Project development: Creaky Floor

[EBK]

I'm working on a project inspired by the pulse-like stick-slip motion of a creaking hardwood floor. 

I plan to use a force-sensing resistor as part of an actuator.  As force is applied to the FSR, pulses will be generated as the resistance changes through discrete steps.  These pulses will control some sort of audio switching, either as on/off or as A/B switching (probably cross-fading).

I have no idea if this will be musically useful when I'm done, but as I've established time and time again, I have more fun with impractical ideas anyway.   

Here is where I am at so far:

The disc sticking up is my FSR (from smallbear).  The IC is a LM3914* dot/bar LED display driver operating in dot mode.  The LEDs light up sequentially (with a small bit of overlap) as force is applied to the FSR (no LEDs are lit when at zero force, and the last LED stays lit at max force).

I next plan to divide the LED output lines (these are current sinks) into even and odd groups, each group going into a separate op amp, i.e., outputs 1, 3, 5, 7, and 9 will form the odd group and outputs 2, 4, 6, 8, and 10 will form the even group.  If all goes well, the two op amps should produce slightly overlapping complementary pulse signals.  I could simply take just the odd outputs and use only one op amp, I suppose, but I'd miss out on the overlap, which might be useful.

Anyway, this is still pretty early in development, but I welcome any thoughts or opinions. 

*The LM3914 happened to already be in my parts bin.  As far as I know, it is no longer produced in DIP form but is still available in a PLCC.  If I didn't already have this chip, I might have considered using a microcontroller instead.

Edit: smallbear still has some LM3914 DIPs.

Edit 2: I actually won't need the op amps I mentioned.  A simpler BJT circuit will do just fine.  More on this later.

[EBK]

Also, part of the motivation behind this project is that I want to see if I can combine an FSR with this actuator:


The actuator has a metal rod connected to the spring.  I plan to place a metal disc (perhaps a coin) on top of the FSR and have this spring/rod push down on that.

[Aph]

I'm working on a project inspired by the pulse-like stick-slip motion of a creaking hardwood floor.

Wanna buy my house?

[Kipper4]

What did I just read ?
I'm gonna have to reread when I'm sober.
Maybe cross fading might be easier to implement with electric druids cross fader and the fsr as part of a voltage divider in lieu of the pot.

[EBK]

What did I just read ?
I'm gonna have to reread when I'm sober.

The short summary: 

1. You step on a force sensor.

2. Up to 5 pulses are generated.  The number and timing of the pulses depends on how much force you apply and how quickly you apply it.

3. The pulses will be used to switch some audio signals back and forth, like a multiplexer.

[GibsonGM]

Maybe I can help!  Here's MY house!    Need a creaky floor???      It's a neat idea, definitely original, I've NEVER seen anything like it; it'll be cool to see where you go with it!

[Kipper4]

Multiplexer? Edit. I googled it. Got it

Sorry to be a nuisance.
I'm loving it anyway.
It's giving me ideas.
Thanks Eric

[thermionix]

Bastard in a basket!

[GibsonGM]

HEY! That's my grandfather!! 

Actually, no...those are the remaining civil war veterans in my area in 1895 at my then 30 yr old house, which was also the school up here.   Grand Army of the Republic reunion.  I tell my wife they talk to me when I'm down in the cellar.  The guy on the far right looks like Col. Henry Blake from MASH.   
This is off-topic; I'll stop   

[EBK]

This is off-topic; I'll stop   

I'll allow it.  The house has creaky floors, so it's relevant enough.   

[thermionix]

I should've used quotation marks.  It was a movie reference.  Dude looks like Daniel Day Lewis in There Will Be Blood.

[GibsonGM]

You know - he really does!  And Henry Blake, too...

[thermionix]

Needs more fishing lures.  Idle hands are the devil's.....oh, too late.

[EBK]

Oh how I would love to live in a world where this was literally true:

There is nothing worse than tiptoeing around your home while people are asleep and hearing a harmony of squeaking floorboards.

(from https://www.411homerepair.com/diy/floors-tile-hardwood/10055-What-Causes-Creaky-Floorboards.html)

[GibsonGM]

You do get used to it; doesn't bother me, and I don't try to avoid the spots.  She's used to it.
Up here, the wind is the worst noise-maker!

[EBK]

Preliminary schematic of the FSR pulse generator circuit:


Some of the unlabeled resistors I've already worked out, but I need to look back at my notes for the values.  The diodes are LEDs, but I just didn't draw the arrows out of laziness.   

P₁ and P₂ are the complementary pulse outputs.

Surprisingly low parts count (surprising to me, anyway).  The LM3914 is a pretty cool chip.

[EBK]

I need to see if I can scrounge up two vactrols.  I have an idea that may simplify this thing even more and get me closer to a demo that makes some sound happen.

I'm thinking I can replace those two top resistors with the vactrol LEDs, and get rid of the BJTs. 

[garcho]

I love where this is going, bravo.

I made an arduino theremin with ping location sensors but instead of a fluid pitch portomento it was in "zones" that triggered samples. Like a drum machine you play in the air instead of pads. Fun stuff sensors are!

[EBK]

I love where this is going, bravo.

I made an arduino theremin with ping location sensors but instead of a fluid pitch portomento it was in "zones" that triggered samples. Like a drum machine you play in the air instead of pads. Fun stuff sensors are!

Thanks!  Fun stuff, indeed. 

[EBK]

I've replaced the BJT/resistor stuff at the top of the schematic with two LEDs and recorded a quick visual demo (I'll update the schematic later):