Glowing Light

Discussion in 'General Electronics Chat' started by mpeng1, Nov 6, 2013.

  1. mpeng1

    Thread Starter New Member

    Nov 1, 2013
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    This is a new post with the same question as my last post. It would seem that the prints that I attached with the old post did not go over too well with this forum and I am sorry for that. Please let me start over with different info to pass on.

    My question is: How is around 40vac being created to make the GHL light slightly light up when the only items that change on the print is (TS2) is closed and (B2) is opened? The GHL should only be getting power after the SSR contacts are closed.
     
  2. BillB3857

    Senior Member

    Feb 28, 2009
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    What kind of indicator is GHL? I would guess it is a neon. Otherwise it is probably a very low current incandescent. If B2 is open, the primary load is removed from the SSR and even though it should be open, there may be leakage current. With B2 closed, the heavy load of the heater will keep voltage developed by the leakage current to a very low level.
     
  3. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Did you manage to obtain the part number for the SSR?
    But it does appear that the leakage current of the SSR is capable of supplying enough current to make the lamp glow.
    Remember the output is a solid state device.
    I deciphered the original prints to a point.
    Max.
     
  4. mpeng1

    Thread Starter New Member

    Nov 1, 2013
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    GHL is a CML #1033QD5 neon 250v. The green ones have a built in resistor but the red ones do not. Makes no difference if the red or green one is connected, the light still glows a little.

    The ssr is a Crydom #A2450.

    The voltage pathway is as follows:
    L3 is at ssr #1 until the relay closes and then it moves on to the L3 side of the heater and the light. The L2 side of the heater gets power when B2 is closed. The light glows when B2 and the ssr are open. B2 does not feed the ssr.
     
  5. tcmtech

    Well-Known Member

    Nov 4, 2013
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    I am guessing the GHL is a mini neon with a rough breakover voltage of around ~40ish volts.

    Given that it is standard design to have a RC snubber across a SSR the small capacitor in the snubber will likely let just enough current through to dimly light the mini neon.

    A simple and cheap fix to keep it off would be to put a 100 - 200K 1 watt resistor in parallel with the B2 device contacts.
     
  6. MaxHeadRoom

    Expert

    Jul 18, 2013
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    A neon will pass enough current to light by connecting one side to the human body without detecting any effect, so in the case of your neon, it is not surprising.
    When B2 is closed, it, together with the grid Htr shunts any leakage current that may be causing the neon to glow.
    The bottom line is a Neon is a bad choice of lamp in the location it is in.
    Max.
     
  7. mpeng1

    Thread Starter New Member

    Nov 1, 2013
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    Fact 1:
    As far as I can tell this is not causing any problem with the operation of the machine and it is not common for the B2 to be open unless there is a problem anyway. In fact I may be able to use the dim light thing as a way of telling that the L2 breaker has opened.

    Fact 2:
    Since it is common for solid state relays to fail in the closed condition it was important for us to put the GHL in the location it is in. As part of the troubleshooting of the machine if the GHL is on and the machine is heating well past the set point value then it is known that either the temp controller or the ssr has failed (the controller has an ssr in it as well).

    Based on that info could you all recommend a better type of light for us to use in this location?
     
  8. MaxHeadRoom

    Expert

    Jul 18, 2013
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    That was my next question, it is aggravated by the fact a SSR is switched by another SSR!

    You can get an incandescent indicator light that has a small transformer in it in order to run a low voltage bayonet cap lamp such as made by Allen Bradley.
    You may also get a low voltage LED that with fit this socket, I believe some have rectification in them.
    I know you can get min. B.C. LED 120vac/dc, not sure about 240v?
    Max.
     
  9. mpeng1

    Thread Starter New Member

    Nov 1, 2013
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    It really depends on the machine that our customers order as to if the temp controller used is the type with an ssr or a mechanical relay built inside of the controller that we purchase.

    Even though we have been building machines like this for years we have just now started to put the line breakers in the last 2 units built and it has been since then that we have seen this dim light thing pop up.

    Does the current leakage happen on the coil side of an ssr or just the contact side? Does this happen with mechanical relays?
     
  10. MaxHeadRoom

    Expert

    Jul 18, 2013
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    It does not happen with mechanical relays.
    On a SSR you can have leakage on both sides under certain conditions.
    Generally most S.S. devices switching the input side of an SSR do not, or should not, pass any significant current when off.
    Incidentally did you try placing the GHL directly across the Grid Htr terminals and then measure any voltage?
    Max.
     
  11. mpeng1

    Thread Starter New Member

    Nov 1, 2013
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    Thanks Max I will have the shop make the next unit with the GHL L2 wire come out the breaker on the same side as the heater L2 wire and check things out from there but that does sound like a fix to this.

    I asked you about the other leakage stuff because the guy in the shop told me that on one occasion he forgot to hook up the T-Stat you see next to the temp controller and the same thing happed about the heat light except he believes the light turned on at full brightness.

    This was before the line breakers were being used so heater L2 was going thru a fuse back to power and the only item switched closed was the TS2.

    The T-Stat is a bimetal disc thermostat and with its lead not connected to the ssr #4 location the GHL turned on. Can you think of why this would happen?
     
  12. MaxHeadRoom

    Expert

    Jul 18, 2013
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    One possibility of GHL glowing is a slight ground leakage on the Grid Htr.
    This leakage may be too small to see any adverse affects other than the lamp glowing.
    It takes a very small current to light a Neon.
    Max.
     
  13. mpeng1

    Thread Starter New Member

    Nov 1, 2013
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    Thanks for all of your help on this matter. I will take the info and advice given and work on improving the assembly. The next time that I need to create a post to discuss I will try to remember to put my original drafts and not the shop prints on here to be looked at.

    Thank you all very much!!!!
     
  14. MaxHeadRoom

    Expert

    Jul 18, 2013
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    Yes, the ladder stye electrical design schematics are much easier to follow and trouble shoot with. even if you include the physical appearance of components rather than the logic symbol.
    The termination or physical layout can be drawn from this, if necessary.
    Max.
     
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