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Cheap 'n Cheerful

Share photos of your Hauptwerk consoles, installations, audio systems, ...

Re: Cheap 'n Cheerful

Postby engrssc » Wed Jun 26, 2013 8:47 am

Regarding the expression pedals, a piece of black, ribbed, stair tread glued to the top surface, with the side edges painted black, they would compete very nicely with the "best of them". 8)

Rgds,
Ed
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Re: Cheap 'n Cheerful

Postby NickNelson » Thu Jun 27, 2013 5:26 am

Hi John,

The optical sensing uses Kingbright KM-4457F3C infrared emitters and L-610MP4BT/BD detectors. I chose these because they are relatively cheap (about 30p per pair). I found it best to mount the pairs quite close together with enough space between them to get a slip of the interrupting material between the emitter and detector. For this material I just use thin matt black card.

A typical circuit is here:

Image

With a 6 volt supply, it is satisfactory to chain the IR LEDs in sets of four without any need for series resistors, two such sets are switched on simultaneously by the transistor. I use surface mount devices MMUN2211LT1G which include the two bias resistors in the package. When the sets of 8 LEDs are switched on by the positive pulse from the encoder, any of the detectors that aren't screened from the beam (ie the key has been pressed and the 'flag' of material lifted out of the gap) switch on.

The eight emitters A to H are commoned with the inputs to the encoder, with a further 7 arrays of the same kind, and a 1k resistor to ground on each line. In this way, the whole system behaves electrically just like an 8x8 common anode matrix. One thing to bear in mind is that the emitter/detector combinations don't switch on, and more particularly off, as fast as a signal diode so the scanning encoder has to allow (about 100uS) settling time before and after 'reading' the input lines. My encoders do this, but I can't speak for any others. Also, for a normal compass of 61/58 notes, there will one or two 'orphan' LEDS which will need a series resistor.

Here are some photos showing the key features and which also show the development from the first rather 'Heath Robinson' efforts to my current implementation.

Image
Image
Image
Image

The flags can be placed horizontally or vertically at the tails of the keys as in the second picture, or above the keys just behind the thumper bar.

Interestingly, the detectors specified actually contain two sensors (there are two emitters from each hence the three legs on the detectors) which ought in principle to allow for velocity sensing. I've only made some brief investigation of this so far, but it would overcome one disadvantage of this optical approach which is that there is very little hysteresis compared to reed relays for example. This means that it is just possible to find a point where the note will repeatedly trigger due to small movements of the flag. This is quite difficult to do, and never occurs in normal playing, but is a consideration. Exposing the array to bright direct sunlight produces some interesting (and noisy) effects too.

Nick
Last edited by NickNelson on Wed Feb 13, 2019 7:10 am, edited 1 time in total.
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Re: Cheap 'n Cheerful

Postby fer_araneda » Wed Jan 14, 2015 7:30 pm

Hi NICK!! Your set up is VERY NICE, just as I want mine to get. would you share how to midify a pedalboard (for dummies please) ;-)

Thanks a lot.
Fernando Araneda
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Re: Cheap 'n Cheerful

Postby NickNelson » Thu Jan 15, 2015 3:40 am

Hi Fernando,

This topic viewtopic.php?f=15&t=5298 has a lot of information about possible options for pedalboards.

I don't know if your DIY skills extend to electronics yet, but you might find this account of my encoders useful: viewtopic.php?f=15&t=12849&p=94757. I could probably be persuaded to send you a pre-programmed microcontroller and PCB, but you would have to assemble it yourself.

This includes some information the usual diode matrix arrangement for a 32 note pedalboard: viewtopic.php?f=15&t=10977&p=83978

The problem with writing a step-by-step guide on how to midify a pedalboard is that there is some variation in the construction of pedalboards, in the skills and confidence of the person doing the work, and the desired balance between cost and time. So while I could describe in detail how I did mine (though it was quite a few years ago) it might not work for yours. On the other hand, providing a very general description might not be sufficient to help someone who has never done it before to be successful. I will have to think about it some more.

With my best wishes,

Nick
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Re: Cheap 'n Cheerful

Postby fer_araneda » Thu Jan 15, 2015 12:40 pm

NickNelson wrote:The problem with writing a step-by-step guide on how to midify a pedalboard is that there is some variation in the construction of pedalboards, in the skills and confidence of the person doing the work, and the desired balance between cost and time. So while I could describe in detail how I did mine (though it was quite a few years ago) it might not work for yours. On the other hand, providing a very general description might not be sufficient to help someone who has never done it before to be successful. I will have to think about it some more.

With my best wishes,

Nick

Thank you very much for your words Nick. I'm learning about this topic going for every bit of information I find. I'm sure I'll be able to get it done soon.
Fernando Araneda
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