Midi Switcher - Using Arduino

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Midi Switcher - Using Arduino

Postby the_ungod » 07 May 2019, 17:48

Hi guys,

After searching around for already build modules, for a looper / switcher i came across this project:

https://www.jimkim.de/guitar-projects/a ... di-switch/

I was thinks in connecting that to this:

https://www.aliexpress.com/item/4-chann ... st=ae803_4

My only concern is about noise... what are your thoughts about it?

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Re: Midi Switcher - Using Arduino

Postby plush » 07 May 2019, 21:11

SPDT relay for a loop switcher is no bueno.
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Re: Midi Switcher - Using Arduino

Postby the_ungod » 08 May 2019, 00:03

plush wrote:SPDT relay for a loop switcher is no bueno.


Already heard that...already working on an alternative...
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Re: Midi Switcher - Using Arduino

Postby the_ungod » 08 May 2019, 00:05

So far...

Schematic_V1.png


Please comment...
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Re: Midi Switcher - Using Arduino

Postby roseblood11 » 08 May 2019, 01:55

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Re: Midi Switcher - Using Arduino

Postby kusi » 08 May 2019, 07:09

the_ungod wrote:So far...

Schematic_V1.png


Please comment...



what optocoupler do you use? R2 seems way to high, i use 470R - 1k for a 6N138. for R3 i use 10k
R6 R7 also too high, probably copy/paste

add 100nF to the psu-pins of the inverter, and tie the unused inputs of the inverter gate to GND.

can't comment on the arduino circuit.
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Re: Midi Switcher - Using Arduino

Postby the_ungod » 08 May 2019, 12:15

roseblood11 wrote:https://www.uk-electronic.de/onlineshop/index.php?cPath=105_348&language=en
https://musikding.rocks/wbb/index.php/T ... /?pageNo=1


Thanks...i already know those (expensive) options....lol

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Re: Midi Switcher - Using Arduino

Postby the_ungod » 08 May 2019, 12:21

kusi wrote:
the_ungod wrote:So far...

Schematic_V1.png


Please comment...



what optocoupler do you use? R2 seems way to high, i use 470R - 1k for a 6N138. for R3 i use 10k
R6 R7 also too high, probably copy/paste

add 100nF to the psu-pins of the inverter, and tie the unused inputs of the inverter gate to GND.

can't comment on the arduino circuit.


what optocoupler do you use? - 6N138
R2 seems way to high, i use 470R - 1k for a 6N138. - my error, already fixed
for R3 i use 10k - In the original schematic (jimkin) its a 1k, i've done some research and found (https://cdn.instructables.com/FHN/J43V/ ... .LARGE.jpg) another schematics who use 10k... i've changed that to 10k

add 100nF to the psu-pins of the inverter, and tie the unused inputs of the inverter gate to GND. - can you explain a bit of this?

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Re: Midi Switcher - Using Arduino

Postby plush » 08 May 2019, 12:34

the_ungod wrote:add 100nF to the psu-pins of the inverter, and tie the unused inputs of the inverter gate to GND. - can you explain a bit of this?


Cap between vcc and gnd, placed near the chip, provides low impedance power path and also filters some interference and ripple. In some cases it is mandatory. In others - just a good design practice.

Connecting unused inputs/outputs of opamps, inverters and other ICs to ground (or to vcc, vee, vbias) is a common technique, helps to prevent self oscillations, unstable behavior and other stuff. It is specified in the datasheed for the particular part.
Read your datasheets. (p.10. and p.11.1)

Image

:horsey:

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Re: Midi Switcher - Using Arduino

Postby the_ungod » 08 May 2019, 14:26

Updated (including the commented changes
Arduino Board.png


And now the PSU
PSU.png
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Re: Midi Switcher - Using Arduino

Postby Fender3D » 08 May 2019, 14:35

If you connect both input AND output to GND you will likely kill that poor 74LS14.....

Just connect input to GND and leave output floating unconnected

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Re: Midi Switcher - Using Arduino

Postby the_ungod » 08 May 2019, 15:14

Thanks for the comments...

New update

Arduino Board
Arduino Board.png


PSU
PSU.png


Relay Board
Relay Board.png
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Re: Midi Switcher - Using Arduino

Postby Fender3D » 08 May 2019, 16:38

Nice...
What's IC2? Check it can supply the current load, I would use a transistor buffer, just in case
Again, it's common practice to use a flyback diode in parallel with the relais coil to eliminate the sudden voltage spike
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Re: Midi Switcher - Using Arduino

Postby the_ungod » 08 May 2019, 16:55

Fender3D wrote:Nice...
What's IC2? Check it can supply the current load, I would use a transistor buffer, just in case
Again, it's common practice to use a flyback diode in parallel with the relais coil to eliminate the sudden voltage spike


Hi,

The IC2 is a unl2803 - it allows 500ma in each output acording to the datasheet
Flyback diode - forgot about that, gonna update
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Re: Midi Switcher - Using Arduino

Postby the_ungod » 08 May 2019, 18:44

One of the features i would like to implement its a On/Off/Auto switch for each effect
I draw this sketch... what do you think?

On Auto Switch.png


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Re: Midi Switcher - Using Arduino

Postby Fender3D » 08 May 2019, 23:20

well.... that's an On\Auto switch.
I used an On\Off\On toggle switch when I put my pedals in a rack enclosure 30 years ago to achieve the On\Off\Auto modes. I did it the very next day I forgot the switches unit at home and I had to hardwire some relays to play....
But that was just to use the unit manually just in case I would forget the switch unit again, if you wanna use a footswitch so you can switch on and off your loops, you'd better use some momentary switches connected to Arduino's inputs and write a proper code.
PS
I wouldn't bother about LEDs
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Re: Midi Switcher - Using Arduino

Postby the_ungod » 08 May 2019, 23:50

Fender3D wrote:well.... that's an On\Auto switch.
I used an On\Off\On toggle switch when I put my pedals in a rack enclosure 30 years ago to achieve the On\Off\Auto modes. I did it the very next day I forgot the switches unit at home and I had to hardwire some relays to play....
But that was just to use the unit manually just in case I would forget the switch unit again, if you wanna use a footswitch so you can switch on and off your loops, you'd better use some momentary switches connected to Arduino's inputs and write a proper code.
PS
I wouldn't bother about LEDs


Hi Fender3D
Thanks for your comments

The whole idea is to make a 2U rack with all the pedals and switching system inside.

The value of the on/off/auto is the following:
On - practice pedal combinations without having to program a patch
Off - eliminate a pedal (faulty one or whatever) on the fly, without programming
Auto - to normaly use the switching system

The LED are there just for warning. Imagine i program a patch with a clean sound and test it adding a "on" fuzz... then i forget to put the toggle switch on the auto position...just in case
Or by mistake i put a pedal in off mode...
This way i have a instant visual sight of the pedals on off or auto mode.

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Re: Midi Switcher - Using Arduino

Postby kusi » 09 May 2019, 06:56

the_ungod wrote:
Fender3D wrote:Nice...
What's IC2? Check it can supply the current load, I would use a transistor buffer, just in case
Again, it's common practice to use a flyback diode in parallel with the relais coil to eliminate the sudden voltage spike


Hi,

The IC2 is a unl2803 - it allows 500ma in each output acording to the datasheet
Flyback diode - forgot about that, gonna update



no need for a flyback diode on the ULN2803, it's already included in the chip, connect pin10 to +5V and you are done (like you already did in the first schematic)
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Re: Midi Switcher - Using Arduino

Postby Ripthorn » 09 May 2019, 09:25

I posted a project in the ready to build section complete with schematics, layout, code, etc. Uses an arduino nano and controls 5 loops.
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Re: Midi Switcher - Using Arduino

Postby the_ungod » 09 May 2019, 10:14

kusi wrote:
the_ungod wrote:
Fender3D wrote:Nice...
What's IC2? Check it can supply the current load, I would use a transistor buffer, just in case
Again, it's common practice to use a flyback diode in parallel with the relais coil to eliminate the sudden voltage spike


Hi,

The IC2 is a unl2803 - it allows 500ma in each output acording to the datasheet
Flyback diode - forgot about that, gonna update



no need for a flyback diode on the ULN2803, it's already included in the chip, connect pin10 to +5V and you are done (like you already did in the first schematic)


Yes, in the auto mode its ok, but in the "manual mode" the IC2 is bypassed and the relay is connected to ground.
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