Shop OBEX P1 Docs P2 Docs Learn Events
hall effect device — Parallax Forums

hall effect device

CheechCheech Posts: 30
edited 2005-07-24 05:42 in BASIC Stamp
Threw a glitch with Currie tech's Tech support, I ended up with a free throttle for my electric scooter (when all I wanted was a gear!).· Anyways I decided to put it to good use with my stamp, but first I need to figure out what makes it tick.· I took it to my neighbors house and he said it looked like a hall effect device because it had a stationary sensor and a magnet that moves with the throttle which expose to the sensor the two poles and everything in between.··He said·if he remembers right it generates voltage that is proportional to the pole and strength of the magnet,·however he could not explain why it had·three wires coming out of it, or·the specifics on how it worked.· So I ask you guys, how does this magic sensor work, and how can I use it with my stamp II?·

Comments

  • KenMKenM Posts: 657
    edited 2005-07-22 02:18
    If the sensor has three wires it the likely case·that one wire is positive supply, one is ground and the other is a signal.

    It is likely the signal wire is producing a pulse from 0 volts to 5 volts as the magnet moves past the sensor.

    Connect a volt meter between a ground and probe each wire one at a time while slowly turning the device with the magnet.

    One wire will likely registor zero volts (your ground), one wire will likely measure 5 or 12 volts (the power), and the last wire might measure 0 volts and 5 volts alternately as you slowly rotate the magnet.

    If that is the case, the stamp can measure the number of pulses in a given time period, or measure high time of the pulse, or the low time of the pulse.....all of which can be translated into angular velocity of the rotating component.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Ken

    Post Edited (KenM) : 7/22/2005 2:50:54 AM GMT
  • CheechCheech Posts: 30
    edited 2005-07-22 02:26
    So any ground? I could ground it to my computer case for instance, and just use the postive lead to test each wire? If it needs a supply voltage to work then how would I get voltage just by putting the magnet next to it? Im still new at this, but I think the ground has to tie into this somehow..
  • KenMKenM Posts: 657
    edited 2005-07-22 02:28
    Is this device hooked up or wired to anything at this time?

    Are there any numbers on the device....what is the entire number?

    Can you take a close up picture of the device and post a jpg?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Ken
  • CheechCheech Posts: 30
    edited 2005-07-22 02:35
    Sure can:
    Picture.jpg
    679 x 479 - 274K
  • KenMKenM Posts: 657
    edited 2005-07-22 02:46
    The picture certainly looks like a hall effect switch. The numbers look like AN502 ??? But a google search did not find what I was looking for....

    I am very confident that device has a ground, a positive supply and a signal wire. To determine who is who I would do the following.

    Connect the negative lead of your meter to the left lead, then the positive lead to the other two while slowly moving a magnet across the device (yes you need three hands).
    Repeat the same with the negative on the center and right leads.

    One of those combinations should yeild +5 volts or + 10 (assume 5 for now) and not vary as the magnet is moved across the device.

    Once you get the +5 volts you have identified the ground (negative lead of meter) and positive. The remaining lead should alternate between 0 volts (actually maybe 0.2 or something) and +5 (or +10 or so), and that is your signal. I explained earlier what stamp commands can be used to read the signal.

    Write back if you have more ??

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Ken
  • CheechCheech Posts: 30
    edited 2005-07-22 02:56
    Thank you Ken, unfortunately I don't have a multimeter with me so I cant get you an answer until tomorrow. Just for clarification: When I figure out all the wires, I would run 5 volts threw it to power it, and depending on what pole it detects, the pulse count varies? So lets say at the neg pole its 2 PP/S and at the positive you might expect 100 PP/S (I'm just making up units and values here)?
  • KenMKenM Posts: 657
    edited 2005-07-22 03:15
    Hard to say exactly without knowing what device it is. The picture (or my eyes) are a little fuzzy, what are the letters and numbers on the device?
    Cheech said...
    Thank you Ken, unfortunately I don't have a multimeter with me so I cant get you an answer until tomorrow. Just for clarification: When I figure out all the wires, I would run 5 volts threw it to power it, and depending on what pole it detects, the pulse count varies? So lets say at the neg pole its 2 PP/S and at the positive you might expect 100 PP/S (I'm just making up units and values here)?
    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Ken
  • CheechCheech Posts: 30
    edited 2005-07-22 03:22
    I got the same numbers as you. I was just trying to wipe away any confusion on how this device should function. (ps check your pm's)
  • YanroyYanroy Posts: 96
    edited 2005-07-22 18:18
    My experience with hall effect sensors (using them as current sensors) tells me that you aren't likely to get a pulse output from this device... unless there's some nice signal processing circuitry somewhere.· The hall effect sensor itself gives a voltage that is proportional to the magnetic flux density.· Without amplification, this voltage will be very small... probably on the order of millivolts.· The sensor (or a nearby piece of circuitry) likely has an amp in it.· Whether or not it converts the signal to a pulse train is something you'll have to figure out for yourself.
  • CheechCheech Posts: 30
    edited 2005-07-23 02:46
    Well I did some more playing today and found out that with 5v going to it, I can get it to range from 2 to 5 ish volts roughly depending on where I put the magnet. I looked up some of these things in digikey and I think what I am going to do is replace it with one that I KNOW what it has in it, and it will have a digital output. Now for the new part I have a few easy questions before I order:
    In the part description it says "Panasonic’s Hall IC is a combination of a Hall element, amplifier, Schmidt circuit, and stabilized power supply/temperature compensator integrated on an identical chip by using the IC technology. It amplifies Hall element output at the amplifier, converts into a digital signal through the Schmidt circuit, and drives the TTL or MOS IC directly."

    Ok, my questions are, what TTL or MOS IC? And what is the difference between an open collector and a pull up resistor, and what one would I want to use with my stamp?
  • CheechCheech Posts: 30
    edited 2005-07-23 18:22
    Ack, after reading up on Schmidt circuits, I think I just ordered a useless sensor. A hall effect IC with one of those on it would either tell me that there is or isn't a magnet, and no in between, which could explain why I got variable voltage reading opposed to on/off +5 v that you would expect to see form a digital IC. So is this true? If so, good thing its saturday, I can still cancle my order.
  • KenMKenM Posts: 657
    edited 2005-07-24 05:42
    What is the part number of the device you ordered?

    What exactly do you want to do with the sensor, sense the rotation speed of an shaft...or?

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Ken
Sign In or Register to comment.