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Has anyone used pressure sensors with the propeller? — Parallax Forums

Has anyone used pressure sensors with the propeller?

turbosupraturbosupra Posts: 1,088
edited 2012-02-14 08:45 in Propeller 1
If so, how did you do it?

Did you use an ADC in between? Which sensor did you use? My application is automotive, so I'd like to use a 0-5v sensor. I'm not sure on resolution, but maybe 0 to 60psi (not psia).

Thanks!

Comments

  • tonyp12tonyp12 Posts: 1,951
    edited 2012-02-07 13:23
    I used a
    1560-02.jpg
    http://www.mouser.com/ProductDetail/Freescale-Semiconductor/MPVZ5004GW7U/?qs=N2XN0KY4UWWThUgghVx%252bFw%3d%3d

    And added the 0603 resistors/caps to the quickstartboard for a ADC.
    This sensor is made for low pressure and what it does not say it specs is that actually can handle a little bit of negative pressure too.
    The range will in that case be 0-5volt.

    -- Lucy, Rest In Peace.
  • groggorygroggory Posts: 205
    edited 2012-02-07 13:24
    What kind of pressure? What kind of sensor?

    I've used quite a few flexiforce sensors with the propeller.

    Flexiforce -> inverting amplifier with low pass filter -> ADC -> Propeller
  • turbosupraturbosupra Posts: 1,088
    edited 2012-02-08 21:24
    Hi,

    Exhaust pressure and atmospheric compressed air pressure, I'm not opposed to using an isolator if heat is a concern. Have you used any flexiforce sensors that might be up to the task of that? How many pins did your ADC consume?

    I would like the ability to have up to a dozen sensors connected to it, which is why I ask.

    Thanks for the reply.


    groggory wrote: »
    What kind of pressure? What kind of sensor?

    I've used quite a few flexiforce sensors with the propeller.

    Flexiforce -> inverting amplifier with low pass filter -> ADC -> Propeller
  • turbosupraturbosupra Posts: 1,088
    edited 2012-02-09 10:53
    How about something like this? (It's an ADC and MUX combining 16 analog channels in to 1 output channel) I'm not sure how complicated this would make the prop code through. I'd really like to have a 12 or 16 analog channels in to 12 or 16 MUX out channels at a 1:1 ratio, to make the code easiest.

    http://www.sparkfun.com/products/9056
  • groggorygroggory Posts: 205
    edited 2012-02-09 11:10
    Go research some sensors that look good to you and we'll help you interface them.
  • tonyp12tonyp12 Posts: 1,951
    edited 2012-02-09 11:10
    The breakoutboard you listed is just an analog muxer, it does not output a digital converted value.
    There are a few ADC that have the 12-16 channels you want.
    http://www.mouser.com/Semiconductors/Data-Conversion-ICs/ADC-A-D-Converters/_/N-4c43gZscv7?P=1z0myi3Z1z0kokw&Ns=Pricing%7c0

    Or you could go with a few 4-6 channel ic, and with i2c or spi select would not waste many pins.
  • groggorygroggory Posts: 205
    edited 2012-02-09 11:50
    tonyp12 wrote: »
    The breakoutboard you listed is just an analog muxer, it does not output a digital converted value.
    There are a few ADC that have the 12-16 channels you want.
    http://www.mouser.com/Semiconductors/Data-Conversion-ICs/ADC-A-D-Converters/_/N-4c43gZscv7?P=1z0myi3Z1z0kokw&Ns=Pricing%7c0

    Or you could go with a few 4-6 channel ic, and with i2c or spi select would not waste many pins.

    True, but the solution will depend on what sensors he wants to capture.

    I think he needs to go find his pressure sensors and see what they spit out. I have learned that not all ADC's are created equal. Filters are the magic that makes the data go round. MUX'ing filtered analog signals can lead to problems, and ADC selection is not a one size fits all.

    Post up the sensors you are looking to use...then we'll see how to interface them.
  • groggorygroggory Posts: 205
    edited 2012-02-09 12:00
    turbosupra wrote: »
    If so, how did you do it?

    Did you use an ADC in between? Which sensor did you use? My application is automotive, so I'd like to use a 0-5v sensor. I'm not sure on resolution, but maybe 0 to 60psi (not psia).

    Thanks!

    Ok, so let me see if I can spec out your requirements for sensors a bit better...

    I'm guessing that you are looking to measure intake manifold pressure and pre-cat exhaust pressure.

    So for the intake manifold pressure, I'm assuming that the sensor will be exposed to between say... 30 in Hg and 74 PSIA (absolute pressure). Also, the sensor will be exposed to oil, gas, and other chemical misting. The temperatures it will be exposed to will be between 30 F - 300F.

    Does that sound right for the intake manifold pressure sensor? Do you want to also be able to read vacuum pressure?

    For the exhaust pressure I'm assuming...
    Temperature range the sensor will see will be between 30F - 800F.
    Pressure will be between 0-30 PSIA
    Chemicals and soot will be present
  • turbosupraturbosupra Posts: 1,088
    edited 2012-02-10 06:21
    Hi,

    Thanks for the response, the intake manifold sensor sounds good, I do not have to read vacuum, but it would be an added bonus :) . Chemicals are correct.

    The exhaust pressure sensor should probably be 30F to 2000F (if they have that). I don't believe it will ever see 2000F temperatures, especially with an isolator, but theoretically the exhaust temperatures can get that hot inside of the exhaust manifold. Pressure capability should be from 0-120psia.

    I've done a quick digikey search and it appears there are no reasonably priced sensors for what I need. These the the most important areas:

    Operating Pressure : 0-100psig
    Port Size : preferably 1/8" NPT
    Output : whatever can be used with the prop
    Accuracy : +- 2%
    Voltage - Supply : 5vDc
    Operating Temperature : as high as possible
    Package / Case : something to withstand the temperatures

    groggory wrote: »
    Ok, so let me see if I can spec out your requirements for sensors a bit better...

    I'm guessing that you are looking to measure intake manifold pressure and pre-cat exhaust pressure.

    So for the intake manifold pressure, I'm assuming that the sensor will be exposed to between say... 30 in Hg and 74 PSIA (absolute pressure). Also, the sensor will be exposed to oil, gas, and other chemical misting. The temperatures it will be exposed to will be between 30 F - 300F.

    Does that sound right for the intake manifold pressure sensor? Do you want to also be able to read vacuum pressure?

    For the exhaust pressure I'm assuming...
    Temperature range the sensor will see will be between 30F - 800F.
    Pressure will be between 0-30 PSIA
    Chemicals and soot will be present
  • turbosupraturbosupra Posts: 1,088
    edited 2012-02-10 06:44
    Mouser is a little more promising, this one looks pretty good, I can handle $11 a piece. It will work great for intake manifold pressure, I'm a little concerned about exhaust heat temperature, but maybe with some creatively lengthened copper tubing, I can make this one work. The have packaged sensors like this at $150 a piece, but I believe they have some sort of built in isolators in them? What do you think?

    http://www.mouser.com/ProductDetail/Freescale-Semiconductor/MPX5700GS/?qs=sGAEpiMZZMvWgbUE6GM3ORvmt%252b06Ud%2f0DqcthTDA2uE%3d

    http://www.freescale.com/files/sensors/doc/data_sheet/MPX5700.pdf
  • turbosupraturbosupra Posts: 1,088
    edited 2012-02-13 09:05
    It appears an isolation kit is being used for longevity
    http://www.optionsauto.com/prodinfo.asp?number=AEM-30-2064
    but that the sensor specs are very similar
    http://www.theboostlab.com/store/products/Aem-Boost%7B47%7DExhaust-Backpressure-Sensor-Kit%252d-5-Bar-Or-75-psi.html
    so that is encouraging. I will use some 5/16" steel brake line tubing to create some isolation.

    Accuracy: +/- 0.5% Full Scale over -40C to 105C includes Repeatability, Hysteresis and Linearity
    Operating Temp: -40C to 105C / -40F to 221F
    Burst Pressure: 750PSI
    Response Time: < 1mS
    Wetted Materials: 304L & 316L Stainless Steel
    Vibration: 100 to 2000Hz, 20g Sinusoidal, 3 Axes
    Weight: <85g
    Supply Current: <6mA at 5 Vdc
    Output: .5 to 4.5Vdc Linear
    Transfer Function: PSI = (18.75*(Voltage))-24.075
  • Mark_TMark_T Posts: 1,981
    edited 2012-02-13 10:02
    turbosupra wrote: »
    Mouser is a little more promising, this one looks pretty good, I can handle $11 a piece. It will work great for intake manifold pressure, I'm a little concerned about exhaust heat temperature, but maybe with some creatively lengthened copper tubing, I can make this one work. The have packaged sensors like this at $150 a piece, but I believe they have some sort of built in isolators in them? What do you think?

    http://www.mouser.com/ProductDetail/Freescale-Semiconductor/MPX5700GS/?qs=sGAEpiMZZMvWgbUE6GM3ORvmt%2b06Ud%2f0DqcthTDA2uE%3d

    http://www.freescale.com/files/sensors/doc/data_sheet/MPX5700.pdf

    Stainless steel conducts heat a lot less than copper, and probably won't corrode so fast when joined to a steel / cast iron manifold...
  • groggorygroggory Posts: 205
    edited 2012-02-13 10:38
    These are starting to look promising.

    Are you looking to build sensor interfaces to plug into megasquirt or something? Just wondering what you're up to.
  • turbosupraturbosupra Posts: 1,088
    edited 2012-02-13 13:46
    Yes you are right, steel is a better choice

    Mark_T wrote: »
    Stainless steel conducts heat a lot less than copper, and probably won't corrode so fast when joined to a steel / cast iron manifold...
  • turbosupraturbosupra Posts: 1,088
    edited 2012-02-13 13:48
    This is actually for the propeller, the prop is going to be doing some control and helping the factory ecu

    Do you know of any ADC's that fit my request? 7 or 8 bit and will serial out in a single channel?

    groggory wrote: »
    These are starting to look promising.

    Are you looking to build sensor interfaces to plug into megasquirt or something? Just wondering what you're up to.
  • groggorygroggory Posts: 205
    edited 2012-02-13 13:59
    turbosupra wrote: »
    This is actually for the propeller, the prop is going to be doing some control and helping the factory ecu

    Do you know of any ADC's that fit my request? 7 or 8 bit and will serial out in a single channel?

    Go look on the obex. There are some nice adc objects for the mcp3202/04/08 adc.

    However, from personal experience, you are going to want to toss those sensors on a scope to see how they behave before you just start blindly doing data capture.
  • turbosupraturbosupra Posts: 1,088
    edited 2012-02-13 14:48
    Will do, thank you!

    Before I read your post, I found this as well http://www.ti.com/lit/ds/symlink/ads7841.pdf but the mcp3204 looks like a better choice, especially if there is already code written! (and it does serial out, so I can use 1 pin for input :D )


    groggory wrote: »
    Go look on the obex. There are some nice adc objects for the mcp3202/04/08 adc.

    However, from personal experience, you are going to want to toss those sensors on a scope to see how they behave before you just start blindly doing data capture.
  • groggorygroggory Posts: 205
    edited 2012-02-13 14:52
    turbosupra wrote: »
    Will do, thank you!

    Before I read your post, I found this as well http://www.ti.com/lit/ds/symlink/ads7841.pdf but the mcp3204 looks like a better choice, especially if there is already code written! (and it does serial out, so I can use 1 pin for input :D )

    You'll want to use 3 pins. It works best over a SPI interface
  • turbosupraturbosupra Posts: 1,088
    edited 2012-02-13 20:48
    Thanks again for the direction groggory, after reading this and the link I found this does not seem nearly as overwhelming as it did earlier.

    I see, I knew it needed a clk signal, and I was hoping that if I had multiple ADC's/objects they could share that clk pin?

    I see from the object it asks for 4 pins but I guess you can tie Din and Dout together? When googling the datasheet I found this http://gadgetgangster.com/tutorials/382 which has a pretty straight forward and down to earth explanation, coupled with the introduction in the object, it doesn't sound like this will be to hard to implement? I also appears that you can piggy back the 1 ADC's CLK and CS pins so that each additional 3208 added would only require 1 additional pin usage?

    '' DTPin: outgoing (from µController) serial data pin (0-31); ignored if 1-channel ADC
    '' INPin: incoming (to µController) serial data pin (0-31)
    '' ClkPin: serial clock pin (0-31)
    '' RSPin: reset, CS pin (0-31)


    tut_analog_8.jpg
    groggory wrote: »
    You'll want to use 3 pins. It works best over a SPI interface
  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-02-13 22:46
    Share Clk and DI/DO. CS should be specific per-chip, though.
  • turbosupraturbosupra Posts: 1,088
    edited 2012-02-14 08:45
    Oh I see, pulling CS low will tell it to transmit over its Dout to the propellers input pin, and pulling it high tells it to stop transmitting, so all chips could share the same clock and same pin to send the propeller data, but the propeller tells them to send data, 1 chip at a time. Have I understood this correctly now?

    This makes sense because it allows the usage of a single cog to do this, instead of 1 cog per mcp3208?

    Circuitsoft wrote: »
    Share Clk and DI/DO. CS should be specific per-chip, though.
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