Which Hall sensor for Hit hat?

[Ken Forgettable]

This topic shows my stuff is not compatible with Megadrum - remember that you need 5v to each pad.

Maybe worth a try though

[JLantz]

Damn, Ken, that is pushing the envelope!

WAY too much for myself at this point, but thanks for the mind expansion.

[rockdude]

YES! It's alive! I finally got this working....I trashed my old computers hard-drive and took a magnet from it. Snapped it in half just as described in this thread and woila..suddenly my MegaDrum liked it! I just have to put it somewhere on my hihat and try the response, but it seems very responsive on my initial tests on the table. I've now tried a variable slider potentiometer design, a optical hihat design and a Hall sensor design for my hihat. I'm not sure, but I have a feeling that this Hall effect sensor design will be my favorite. It's so simple to build and put on the hihat.

I've found a good place on ebay to buy Hall effect sensors too:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=320493004759&_rdc=1
Only 8 euros shipping included for 5 Hall effect sensors!

If I would buy 5 of the same Hall effect sensors in Sweden (where I live) it would cost me approximately 26 euro.
Now I can order it from France for 8 euros and I'll have it in my mailbox within a couple of days. It's a funny world we live in.

[Ken Forgettable]

I have a feeling that this Hall effect sensor design will be my favorite. It's so simple to build and put on the hihat.

You need to know that magnetic fields grow weaker with the square of the distance. To get a linear response you'll need to bias the sensor with another magnet in some manner.

[mackanov]

Or you could apply a curve on the output. Or use a logarithmic sensor, perhaps?

[rockdude]

But it would be enough to just put another magnet below the hall sensor like in the picture below?

[Ken Forgettable]

But it would be enough to just put another magnet below the hall sensor

Linearity is fundamental to modeling the real thing and using broken bits from hard drives is not a good idea.

Fixing a weaker bias magnet to the back will give you the full range output of 0-5v but it will still be non-linear. It is most sensitive as the stronger (stronger) magnet comes towards the sensor. You need to have two magnets separated by a fixed distance moving at either side of the HES to get a near linear response (or move the sensor).

I get 20 - 25mm accurately using these EP301B from <http://e-magnetsuk.com/magnet_products/neodymium_magnets/ring_magnets.aspx>, but be warned - the inside diameter is a bit odd.

[rockdude]

But it would be enough to just put another magnet below the hall sensor

Linearity is fundamental to modeling the real thing and using broken bits from hard drives is not a good idea.

Fixing a weaker bias magnet to the back will give you the full range output of 0-5v but it will still be non-linear. It is most sensitive as the stronger (stronger) magnet comes towards the sensor. You need to have two magnets separated by a fixed distance moving at either side of the HES to get a near linear response (or move the sensor).

I get 20 - 25mm accurately using these EP301B from <http://e-magnetsuk.com/magnet_products/neodymium_magnets/ring_magnets.aspx>, but be warned - the inside diameter is a bit odd.

How will this non-linear output show when playing? Some say it works flawless with harddrive magnets. Are they less picky then you? How will I notice that it's non-linear?

[Ken Forgettable]

Are they less picky then you?

Yes, I'd say so.

How will this non-linear output show when playing?

It will most likely bunch the sensitivity up at the hard hits.

Some say it works flawless with harddrive magnets?

You can't predict a magnetic field or the lines of force in a shattered magnet - and if it works you're on your own.

The permeability of the mounting will affect things too so try to use non magnetic materials like plastic or fibreglass. Stainless steel, brass and copper will induce eddy currents too but should be fine in our application.

Having a steel hi-hat rod through the centre of a ring magnet will move the concentration of the magnetic field towards the rod a wee bit.

[rockdude]

Thanks for the info. I'll have to play my new setup and see if I notice anything before I try to change anything I can be pretty picky at times too, but I hope my snapped hdd magnets will offer a holy field of harmony and linear output. I have a few ringmagnets at hand that I can try placing them behind my hall effect sensor, but I guess that's all I could do to improve range and not linear output at the moment if I understand you correctly.