Trying to fluxuate a voltage signal

Discussion in 'Homework Help' started by act4leader, Mar 12, 2011.

  1. act4leader

    Thread Starter New Member

    Mar 12, 2011
    Hey all. I am trying to work on a real life simulator for a magnetic pickup without using an actual working motor. Currently I am trying to simulate a pump jack rpm speed sensor and have no problem using a 12-17 volt supply to simulate the speed sensor. What I need help with is I want to show the "speed signal" fluxuate so that my demonstration can show my motor slowing down and even stopping without having to open the door and remove the power supply. Also, this would be used to simualte the motor warming up and picking up speed. Is a potentiometer the way to go with an added resistor to dial in the speed I am looking for? Or is there another device out there (cheap) that I can use to change the voltage and speed signal? So no matter what the speed signal is showing I can change the rpm count by changing my teeth count, what I need is the best way to fluxuate the power signal with a rotating positional arm liek that of a potentiometor or reostat. Thanks for all your help.
  2. Kermit2

    AAC Fanatic!

    Feb 5, 2010
    This needs more details. Check a dictionary for the words you want to describe the process. I can't figure out what it is you want exactly

    How exactly should the 'device' SHOW the fluctuation in speed? With a blinking light, with display of numbers(amp or volt meter). Using a pot. in series with the motor current means you need a heavy duty(expensive) rheostat. Regular 1/8 W pots will 'smoke' with large current flows through them.

    Changing the teeth count? are you using a hall effect device?

    More detail of your project and how it operates is needed, as well as a better description of what exactly you want us to do for you.
  3. Adjuster

    Well-Known Member

    Dec 26, 2010
    Yes, this is too hard to understand. Could you please post a schematic diagram of what you are trying to do.

    Are you trying to simulate the signal from the sensor by using a potentiometer? That might be practicable.
  4. act4leader

    Thread Starter New Member

    Mar 12, 2011
    Ok sorry for the confusion. I am working with an Arrow Autostart device that monitors a Arrow C- Series motor for high/low speed, temp, oil presssure, oil level and an Emergency Shutdown System.

    This autostart device is now a digital system that actively shows the RPM of the motor and set points can be programmed to show warming up, running, high speed and over speed.

    I am trying to set this autostart device to be able to demonstrate its usefullness to other potential customers and current customers on its new abiliites without taking loads of people out into the oilfield where the device will be use.

    Currently we are using a 6 volt dc constant power supply to simulate the speed sensor from the magnetic pickup and as it is set shows 735 rpms at 6 volts dc.

    So my original question should have been what device can I use to manually dial in 0-6 volts dc to show a simulated rpm of a starting engine to running engine to an overspeed engine?
  5. GetDeviceInfo

    Senior Member

    Jun 7, 2009
    we need to find out if your sensor translates rpm into voltage, or is it frequency. If it's sensing a magnetic pickup, you'll need an adjustable oscillator. An astable multivibrator based on the 555 timer should do fine.

    This statement needs to be flushed out a bit. A magnetic pickup is a pulsed signal, while your dc supply is constant, and should read 0 rpm. An rpm reading at 6 vdc as you've stated, indicates a voltage input, in which case you need to find out what is your full scale input, then divide that with a poteniometer for variance.

    Can you provide us with specs for the monitor?

    I think I just looked at them. Google 555 astable for basic variable frequency circuits. Your output from the timer will drive a transistor that switches your sensor leads.
    Last edited: Mar 12, 2011
  6. Adjuster

    Well-Known Member

    Dec 26, 2010
  7. beenthere

    Retired Moderator

    Apr 20, 2004
  8. mjhilger


    Feb 28, 2011
    If you have access to and minimal knowledge of PIC's you could use one with the PWM to generate your output voltage (you would need to throw a few parts to low pass and perhaps an OP-AMP to get your 6v out). Maybe $10 - $15 and and 1 to 2 hours work if your are a little familiar with PIC's. I still don't understand if you want to manually adjust, or if you want the device to behave on its own, the PIC could be used either way with a few lines changed in the code.
  9. Adjuster

    Well-Known Member

    Dec 26, 2010
    Last edited: Mar 15, 2011