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Yamaha's LP1 has to be attached to a wooden stand that I don't have and don't intend to buy. I would like to make a triple pedal unit that can just sit on the floor. Does anyone know what is the internal wiring of the LP1 unit. In particular I would like to know the following.

1) Is the right pedal connected to a potentiometer? If yes what is the resistance when pressed and depressed? If not is it based on 2 switches to support half pedaling?
2) Are middle and left pedals just switches or also use potentiometers?
3) How LP1 plug is actually wired - circuit diagram would be great.

Any chance I could get somewhere an service manual for yamaha LP1 pedal unit?

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Are you going to try to modify a 3p 3-pedal unit? If so you're likely going to have to deal with more than just wiring (as you already know).

The right damper pedal is certainly connected to a pot, in order to support half-pedaling and partial pedaling through variable reaistance. What the voltage ranges are, and whether the pot is linear, and what the polarity is, are probably things you will have to seek out.

The middle and left should be on-off switches and not driven by pots.

I would say this kind of endeavor is only "worth it" for most people if it's something you really enjoy DIYing. Chances are the requirements are different enough between the DP and the pedals to require direct electrical modification to whatever unit you find, plus the cost of a 3-pedal unit with half-pedal support in the first place, to not make financial sense.


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Have a look at

https://www.thomann.de/it/fatar_vfp...I8Z1F6c7_rF2KH3s_Uz-9XAuBMBoC7PkQAvD_BwE

Fatal/ studiologic 3 pedal unit compatible with Yamaha wiring. Bought this for my Yamaha cp88 and works beautifully. Saves you a lot of money also.

You need to be careful and get the 315 model not the 310

Also it has one mono and one stero jack, so depending on your use you might need a stero splitter

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Ah, interesting that they have a version with Yamaha wiring! A couple of caveats:

1. If this is the same Fatar unit the Kawai outsourced for the MP11/VPC-1's F-30 triple pedal unit, know that it doesn't have the best reputation for reliability (the pot on the right sustain pedal is known to fail).

2. I'm not sure how the TRS/TS jack is wired, but a lot of Yamahas such as the P-515 only have a single TRS jack for the sustain pedal (along with the DIN 3-pedal jack). How you would wire up the left and center pedals are a bit of a mystery (you'd probably end up having to deputize that 3-pedal jack anyways)?

3. At 60EUR + shipping + wait time from Europe + modification, is it really worth it versus just getting the $90 LP-1?

There's also a 3rd party unit on Amazon that already has the Yamaha connector (https://www.amazon.com/DAOK-3-pedal-digital-keyboard-Electric/dp/B07ZKY2TH4) but they have some dire warnings about it not working with even Yamaha DPs that are not of the specific models listed. But again, it's only $20 cheaper than the official Yamaha unit, is it really worth the savings?

Another option is to find a used LP5A that presumably uses the same DIN jack, and has been the triple pedal stand add-on for the Yamaha P-series for decades. It has just a good of a chance of working with whatever Yamaha DP you have now, and you don't have to mess with the electronics or wiring at all. Just find a way to prop it up on the floor.


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You could also order a FC3A pedal (relatively inexpensive) - and open it up to take a look around. That one will be pretty much the right-most pedal.

I assume that the left-most and middle pedal of the LP1 are switches only.

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Is buying this LP1 and modifying it an option? Long ago I saw a modification on a IIRC Roland KDP-70 triple pedal unit. Basically, the person cut the sides of the wood close to the pedals and added some black covers and a wood base. The final result had a good look and the person had a triple pedal unit at a reasonable cost. It seems something similar can be done on the LP1.


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Also .... which instrument you want to connect to? I think the 3 pedal unit goes to a paricular socket on the instrument, while the single pedal goes to a different one.

Unfortunately ..... can't see any circuit diagrams plus connector configurations anywhere online yet.

Having a LP1 at least allows it to be opened up to trace the wire paths between connector pins and each pedal component. And can even check out what sort of potentiometer it has in there.

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Originally Posted by SouthPark
Also .... which instrument you want to connect to? I think the 3 pedal unit goes to a paricular socket on the instrument, while the single pedal goes to a different one.

Typo ---- 'particular' - was typing on mobile/cell phone before.

Also consider this ------- LINK

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This following information appears to shed some more light ----- but not the full light. LINK

Their connector diagram appears to be looking directly at the holes of the female/socket side. It's just an assumption. This is the reason behind which ----- there needs to be a requirement for all pin-out diagrams (regardless of sockets or plugs or transistor legs etc) to be absolutely clear about the view-point. This really needs to be done for all specs sheets - connectors, transistors etc.

Will be interesting to see if both pin 1 and pin 2 are used. Or if only pin 1 is used (and pin 2 unused).

Also - apparently - which is pretty good ------ that sort of din connector appears to the exactly the same sort as a PS2 connector. Nice.

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I did consider buying the LP1 triple pedal to modify it (mount it on a base), but I quite like DIY projects and have experience with both electronics CAD and 3d printing. It would help me tremendously if an owner of LP1 could use an ohmmeter and measure the following resistances between pins of the pedal plug of (disconnected) LP1. Pin numbers I will refer to are shown on this page:

Link

1) resistance between pins 6 and 5. Is it zero? If yes then:
2) resistance between pin 6 or 5 and all other pins one by one with no pedals pressed and with pedals pressed down one by one.

I would hope to get results that might look something like this (just an example, real results would most likely be different).

6-4 initial resistance infinity and goes to zero when left pedal pressed. Other pedals - no change.
6-2 initial resistance infinity and goes to zero when middle pedal pressed. Other pedals - no change.
6-1 initial resistance 10 kOhm and goes gradually to zero as right pedal is pressed. Other pedals - no change.
6-3 Infinity and does not change when pedals pressed.

Any chance that someone could actually measure this?

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Originally Posted by witor
I did consider buying the LP1 triple pedal to modify it (mount it on a base), but I quite like DIY projects and have experience with both electronics CAD and 3d printing. It would help me tremendously if an owner of LP1 could use an ohmmeter and measure the following resistances between pins of the pedal plug of (disconnected) LP1. Pin numbers I will refer to are shown on this page:

I have an LP1 bolted to one of my P-515 instruments - using the counterpart stand for the P-515 from yamaha. I won't be removing it to open it up to take measurements. For my other P-515 --- it is currently just using the FC3A pedal only, with solid double-x stand. I have just ordered an LP1 just a moment ago - as I'm interested to open one up to see what's in there. If you don't get any more details about the LP1 from anybody, then no problem --- I'll do some measurements for you when it gets here. Taking a look inside also will give me an idea about whether (if we actually wanted to) somebody could whip up a 3 pedal unit based on say a couple of FC4A pedals and one FC3A pedal.

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You don't have to open it. I would never expect that someone will open it to make measurements.

I was just thinking about making measurements between the pins of the plug when pedals are not plugged in. If you have an Ohmmeter (or multi-meter set to resistance) please measure resistance between pins of the plug as I described in my previous post. It should not be too difficult when you get a new unit before you mount it.

If you are actually going to open it anyway (out of curiosity) please take some pictures of what is inside smile I am only interested in LP1 pedals as this is what I need for my DGX670.

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witor ----- the PS2 type din plug is ultra tight fitting ----- super tight fitting. So tight that disconnecting the plug from the instrument will be a bit of a challenge. The tight fit is probably a nice thing actually. When the LP1 gets here, I'll take take some really good pics to share, and also give a proper/accurate account of the pin-outs - as in conveying clearly the observer's viewpoint, plus the resistance measurements between those pins you mentioned. Thanks for mentioning the instrument --- DGX-670.

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It would be much easier to get the real LP1 and build a sturdy floor stand for it.
The pedal unit has 2 mounting holes on top of it; a simple but sturdy plate with attached U-, or L- arm(s) would work.

Last edited by VladK; 05/17/22 07:43 PM.

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Originally Posted by VladK
It would be much easier to get the real LP1 and build a sturdy floor stand for it.
The pedal unit has 2 mounting holes on top of it; a simple but sturdy plate with attached U-, or L- arm(s) would work.

That is certainly one way to go - as in getting some relatively heavy block/mass, that the pedal can be connected to. The long arms of the LP1 could even possibly be removed, or shortened ---- with the LP1 simply bolted to the heavy-enough mass.

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At the moment, I'm thinking that a couple of FC4A and one FC3A pedal (with double-sided tape underneath - even if it is say painter's tape) -- all connected to the PS2 type connector ----- could get the job done quite nicely too. And - if necessary - some machine grinding could be done to make each pedal unit 'narrower' - to get the pedals a little closer together.

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Originally Posted by SouthPark
Originally Posted by VladK
It would be much easier to get the real LP1 and build a sturdy floor stand for it.
The pedal unit has 2 mounting holes on top of it; a simple but sturdy plate with attached U-, or L- arm(s) would work.

That is certainly one way to go - as in getting some relatively heavy block/mass, that the pedal can be connected to. The long arms of the LP1 could even possibly be removed, or shortened ---- with the LP1 simply bolted to the heavy-enough mass.

Actually, these arms are not attached when shipped, you have to bolt them to.


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Originally Posted by VladK
Actually, these arms are not attached when shipped, you have to bolt them to.

Thanks vlad. I didn't even remember bolting them on haha. This was around June or so last year. Your idea of using the LP1 is actually a good one. A heavy-enough block or rectangular container - with the LP1 fastened to it - such as bolting on, or welding on ----- I can't remember what material it is for the chassis. Will have to check. And then fill up the container with sand or heavy rocks etc (and put a secure lid on it). So when we press down on the pedals, the structure won't move if it is heavy enough.

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Not Yamaha, but works:

[Linked Image]

That is also originally a triple pedal "lyre" for the Kawai ES6.

There needs to be enough surface area of the bottom plate in front of the pedal box, so that it doesn't tilt when a pedal is pressed.

One potential problem is the pedal touching the bottom plate when it's pressed down. That's why the bottom plate is so small.

Whether it stays in place or not depends on the floor. And of course in my case it was against the wall, so it wasn't an issue.

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Originally Posted by clothearednincompo
Whether it stays in place or not depends on the floor. And of course in my case it was against the wall, so it wasn't an issue.

A suitable sort of double-sided tape should work. I'd most likely use a mild painter's tape, just to avoid damage to the floor.

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Some rubber/silicone pads also help.

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SouthPark, any updates? Have you received the LP1?

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Not yet arrived witor. But I decided to shimmy/jimmy the plug loose from the connector of the P-515, and will be able to give you some measurement results today. And once the incoming LP1 arrives, will open it up and show pics etc of what's in there. Will have measurement details in the next post.

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Originally Posted by VladK
Originally Posted by SouthPark
Originally Posted by VladK
It would be much easier to get the real LP1 and build a sturdy floor stand for it.
The pedal unit has 2 mounting holes on top of it; a simple but sturdy plate with attached U-, or L- arm(s) would work.

That is certainly one way to go - as in getting some relatively heavy block/mass, that the pedal can be connected to. The long arms of the LP1 could even possibly be removed, or shortened ---- with the LP1 simply bolted to the heavy-enough mass.

Actually, these arms are not attached when shipped, you have to bolt them to.

Also, forgot to mention - the bottom surface of LP-1 has 2 adjustable rubber feets screwed in. If these are removed you will get a pedal with flat bottom which can be probably bolted directly to a top of a base plate. In which case there is no need for L-plates. Obviously I do not know how rigid these threads are. The safest approach would be to utilize all 4 threads IMO.

Last edited by VladK; 05/21/22 08:16 PM.

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Originally Posted by witor
I did consider buying the LP1 triple pedal to modify it (mount it on a base), but I quite like DIY projects and have experience with both electronics CAD and 3d printing. It would help me tremendously if an owner of LP1 could use an ohmmeter and measure the following resistances between pins of the pedal plug of (disconnected) LP1. Pin numbers I will refer to are shown on this page:

Link

1) resistance between pins 6 and 5. Is it zero? If yes then:
2) resistance between pin 6 or 5 and all other pins one by one with no pedals pressed and with pedals pressed down one by one.

I would hope to get results that might look something like this (just an example, real results would most likely be different).

6-4 initial resistance infinity and goes to zero when left pedal pressed. Other pedals - no change.
6-2 initial resistance infinity and goes to zero when middle pedal pressed. Other pedals - no change.
6-1 initial resistance 10 kOhm and goes gradually to zero as right pedal is pressed. Other pedals - no change.
6-3 Infinity and does not change when pedals pressed.

Any chance that someone could actually measure this?

Slight delay with the measurements, as I currently can't see the pinout diagram due to wikidots being hacked - as can be seen when we click on that weblink above. Looks like wikidot is still sorting things out.

I'm ready to do the measurements though. Here's a pic with some test connections. The measurements would be way too fiddly and unreliable using regular multimeter probes. Just making use of breadboard type jumper connectors and alligator clips, which works nicely.

Once the wikidot site comes back up, I'll definitely continue on with the measurements.

[Linked Image]

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Great job!

As far as I know LP-1 plug is simply a standard PS/2 plug. The pin numbering can be seen here

LP/2

I believe pins 5 and 6 are both grounds (internally connected). You could test this by measuring resistance between pins 5 and 6. if it is zero then both pins are connected and you could then do the following:

Connect the ohmmeter between pins 6 and 4 and then produce a table something like this:

6-4
LP off - infinity
LP on - infinity
MP off - infinity
MP on - zero
RP off - infinity
RP on - infinity

then repeat for 6-3, 6-2, 6-1. This four tables would clearly show what is going on. For one pair reading instead of going from infinity to zero will probably gradually change giving one line in the table something like this

6-2
...
...
RP off - 2.5 kOhm
RP on - gradually decreasing from 2.5 kOhm to zero as pedal is pressed.
...
...


The above results are just guesses, but I hope you will get something similar.

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Awesome. Thanks for that information witor. Looks like the wikidot site isn't back up yet --- so I'll use that information that you provided from the wikipedia site. What I'll do is ----- I'll take their diagram of the female connector (at the wikipedia site) - looking directly at the holes, and I will just switch the numbers (eg. swap 5 and 6; 4 and 3; 1 and 2) --- so that my new diagram will represent a male connector looking directly at the metal pins. Thanks witor.

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Nice news witor. The module arrived this afternoon. Will be doing the measurements first according to the configurations you provided. And then slowly open up the new module ----- slowly heheh - in case the springs do something nasty. They're probably not super charged ---- but - just in case!

[Linked Image]

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Can this mounting silver pieces of metal sticking up be somehow removed/unscrewed?

Would it be possible to unscrew the 2 legs on the bottom and use holes/threads to mount it to some sort of flat base that would sit on the floor? Would the base of the pedal unit be strong and stiff enough?

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Originally Posted by witor
Can this mounting silver pieces of metal sticking up be somehow removed/unscrewed?

Would it be possible to unscrew the 2 legs on the bottom and use holes/threads to mount it to some sort of flat base that would sit on the floor? Would the base of the pedal unit be strong and stiff enough?

Witor. The short arms poking from the module out can indeed be completely removed - very easily and conveniently. Once we remove the screws to remove the plastic material cover of the LP-1 ----- black coloured plastic cover in this case for the LP-1B (or white coloured plastic cover for the LP-1W), you can easily get a screw-driver to undo 2 screws for each arm. These screws are easily accessible.

The two rubber 'stoppers' - that protrude from the bottom of the LP-1, at first glance appear to be quickly removable. And they probably are easy to remove ---- possibly just stuck to the wooden blocks seen in the image (maybe double-sided sticky stuff).

If both the stoppers and the wooden blocks need to be removed, then it looks like it should be relatively straight forward to do that, by first undoing 2 screws each for removing the left pedal and the right pedal, which then gives access to the wooden blocks. Each of the small wooden blocks are removed with undoing two screws (for each block). Those screws can only be accessed by screwdriver when the left-pedal and right-pedal are removed. It doesn't appear to be difficult to do ----- so no problem. The wood blocks are 'external' - as can be seen in the image.

[Linked Image]

[Linked Image]

[Linked Image]

[Linked Image]

I started doing measurements last night before opening up the LP-1. The pin number assignment is based on the numbering in the image above, looking directly at the pins of the male connector, as we would see when looking directly at the pins of the connector of the LP-1.

I have a bunch of resistance measurements between pins (such as pin 1 to pin 2 --- shorthand "1-2"). So I did 1-2, 1-3, 1-4, 1-5, 1-6, 1-shield for the case where no pedals are depressed. Then 2-1, 2-2, 2-3, 2-4, 2-5, 2-6, 2-shield with no pedals depressed. Then 3-1, 3-2, 3-3, 3-4, etc ------- we get the drift heheheh. For sure, some of the measurements overlap (are common) - handy for double-checking maybe.

And then I did the same sets for the case where right-pedal fully depressed. And the same sets with middle-pedal fully depressed, and a set with left-pedal fully depressed. I can certainly put the measured values in a spreadsheet, and send out the spreadsheet and/or a pdf of the measurement sets.

It looks like not much meaningful results so far with the measurements. Pin 5 and 6 are found to be not internally shorted .... completely isolated from each other for all pedal conditions. Pin 1 and 2 has 3.9 kilo-ohm across them (ie. one probe on pin 1 and other probe on pin 2, results in 3.9k reading).

None of the pins are connected to the metal shield of the connector. Always 'infinite' resistance measured for each pin to the shield.

I didn't encounter any case (between any pair of pins) that had a spectacular change in resistance ---- such as flipping from 'infinite' resistance to zero resistance, or vice versa. There were even no cases encountered for occurrences of regular resistance (eg. 3k) flipping to zero resistance across any pair of pins.

So - it was necessary to open up the LP-1, to see what we can find. We will see a single long circuit board in there, which accommodates what appears to be three potentiometers. Or at least, I just assume all of them are potentometers - all three. They look identical.

The board has three lots of triplets of pins ---- with actual white-coloured print circuit board labels -- VD1, VD2 and VD3 ----- associated with the right pedal, middle pedal, and left pedal, in that exact order. Each triplet of pins, as can be seen in the image, are arranged in a row.

From preliminary resistance measurements, we will find that the pin (in each and every one of these three triplets) that is closest to the 'blue coloured grease' has zero resistance to pin 5. For convenience, I just label all triplet pins closest to the blue coloured grease as being 'a', which are all electrically shorted together.

Similarly, the middle pin from each and every triplet (which we can arbitrarily labeled as 'b' for all the middle pins) ---- has 2 kilo-ohm resistance to pin 5.

And, for all triplets, the pin (arbitrarily call them 'c') furthest from the blue coloured grease has 3 kilo-ohm resistance to pin 5 (not 2k .... but 3k). I found that all of the 'c' pins are shorted together.

I arbitrarily chose another reference pin to check out ---- such as pin 1. Each 'a' pin to pin 1 gives a 3k reading. And each 'b' pin to pin 1 gives a 3.7k reading. And all 'c' pins to pin 1 gives '0' resistance reading.

A resistance measurement between pin 'a' and pin 'c' is 3 kilo-ohm. Gradually making progress with seeing what's going in the LP-1. I'll do some more scouting to find out more, and will also double-check everything to make sure the info I've given so far is accurate. I reckon it's accurate --- but will double-check. And will later just write about what's most relevant or of interest to us.

Also - regarding the plastic cover. I believe it is definitely possible to do some drilling - and add extra small bolts that goes through the cover, and even can drill the metal internal frame ------ in order to attach that module to anything substantial (in terms of weight - some heavy block of own choosing) --- heavy enough so that nothing moves or slides when pushing the pedals with the feet. I think that this unit can be disassembled fairly easily - and some DIY can be done to mount this unit to something. Shouldn't be a problem.

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Just adding a note. With the image that has some of my added red-coloured text 'blurred'. That's not my fault. I think that is due to the pianoworld image uploading system, which does some more 'processing' on our images. For example, my 1600x1200 image gets uploaded, but the pianoworld upload software appears to cut it down to 800x600 ---- and not only that, it also compresses the image, leading to the lower quality, and blurred text ------ that is, the pianoworld software compressed it down to a 60 kilobyte image. The original images don't have blurred red-coloured text at all.

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Originally Posted by SouthPark
I didn't encounter any case (between any pair of pins) that had a spectacular change in resistance ---- such as flipping from 'infinite' resistance to zero resistance, or vice versa. There were even no cases encountered for occurrences of regular resistance (eg. 3k) flipping to zero resistance across any pair of pins.

Just for clarification. I meant for the case when a pedal was depressed and/or released. No spectacular change in resistance was seen, such as finite resistance to zero (or the reverse), or even relatively large resistance to zero (or the reverse).

I did notice that the depressing of the right hand pedal, and other pedals resulted in change of resistance such as from 3kohm to 2kohm etc. That is - some changes in resistance, which could be considered 'significant' change.

The situation will become clear (or clearer) with some more scouting/probing. Will keep looking into it tonight.

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Wow excellent job!

From what you have dome so far if would seem that VD1, VD2 and VD3 probably stand for 'voltage divider'

3k Resistance between pins 1 and 5, all 'a' being shortened together and all 'c' being shortened together would suggest that there are three 9k potentiometers connected in parallel between pins 1 and 5. Sliders of each potentiometer are probably connected to pins 2,3,4,6 (one of the pins is not used at all)

Could you check what happens with resistance 5-3, 5-2, 5-4 and 5-6 as you press the pedals?

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witor ------ sure can. That makes sense what you wrote - about VD being voltage divider. Nice catch!

Sure can witor. I'll get those measurements into a document, and will upload it. Those 5-3, 5-2 etc measurements were done too.

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Witor ...... just adding the measurements. I can update if I spot anything out of place. Also, just mentioning again that all of the 'c' pins of the VD1, VD2 and VD3 triplets (the pins furthest from the grease) are connected to pin 1.

And all of the 'a' pins of the VD1, VD2 and VD3 triplets (the pins closest to the grease) - are connected to pin 5.

Also ---
Pin 'b' of VD1 (pot associated with right-pedal) is connected to pin 2.
Pin 'b' of VD2 (pot associated with middle-pedal) is connected to pin 3.
Pin 'b' of VD3 (pot associated with left-pedal) is connected to pin 4.

Each pin 'b' is the suspected wiper point of a pot. It looks like the three pots are configured in a parallel circuit arrangement. At least we know that the left pedal and middle pedal aren't just switches. Interesting!

The values in the table have units of kilo-ohm. And the 'inf' just means relatively large resistance. And 'sh' just means the metal shield, which isn't connected to any of the pins at all.

[Linked Image]

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Let's go with this circuit for the moment.

Three 9 kilo-ohm potentiometers in parallel arrangement. The tap (wiper) points for the left pedal, middle pedal, and right pedal (in this order) are associated with pin 4, pin 3 and pin 2 (in that same order).

At the moment, just assuming that - when a pedal (eg. the middle pedal) is not depressed, then the resistance 'x' between the tap (wiper) point and pin 5 in that particular potentiometer branch ----- is approximately 2.8 kilo-ohm. That's the middle pedal tap point (pin 3) to pin 5 resistance associated with that potentiometer only.

And when the middle pedal is fully depressed, then that resistance 'x' can become approximately 5.7 kilo-ohm.

The resistance 'x' won't be directly measurable, because these potentiometers are all connected up. These estimated resistances are based on (for example) what was measured for resistance between pins 5-3 for the various pedal cases. That is, assumed 2.2 kilo-ohm measured between pin 3 and 5 for middle pedal not depressed. And we get 3.3 kilo-ohm for the pin 3-5 resistance with middle pedal fully depressed. Those values can be used to calculate resistance 'x' for the two cases, which led to the 2.8 kilo-ohm and 5.7 kilo-ohm values.

[Linked Image]

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Also ... just mentioning that the potentiometers in the circuit diagram look like coils. The regular zigzag resistor could have been drawn instead.

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Thank you very much for all the effort you have put into making all that measurements. Your circuit is exactly what I had in mind. I am just a bit puzzled by the small change in resistance 1-2 when right pedal is used. it is not the same change as with other pedals and their corresponding resistances. Is there some sort of option in the keyboard to calibrate the pedals?

If you still have the pedals open there is only one last thing you could measure that would give full picture of how this pedals work, but it is a bit risky and please do not attempt it if you are not sure if you can do it without accidentally shortening something. You could measure voltages across pots when pedals are connected to the instrument. Firstly voltage between 'a' and 'c' (pins 1 and 5) to check how much voltage comes from the instruments and which pin is the ground. Then voltages between ground and middle of each pot (pins 2.3.4) as pedals are moved through the full range of motion. Again, if you decide to do it please be very careful as touching 2 pins of the pot with the same probe of the voltmeter (shortening them) could potentially damage your instrument.

By the way, is there a chance to see any markings on those pots? Would be nice to know which pots Yamaha decided to use and maybe even use the same ones in a diy project.

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Most welcome witor.

I'll be happy to connect it up to the instrument. Based on the 2.8 and 5.7 kilo-ohm predicted values for the branch resistance from wiper to pin 5 (for no pedal depressed and full depressing), the voltage from the 'b' point to pin 5 for these two cases (based on the 9 kilo-ohm total potentiometer resistance) will be 31 percent and 63 percent of the DC voltage applied across pin 1 and pin 5.

What I can do is - when plugged into the instrument - I can check to see what voltage measurements I get for the actual case. And also can determine the polarity .... ie. whether the higher voltage side is pin 1 (relative to pin 5), or whether it is pin 5 (relative to pin 1).

I'll be careful. Don't worry. I'll fill you in with the rest of those details soon.

I'll check out 1-2 for you as well.

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Also ----- just quickly adding. For actual measurements when probes were placed across 1-4, getting 3.7 kilo-ohm with no pedal pressed ...... I was expecting to actually measure something lower, such as 3.2 kilo-ohm for the pair of probes placed across pin 1 and pin 4. I got to look into that too.

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witor -- I don't think the P-515 has a pedal calibration function feature.

But I managed to do the voltage measurements, and was able to find out that Pin 1 (connected to all the 'c' pins) gets +3.2 volt DC on it. Pin 5 will be the 0V reference. So pin 1 is the higher voltage pin, 3.2 volt higher than pin 5.

For the right-hand pedal (ie. sustain/damper pedal), the node 'b' voltage (ie. pin 2 for the right-pedal) for no pedal depressed is 0.85 volt. So that's around 27% of the full DC voltage.

And with the right-hand pedal fully depressed, I measure 1.8V for node 'b' voltage (ie. pin 2 is 1.8 volt higher than pin 5 when the right-hand pedal is depressed). That's around 56% of the full DC voltage. Although - in order to make the pedal 'depressed' - I have to insert plastic tabs after trying to hold down the pedal with one hand ...... so slotting a bunch of plastic tabs into the gap to keep the pedal down. It's possible that the pedal could have gone down a bit more --- could even reach 2 volt. But this gives is a good idea about what the voltage levels are for no-pedal and full-pdeal (or near-full pedal). And also the applied DC voltage and polarity.

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FWIW, 3.2V makes sense, 3.30V is a common voltage for logic circuits and they took that to supply the pedal pots.
About the pedal going only down to 1.8V when fully depressed, it makes sense to, the mechanism probably turns the pot just halfway its entire range.


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Originally Posted by EVC2017
FWIW, 3.2V makes sense, 3.30V is a common voltage for logic circuits and they took that to supply the pedal pots.
About the pedal going only down to 1.8V when fully depressed, it makes sense to, the mechanism probably turns the pot just halfway its entire range.

Nice post EVC. Thanks for adding that information as well! Definitely appreciated.

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Yes 3.3V is a common voltage in this type of applications. Are voltages on the sliders of middle pedal and left pedal the same as for the right pedal? Do they also go from 0.85 to 1.8

I asked about calibration because in practice it is difficult to build a set of pedals like this and get very precise and consistent voltage range for all pedals. That's why I was expecting some sort of calibration mechanism that would tell the keyboard which voltage corresponds to pedal being released and which to pedal being depressed.

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Originally Posted by witor
Yes 3.3V is a common voltage in this type of applications. Are voltages on the sliders of middle pedal and left pedal the same as for the right pedal? Do they also go from 0.85 to 1.8

I asked about calibration because in practice it is difficult to build a set of pedals like this and get very precise and consistent voltage range for all pedals. That's why I was expecting some sort of calibration mechanism that would tell the keyboard which voltage corresponds to pedal being released and which to pedal being depressed.

witor ..... I found this link .... where the P-515 doesn't have a cal feature, but instead has a way to alter the pedal's active zone ....... LINK

I checked the right-pedal during this afternoon. I will check the middle and left pedal as well. I just didn't get around to it ..... as this was done during lunch time. I live close to where I work. Stay tuned for the results on those other two pedals!

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Originally Posted by SouthPark
For the right-hand pedal (ie. sustain/damper pedal), the node 'b' voltage (ie. pin 2 for the right-pedal) for no pedal depressed is 0.85 volt. So that's around 27% of the full DC voltage.

And with the right-hand pedal fully depressed, I measure 1.8V for node 'b' voltage (ie. pin 2 is 1.8 volt higher than pin 5 when the right-hand pedal is depressed). That's around 56% of the full DC voltage. Although - in order to make the pedal 'depressed' - I have to insert plastic tabs after trying to hold down the pedal with one hand ...... so slotting a bunch of plastic tabs into the gap to keep the pedal down. It's possible that the pedal could have gone down a bit more --- could even reach 2 volt. But this gives is a good idea about what the voltage levels are for no-pedal and full-pdeal (or near-full pedal). And also the applied DC voltage and polarity.

Amendment to be made with the information above. The measurements for the above was actually for the left-hand pedal. All other references to left, middle and right pedal for all other information are correct.

These are voltage measurements with the probes placed across the wiper point for each pedal's associated potentiometer and pin 5.
[Linked Image]

Also, the resistance of 1-2 was re-measured - and triple-checked, and turned out to be 3.4 kilo-ohm, so just including the updated resistance measurements in kilo-ohm units.

[Linked Image]

Also showing some extras - such as needing to jam enough plastic strips into a gap, in order to keep the pedal 'down'. That was a bit fiddly with not much to grip onto ----- while also avoiding touching the grease on the plate at the back. This plastic strip jamming needed to be done for each of the three pedals.

[Linked Image]

And - a look at the potentiometer, which appears to have no writing or details on them. They're 9 kilo-ohm pots though ----- at least we know that.

[Linked Image]

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Once again big thank you for all your measurements. I have not yet decided if I will go ahead and build my own set or just buy one and mount it to something, but it is amazing that you have put all this effort just because some guy on the internet asked you to do so. I find this forum to be one of the best and it is because of people like you SouthPark.

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Originally Posted by witor
Once again big thank you for all your measurements. I have not yet decided if I will go ahead and build my own set or just buy one and mount it to something, but it is amazing that you have put all this effort just because some guy on the internet asked you to do so. I find this forum to be one of the best and it is because of people like you SouthPark.

You're most welcome witor. You helped me too - as we had the same interest with finding out what's in one of these. And I also thought that the existing details on the internet were a bit unclear ----- as in there was even uncertainty about whether the pin numbers on those existing diagrams were accurate or not. That is, they have some pin outs, but no clarity about whether they were looking at the holes of the female socket or looking directly from the front at the actual metal pins of the male connector. Whichever option you go for - it will be great. At least we know the voltage levels that the instrument needs for the pedal functions, and also found out that the left and middle pedals aren't just switches. I didn't expect that! And thanks for such excellent and most courteous posts from you witor. All the best!

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Just to add one more thing if anyone ever wants to replace faulty LP1 potentiometer. The LP1 potentiometers look very similar to xbox 360 controller trigger potentiometers.

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Nice one witor! I just did a search just a moment ago. It really does look like them. Excellent find. Thanks for mentioning that.

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