Lllehaze, anybody interested in midification;
Great explanation on PSU design!
You bring up an interesting point regarding use of caps for reduction of spikes, especially with operating frequencies above 40mhZ
My midified organ console is built with midibox components from SMASHTV, some dating back to 2004. Back then, the small caps were not used on each chip as they are now on the recent kits. Recently I upgraded to an LPC-17 core merging it with an old 8bit core. the LPC-17 is used primarily for encoding 3 keyboard, and 64 SAMS contacts thru 2 attached KB cards. The 8bit core has 4 DIN and 4DOUT which handles pistons inputs, and SAMS coil drivers..
The system functions, but it is experiencing “cross talk”, for lack of a better word. SAMS are being actuated by pistons when not set . The gen cancel clears set SAMS, but also turns on SAMS that were off as well.
The system uses jOrgan and strangely, the behavior described occurs only when using the hardwired devices on the console. Actuating stops or pistons with a mouse on the display does not produce the same effect.
The power supplys are simple; The LPC through the USB connection to the PC, and the core 8 thru a wall wart module. The SAMS operate with a 12vdc - 30amp powersupply. The negative side of the 12VPSU is common with the negative side of the core8 PS by virtue of the card design, and the ULN2803 drivers mounted on the DOUTS.
Actually, there is a lot of 26ga wire floating around to act as transmitters and receivers, probably not good!
Question;
1. Would addition to small caps on the core8 DINS and DOUTs help?
2. Would going to a better common, better filtered, regulated power supply for the LPC and the Core8 Help?
3. Would putting some type of caps on the SAMS coils help dampen out high freq. spikes and switching noise?
Hopeing for some help, suggestions, etc.
johnc