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Tachometer with the BASIC Stamp — Parallax Forums

Tachometer with the BASIC Stamp

ottootto Posts: 5
edited 2006-07-05 21:00 in Propeller 1
I just recieved a BASIC Stamp at work and am trying to figure out how to wire it up to be used as a tachometer for measuring the RPM of our airplane props.· I have it wired up with a capacitor and a photoresistor and have the code written that measures the time it takes to charge the capacitor (which is directly affected by the change in resistance).· This is printed out to the screen in the debug window when I run the code, but what I would like to do ultimately is somehow store the data(sampled every millisecond) every 1 second and use my equations to convert the data to RPM.· I would like for all the measured data to be stored somewhere and be accessable(like in a text document maybe), but also would like to have each second's worth of data used to compute an RPM and read it out to the screen so that i have a continuous reading of RPM.· The prop will be spinning at about 10,000 RPM.· Like I said though, I am new to the BASIC Stamp and don't really know the language, so if anyone has done this before or knows how it could be done, I am open to any help.· Thanks.

Comments

  • El PaisaEl Paisa Posts: 375
    edited 2006-07-05 14:20
    Are we talking about the same propeller?
  • ottootto Posts: 5
    edited 2006-07-05 14:32
    The propellers we are using are all the same for now and have two blades, but the equations for conversion should be able to be simply altered if we ever switched to a 3 blade prop. I will try to better explain exactly what I am doing also so we can be on the same page, so here goes. I will rig up the circuit so that a light will be positioned over the photoresistor. When the light intensity increases on the photoresistor, its resistance decreases, this will make the capacitor charge faster. As each blade swings in front of the light, a shadow will go over the photoresistor. This will decrease the light intensity and cause the resistance to increase, causing the capacitor to take more time to charge. So the data being read out is the capacitor charge time and it will look like a bunch of 1's with higher numbers every time a shadow passes by. I will take the number of spikes every second (higher numbers from the shadow) and use something like this equation to solve for the RPM:
    RPM = (# of spikes/sec)*(rev/# of spikes)*(60 sec/min)

    Does this help better explain what I am doing? Thanks again.
  • El PaisaEl Paisa Posts: 375
    edited 2006-07-05 14:52
    We are talking about two different propellers.
    Airplane propellers and Parallax Propeller.
    Seems you are in the wrong forum. Try the Basic stamp forum·
  • ottootto Posts: 5
    edited 2006-07-05 14:56
    I'm an idiot. Thanks.
  • CJCJ Posts: 470
    edited 2006-07-05 21:00
    not a true idiot, you have error handling routines

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Who says you have to have knowledge to use it?

    I've killed a fly with my bare mind.
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