HELP I got an old Accordion with Midi interface

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
The LED display alone will draw way more than 20 milliamps.

You've got everything you need to know how to wire it up now.

Gary ;)
 
Joined
Jun 11, 2019
Messages
43
Reaction score
0
i think i just gonna plug the midi to usb cable, then in parallel add a 3.7v lithium battery inside, just to see if i get enough current to get the display on.
 

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
That will probably blow up the lithium battery.

VERY BAD IDEA@!@!@!

NEVER PLUG VOLTAGE SOURCES IN PARALLEL!!!!!!!!

DO NOT DO IT!!!!!!
 

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
DO A HALF ASSED JOB AND YOU WILL DESTROY YOUR EQUIPMENT.

THERE ARE NO SHORTCUTS TO HARDWARE HACKING!!!!!!!!
 
Joined
Jun 11, 2019
Messages
43
Reaction score
0
1476


Hey wouldnt i be better off using the cable instead of waiting for parts to mod?

Couldnt i just cut the red wire on the usb side?
And get power from a better source at the usb side?
Or must this happen at the midiport side?
 

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
NEVER CONNECT BATTERIES IN PARALLEL.

SLIGHT DIFFERENCES IN VOLTAGE AND IMPEDANCE WILL CAUSE ONE TO FEED BACK AND DRAIN INTO THE OTHER CAUSING AN EXPLOSIVE CHEMICAL REACTION.

NEVER! NEVER! NEVER!!!!!!!!!

Gary ;)
 

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
You have to disonnect the VCC+ 5 VDC from the MIDI side of the interface. If you cut power to the interface bad things will happen.

Gary ;)
 
Joined
Jun 11, 2019
Messages
43
Reaction score
0
Whaat. Thats not what i learned. I have tons of devices with batteries in parallel hehe.
And even some flashlights, and the headlight i got right now on my head got two liion batteries in parallel. Sometimes they drain a bit uneven. Never had any explosions though.
 
Joined
Jun 11, 2019
Messages
43
Reaction score
0
You have to disonnect the VCC+ 5 VDC from the MIDI side of the interface. If you cut power to the interface bad things will happen.

Gary ;)
Ouch.. i just wanted this fired up today.
Maybe i just do it the first way you suggested, instead of modding the cable, i mod inside the instrument and just drill a hole for the power cable. Gotta take a closer look at the drawings.
Did i need a specific type of resistance? Any regular resistance of noted ohm will work? If so i might smash something useless and loot it.
 

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
Ouch.. i just wanted this fired up today.
Maybe i just do it the first way you suggested, instead of modding the cable, i mod inside the instrument and just drill a hole for the power cable. Gotta take a closer look at the drawings.
Did i need a specific type of resistance? Any regular resistance of noted ohm will work? If so i might smash something useless and loot it.

I'm not 100% certain the resistance is needed but it is MIDI spec and should be required to protect the circuitry.

Any 220 Ohm resistor will do as long as it's rated 1/2 watt or better. I wouldn't risk anything smaller or again, magic smoke may be released. :eek:

Electric-Power-Magic-Smoke-720x400.jpg


Gary ;)
 

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
Actually I just realized the resistor is not necessary and may actually be detrimental.

It would have to dissipate I^2 * R wattage which is a ridiculous amount of power.

Leave the resistor out.

Gary ;)
 
Joined
Jun 11, 2019
Messages
43
Reaction score
0
Alright. Then im pretty certain i could get this done soon without ordering any parts.

But i want to do it like this:

Inside the accordion behind the midi input,
I cut the yellow wire (5) so that the usb doesnt power it anymore.
I then use that yellow wire which now is cut off the midi port put a resistor as you noted, at the end of it.
Then i use a dc adapter rated to 5v to the yellow wire.
The ground from the adapter straight into the ground of the accordion.

Or would that cause grounding issues?

I was thinking of just buying an adjustable dc adapter tomorrow and a input port.
And get the port fitted to the instrument, and wired as i said above.

This would go like a hand in glove? :D
 
Joined
Jun 11, 2019
Messages
43
Reaction score
0
Actually I just realized the resistor is not necessary and may actually be detrimental.

It would have to dissipate I^2 * R wattage which is a ridiculous amount of power.

Leave the resistor out.

Gary ;)
Good news. But i preffer to be safe if needed.
Aaaaaaa i feel so close now to get this working!
If it doesnt work after this, i rip all the electronics out and play the instrument with its original italian reed plates from the 60's haha
 

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
Here's how I'd do it.

1) Clip the yellow wire and extend it to a 3.5 mm phone jack. Run a wire from ground to the sleeve of the jack.

2) drill the case and install the jack.

3) Plug in a 5 V REGULATED DC Adapter with a standard 3.5 mm plug output.

4) If noise is a problem be prepared to replace the adapter's cable with a shielded wire instead of a stranded pair.

5) Either that or else add a noise rejecting filter circuit to the internals of the jack. Easier to shield the cable though.

Gary ;)
 

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
Remember. Digital logic requires REGULATED power. I'd say 5V DC at 1 Amp should be more than enough.

Don't use a cheap variable supply that isn't regulated.

Gary ;)
 
Joined
Jun 11, 2019
Messages
43
Reaction score
0
Ok thanks. Now i need to rip apart a headset.
So if the power and ground comes from an external supply like this, does that mean i could cut pin2 too? The shield?
Is ONLY pin5 needed to provide all data needed to the computer?

Im just asking to know the actual usb cable will still be able to function after i added an external source of power.

If i gonna test this with batteries first just to be sure, my options would be:

3x aa 1.5v =4.5v
Or
4x aa 1.5v =6v

I guess 6v would be a bit unsafe.
 
Joined
Jun 11, 2019
Messages
43
Reaction score
0
Remember. Digital logic requires REGULATED power. I'd say 5V DC at 1 Amp should be more than enough.

Don't use a cheap variable supply that isn't regulated.

Gary ;)
Thats why i wanna test with batteries first cause i got nothing like that lying around at the moment.
What in the world uses 5v that i could use xD haha.

Well my computer got a 5v and a 12v from its power supply. Hmmmm
 

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
DATA signal WILL NOT WORK without a reference ground.

The ONLY wire you cut is the yellow one and piggy back the power supply ground onto the signal ground.

Nothing else would work.

Gary ;)
 

happyrat1

Destroyer of Eardrums!!!
Joined
May 30, 2012
Messages
13,746
Reaction score
5,531
Location
GTA, Canada
Any USB charging unit or Wall Wart can deliver +5V DC at 1 or 2 amps depending on the model. They are switching supplies and pretty well regulated.

The only thing you need is a USB A to coaxial plug and you'd have a well shielded, regulated, power supply.

You'd also require a suitable coaxial jack for the accordion.

They do sell those cables from suppliers in China but I'm not sure where you'd buy one locally.

Don't even try to hack a regular USB cable though. Those things use like 3 strands of 80 guage wire per cable. Impossible to solder reliably.

Gary ;)
 

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments. After that, you can post your question and our members will help you out.

Ask a Question

Members online

Forum statistics

Threads
13,995
Messages
86,232
Members
13,100
Latest member
Su_uh Innocent Nelson

Latest Threads

Top