Planning build with 56 input with positional sensing

[drjones]

Hey, I'm planning to make a 56 input module with positional sensing - got only one question right now and that's if the designs in this .zip
https://www.megadrum.info/forums/download/file.php?id=2361
are all I need to get started? Couldn't find anything specific regarding differences in 32/56 input & with/without positional sensing.

Cheers

[ignotus]

The only difference between the 32 and 56 versions is the number of multiplexers and related passive components. The thing with that design is that it uses an atmega chip, and if you want the latest firmware it has to have the encrypted bootloader which only Dmitri can load it with, meaning you'd have to send it to him. Otherwise you can use the last unecrypted firmware and load it yourself, but that's from about 2010.

Positional sensing is enabled with a separate circuit. In practice, you're only going to be able to use PS with the snare as that's all VSTs support (some support ride cymbals too but it won't work with Megadrum), so you can just make a small PS board for the snare, which is what I did.

[drjones]

Thanks for the quick answer, is the difference from 32/56 input simply the number of triggers that can connect or does it offer some functionality beyond that? Could be interested getting the 56 one if it's worth it - what's the benefit of the more recent bootloader, more functionality?

As for positional sensing, are there schematics on here that I can use - or can you give me a copy of whatever solution you went with? Having it only on the snare is fine as it's where most of the fine work is done.

Another thing I'm curious about is the ratings for the components - from the link here:
https://www.megadrum.info/content/buying-components
I can see some of the values for the component, farads, resistance and such.
The links for some of the components are not working, and the power rating - as well as info regarding the size of the components is missing (the size I can work out from the pcb).

Most importantly I'm wondering what the power rating the resistors need to have, and if any of the other components have properties or values which are important. I saw someone noting the material of the component influencing it's properties somehow.

Cheers

[ignotus]

Yes, the difference is simply the number of triggers. Note that with the Atmega644, later firmwares (after 2014) are limited to 48 inputs.

I'll attach the schematic for the rectifier. The recommended op-amps are MCP6L04T, MCP604 or MCP6004T instead of the one on the schematic. C3 and C4 can be omitted.

I think as long as you get components with the values listed you're fine - 1/4 W for resistors, which is the most common. I suppose the tolerance is probably more important; if you can get ones with 1% tolerance instead of 5% all the better. The voltage in the module is about 5v max so I reckon any power rating will do for capacitors, which will typically be far higher than that.

[drjones]

Thanks, I'll go for the 32 input one and should be able to get started ordering components for the build soon.

[ignotus]

Sent you a private message.