Using Force Sensitive Resistors to trigger notes

[mbira]

Hi folks,
Has anyone here used FSRs to trigger Megadrum? I've been using Piezos but there are some times when we are playing a show where the Subwoofers are under the stage or when the PA at the venue is very loud, and I'm getting false-triggering. Malletkats use FCRs and supposedly this completely eliminates the issue of crosstalk as resistance goes down only when the specific zone is struck.

I got samples of these:
http://www.digikey.com/us/EN/ph/Interli ... 20Products

While Piezos create voltage when struck, FSRs reduce their resistance, so I'm thinking I need to create a voltage divider and have a DC power supply.

What is the voltage that Megadrum needs to see to register a strike? In this specific need-I am using these only as on/off triggers, so I don't need to worry about velocity sensitivity...

[mbira]

I just read the 5 page post on FSRs. Since I'm not using these in a drum application, but only for triggering samples, I just need to know the minimum voltage needed to trigger the megadrum and I'll make a voltage divider to achieve that...

[Sylv1co]

You have to know that if you let your stick or your finger pressed on the FSR, it will trigger many notes.

Since I'm not using these in a drum application, but only for triggering samples

What do you you mean, you don't need velocity, just a midi note when you touch your FSR ? If it is, there's probably an easier solution than FSR.

[mbira]

Without spending a lot of time on details, I run several marimbas with piezos in each key into a dual 56 channel megadrum (112 channels total). Each marimba also has a "thumper" which is 8 trigger pads that are used to control sample triggering and Ableton scene triggering. I don't hold the mallets on the thumpers. We are playing, then you whack one of the thumper triggers to trigger a scene. Those triggers have been falsely triggering a a few of our bigger shows (when it is a huge stage with many subs under the stage-we do electronica music with heavy bass). We have done hundreds of shows with no problems, but a couple where the PA has been so big that there was a problem, so I want to make sure it never happens again-hence the FSRs.

But-yes-for those thumpers, we only need a "switch" type function, but we need to strike them with mallets, so somethign like an actual footswitch wouldn't really work well.

[Sylv1co]

Try to put one piezo in series with one FSR on each pad of your "thumper", it should work perfect for what you need. this way, no need to get power source, and no false triggering since the FSR need to be press to let the piezo signal pass, and no problem if you let your mallet pressed on the FSR since the piezo will only provide current for a few ms.
Be sure that there's no weight on the FSR, it is really sensitive. Measure its resistance on the finished pad, if it's less than 100k, it may be troublesome, but you still can use the threshold to prevent false triggering in this case.
The resistance on this fsr deacrese really quickly to about 50K, so you should not have any sensitivity issue, but please try with one before buying 16 FSR, I can't provide any guarantee...
To test it, you will also need to reproduce the scene condition to see if the subs vibrations can't make the FSR to be pressed... the problem should persist...

[mbira]

Interesting idea. I'll have to think on it a bit. I've already got 5V going to the thumpers because there are LEDs lighting, etc when the pads are struck. It would actually be more work to do a series circuit with the piezo and fsr than a voltage divider, but whatever works is the solution I need to go for. My understanding is that FSRs essentially eliminate any crosstalk issues...

Thinking about it though, the series piezo thing doesn't seem like it would help me because:
When I am in a situation where this problem is happening- the subs are really pounding, then those piezos are being activated constantly anyway. When I hit the FSR, then the voltage from the piezo is just allowed to pass through. That is really not any different than if I just have a voltage divider with a constant voltage...

It's actually not a problem if I get a bunch of note on messages in quick secession-the samples and scenes are all set to oneshot, so they would not retrigger if the same message is seen within even up to 1 or 2 seconds...