Hall Effect switch logic output

Discussion in 'The Projects Forum' started by mkenney, Feb 14, 2009.

  1. mkenney

    Thread Starter Member

    Feb 14, 2009
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    Hi all. I'm a newbie and recently found this forum. I really tried to search on my issue and was unable to find a solution. Here is my issue:

    I'm trying to use a Hall effect switch (US5881) as a home/limit switch on my mini-milling machine that I recently converted to CNC. The input voltage is 5 volts and with the 10k pull-up resistor connected per the 12.1 wiring diagram. What I'm seeing on the output side is .535 Volts when on and .022 Volts when the magnet is close enough to trigger the switch. From what I understand from the break out board that I'm using is that off is .8 Volts or leass and on is 2-5 Volts. I tried decreasing the size of the pull up resitor and ended up frying the hall effect switch.

    I'm not sure what I'm doing wrong as it seems like a lot of people are getting this to work with just a 1k pull up resistor and nothing else (i.e. the capictor's) that I'm using.

    I hope I'm posting the info needed for someone to help me out if willing.

    Thanks in advance and great to see such a great resource for electronics on the web!

    Mark [mkenney]
     
  2. beenthere

    Retired Moderator

    Apr 20, 2004
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    From the data sheet, I can't see why you're having a problem. 5 volts is inside the limits for supply voltages. I wonder, though, if you might have some stray magnetism around. Can you wire up a spare to ground and +5 at some distance from the mill and check operation with the 10K pullup resistor? All you need is a magnet and a meter. The output should be +5 away from the magnet, and 0 volts when the magnet gets close.

    If the sensor works away from the mill, move it where you intend to mount it, and see if the sensor still works. If you have got it close to an existing magnet, like one of the stepper motors, then it may be in saturation all the time - at least that is what it sounds like.
     
  3. mkenney

    Thread Starter Member

    Feb 14, 2009
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    I have it bread boarded out now and have even tried it in different rooms. I still see the away from magnet as .535 volts max and then .022 Volts when I put a magnet near it. I'm really confused as I can't figure out where the missing 4.5 volts is going too???

    Thanks for looking at it, very appreciatted and hopeful I can get this working while I still have some hair left:)

    Mark [mkenney]
     
  4. beenthere

    Retired Moderator

    Apr 20, 2004
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    Got another one? It is possible to get a defective unit. Also, verify the pins and orientation of the device.
     
  5. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Did you try bothe ends of the magnet (north and south) ?
    The sensors seem to be sensetive for the different directions.

    Greetings,
    Bertus
     
  6. mkenney

    Thread Starter Member

    Feb 14, 2009
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    I went ahead and tried another sensor and had the same result. Confirmed that I'm using the south pole and that it will ignore the north pole. It seems to be working fine as far as the magnet goes since the voltage drops to .022 every time a put the magnet close to it. As soon as I remove the magnet it goes up to .535 volts which doesn't seem like it is enough voltage for the board to read as a 1 from what I can gather.

    Checked again that I have the pins correct, already burnned one up by not last night:(

    I tried to take a picture of my actual circuit to see if that would help. Not the best but worth a try and I'm attaching it...

    (Green wire the output, read and yellow are +5Volt, Orange goes to the ground strip.)

    Mark [mkenney]
     
    Last edited: Feb 14, 2009
  7. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    Do you use a resistor (100 Ohm if I see it correct) from the device to + 5Volts ?
    Wich schematic are you using ?

    [​IMG]

    Greetings,
    Bertus
     
  8. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    Did you try a 1k pullup? Your interface board appears to require as much as 1.1mA, which you won't get from a 10k resistor, although you should be getting more than 0.535V.
    Are you measuring from GND to output?
    You shouldn't need the 4.7nF capacitor.
    Are you operating in the presence of a strong AC magnetic field?
     
  9. mkenney

    Thread Starter Member

    Feb 14, 2009
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    0
    I do have the 100 Ohm in now, just for testing. I started with the 12.1 circuit and am kind of using a little from the 12.3 (admittedly without the knowledge to know what I'm doing:)

    I don't have a strong AC field from what I know and get the same result in different areas of the house.

    I tried the 1k pull up and the values changed to (.600 volts without a magnet and .055 volts with the magnet). Seems to go in the right direction but figure I can't just keep dropping the resistor value or I'll end up frying the chip again, is this correct?

    If I leave everything as is and pull the hall effect sensor out of the circuit, the ouput goes to 5 volts. Does this mean that the sensor itself is the guilty party of taking away the voltage?

    Thanks again for the help!!!!

    Mark [mkenney]
     
    Last edited: Feb 14, 2009
  10. bertus

    Administrator

    Apr 5, 2008
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    Hello,

    What happens when you change the 100 Ohm to a wire (as in 12.1)?

    Greetings,
    Bertus
     
  11. mkenney

    Thread Starter Member

    Feb 14, 2009
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    The voltages went to .538 and .023 when I removed the 100 ohm resistor. Almost bald now trying to get this thing to work:)

    Mark [mkenney]
     
  12. kubeek

    AAC Fanatic!

    Sep 20, 2005
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    Are you sure you have it connected right? The bottom pin on the photo is GND, the middle OUT and the top is VDD. To me it looks like the middle is connected to VDD and you try to use the output of the top pin.
     
  13. mkenney

    Thread Starter Member

    Feb 14, 2009
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    Just a bad photo:) The top is connected to 5volts directly. The middle is connected to 5Volts thru the 10k pull up resistor. The green wire that I'm measuring on is connected to the middle pin.

    Mark [mkenney]
     
  14. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    I don't see it that way.
    Mark, what are you using to provide +5V?
     
  15. mkenney

    Thread Starter Member

    Feb 14, 2009
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    Right now I have a 78L05 stepping down a 9Volt battery. Attaching a picture...

    Mark [mkenney]
     
  16. jpanhalt

    AAC Fanatic!

    Jan 18, 2008
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    What are the voltages measured at Pin 1 of the Hall sensor when it is turned on and off?

    John
     
  17. mkenney

    Thread Starter Member

    Feb 14, 2009
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    When turnned off (no magnet) I read 4.763 Volts. When magnet turns it on I get 4.739 Volts.

    Mark [mkenney]
     
  18. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    If I had this problem, I would give up for today, get a good night's sleep, and get up on the other side of the bed tomorrow.:D
    Then I would look closely at the label on the package to make sure it's the right part number, and then try as many ICs as I have, or until I find one that works.
    They may be very sensitive to static discharge. Are you taking the standard steps to protect them from this?
     
  19. mkenney

    Thread Starter Member

    Feb 14, 2009
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    Tried to touch somwthing to ground myself but it was a very static rich day now that you mention it. Lots of shocks when openning doors etc. Hopefully these things are robust enough as they are intended to be on a milling machine.

    Stupid question, is it possible that it is working within the specs it is supposed to? It does reliably vary outputs between the .5volt and .022 volt, just not enough voltage to trigger the break out board. Is there something I can do to boost the signal for the break out board or something like that?

    Thanks again for the help!!!!

    Mark [mkenney]
     
  20. Ron H

    AAC Fanatic!

    Apr 14, 2005
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    The part is definitely out of spec, unless your controller board is loading the output. Have you tested it with the green wire disconnected?
    Do you have the ground of the Hall effect device connected to the ground of the controller board (you should!)?
     
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