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  #1  
Old 02-24-2009, 03:26 PM
greysound greysound is offline
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Default VL-1 Power Issues etc.

In the process of installing my modified VL-1 in a new cabinet, I've run into two issues that puzzle me.

1. I've added external power and branched it to feed the VL-1 and the Highly Liquid board in parallel. It seems to work, but after I play a few notes through MIDI, the VL-1 shuts down. Is this the auto-shutdown misfiring? Or is there some kind of nasty side effect of external power?

Additionally, I seem to do better when powering with a battery pack rather than a wall-wart. The wall-wart is 5v or 7v (switchable) DC 800mA which seems like it would be more than enough to power both the Highly Liquid board and the VL-1.

2. I suspect I've pinched a wire in the process of installing the VL-1, because I'm unable to play most of the white keys by MIDI but I can still play the black ones. Given those symptoms, do you have any idea where I should start looking to diagnose the problem?

As soon as I get this working, I'll send pictures.
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  #2  
Old 02-26-2009, 04:42 PM
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I'm not sure what exactly is causing these issues. I'd recommend sticking with battery power, at least until you get everything sorted out. The MIDI kit was developed & tested using battery power. On an unusual device like the VL-1, sometimes different supply voltages can effect the interplay with the MIDI board.
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  #3  
Old 02-26-2009, 06:35 PM
greysound greysound is offline
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Default VL-1 Power Issues etc.

How about the pinched wire issue? Any idea which connection would control the white keys?
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  #4  
Old 02-27-2009, 12:10 PM
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Quote:
Originally Posted by greysound View Post
How about the pinched wire issue? Any idea which connection would control the white keys?
The individual keys are mapped rather randomly to the matrix lines...so I'll need to go back and look at the code for this. More soon...
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  #5  
Old 02-28-2009, 09:19 PM
greysound greysound is offline
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Default VL-1 Power Issues etc.

Hi John,

I'm so close to having this thing working, but there's one remaining issue I can't seem to track down. I have a series of notes that play fine locally, but do something weird when playing from MIDI. The notes play slightly louder than other notes, and pitch up to the next whole step until the key is released, then they sloppily bend down a half step to something close to the right note.

The notes all appear to be on one data line and cover the following notes:
G#3
A#3
C#3
D#3
F#3
G#3

While I can play other notes quickly without issues, if I play these notes fast, the VL-1 shuts down.

I have checked the line with a continuity check and it seems to be fine, though I don't have an oscilloscope or the knowledge of how to use one. It seems like a firmware thing, though I can't be certain of that.

I also need to know what the proper dipswitch settings are for the VL-1.
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Old 03-03-2009, 12:49 AM
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Quote:
Originally Posted by greysound View Post
Hi John,

I'm so close to having this thing working, but there's one remaining issue I can't seem to track down. I have a series of notes that play fine locally, but do something weird when playing from MIDI. The notes play slightly louder than other notes, and pitch up to the next whole step until the key is released, then they sloppily bend down a half step to something close to the right note.

The notes all appear to be on one data line and cover the following notes:
G#3
A#3
C#3
D#3
F#3
G#3

While I can play other notes quickly without issues, if I play these notes fast, the VL-1 shuts down.
Did you have this problem before rehousing the VL-1?

Quote:
I have checked the line with a continuity check and it seems to be fine, though I don't have an oscilloscope or the knowledge of how to use one. It seems like a firmware thing, though I can't be certain of that.

I also need to know what the proper dipswitch settings are for the VL-1.
SW1 settings are ignored by the VL-1-MIDI firmware. The SW2 settings only affect the MIDI channel.

My guess would be that the power supply is the issue. The UMR board needs to run on the same voltage as that used by the host for the the keypad scan.

The VL-1 takes the power supply voltage (or battery voltage) and steps it down to ~3.3 volts or so. The select pulses sent by the microprocessor to the keys (and the resulting data signal coming back) is at this same ~3.3V voltage level.

If the UMR board is receiving, say, 5V directly from your power supply (or 4.5V directly from the batteries), it is injecting a 5V (or 4.5V) data pulse to the keys. So, the VL-1 circuitry is such that for those particular keys, the higher-voltage data pulses happen to cause problems. This is consistent with the pitch problems, which definitely sound like some sort of analog issue.

Hope this makes sense. So, first, I would change the UMR "5V" power connection back to that shown on the installation diagram. Does that eliminate the problem?

Then, since that power connection has the other issue causing the UMR to shut off during ADSR mode:

1. Measure the voltage at the "+5V" connection point in the install diagram. It should be around 3.3V when the VL-1 is powered on.
2. Find a different supply point on the VL-1 circuit board that has the same voltage. First I would try the different pins on the little ribbon cable there--I think one of the other pins qualifies.
3. See if the new connection does not cause the UMR to shut off during ADSR mode.

Hope that makes sense...let me know. I would be careful with your current setup--it's possible that the VL-1 could be damaged eventually if the UMR is continuousy used to send over-voltage pulses into the microprocessor...
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  #7  
Old 03-22-2009, 04:48 PM
greysound greysound is offline
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Default VL-1 Power Issues etc.

Ok, I took a break from this for a bit, but I'm back at it again.

Since I've had so much trouble with pinched wires, I really hate opening this thing up again and messing with the power routing, but your explanation makes perfect sense.

I was making the dumb assumption that the Highly Liquid board would run at the same voltage as the incoming power, not the voltage that the keys receive. Doh!

But...

Couldn't I just add a resistor or two to the incoming power supply branch to the HL board and drop the value to 3.3 volts? This would be far easier and less problematic than looking for another internal 3.3 source.

What do you think?
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  #8  
Old 03-24-2009, 06:52 PM
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Quote:
Originally Posted by greysound View Post
Couldn't I just add a resistor or two to the incoming power supply branch to the HL board and drop the value to 3.3 volts? This would be far easier and less problematic than looking for another internal 3.3 source.

What do you think?
It's possible that this would work. You might have to experiment to get it right.

However, it's not really the "theoretically correct" solution, since the UMR board's current draw fluctuates during operation, and thus will cause the supply voltage to the UMR to fluctuate as well.

You could also add a 3.3V voltage regulator and operate the UMR from that.
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