Ultrasonic Range Finder Project

Discussion in 'The Projects Forum' started by lio2000, Jun 1, 2011.

  1. lio2000

    Thread Starter New Member

    Jun 1, 2011
    I'm trying to build an Ultrasonic Range Finder as my graduation project
    I had some major setbacks for my main ideas for the project so for lack of time "since the deadline is near" I decided to use a ready model so I choose this model "since it is simple and straight forward "

    the reciver with the signal detector works fine
    but the transmitter circuit refuse to work when i tried to simulate it using Multisim v11.0
    it won't simulate "giving me an error without knowing where the error is"
    the photo for my circuit is below
    if the pic didn't open keep refreshing

    is everything right their?

    I think it is in the resistors but can't but my finger where the problem is exactly..
    I'm attaching the design file if someone using the programe

    thanks for your time
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Did you actually build this thing or are you just simulating it?

    I imagine the error is connecting the bottom output to the scope return.

    Don't do that.

    Forget about the cap, connect one output to Scope A, the other to Scope B, and see that they are out of phase. If they are you're good.

    (And while you're at it look hard at Q1 and Q2, they don't seem to be doing anything that a piece of wire can't.)

    You do know you can buy these things complete, right? Just stick one onto your micro controller? I know the Basic Stamp people have some, and lots of other people do too.
  3. lio2000

    Thread Starter New Member

    Jun 1, 2011
    I'm trying to simulate it..didn't reach the building process

    I did remove the cap. and the error still appears
    Error Message From Simulation: doAnalyses: Timestep too small
    Error Message From Simulation: tran simulation(s) canceled

    and if I changed the connection points from Q1 &Q2 the outputs from the inverters will be 1 always...and I want them out of phase

    I did re-simulate it using a program named "circuit wizard" and showed the current flow.. i saw all parts are working fine.. but the output from the circuit is 0

    any more ideas??

    the design of the circuit is in the pdf I added in the post.. i just need to verify the outputs before building my circuit on the test board
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    Ummm, make the Timestep larger? I don't use that simulator. I don't like simulators in general, I prefer excel and a breadboard.

    The inputs to Q1 & Q2 are out of phase. That's what makes the outputs out of phase. If I want a device with 2 out of phase inputs and 2 out of phase outputs I can build that with two pieces of wire.

    In fact, I just noticed this is built with 5 discrete CMOS gates, 4 resistors, 2 transistors, and that cap. Toss em all but the cap and get a hex inverter. You even get a spare inverter for your trouble, and 8 less power supply connections to make.

    Now don't get scared, but when I made an ultrasonic device controller I got my two out of phase signals from two pins off my micro and connected then direct to the transmitter. No IC, no cap, direct connection. Two pieces of wire period.

    See if that sims.;)

    You should know about the PING))) ultrasonic sensor. They used to have a schematic link there, I didn't find it today.
  5. lio2000

    Thread Starter New Member

    Jun 1, 2011
    sorry for the late reply:
    here is what's going on now:
    I switched from Multisim Simulator to circuit wizard
    So the transmitter finally worked
    the output is not to my liking...
    first: I noticed that the trigger in 555-timer "logically" is set to Don't care condition -have no effect over the timer-

    second: the variable resistor is not effecting of the output of the timer or the final output

    third:The output as not stable -has no periodic cycles-[considering that the output in the attached file in practical will be the combination of both signals in the chart-

    the receiver part is not bad
    almost working
    just trying to figure what the error "exp: overflow error" is means

    I have a feeling it is all in the resistors but can't verify that for sure
    any idea
    both circuits are added along with the results