Idea with old Hammond

[PermO]

Today was boxing day, here's the box;

I'm trying to keep it as small and "lightweight" as possible, the assembly will sit on neoprene strips inside the box and it just fits. I ordered some black Tolex to finish it nicely.

I've decided to not order the mechanical relays and just go for the solid state ones as I don't see why these would not work in this situation and they seem to have so much advantages.

Put a bypass pot on the clickfilter so I can open it up... have not played it yet.

 

[PermO]

So now it's in the box, this was my first Tolex job, I did not like it lol, I hate wallpaper, glue, paint, cloth, stickers and spraycans... anything not solid.
But it's ok, did not have enough glue to finish the lid, so I need to get some more. If you ever go Tolex, make sure you have lots and lots of glue.

I managed to save the little "H" Hammond logo from the organ and put it on the box.

Made a little test setup on a protoboard to see if all my triggers arrive in the right order and they did.
Solid state relays came in also.
So I'll finish the lid and do a little test with one of the solid state relays.

 

[PermO]

Quick update...

Those solid state relays work just fine !
It's really that simple, apply 5V over a current limmiting resistor (330Ohm) to pin 1 and it will conduct from pin 4 to 6 (in the case of AC source)

No clicks, and superfast !

Now with this in mind.. I see the possibility to bring back the whole organ again.
Simply apply a relay to every tonewheel output, sum the apropriate harmonics (9 lines) into the drawbar section.
With a Arduino you can now set what relays should open for what note being played, you can also reacreate the slight time delay and not hit all harmonics at once just like the real thing.

This is for the future, bass first,.... but I really like the idea of doing this.

I can pick this up and put it in the back of my car without help... try that with a Hammond organ lol.

 

[dmp]

Are you keeping the drawbars, or?
I don't know how the drawbars work so maybe that's why I don't get it.

 

[PermO]

Yes, I have still got all the parts exept from the broken keybeds, the woodwork and all the chuncks of steel.

I cleaned up the drawbar fadersection and they run smoothly now with nice clicks for every step.
The drawbars are like a "summing mixer" for all the harmonics, you can see it in the schematic on the previous page, the output goes to the matching transformer that is connecting to the first tube stage.

So in order the make this into a full MIDI tonewheel organ it will need to have the drawbar section back in it's original position.
So a desktopbox with a drawbar section, the matching transformer and a little tube pre amp... yeah that would be nice.
Build a compact Leslie with a class D power amp and you've got a real travel Hammond, just add MIDI.

 

[dmp]

I read the service manual a bit and now it makes more sense. You put relays on each tone wheel (13 for the bass and 74 for the manual on the L-100)
In the arduino, you take a midi note and turn on the correct 9 relays to feed the 9 busbars, which go to the "summing mixer"
In the arduino you need to reproduce the "manual wiring chart (1-7)" for which 9 notes to turn on for each key/pedal depressed (upper manual).
You could also put two relays on each tone wheel to have a upper and lower set of busbars. The lower has 7 notes to the busbars. So to have the full capability you'ld need 13 (bass) + 74 (upper) + 74 (lower) = 161 relays
And the arduino needs to be able to work with multiple midi notes, so it is pretty complex logic. Have you looked into whether this can be programmed into the aurdino?

 

[PermO]

You just put it better in words than me !

That's exactly how this could / should work...

Edit, no I have not looked into the Arduino programming yet... so far it's just an idea, but I will have a chat with a friend of mine who is very good at programming these things, see what he says.

I know there is this matrix addition board that has 100 outputs.

 

[dmp]

With multiplexing you have n^2 controls. With 14 digital outputs on the Arduino you can then control 196 relays.

My M3 has almost the same control matrix (wiring chart) except has 9 drawbars in both the upper and lower.

This might be my reason to learn about Arduino programming.

 

[Disco Volante]

Mindblowing. I am enjoying this thread ever more...

 

[dmp]

actually... need a relay on each note for each of the 9 busbars I think

Simply apply a relay to every tonewheel output, sum the apropriate harmonics (9 lines) into the drawbar section.

This would be limited to one note, monophonic, I think. Each busbar needs a seperate switch (or relay) on each note. The bass only has one busbar though so it works for that.

So for the upper+lower on the M3: 719 for the L100: 654 (since it has 2 less drawbars on the lower)
The wiring chart shows for each note which tone wheels should be turned on for each busbar. The number of relays is the number of boxes.
Would be good to have a better routing solution. Maybe FET as switches?

Since the switching logic is simple (index each busbar freq# +1 for each higher note) should be able to make this controllable with less controls from the Arduino than the number of relays / switches

 

[PermO]

Ok, so with the lid it's really nice, I like it a lot...

And then...

This happens every time...

You think you got it figured all out, but nope... it's not working.
It was working fine on the bench with a little 5V wallwart psu but now it is hooked u to the Arduino the voltage drops below 2V... yes, lowered the current limmiting 330R resistor to 150R, 56R.. no R at all... nothing.
Thought the 80mA from the Arduino would be plenty to drive these, they are also advertised to be able to be driven from the Arduino outputs directly...

Aaaaaarg @#$%$##!!!


This can be solved with the addition of 13 transistors at the Arduino side and a bit of power... but this was not supposed to happen

 

[PermO]

actually... need a relay on each note for each of the 9 busbars I think


This would be limited to one note, monophonic, I think. Each busbar needs a seperate switch (or relay) on each note. The bass only has one busbar though so it works for that.

So for the upper+lower on the M3: 719 for the L100: 654 (since it has 2 less drawbars on the lower)
The wiring chart shows for each note which tone wheels should be turned on for each busbar. The number of relays is the number of boxes.
Would be good to have a better routing solution. Maybe FET as switches?

Since the switching logic is simple (index each busbar freq# +1 for each higher note) should be able to make this controllable with less controls from the Arduino than the number of relays / switches

Sorry I can't follow you...

I don't see why my solution would be monophonic, just strike a chord and the Arduino will know what notes you hit and which relays to open, the only sound sources are the tonewheels so only these would need to be switched on or of.
When I had the LED's on the Arduino outputs first I had a scale running from C1 to C2 to check my order, then I decided to draw 13 lines for 13 notes in Nuendo and it will light up all 13 LED's ... I don't see a problem there.

The interesting thing in the programming is the "shared harmonics thing" as not for every note and it's harmonics there is a separate tonewheel in the unit... that's also largely "the sound" of a Hammond.
When you have a piano and hit a chord and two of these notes have a shared harmonic they will add up and become the dominant harmonic.
In case of the Hammond organ, same chord, but now this harmonic will not be dominant as there is only one tonewheel in the set... so a Hammond never "peaks" whatever you play it always sounds "even"

 

[PermO]

Grumble...

So I removed the header from the Arduino and used the small 5V psu that is driving the MIDI optocoupler as a power source directly on the pins. (330R resistor at the SSR)
Now the SSR does open up... but I noticed this, level was very low, I used to get a lot hotter level from the generator, so these SSR's DO affect your signal, it sounds ok, but I don't want a 25dB level drop.

The bass notes have the highest level on the generator, about 225mV, the other harmonics produce a lot less output, running these trough SSR's will probably not end up well.

I think I will order the mechanical miniature signal relays and see where that goes, they will probably need more power so I will have to add transistors at the Arduino side anyway.

I was so hoping I could record a nice groove this weekend...

 

[dmp]

What is the part number of your SSR? I'd like to check the datasheet to see why it isn't working.

Sorry I can't follow you...

Haha, maybe I don't understand how the hammonds work. Maybe the 'monophonic' description was wrong. For the bass, I agree with you you can put one relay on each of the 13 tonewheels to connect them to the bass busbar. Opening more than one at once will have them mixed at the busbar.

But I was thinking about the upper and lower registers with multiple busbars. The 9 busbars need separate relays to the tonewheels I think. Otherwise all the busbars would share the same bus and have the same signal.

I'm thinking about the upper& lower because I would like to put my M3 into a box like yours and have it fully playable with MIDI.

How much does yours in the box weigh?

 

[PermO]

I myself am also not sure about all the inner workings of the Hammond organ, but I've learned a lot from disassembling one, now I also understand, once disassembled these things never get back into one piece again (all wiring is black and uncoded)

I'll see if I can make a signal flow drawing on a piece of paper the way that I have this playing in my head.

This is the SSR that I got from Farnell;
https://4donline.ihs.com/images/Vip...7-1.pdf?hkey=6D3A4C79FDBF58556ACFDE234799DDF0
I always have a lot of problems understanding datasheets... I'm not a electronics guy.

As ar as weight goes, I don't think my kitchen scale can handle this box, but if I had to estimate I'd say it's roughly about 50 pounds / 25 kilo.
I think my box only adds 5 to 6 pounds to the total weight, the generator is rather heavy itself.
I did not bluild a heavy case like a flightcase, I only used 9mm MDF board for the box, it's not a touring enclosure, it's just a box to keep the dust out and make it look nice. It can be transported safely this way, but it's not truck & trailer roady proof.

 

[dmp]

The SSR is turned on with a IRED on pins 1 and 2, which is just an infared LED. This needs much less current than a mechanical relay
It needs a current limiting resistor and the voltage needs to be pos p1, ground p2
The absolute maximum current to the LED is 50mA, so with 5v the smallest series R should be 100 ohm. That gives you some safety factor too because the IRED has a forward voltage drop (~1.36v)
Lower resistance (more current) would blow out the IRED (Maybe you fried the SSR?)
The 'typical' turn on current is 0.4 mA so a ~10k resistor could be used with 5v
The datasheet also specs 5mA which would be about 700 ohms.



On the load (p4 to p6) the 'ON' resistance should be low, for DC ~3.6 ohm
The DC load current can be up to 370 mA

 

[PermO]

Hmmm, that's sort of what I figured, so yes this should work just fine.

I think the SSR's are fine, there must be something else goin on, I noticed in my previous test with the LED's that they did not light really bright... at some point I got a LED and just held it against pin 1 on my cable and screen (ground) and it lit up dimly.... that's wrong, it should flash and be dead... there should be 5V 80mA at that pin.

The level drop could be caused by something else... for what I see in the datasheet the 3.6 Ohms added to a high impedance coil should not result in a 25dB level drop.


More troubleshooting required, it ain't over till the fat lady plays the bass...

 

[Disco Volante]

It sounds like something is pulling down your PSU's, sucking them dry. As far I understand you've tried two different power sources, one small (no fun at all) and one bigger (low signal), right?
Would a big (huge) amount of 5V make fun or fire, I wonder? Maybe an ammeter in various places would give us a clue? I'm excited to hear the next episode!
Cheers, thank god it's friday;-)

 

[PermO]

Ok, I found something is "wrong" with my Arduino... these outputs should put out 5V @20mA (I thought it was 80mA but my friend told me that was wrong)

I stick a LED directly into the output header and it barely lights up with no resistor in place, so it does not put out the power it should.

This should go pop... (I'm playing a note on my keyboard to trigger the output)

The Arduino runs from it's own dedicated 9V regulated PSU.

Also found two notes don't trigger at all, so there's a fault on my relay board.
maybe that is causing the level drop also...

Adding transistors at the Arduino side could solve this, but it should not need that.


More coffee,... and a smoke...

 

[dmp]

They have a per pin limit and all pins together limit. Are you putting out current from any of the other digital outs?

Using a transitor to source current is probably the way to go