I need help to detect an AC burned heater element


Closed Thread
Results 1 to 16 of 16

Hybrid View

  1. #1
    Join Date
    Jun 2011
    Posts
    25


    Did you find this post helpful? Yes | No

    Default Re: I need help to detect an AC burned heater element

    Quote Originally Posted by Archangel View Post
    Hello igeorge,
    Could you elaborate a bit on the conditions you want to test the device? It seems you want / need to test during the welding operation. Can you install a tiny reed switch along the power wires? Honestly I do not know if a reed will activate on an A/C load wire, a coil like a Tape Head or a guitar pickup will. If you do not need to test during operation, then a simple continuity test should work, neon lights used to work very well for that.
    Thanks Archangel for reading my post and offer to help.
    Here are the conditions:
    I must check during the weld process, and i have to make sure that the current going through the wire is over 1 amp.
    I do not think the other solution is feasible, due to the number of wires involved.
    What i have in mind is to have a PCB for 16 heaters and bring the wire heater to it to one terminal, run a trace through some device to get the current, then get out on the next terminal and go to heater.
    Current transformers is not a solution, as they are bulky, not to many models PCB mount and i still need to interpret the reading.
    My option was for ACS712 , but if you look at the attached graph you will see that the output is + and -
    I need somehow to convert it, or do something that i will get only the + portion, but not pulsating, i need it as a continuous line.
    Also, i need that any voltage over 2.6 volts to be a logic 1 and any voltage from 0 to 2.6 to be a logic ZERO. In this case, i will have my inputs to PIC set to read 1 for a good heater, and 0 for a bad heater.
    Thank you
    Attached Images Attached Images  

  2. #2
    Join Date
    Aug 2006
    Location
    Look, behind you.
    Posts
    2,818


    Did you find this post helpful? Yes | No

    Default Re: I need help to detect an AC burned heater element

    Quote Originally Posted by igeorge View Post
    Thanks Archangel for reading my post and offer to help.
    Here are the conditions:
    I must check during the weld process, and i have to make sure that the current going through the wire is over 1 amp.
    I do not think the other solution is feasible, due to the number of wires involved.
    What i have in mind is to have a PCB for 16 heaters and bring the wire heater to it to one terminal, run a trace through some device to get the current, then get out on the next terminal and go to heater.
    Current transformers is not a solution, as they are bulky, not to many models PCB mount and i still need to interpret the reading.
    My option was for ACS712 , but if you look at the attached graph you will see that the output is + and -
    I need somehow to convert it, or do something that i will get only the + portion, but not pulsating, i need it as a continuous line.
    Also, i need that any voltage over 2.6 volts to be a logic 1 and any voltage from 0 to 2.6 to be a logic ZERO. In this case, i will have my inputs to PIC set to read 1 for a good heater, and 0 for a bad heater.
    Thank you
    Ok so I am thinking, use 2 diodes in parallel with their polarities reversed so there is a path for both phases, then only run the forward phase through the device.
    0 amps = 2.5v 1 amp or more, is above 2.7v.
    What do you think, will this work?
    If you do not believe in MAGIC, Consider how currency has value simply by printing it, and is then traded for real assets.
    .
    Gold is the money of kings, silver is the money of gentlemen, barter is the money of peasants - but debt is the money of slaves
    .
    There simply is no "Happy Spam" If you do it you will disappear from this forum.

  3. #3
    Join Date
    Apr 2006
    Location
    New Hampshire USA
    Posts
    298


    Did you find this post helpful? Yes | No

    Default Re: I need help to detect an AC burned heater element

    Hi igeorge,

    If you just need an un-calibrated “Go - No Go” measurement, a simple “peak detector” could work.
    If a silicon diode has too much junction drop, maybe a germanium or Schottky diode would work.
    Just a diode to a capacitor circuit on the output of the ACS712.

    Name:  PeakDet.gif
Views: 5514
Size:  2.1 KB-Adam-
    Ohm it's not just a good idea... it's the LAW !

  4. #4
    Join Date
    Jun 2011
    Posts
    25


    Did you find this post helpful? Yes | No

    Default Re: I need help to detect an AC burned heater element

    Hello Adam,
    Thanks for reply but i am afraid, like i mentioned before about the power dissipation on the diodes.
    I have to do some tests to see if it will work.
    Thanks
    Ion

  5. #5
    Join Date
    Apr 2006
    Location
    New Hampshire USA
    Posts
    298


    Did you find this post helpful? Yes | No

    Default Re: I need help to detect an AC burned heater element

    Hi Ion,
    You are right to be concerned with the several watts per diode dissipation with diodes passing Amperage..
    But I am proposing using them in the 5V output circuit of the ACS712.
    They would have almost no current. and would give your digital pin a 2.5V to 5V swing.
    If the peak Voltage was a little too high for your logic levels then add a “Voltage divider (= two resistors).
    -Adam-
    Ohm it's not just a good idea... it's the LAW !

  6. #6
    Join Date
    Nov 2003
    Location
    Greece
    Posts
    4,132


    Did you find this post helpful? Yes | No

    Default Re: I need help to detect an AC burned heater element

    Maybe a simple diode bridge with a optocoupler can give a low cost solution.

    Put the ac pins of the bridge in series with the element. Short the dc pins together.

    Put an optocoupler with a small series resistor in parallel to the ac pins of the bridge. Use a small integration of the pulses of the output optocoupler.

    You are done!

    Ioannis

  7. #7
    Join Date
    Jun 2011
    Posts
    25


    Did you find this post helpful? Yes | No

    Default Re: I need help to detect an AC burned heater element

    Adam and Ioanis, both of the solutions will works if i combine them. Optocoupler in series with heater is not feasible due to the amount of heat dissipation on the limiting resistor for the diode on the optocoupler. Also , as current varies from 0 to 5 amps, will be difficult to get a resistor value to light the led in the opto at everything over one amp, but do not fry the LED at 5 amps. Like Adam suggested, i will try to use the output from the ACS712. Here, i am going back to Ioannis advice to use an integrator to get a proper DC voltage out of the sine wave. From the DC voltage i need to use a comparator to get an output fro any voltage over 2.6 volts.
    Ioannis, do you have any schematic for an integrator which will works on the voltage diagram posted above.
    Let's say the Amps going through the heater are 5 A, so i will have a sine wave going up and down between +2vdc to +3vdc, where the 2.5 volts is the zero crossing point for zero amps. I need some kind of schematic to convert that sine wave to a dc line at 3 volts
    Best regards
    Ion

  8. #8
    Join Date
    Jun 2011
    Posts
    25


    Did you find this post helpful? Yes | No

    Default Re: I need help to detect an AC burned heater element

    Thanks Archangel,
    I do not know if it will works, but i will try it. I am some how concerned about the power dissipation as they are 5 amps going through the diodes, and they will be 32 on one PCB for 16 heaters. I will test and let you know.
    Thanks again
    Ion

Members who have read this thread : 0

You do not have permission to view the list of names.

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts