Hi,

I'm looking for ideas! I am creating a Floor Piano - like the large one used in the film "Big" (Chopsticks etc).

The Keys are 600mm X 200mm and my current design uses microswitches at the front of the keys. This means hinging the key at the back and obviously the key moves up and down slightly as it is walked on albeit only 2mm.

Looking at Videos of professional Floor Pianos, the keys do not move so I guess the use something other than a microswitch to sense a key press.

Possibly pressure strip? Does anyone at least has a pointer for me as I have come up blank.

As always, any advice will be gratefully received.
Kevin

 

Ah "BIG" those were the days.. good films.. no explosions!

My dad used to make burglar alarm pressure pads (very home made!), a sheet of card or something thick-ish, with holes punched in, then a layer of silver paper top and bottom. When you step on it the 2 sheets of foil touch, in some places.

I dare say you could make something a bit more sophisticated, like use some neoprene instead of card.. but very cheap to make on a large scale

 

Look up "force sensing resistors".
SG

 

pmd34 - funnily enough, that's almost where I started: a couple of squares of 3mm Neoprene tape for "suspension" but I think it would become compressed after a few hundred steps from a 20 stone bloke!

SG - looks promising, thanks.

Also, it has to work for a 1 Stone Toddler and a 20 Stone bloke (That's 14lb and 280lb!)

 

A cheap piezo speaker could be used as a sensor of sorts, using the right interface circuitry.

​

 

Haha, great minds think a like huh!

You could get sophisticated and use a capacities touch system, a module such as this:
https://www.aliexpress.com/item/10P...lgo_pvid=71bd5a55-4745-4d0d-8ffa-eac08e564082

Again using silver foil to form an electrode, but you could place it on the underside of something like a sheet of plexiglass.
It would at least give you a direct clean switch action. But I am not sure how well they work with big areas, it would need some tuning and testing.

 

I used to run a Haunted House. We used several pressure sensitive mats to trigger illusions. Hence, the Halloween industry is a good place to start. If you were to Google “Halloween pressure mats”, you’d see this!

 

How would I make a Force Sensing Resistor act like a switch? I presume they simply increase/reduce resistance with pressure rather than provide a digital switch?

 

Also, check out “Velostat” from Adafruit. Using this material your pressure sensitive switches can be any size, with appropriate electronics and/or coding.

 

How would I make a Force Sensing Resistor act like a switch?

Depends on your design, are you thinking digital or analog? Do you have a design?
SG

 

How would I make a Force Sensing Resistor act like a switch? I presume they simply increase/reduce resistance with pressure rather than provide a digital switch?

There are a couple of ways. One is to use the force sending resistor as input to a comparator. IC comparators are available.

The second way is to use a microprocessor. You’d read the voltage drop caused by the force sensing resistor and take appropriate action based on the value.

 

Also, check out “Velostat” from Adafruit. Using this material your pressure sensitive switches can be any size, with appropriate electronics and/or coding.

Ooo that looks good for something I was thinking of making! Cheers @djsfantasi

DOH... someone has beaten me to it!
http://www.stopabductions.com/

 

There are a couple of ways. One is to use the force sending resistor as input to a comparator. IC comparators are available.

The second way is to use a microprocessor. You’d read the voltage drop caused by the force sensing resistor and take appropriate action based on the value.

An ATTiny13a is <$1.00 and has a comparator... best of both worlds.

 

An ATTiny13a is <$1.00 and has a comparator... best of both worlds.

However, you'd probably need on for each note. Might get complicated.

 

However, you'd probably need on for each note. Might get complicated.

So cheap though, and SPI! Come, you know you'd like to do that project!

 

While you will need to purchase force sensing resistors you can build force sensing capacitors. And they could be quite cheap, two slices of aluminum foil with a conveniently compressible elastomer in between, Copper foil would be simpler to solder to, though. The interface would need to be nearby, but that can be a simple surface mount IC device. Substitute a piezo device and it does get even simpler, but you still need shielding. And the piezo approach is probably by far the cheapest and easiest to make work.

 

Here's an example of a comparator circuit for interfacing.
SG

 

Hello,

Perhaps this page will give you some project ideas:
http://www.geocities.ws/JDPetkov/Hardware/hardware.htm

Bertus

 

Depends on your design, are you thinking digital or analog? Do you have a design?
SG

I have a simple brain!

I have a design (attached). Just a series of microswitches - nothing fancy, if I could replace the switches with a sensor that has less travel then great!

@DJFantasi: I did see the velostat idea earlier but I'm pretty sure the keys either side would be triggered too.

The Schematic shows 4 and a half octaves but I aim to make it modular - the green line denotes an octave which will be a single floor panel.

The two connectors are on the guts of a Synthesizer that I ripped out - all of the microprocessing is done using a £30 PCB which has volume and voices built in.

 

The Schematic shows 4 and a half octaves but I aim to make it modular - the green line denotes an octave which will be a single floor panel.

How many switches do you need for the finished project?
Seems like the micro switches are your best bet with the micro.
SG