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Ultrasonic Range Meter

Discussion in 'Electronic Basics' started by roots_of_culture, Mar 27, 2006.

  1. Hi,
    I am trying to build an ultrasonic range meter using an AU5550
    (http://www.jaycar.co.nz/products_uploaded/AU5550.pdf) - 40 khz
    transducer. i am using the pic16f877a to send the 40 khz pulse to the
    transducer, 12v supply.

    -- I realise that i need to use P/N channel hexfet power mosfet totem
    pole, but i am stuck at which driver to use and how.

    -- Other Driver Ideas....Circuits...
    Any and all sorts of help appreciated.
     
  2. Nav2u

    Nav2u Guest

  3. Stef Mientki

    Stef Mientki Guest

    Why 12V supply ?
    In my opinion 5V is enough,
    take a look here
    http://oase.uci.kun.nl/~mientki/pic/projects/rapid_prototyping/rapid_prototyping_us_ranger.html

    Stef Mientki
     
  4. Nav2u

    Nav2u Guest

  5. Why 12V supply ?
    Im looking for a range of about 10cm- 6m, and i didnt think that a 5V
    supply would be enough to drive the transducer hard enough to get the
    range i desire.
    And specifically 12 v supply, because i am using a 12 v car battery.

    And i was also thinking that i will need a voltage regulator after the
    12V battery, which will then leave me with a voltage of around 10.5 V.

    i would like to use a driver circuit because the transducer is highly
    capacitive and i didnt think i would be able to get sharp rise and
    falls in the pulses i wish to transmit otherwise.
    In the schematic below i have used schimdt trigger chip. But i want to
    use a driver chip, something apart from the schimdt trigger.
    (http://navdeep2u.googlepages.com/transmitting.JPG)
     
  6. Chris

    Chris Guest

    Hi, Roots O' Culture. Your transducer can be seen as a capacitive
    load. You're basically trying to do this (view in fixed font or M$
    Notepad):

    |
    | .---------------.
    | | |
    | | | 5V-to-12V
    | | | Level Translation/
    | | | High-Current source/sink
    | | | Buffer
    | | | (Non-Inverting) |.--.| (Inverting)
    | | | |\ || || /|
    | | PIC o----o-----| >-----|| ||-----O< |---.
    | | | | |/ || || \| |
    | | | | |'--'| |
    | | | | Transducer |
    | | | | (1800pF) |
    | | | '-------------------------------'
    | | |
    | | |
    | | |
    | '---------------'
    |
    (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

    Since you're already going with a PIC, Microchip has a pair of drivers
    that will do exactly what you want -- the TC4420 (non-inverting) and
    the TC4429 (inverting) high speed MOSFET drivers. They have the
    capability to drive up to 6 amps with low Rds(on) MOSFETs built in, and
    the IC takes care of the level translation for you. Put one on each
    side of the transducer, and you're good to go. They're made to drive
    capacitive loads, and have crossover protection built in. They'll
    smack that T/R40-16B around real good (140 volts max!?! Is that an
    aluminum, steel, or titanium case?).

    Unless this is a high volume application, I don't think you're going to
    be able to do better than this. The ICs are available in 8-pin DIPs,
    too (CPA suffix).

    Here's the datasheet:

    http://ww1.microchip.com/downloads/en/devicedoc/21419c.pdf

    If you want to be really safe, add a 2.2 ohm non-inductive resistor (a
    1 watt carbon comp is good here) in series with the transducer to limit
    maximum current doesn't exceed 6A.

    |
    | .---------------.
    | | |
    | | | 5V-to-12V
    | | | Level Translation/
    | | | High-Current
    | | | Buffer
    | | | (Non-Inverting) |.--.| (Inverting)
    | | | |\ || || ___ /|
    | | PIC o----o-----| >-----|| ||--|___|----O< |---.
    | | | | |/ || || 2.2 ohm \| |
    | | | | |'--'| |
    | | | | Transducer |
    | | | | (1800pF) |
    | | | '-------------------------------------'
    | | |
    | | |
    | | |
    | '---------------'
    |
    (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

    On the power supply end, the TC4420 and -29 are good to 18V, so you
    shouldn't need another regulator. You also want to maximize voltage.
    I'd recommend using another 2.2 ohm series resistor or choke and a
    large (2200uF or greater, 25WV) cap with a Transzorb for a localized
    charge source and to protect against load dump.

    |
    |Battery ___ To XDCR Power
    |B+o----|___|--o---o->
    | 2.2 ohm | |
    | +| /-/
    | 2200uF --- ^ P6KE16A
    | 25WV --- |
    | | |
    | | |
    | === ===
    | GND GND
    (created by AACircuit v1.28.6 beta 04/19/05 www.tech-chat.de)

    Good luck
    Chris
     
  7. Chris,
    Thanks, that has solved my transmitting circuit.

    Andrew,
    you are right TC4420 is not available at hand locally, but Farnell (
    $4.40) delivers within 3 days, so that is good.
    Though in order to get going im using the TC4428CPA, it has a low
    Rds(on) 40 ns.

    As for the recieving circuit, i saw a design from national in the
    Electronic Design (jan 2006) journal. it uses a 2 stage LMP7711 (17MHz)
    as active filters (band pass), with a gain of 100 * 10, but these are
    not available locally either. I am trying to find substitutes.
     
  8. Mebart

    Mebart Guest

    On 28 Mar 2006 01:38:52 -0800, "roots_of_culture
    <
    wrote
    My receiver is a POS affair without automatic gain so I've set th
    transmitter PIC to be able to PWM at two different rates and as ye
    the bandpass filter eludes me (rank novice). Need to do more researc
    when I'm fresh. I'm using the Dual LM833N 8pin DIP (Min 10MHz, Ma
    15MHz), high slew rate. I'll have a look at the LMP7711 too

    Regards

    Andrew
     
  9. Chris

    Chris Guest

    HI, Andrew. The sun never sets on Farnell (I'm in the States -- it's
    Newark here). Unfortunately, the Farnell website is being updated.
    But looking at the Newark site, it seems they have the same issue.

    You may want to try the TC4426 (dual inverting) and TC4427 (dual
    non-inverting). You'll have to leave half of each chip dormant, unless
    you have something else to do with them. To my recollection, you can't
    parallel outputs safely.

    The datasheets for the TC4426CPA (8-pin DIP, commercial temp range) and
    TC4427CPA are available at the Microchip website:

    http://ww1.microchip.com/downloads/en/devicedoc/21421d.pdf

    The datasheet says they're rated for capacitive loads, and after all,
    this isn't continuous use. You're only snapping the transducer a
    couple dozen times, eight to twelve times a second. You really
    shouldn't need a series resistor with the transducer unless you're
    really cautious, especially considering the Rds(on) is typically 7 to 8
    ohms. But by rounding the edges of the transition with the additional
    Rds(on), you're losing some power.

    http://ww1.microchip.com/downloads/en/devicedoc/21422d.pdf

    Good luck
    Chris
     
  10. Rubicon

    Rubicon Guest


    Chris,

    Great diagrams and advice. I've been trying myself to create a simple
    but "as long a range as I can get" ultrasonic remote control using the
    same transducers and 16F628A PICs. The transmitter uses an AND gate to
    switch a 100V N-mosfet with the transducer, 1000uH inductor and a
    100ohm resistor. At 9.5V, 60% duty cycle sending two bytes over and
    over at 300bps it does work up to approx 11 meters from the receiver.
    I'm working again on a bandpass filter for the receiver and once I
    figure that out I'll need help hopefully from the members of this
    group to get an automatic gain cirucuit built. The last time I fiddled
    with bandpass filters I cut the range down to two centimeters! Not
    much of a remote then!

    The initial link that roots_of_culture provided for the transducer PDF
    is a Jaycar branch in New Zealand and assuming that he too lives here
    then acquiring the drivers may be a problem for both of us.

    For roots_of_culture - one company, South Island Components, is
    trade/retail has only the TC4429CPA but doesn't stock the 4420 while
    other retail outlets like Jaycar, Dick Smith and Altronics don't stock
    them or any of the range at all. RS components deals with the trade
    and requires a company account to be opened but they do have the:
    TC4421CPA - 9A Single Inverting
    TC4426CPA - 1.5A Dual Inverting
    TC4427CPA - 1.5A Dual Non-inverting
    TC4428CPA - 1.5A Combined Single Inverting and Non-invereting
    TC4429CPA - 6A Single Inverting
    (Note - RS sells the TC4429CPA for NZ$10.70 + GST eachwhile South
    Island Components sells them for NZ$5.48 + GST)
    Other than trying a few more companies I've found online in the Yellow
    pages there's Farnell in Australia I suppose. Should my assumption be
    correct and you do find a source for the TC4420 in NZ could you please
    post it in this NG as I'd greatly appreciate that.

    Regards

    Andrew.
     
  11. Rubicon

    Rubicon Guest

    My receiver is a POS affair without automatic gain so I've set the
    transmitter PIC to be able to PWM at two different rates and as yet
    the bandpass filter eludes me (rank novice). Need to do more research
    when I'm fresh. I'm using the Dual LM833N 8pin DIP (Min 10MHz, Max
    15MHz), high slew rate. I'll have a look at the LMP7711 too.

    Regards,

    Andrew.
     
  12. Rubicon

    Rubicon Guest

    On Wed, 29 Mar 2006 08:14:52 GMT, (Rubicon) wrote:

    First off it was rude of me not to thank you in my last post for the
    Farnell source confirmation - Thanks.

    Secondly where did you get that Electronic Design Jan 2006 publication
    from? I've looked on the net, found its publisher (Penton
    Publications) and searched the CHCH city libraries to no avail. The
    Electronic Design website is only a front page that constantly reloads
    itself. The Europe one wasn't helpfull either.

    Regards,

    Andrew.
     
  13. I only today noticed that Radio Shack is selling a completed
    ultrasonic ranger as part of the VEX robotics stuff they sell.
    Everything is "half off" until June, I'm told. The ranger is normally
    $29.99 but is now selling for $14.99. It uses 5V supply and 3cm to
    300cm ranging with 40kHz. Paperwork says it uses a 10us pulse; but
    with a 25us single cycle width I doubt this spec. I might believe
    100us, though, or 4 cycles. (Their minimum distance of 3cm
    corresponds to a trip time of 175us.) Comes with screws for mounting
    and a nice enough enclosure.

    Just to let you know...

    Jon
     
  14. Rubicon

    Rubicon Guest

  15. Guest

    Hey Chris,
    I'm doing a project on ultrasonic ranging too and the desired distance
    is 50m. It seems rather far and I wonder if TC4420/4429 could help? And
    can you explain how these things work cos I'm really confused about how
    6A would help driving my transducer. :-/
    Thanks
    Martin
     
  16. Martin

    Martin Guest

    Hey Chris,
    I'm doing a project on ultrasonic ranging too and the desired distance
    is 50m. It seems rather far and I wonder if TC4420/4429 could help? And
    can you explain how these things work cos I'm really confused about how
    6A would help driving my transducer. :-/
    Thanks
    Martin
     
  17. Hi, Martin. I'm no expert on this stuff, but am generally interested.
    But it seems to me that 50m really is a far distance. Two problems
    pop into mind -- (1) energy spreads out (ignoring dissipation of
    energy at 40kHz in air) at D^2 and returns with another D^2 factor, so
    this suggests to me a D^4 hurdle to overcome and that would mean a lot
    of initial energy (read as very high driving voltage) to get there;
    and (2) reasonable resolution over that kind of range seems vaguely
    problematic, too. I also don't know what the attenuation of the usual
    40kHz is in (wet) air or if there are better or worse bands nearby you
    might prefer. I wonder if there is a page documenting it over
    frequency...

    Have you found any existing ultrasonic ranger that works at 50m?

    Jon
     
  18. Martin

    Martin Guest

    Hi Jon,
    I think 50m is way too far too actually. There's this paper on
    ultrasonic ceramic transducers on
    www.senscomp.com/specs/piezo%20application%20note.pdf and it explains
    all the losses and such.
    For a 100V pp driver with a transducer's SPL of 108dB and the
    receiver's sensitivity of -75db, according to my calculations, the
    voltage at the receiver at 50m is about 0.2uV :)) With the help of a
    cone I think this could get up a bit but still... Do you think I can do
    anything with this?
     
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