Best way to convert stepped HH pedal to continuous?

[LooseSends]

I have two HH pedals. One is a brand new DMHat Alesis pedal, and the other is an ancient beast of a Roland FD-7 pedal.

Oddly, the old brick Roland pedal works like a dream once set up for all the HH levels that Addictive Drums can handle, while the brand new Alesis pedal only outputs 3 levels, which I obviously can never go back to at this point. The new Alesis pedal, ironically, was a warranty replacement for the original one I had that stopped working altogether for some reason once I received the ED10.

This puts me in a dilemma. I'd just continue to use the Roland but I do have to return it to the person who lent it to me originally, although they may have lost interest entirely. Still, I don't like having other people's stuff if possible. Plus the Alesis pedal has a slimmer footprint and doesn't get in the way of the left rack post as a bonus.

So, my plan is to convert the old broken (electronically, not physically) pedal to a simple continuous type like the Roland. I have no idea why Alesis calls their pedal continuous/variable when it only outputs a few discreet levels but I'm sure it's not difficult to just convert it to something useful.

I have some basic electronics knowledge and the tools to do it so soldering together a couple resistors and caps shouldn't be too much to ask.

The point of my post is to ask if there's a specific build someone can point to, to save me some research and failure time. Things to watch out for; specific resistors/caps/hall sensor for the best dynamic range, and perhaps some tips for setting it up physically.

Any advice would be appreciated.

[LooseSends]

Ok, I'll try again...

So I picked up some A1302 hall sensors and soldered one to a 1/4" TRS jack according to the design specified in the manual.

Unfortunately I can't get it to work whatsoever. It simply doesn't react to any amount of magnets I can put in it's vicinity. I've tried twice with a second hall sensor and a different input jack.

I must be missing something. I've triple-checked the wiring layout. Am I missing a capacitor or something?

Any help at all would be greatly appreciated at this point.

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[Rob]

The 1302A datasheet indicates that it needs 4.5 - 6V. As the pedal inputs only provide 3.3V, it's not a good choice. You could probably power it eternally, but you would want to make the voltage never goes above 3.3V.

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[LooseSends]

Thanks Rob. Turns out though that I had to change the input to Expression Pedal for it to get the voltage from the ED, and I start to see some life.

It's not the greatest range, but surprisingly about as much as I was getting from the old Roland pedal.

In fact, it looks like I can get away with only 1 tiny little 2mm rare-earth disc magnet stuck on the end of a hex bolt on my junked Alesis pedal. It approaches to stop at the sensor, pedal fully depressed, within a hair's breadth.

The flux is tiny but pretty accurate so I think I can get away with a slightly larger magnet to widen it enough to allow a bit more travel through the flux before stopping at it's strongest point. I found adding additional magnets adjacent to the primary one tends to make the field non-uniform, resulting in fluxuations in strength throughout the min/max depression so it seems better to go for a bigger magnet.

Would you recommend adding a capacitor near the sensor to help with background noise? Thought I read that here somewhere. I happen to have a salvaged ceramic cap (labelled "120" so I don't know what the uf is) lying around if you think it would help and you could tell me which pin it should be on.

I'll probably just buy your recommended one anyway and redo it as I'm sure it provides a better range and works better for 3.3v

[LooseSends]

Just to follow up...

I'm getting a decent, workable range out of just powering from the ED and it's running splendidly without capacitors or outside power which is ideal.

I settled on a 5 mil round magnet with a couple stacked 2 mil in the center, set in place with some hot glue.

Of course you want that magnet to come in very close to the hall sensor on full depression (or vice versa depending on your preferred setup). Ideally you can set up the magnets on a screw that you can turn in slight increments to adjust.

Great little DIY project and thanks for all the help!

[Ronyd]

Using an fsr better approach? Realizing you need the right foam under the pedal to actuate the fsr. Had good luch using fsr.

But interesting with hall effect. Are you positioning the magnets perpendicular to the 1301?

[LooseSends]

Using an fsr better approach? Realizing you need the right foam under the pedal to actuate the fsr. Had good luch using fsr.

But interesting with hall effect. Are you positioning the magnets perpendicular to the 1301?

Sorry for the late response. The magnets are on the travelling pedal perpendicular to the hall sensor so that they are only about a millimeter apart when relaxed, and move away from the sensor when depressed.

You have to be careful that the rest position doesn't go past the sensor so that you don't get a sudden dropoff when at rest. It can be tricky getting the right balance of magnet strength, distance from sensor, and travel sorted out but if you have a variety of rare-earth button magnet sizes available it's not too much work to find the right combo and just lock it all in with a glue gun.

I can post some closer pics of my setup if necessary but I think you get the idea.