What and where did you get the midi relay board? I've been interested in something like that for awhile and couldn't really find anything.
That's a great question and the answer is I made it myself. Here's a little bit on how I developed it.
In the picture you see 3 versions: V1.0 in the top left, V2.0 in the middle and V2.2 in the top right.
V1.0:
This was the original idea. It has an Arduino Pro Mini 5v in the center and the pins are simply connected to standard relay, LED and momentary switch circuits. There is a bridge rectifier and regulator circuit at the very bottom to power the board from the heater line and the MIDI input at the top. I bought it using OshPark's after dark service which gives a black substrate with clear soldermask. Very cool but pretty expensive and takes a full 3 weeks to arrive.
V2.0:
This came about after I realized there was definitely not enough space for the board to be mounted card style (the original was based on recording console boards). I moved to a parallel control board and perpendicular switching daughter board, as well as an on-board chip rather than a soldered in Arduino. This board was just fine until I realized how annoying it would be to have your amp reset its settings every time you turn it on so I wired in an Adafruit SPI FRAM chip to the bootloader programming header. The board on the bottom was soldered into the amp for a week.
V2.1:
I did this layout when I ordered the Adafruit breakout just in case. It was never put into production; the only change was the addition of the chip and its supporting parts.
V2.2:
This is the board you see in the amp. You see that adorable little electrolytic at the bottom of V2.0? It's only 15uF and every time the board finished its setup code the capacitor output would dip below the regulator's dropout voltage and the processor would brown out, resetting itself. Therefore I put in the "Heater" board near the power input with a 4700uF capacitor and a full-size regulator (this board also has a humdinger for the heater supply on the other 6.3v line). This both saves on component count and keeps AC out of my preamp area.
I have a few more boards if you fancy having a go at the majority 0603 and small lead spacing packages I used. These things are prohibitively expensive and very difficult to make; really more of a thought exercise than anything. The parts to populate the board are 30 bucks plus shipping, and the FRAM chip has to come from Digikey since Mouser doesn't stock them. Above that, you have to be able to actually solder the things together. Without an oven, this takes me about 2 hours for the main board, and the switch board is so difficult to put together I pulled it off the first installed one rather than making a new one. Next, you need to solder another Arduino to the SPI header to bang in the bootloader. Finally, you have to develop code for it. This is pretty easy, and I can share mine, but I don't have any MIDI code in there yet so you would have to develop and debug that yourself.
If all that sounds fun to you then you have a few options:
1) I'll make you one for like 100 bucks and load the bootloader. I'm not kidding they're that hard to make. You'd still need a programmer and to add in the MIDI code I haven't done.
2) I'll mail you the boards and send you a parts list and you can make one yourself
3) Use the schematic I posted to develop your own. As you can see above, even if you really know what you're doing this can take months to get right.
4) Buy an Arduino Nano-this board has an FTDI chip on it so you don't need a programmer. Solder it to a bit of perfboard and use through-hole components to build something based on my schematic.
This is what I would do because it lets you customize the board to your needs without much risk of expensive failures. If you need an extra relay or more buttons or fewer LEDs or a different layout etc. you can do that without needing a new PCB order. It won't be nearly as small as my solution, but you'll learn something. Again I'm happy to share the code.
Topic: 2 channel based on a Top Hat/Matchless (Read 2981 times)