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Problem with Doepfer WE Wheel Electronic installation
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Problem with Doepfer WE Wheel Electronic installation
tioJim
Hello

I have an issue with a Doepfer WE Wheel Electronic installation (product details here)

Four wheels (also Doepfer, 10k lin pots) are connected as is a jack for a foot pedal. It’s set to the basic preset (pitch, mod, channel volume, channel pressure, sustain) and I’m using a regulated 9V 300mA supply.

Often the wheels will transmit continuously but if nudged they’ll stop. If one wheel is transmitting continuously sometimes the other wheels will transmit as well. The sustain pedal input behaves the same. The wheels seem correctly calibrated as I have the proper ranges of values (or close enough for pitch anyway, pitch -8064 to +8192 and the others spot on at 0 - 127).

There's a video here (3.4Mb, MP4, 76secs) showing the behaviour and output to a MIDI monitor

I have no open inputs and have followed this advice from the manual

“We recommed the usage of three-pin cable sets with suitable female connectors to establish the connections between WE and the analog controls. In this way the controls might be disconnected from the electronics very easily.”

There’s one obvious place to look first. The manual states

"Before WE is put into operation the board has to be fixed on a suitable support and built into a metal case together with the controls (refer to EMC notes on page 2). The metal case has to be connected to GND of WE. We recommend to use the metal plate of the voltage regulator 7805/IC3 or the GND terminal of the power supply socket for this connection."

The EMC note on page 2 reads

"On the WE preventing measures against electromagnetic radiation are taken (e.g. an RF filter at the power supply input). But it is impossible to estimate to what extend the components added by the user affect the EMC properties of the complete assembly. Therefore the complete device has to be shielded against electromagnetic radiation (incoming and outgoing). These demands are normally met by a closed metal case that covers the complete assembly. The metal case should be connected to GND of the WE."

I am using a plastic enclosure with a laser cut wooden front panel ...

Is this my problem and if so how do I fix it without changing my enclosure? The behaviour does seem similar to an open or floating input or grouding issue.

Thanks
Jim

Some build photos





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AndyHornBlower
Did you solve the problem? You could email hardware@doepfer.de (if I've remembered that right).

I was going to suggest copper foil screening your box - you can buy sheets big enough to go under the scratch plate of an electric guitar, or use the sticky backed copper tape, but you need to solder between the pieces, or it will go off, after a while. You need to ground it too, of course - a screen that isn't grounded to the power supply, or earthed, does very little.

However, from the MIDI monitor, that doesn't really look like a noise problem. I'd expect the values to jitter by +/- 1 or 2, but that seems much more serious.

Is your power supply stable? How are you powering it? I'd check for dry joints too - bad solder connections. They are easier to spot if you've used lead/tin based solder, but the lead free stuff always looks like dry joints.
AndyHornBlower
What did you have your reference voltage set to?

From your JP2 jumper settings - all open, in the picture, you were telling it to use the adjustable reference range, for all inputs.

The manual says it's possible to set that to a range that will cause problems (below 3V).

"Function of the trimming potentiometer P1

The trimming potentiometer P1 is used to adjust the reduced voltage range V+. Any voltage between 0V and +5V can be adjusted though only voltages in the range +3...+5V should be used. Reference voltages below +3V cause malfunction of the analog-to-digital converters though nothing can be damaged. The reduced voltage V+ becomes valid for an input if the corresponding jumper of JP2 is removed (see above table). "

FWIW, I bought one but haven't used it yet, beyond checking it works. One thing I noticed is it sends a lot of bad readings if not all inputs are connected to something - so I guess add jumpers to unused ones, though I see you were using them all.
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