[sdiy] Very cheap SPI pressure sensors.. anybody ??

Sat Mar 20 17:30:33 CET 2021

oh, you meant air pressure sensor... sorry... i thought you meant
polyphonic aftertouch.

On Fri, Mar 19, 2021 at 10:34 PM Jean-Pierre Desrochers <jpdesroc at oricom.ca>
wrote:

> *>**As for the option of light sensing, the assumption of freedom to
> design, would allow you to simply have an array of LEDs directly on the top
> and a array of sensors directly under, >mounted on boards. To me at >least,
> using optical fibers for this purpose and placing the sensing elsewhere
> seems like an overcomplication. Unless there's some design requirement I'm
> not seeing*
>
>
>
> An optic based reader would look about like this:
>
>
>
>
>
> Notice the big horizontal LEDs bar over the row of holes in reading..
>
> Not very nice..
>
>
>
> On the other hand a vacuum based reader would look like the original thing:
>
>
>
> The rolling mechanism will be using a DC brushless speed controlled motor
> connected to the right gears assembly.
>
>
>
>
> *>I would consider designing boards where you have the sensors in a row on
> the board. You could for example have 15 sensors per board and 6 groups for
> the target of of 90. You could >then either >have a multiplexing
> arrangement like the one I suggested, or a microcontroller on each board
> for local processing. *This is about the way I was thinking to do it..
>
> *>You could then have a physical piece (3D printed or >otherwise
> fabricated) that fits over the board to create a chamber for each sensor.*
>
> Very good idea ! My first ideas were to glue very small silicon hoses over
> each sensors
> but a separate chamber for each sensor is much better..
> These chambers could have a small pointing upward ‘chimney’ to insert
> the vacuumed hoses. About like this housing:
>
> And by the way, this reader will have its own audio player
> playing ‘honkytonk’ sounding notes with a MIDI output !
>
>
>
> *De :* Didrik Madheden [mailto:nitro2k01 at gmail.com]
> *Envoyé :* 19 mars 2021 16:13
> *À :* Jean-Pierre Desrochers
> *Cc :* SDIY List
> *Objet :* Re: [sdiy] Very cheap SPI pressure sensors.. anybody ??
>
>
>
> So that gives me one important piece of information: the sensors could be
> placed in a linear pattern, as opposed to, for example, being spread out
> and needing to be wired up individually.
>
>
>
> I would consider designing boards where you have the sensors in a row on
> the board. You could for example have 15 sensors per board and 6 groups for
> the target of of 90. You could then either have a multiplexing arrangement
> like the one I suggested, or a microcontroller on each board for local
> processing. You could then have a physical piece (3D printed or otherwise
> fabricated) that fits over the board to create a chamber for each sensor.
>
>
>
> I'm assuming here that this is a machine that you are either designing
> from scratch, or have relative freedom to modify. In particular that you
> control fully what's above and below the line of notes that's currently
> being read. But from the rest of your description I realize that this may
> not be the case. Are you for example retrofitting an old machine, or you
> feel that you want to be true to the original principles? Or do you just
> want a solution that works for as cheap as possible?
>
>
>
> As for the option of light sensing, the assumption of freedom to design,
> would allow you to simply have an array of LEDs directly on the top and a
> array of sensors directly under, mounted on boards. To me at least, using
> optical fibers for this purpose and placing the sensing elsewhere seems
> like an overcomplication. Unless there's some design requirement I'm not
> seeing...
>
> /Didrik
>
> On Fri, Mar 19, 2021, 20:27 Jean-Pierre Desrochers <jpdesroc at oricom.ca>
> wrote:
>
> Good idea here Didrick !
> But a little too complicated for my design..
> This futur project is a piano roll scanner/player.
> This has been a project done many times by DIYers all over the place
> but they mostly used optical approach to read paper holes
> (fiber optics + photo-transistors).
> This needs a LED array bar put over the rolling paper holes rows
> for the fiber optics holes detections,  which I don't like at all..
> I'd like better to read the punched holes using vacuumed air
> like antique piano did. A small vacuum pump will do that.
> This is why I'd use pressure sensors to detect any holes
> coming up while the paper roll is playing.
> But I'm still looking any design possibilities.
> I'll need around 90 sensors (SPI communications) to get the job done.
> This will obviously need some multiplexing to access each of them.
> Doable..
>
>
> -----Message d'origine-----
> De : Didrik Madheden [mailto:nitro2k01 at gmail.com]
> Envoyé : 19 mars 2021 14:16
> À : Jean-Pierre Desrochers
> Cc : SDIY List
> Objet : Re: [sdiy] Very cheap SPI pressure sensors.. anybody ??
>
> Here's an idea. It's a bit janky, and requires some extra circuitry, but
> it might work for you. The basic idea is to use a chain of 74hc595 serial
> to parallel shift registers to generate either a chip select or clock
> signal. You feed in a single 0 into the shift register, which you move
> forward one step at a time.
>
> In the case of a chip select signal, this selects one chip at a time.
> To select the next chip, clock the register chain one step to forward the
> 0 bit one step.
>
> In the case of a clock signal, it's a bit more complicated. But this could
> be used to multiplex I2C. In this configuration, all the data pins are
> commoned. (Or commoned in multiple groups if needed for signal integrity.)
> You have a similar idea as in the example above in that a 0 bit travels one
> step at a time. You could do this the slow way and send out the full chain
> of bits just to flip one bit and clock the local I2C bus. Or, you could do
> it the slightly quicker way and use the output enable of the 74HC595's to
> clock the selected device.
> It would work like this:
>
> Most bits in the register are ones. For those bits, turning the output
> enable on or off would do nothing because you're switching between driving
> the clock signal high, or leaving the clock signal with a pullup resistor
> which also keeps at logic high.
>
> One or multiple bits are zeros. When output enable is off, that output is
> high from the pullup that you add, or which exists on the module you use.
> When you turn on the output enable, voilà! The clock signal for that device
> goes low, and you have fed clocked one I2C bit. I think you can fill in the
> rest. All the other devices will also see the data line change, but they're
> in high impedance mode, and will not react to data without a corresponding
> clock.
>
> If you are able to design a board and have it ordered from JLCPCB using
> their PCB assembly service, you could use SPL06-007. It costs, currently,
> $0.6622/pc in 100 quantity. There's some extra cost for the board and
> assembly service, but that should be relatively cheap in comparison.
>
> To give even more precise advice, it would also help to know more about
> the details of the project. In particular the physical arrangement of the
> sensors. If they need to branch off from a central point using cables, if
> the cables need to be detachable etc. If you want to discuss these things
> closer in private, feel free to contact me off-list.
>
> /Didrik
>
> On Fri, 19 Mar 2021 at 16:14, Jean-Pierre Desrochers <jpdesroc at oricom.ca>
> wrote:
> >
> > I'm looking for very cheap SPI pressure sensors (around $1.00 a piece
> > or less)
> >
> > For a future project. The pressure value doesn't matter but the size and
> cost do.
> >
> > I will need around 90 of these sensors.
> >
> >
> >
> > For example I found this:
> >
> > BMP180 GY-68 GY68 3.3V 5V BMP-180 Temperature Pressure Sensor Module
> > Barometric IIC I2C Interface Sensor Module Replace BMP085  $0.90CAD
> >
> > https://www.aliexpress.com/item/32832330585.html?src=google&albch=shop
> > ping&acnt=708-803-3821&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shoppi
> > ng&aff_platform=google&aff_short_key=UneMJZVf&&albagn=888888&isSmbAuto
> > Call=false&needSmbHouyi=false&albcp=7386552844&albag=80241711349&trgt=
> > 743612850714&crea=en32832330585&netw=u&device=c&albpg=743612850714&alb
> > pd=en32832330585&gclid=CjwKCAjw9MuCBhBUEiwAbDZ-7mU2hTS0J2DLxvsPsj8F40L
> > -zV8vtApw9ds_ks1c2Qjg7dLiKgsy3RoCq-EQAvD_BwE&gclsrc=aw.ds
> >
> > But because I need 90 devices and the BMP180 is I2C and has only one
> > address value I would need somekind of multiplexer to address 90 devices
> (one at the time obviously).
> >
> > So.. SPI devices would fit better here.
> >
> >
> >
> > One other possibility would be to use this type:
> >
> > MPS20N0040D MPS20N0040D-D Sphygmomanometer Dip Air Pressure Sensor
> 0-40kPa DIP-6 For Arduino Raspb   $0.74CAD
> >
> > https://www.aliexpress.com/item/4000354356373.html?src=google&albch=sh
> > opping&acnt=708-803-3821&isdl=y&slnk=&plac=&mtctp=&albbt=Google_7_shop
> > ping&aff_platform=google&aff_short_key=UneMJZVf&&albagn=888888&isSmbAu
> > toCall=false&needSmbHouyi=false&albcp=9604672960&albag=100679328364&tr
> > gt=296904913880&crea=en4000354356373&netw=u&device=c&albpg=29690491388
> > 0&albpd=en4000354356373&gclid=CjwKCAjw9MuCBhBUEiwAbDZ-7kff0q--0F6YUo73
> > aVqE_HAtqkRyIslFbEMRTWz7QICR2szctlC7zxoCrMUQAvD_BwE&gclsrc=aw.ds
> >
> >
> >
> > But I’ll need some analog IC to manage the output..
> >
> > Again the part’s pressure specs value do not matter.. I will manage a
> way to use it.
> >
> > but the size and cost do.
> >
> >
> >
> > So far the best would be a SPI equivalent of the BMP180 IC..
> >
> > Let me know if someone googled something I did not spot !
> >
> >
> >
> > JP
> >
> > _______________________________________________
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>
>
>
> --
> /Didrik
>
> _______________________________________________
> Synth-diy mailing list
> Synth-diy at synth-diy.org
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>
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