Questions concerning the schematics

[tanatos]

Hi Dmitri,
first of all i want to thank you and gratulate you for your excellent work. This is fabulous!
I´m not that good at electronic. Actually this is my thirst project. I hope you don´t mind if i have some questions:

If i use the avr-cdc do i still need the 6n138?

At the connection between the digital and the analogue board you use 15 pins on the one and 13 on the other hand. Is this because you just use 12 trigger? Do i have to use these 2 if i want to use more trigger? I want to use as much trigger as possible. How many can i use and do I need a third 4051 for this?

Which controller do i need for lcd? Is a HD44780 fine?

Thank you.

[dmitri]

Hi Dmitri,
first of all i want to thank you and gratulate you for your excellent work. This is fabulous!

Thanks!

I´m not that good at electronic. Actually this is my thirst project. I hope you don´t mind if i have some questions:

If i use the avr-cdc do i still need the 6n138?

If you're only going to use MIDI over USB than you don't need the 6n138. In fact, you will need neither J8 nor J9 DIN5 MIDI sockets.

At the connection between the digital and the analogue board you use 15 pins on the one and 13 on the other hand. Is this because you just use 12 trigger? Do i have to use these 2 if i want to use more trigger? I want to use as much trigger as possible. How many can i use and do I need a third 4051 for this?

Pins 13 and 14 on J5 connector are not used and reserved for possible future use. You don't need a third 4051. The number of inputs only depends on the type of Digital Board: with MegaDrum32 you'll have 22 and with MegaDrum8 - 20.

Which controller do i need for lcd? Is a HD44780 fine?

Thank you.

Yes, it's any HD44780 compatible 16x2 LCD

Regards

[tanatos]

Thank you for the fast answer. This helps a lot.

[Andrums]

Have you tried it with any commercial pads such as Roland PD-125, or Hart TE3.2 Snare? If so, I wonder how well it triggers compared to a Roland module.

BTW, I looked at the analog input board schematic, but I don't see any attenuation of the piezo signal prior to the 4051 analog mux. I see that you use diodes to clip the peaks of the waveform if they go beyond VCC. But, don't you have to attenuate the signal to make sure that you are not always clipping the peaks to valid velocity information? Maybe I am missing something?

[dmitri]

Have you tried it with any commercial pads such as Roland PD-125, or Hart TE3.2 Snare? If so, I wonder how well it triggers compared to a Roland module.

I've tested it with home made pads, cheap Alesis pads, dual Yamaha TP80S piezo-switch pads, pads and cymbals from this drum kit http://www.thomann.de/gb/millenium_mps100_edrum_starter_set.htm, and the pads from the same drum kit converted to mesh head pads. I will test MegaDrum with any pad/drum kit if someone wants to arrange it and compare it with Roland, Yamaha - you name it.

BTW, I looked at the analog input board schematic, but I don't see any attenuation of the piezo signal prior to the 4051 analog mux. I see that you use diodes to clip the peaks of the waveform if they go beyond VCC. But, don't you have to attenuate the signal to make sure that you are not always clipping the peaks to valid velocity information? Maybe I am missing something?

Most of pads don't produce signals higher than 5V (none of my pads do). In case one does it is better to place a preset potentiometer in the pad just as e.g. Yamaha does.

[baguette]

Hey guys this is all really great stuff! I LOVE IT!
I am about to buy a alesis dm5 but this makes me reconsider...

Concerning high input voltage levels did you consider... EDIT: forget about that, i misunderstood the OP...

Just another question, do you also provide atmega source code?

greets, chris

[baguette]

Concerning high input voltage levels did you consider... EDIT: forget about that, i misunderstood the OP...

I wrote something about Z-Diodes here, which leads me to a suggestion:
Don't you think you could replace the two diodes at the analog inputs by a single Z-diode?

if the level goes beyond gnd -> pull to gnd (diode characteristic)
if the level goes above the diode breakthrough voltage -> pull to gnd (Z-diode characteristic)

chris

[dmitri]

By Z-diode you meant zener diode, didn't you? In short, no. You have to use schottky diodes for a speed reason.