meter's will look a lot more interesting then pot led rings. 

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One more thing then. 

I've been looking at the wiring diagrams and I'm not really sure how to adapt one of them (say the lc_ledrings) to a different size matrix or what my matrix options really are.

24x10 I guess would be an ideal size which would bring me to 240 LEDs and give me 10 LED's per peizo input.

Can that be driven by one DOUTx4 board? I'm thinking it can't.. but what do I know :)

I guess there is no reason I couldn't have say 2 12x10 matrix's, or hell even 4 6x10 matrix's right?

What do you think my best option would be?

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