Lemon two piece hi-hat setup

[IrrationalJoe]

New user, love my Drumit5 module (it is a mark 1). The hi-hat setup is a massive pain with a Lemon 2-piece hi-hat controller so I figured I capture my findings here.

The good news is that I was able to hook up the hi-hat. There are two issues, one is that the Drumit5 (the older, mark 1) only has 1 TRS connector for hi-hat as opposed to the modern ones with 2. Also, the current sensing circuit in the module does not like very low currents.

The Lemon hi-hat has two connectors, one for the cymbal with the piezo and one for the pedal with a potentiometer.

For the connector, the tip of the piezo (cymbal) TRS has to be hooked up to the tip of the connector that goes to the module. The tip of the other, the pedal connector has a ~36 KOhm potentiometer on it (between tip and sleeve), this is in essence the pedal controller. This has to be hooked up to the ring of the connector that goes to the module.

The Drumit module outputs 4.1 V on the ring connector of the hi-hat TRS jack. Based on the schematics online, this goes through a diode, dropping the voltage somewhat and then goes to that Hall-effect sensor chip of the original hi-hat. So let's say we have 3.6 Volts on that ring connector. The module then tries to sense the current drawn on that connector. The issue is that 3.6 V / 36 KOhm = 0.1 milliamp. This is way too small for the module to detect so - at least in my case - it shows that there is no hi-hat connected when hooked up with the wiring above. It may detect the hi-hat when the pedal is fully pressed and the pedal controller resistance is down to ~100 Ohms.

The current has to go up for the module to detect it, which means the resistance has to go down. After some experimentation it turns out that with a 220 Ohm resistor in parallel with the controller, the module detects the hi-hat, calibration is a breeze and basically everything works.

(The net resistance in this case is between 220 || 36K = 218 Ohm and 220 || 100 = 68 Ohm. I don't think 68 Ohm is going to hurt the controller as 3.6 V on 68 Ohm is ~50 mA so like 2 LEDs.)

Here is the terrible drawing, hopefully people will be able to make out what it is. Basically connected the tip of the pedal one to the ring of the output (input to the module) and put a 220 Ohm resistor between this wire and the ground (sleeve)

https://ibb.co/P95h2XT

This is the type of Lemon hi-hat I am talking about:

https://ibb.co/dfXpNKj

Still to be figure out how to connect the ring of the cymbal side (the piezo side) to the output. This is the edge switch which is basically an open circuit and then if one grabs it, it goes down to ~50-100 Ohms.

[edcito]

I like turtles

[Deve Loper]

Hi Joe!
Basically good idea. However, putting a 220 ohm in parallel will make the range very non linear. With the 36k halfway, the total is still 217 Ohm. So not much happening there.
Sort of coming to 1/10 of the range, it is still 207.
When the pot is 1k, then you get 180, now its doing something, but at 1/36 of the pedal range.
Best, Deve.

[IrrationalJoe]

Dave, yes, you are right, basically half the range is gone with the 220 in parallel.

Even with the 1K the current (to be sensed) would be 19 mA (at 36K) vs 20 mA (at 18K) so I guess this is a bit of a price one has to pay for trying to fit a Lemon/Roland (square) peg into a Hall sensor-based (round) hole

Inverse-log taper could have helped - I just checked and as far as I can tell the pedal is linear taper.

The actual hi-hat works remarkably well btw, probably due to the fact that the travel of the pedal is not that much anyway.



 

[ANGR77]

Nice captured knowledge...

The implementation of the original 2box hh hall sensor tied together with the hh edge is a pain to solve and instead using a resistant based hihat. The 2box measures power on the pedal...not resistance.

It took me many hours to solve the case and more electronics than I ever thought.

But after have been selling many hundreds of the Roland to 2box conversion modules...it was maybe worth the investment. :-)

Note: These modules also works for the Lemon Hihat.

Keep up the good work!

Best regards

Anders / Zourman.com

[IrrationalJoe]

Anders, thank you!

Since then I ordered one of your converter boxes. Figured it's going to be nice to have an official product, rather than my soldered-in-the-connector 220 Ohm resistor 

[Harm]

I'm considering to buy that Lemon two-piece hi hat as well. Does it work on a DrumIt Three without convertor?