The ultimate pad challenge (circuit gurus please look)

[-Aj-]

OK big edit here: My original post was written rather quickly and rather poorly too I hope this one is better

I'd like to reproduce the capabilities found in the yamaha TP-100 pad (dual rim switch trigger, sensitivity adjustment and the controller knob) on a Mesh head pad

I have never seen the inner workings of a TP-100 before so I decided to take a look, I hope that this is informative for others too, I found it very interesting to see how yamaha do what they do..

For starters lets take a look at the unique parts of the pad that I'd like to replicate



Here is the Rim triggers exposed. They appear to be ribbon switch triggers, two pieces of thin metal that contact each other to complete the circuit. They are covered by a plastic/resin, it appears as if both the top and bottom metal pieces are embeded in this resin. I think this is how they stay seperated however I then have no idea how they could connect with each hit. I have always found that these pads trigger VERY well on the rims so I am keen to work out how they do this. Does anyone have much experience with Ribbon switch triggering? I believe some people use it here for cymbal chokes and I was hoping they could shed some light on how the yamah does it.



heres a close up of the rim trigger interface, you can see the bottom layer is lighter and the top layer is darker...Unlike piezo's switch triggers do not generate their own voltage so I'm assuming it comes down the ground (middle) wire? if you look at the 3 wires the left is for the main trigger, the middle appears to connect to the lower layer to provide voltage and the right is for the secondary trigger... this is my understanding anyway can anyone confirm this?



heres how the rim trigger connects to the board (connects to CN2 on the circuit board)


Ok now onto the circuit board..


So thats the top view.. on the left is the control knob which seems to just be a potentiometer of some kind. The middle wheel is the sensitivity adjustment. CN 2 connects to the rim triggers and CN1 connects to the piezo in the center portion of the pad



Thats the bottom, the numbers correspond to the top view.



Theres another bottom veiw, I used photoshop to layer over what the components are, just so its easier to get an understanding of what corresponds to what, I know I lost track when I was constantly flipping the circuit board over...

That concludes the quick tour of the inner workings of the TP-100..

I do not come from an electrical engineering background so I would like some help (if you would be so kind to give it). I'd eventially like to understand what each stage of the circuit does and create a diagram for it, that I can use as a blueprint to (attempt to) build my own version of this circuit.

The resistors have the following markings on them which I assume are for indentification, is anyone able to indentify the resistors by the colour banding?
R1 = (L-R)brown/black/red/grey
R2 = Brown/black/orange/grey
R3 = Brown/black/orange/grey
R4 = Brown/black/yellow/grey
R5 = Red/purple/orange/grey

I never fully inderstood how yamaha could get three signals AND a controller knob despite only using TRS jacks, but I think I understand now..This is my theory.. Its probably be wrong, I'd love to be corrected...

To me it appears as if the main piezo signal, after being controlled by the Sensitivity adjustment and going through R1 and R2, goes to one side of the jack (I couldn't work out pos/neg position sorry ) The controller knob and rim 1 and rim 2 all go through the other side, however I think they are all different voltages and the module is capable of picking this up.

it appears as though from one of the rim switches goes straight from CN2 to the jack. The other passes through R3 first and then to the jack. The Control knob +/- pass through R4 and R5 before going to the jack.

So I believe the module is programmed to pick up 4 different voltages or voltage ranges - Rim 1 Rim 2 Control + and Control -.

The layout of CN2, what pins correspond to where etc why its setup the way it is, is out of my knowlege so anyone who could shed light on this subject would be much appreciated..

So theres a bunch of information, and my musings about what I think is happening. I have asked a few questions throughout if anyone could answer any of them it would be much appreciated.

thanks V-drums, you guys seem to know how to DIY so I hope someone her is willing to help me

Aj

[PumaPhreak]

Cool stuff. Sorry I can't offer any help here. Good luck.

[SiliconDrummer]

In general, your theory is correct. If you want to dig further, you can find a pretty detailed description in Yamaha's US Patent #6,753,467. Here is a link to the doc from the USPTO: Patent #6,753,467

Also, I'm attaching a portion of figure 14 from the patent which shows the section of the rim trigger circuit that you are interested in.


You can see from the above schematic that item 57 is a pot that is used as the control pot to adjust the "tuning" of the drum. Because it is in series with the 47K resistor R3, it will always be higher than the resistor R1a which is only 10K. So, when you strike the rim to close SW2, R1a will be connected in parallel to the "tuning" resistor and this will drop the total resistince seen by the module to less than 10K, so the module will be able to tell that the rim was struck. When you strike it so that SW1 closes, then the parallel resistance will be 0 since this circuit is a direct short. So, this will produce an even lower vlotage than the other two options and the module will be able to produce the other rim sound. If both switches are open then the voltage will be above either rim striking value, so the module will use that variable voltage as the head "tuning" voltage.

BTW, I cropped out a section of the figure that shows the pull-up resistor in the module is 47K. I don't know if any of these values are actually what Yamaha used in the module you have, but at least it helps to show the ratio of voltage that is generated by the above circuit for each voltage range.

-SD-

[SiliconDrummer]

The resistors have the following markings on them which I assume are for indentification, is anyone able to indentify the resistors by the colour banding?
R1 = (L-R)brown/black/red/grey
R2 = Brown/black/orange/grey
R3 = Brown/black/orange/grey
R4 = Brown/black/yellow/grey
R5 = Red/purple/orange/grey

Here is a link to a resistor color code to help you decode those resistance values. You might want to double check your colors and determine which is the tolerance color so that you can start from the correct side.

http://www.elexp.com/t_resist.htm

You can probably use an ohm meter to measure the resistance at the jack with the tuning knob turned fully clockwise and again fully counter-clockwise since you know that both switches will be electrically open since you don't have the cable hooked up to CN2.

-SD-

[-Aj-]

Thanks very much Silicondrummer some very informative posts. The patent document looks great I'll be reading through that in greater detail, however none of the images or schematics appear for me, the pages they are supposedly on just bring up non-loading quicktime logos... which is frustrating.

Thanks for helping me understand the circuit better, although some parts still escape me as I'm not the most proficient guy out there when it comes to reading circuit diagrams. I'm sorry, but what is 10a on the digram?, and also is there a website where I can brush up on circuit reading so I dont have to ask noob questions every 30 seconds? is wikipedia a good source of information in this case?

if yamaha's values are to be taken as correct the Pot is a 200K variable pot yes?

Thanks for your help, is there anyone out there who can help me on the subject of ribbon switch trigger construction?

thanks

Alex

[SiliconDrummer]

...The patent document looks great I'll be reading through that in greater detail, however none of the images or schematics appear for me, the pages they are supposedly on just bring up non-loading quicktime logos... which is frustrating.

You need to install a tiff viewer. Try this one:

http://www.alternatiff.com/

I'm sorry, but what is 10a on the digram?

10a is the piezo -- they use the same schematic symbol for a crystal or ceramic resonator.

... is there a website where I can brush up on circuit reading so I dont have to ask noob questions every 30 seconds? is wikipedia a good source of information in this case?

Not sure what would be a good source, but maybe try googling "shematic diagram" or "electronic schematic symbols" or something like that. You could also try some of the links on this page: http://www.elexp.com/links.htm#basic

if yamaha's values are to be taken as correct the Pot is a 200K variable pot yes?

Yes 200K is correct.

is there anyone out there who can help me on the subject of ribbon switch trigger construction?

What exactly is your question? Are you asking how you can build one on your own?

-SD-

[-Aj-]

What exactly is your question? Are you asking how you can build one on your own?

-SD-

In a sense yes. I'm wondering how the yamaha one is able to work so well; ie how they seperate the pieces and how (given that they are seperated) they are still able to complete the circuit when struck at any point on the pad

The eventual aim is to be able to construct my own ribon switch trigger, however I realise the materials and processes available to a DIY builder as opposed to a large corperation are rather different so I'm curious as to whether its possible.

Thanks again for the help

Aj

[drum4ever]

If those colors are correct
R1=1k
R2=10K
R3=10K
R4=100K
R5=27K
all are 10% resistors(the grey band is silver) probably 1/2 watt from the scale of the photo

You would do well to test those resistors with an ohmmeter with no power applied to be sure of the values.

According to the diagram the pot is 200K probably linear.
(of course the diagram also shows R3 as 47K not 10K)

To test the pots touch one side lead and the center lead then turn the knob all the way both ways. The highest reading you get should be close enough.

[JmanWord]

The eventual aim is to be able to construct my own ribon switch trigger, however I realise the materials and processes available to a DIY builder as opposed to a large corperation are rather different so I'm curious as to whether its possible.

Thanks again for the help

Aj

Well, All things are possible for him that believes But finding the ribbon switches and how economical it would be is another question. To my knowledge NO DIYer has come close to pulling off a sophisticated 3 zone DIY mesh pad on par with that Yami pad. J

[-Aj-]

Well, All things are possible for him that believes But finding the ribbon switches and how economical it would be is another question. To my knowledge NO DIYer has come close to pulling off a sophisticated 3 zone DIY mesh pad on par with that Yami pad. J

Indeed they are Jman! I've done some searching around and think it might just be possible, it helps when you knwo what you are looking for.

I was searching for "ribbon switch's" as I believed thats what they were, turns out they are much larger version of membrane switches (like those that feature on your microwave) Searching for membrane switches produced a lot of results, including places the specialize is producing prototypes

So the plan is this, I want to create an 8,10,12, 12snare,14,14 mesh head kit with roland heads. (hence the limited sizes) For my kick I'm unsure, probaly go for a 20 or 22x12 with a Tama or pintech mech head or something. I think it will be possible to create the pads I want with some guidance from the forum

a couple questions.. regarding testing the pots, the controller knob appears to be a rotary encoder rather than a pot, as it is infinitely adujustable. So is the voltage that it outputs then determined by R4/R5 then?

also with the board design ground is supplied to almost the whole board (apart from the seperated circuits of course), however there are studs all through the board that go to nothing.. what are these for? to stop interferance? direct the ground current?

thanks

Aj

[SuperPuss]

..........also with the board design ground is supplied to almost the whole board (apart from the seperated circuits of course), however there are studs all through the board that go to nothing.. what are these for? to stop interferance? direct the ground current?

thanks

Aj

The PCB you have there is known as a double sided, through hole plated board with a ground plane on both sides. The connections that appear to go nowhere simply connect the two ground planes together in a uniform way to form good shielding.

Rotary encoders are a totally different beast to a potentiometer. They are a form of switch that produces a train of pulses that the module uses to detect direction and rotational speed.

[JmanWord]

I was searching for "ribbon switch's" as I believed thats what they were, turns out they are much larger version of membrane switches (like those that feature on your microwave) Searching for membrane switches produced a lot of results, including places the specialize is producing prototypes

So the plan is this, I want to create an 8,10,12, 12snare,14,14 mesh head kit with roland heads. (hence the limited sizes)
thanks

Aj

Yes those are membrane switches. Roland uses membrane switches also. The problem normally is getting something that will work for a particular application. The pricing for getting something custom built (prototypes) for a small project will normally exclude us little DIYers ..... Big $ companies with big pockets and big orders ..... no problem....

I'd love it if someone discovers some handy membrane switches usable for DIY cymbals, and pads..... but so far I haven't seen it.... Let me know what ya come up with.... I could use 50 or 60.... ummm, maybe 100 .....

[Gastric]

What about a flexible bend sensor. Here's one product description. http://techconnect.org/Summit2006/pr...ml?absno=11085 Since they are fully variable and it's noted they can detect vibration they could potentially be adopted for all sorts of drum applications I'd think. However, they're not a simple "dumb" on/off switch so it adds complexity, though I couldn't possibly say how much as that's beyond my personal knowledge.

I just know they must be cheaply available as I have a $45 paintball loader that uses (a very small) one to determine when a ball passes down the feed tube in order to cycle the loader motor.

[SiliconDrummer]

Hey AJ, have you tried triggering a mesh pad on your Yamaha module? If you haven't, you really should try this to see if you like the response before you dive into the rest of the pad design.

I have a friend that spent tons of time trying to get his Yamaha module to work well with his Roland PD-120. It triggered, but just not as well as a Roland module. He inverted the jack polarity, added an external gain pot, and all sorts of other things, but he was never 100% happy. He eventually just gave up and bought a Roland module. Now, this was years ago, so things may have changed. But, Yamaha still doesn't sell any mesh pads, so there really is no guarantee that mesh triggering will be acceptable to you.

-SD-

[Hellfire]

Yes those are membrane switches. Roland uses membrane switches also. The problem normally is getting something that will work for a particular application. The pricing for getting something custom built (prototypes) for a small project will normally exclude us little DIYers ..... Big $ companies with big pockets and big orders ..... no problem....

I'd love it if someone discovers some handy membrane switches usable for DIY cymbals, and pads..... but so far I haven't seen it.... Let me know what ya come up with.... I could use 50 or 60.... ummm, maybe 100 .....

If someone really wants to diy a membran switch, maybe this website can help.
Make Conductive Glue and Glue a Circuit

Or you can try something like this: (not really a "membrane" switch but might work)
Get a Choke Hold (eCymbal Choke Switch)