Automotive Charger/Booster

Discussion in 'Power Electronics' started by Vigge, Feb 5, 2018.

  1. Vigge

    Thread Starter New Member

    Feb 5, 2018
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    Hi
    I need help identifying a problem with this battery-charger/booster
    Owner changed an faulty resistor (Burned) on the circuitbord.
    Not sure what size. He chose a 82 Ohm resistor because he thought they looked simulor.

    I can find no faulty components.
    Problem is I do not have more than 17 VAC at D2. Not enough to activate the DIAC and hereby the TRIAC.

    This is some old equipment and no data is available. 1986 as far as I can tell.
    I did my best to draw the schematic
    I am not strong in calculating AC currents.

    Hopefully someone can help. Maby even point out a flaw I have not seen.

    [​IMG]

    Simplyfied

    [​IMG]
     
  2. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    There are errors in the diagram.
    The 470uF value is definitely wrong. I expect it is 0.47uF.
    The two 470k pots seem wrong. Could they be 470Ω?

    [EDIT] Is the charging timer some kind of mechanical timer which operates S2 at the end of the timing period?

    [EDIT2] What is the part number on the opto-triac?
     
  3. Vigge

    Thread Starter New Member

    Feb 5, 2018
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    You are absolutly right about the 470uF being 470nf
    I labeled it wrong

    The two resistors though are both 470K
    Charging timer is a mechanical timer NC when counting.

    I have updated the schematic

    [​IMG]
     
  4. Vigge

    Thread Starter New Member

    Feb 5, 2018
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  5. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    OK.
    I think the 82Ω is a not unreasonable value for that resistor.
    A fault caused the original resistor to burn up.
    Has the new resistor burnt or is it still OK?

    I suspect that the original fault may be that the main triac is faulty - open circuit.
    This would cause damage if the 'amp adjusting' pot was set to a very low value (maximum current) and might also have damaged the diac and possibly C1.
    Neither the diac nor the triac are easy to test.

    The link below describes how to test a triac however it is wrong! The multimeter check is OK, but it doesn't test whether the triac can be triggered. The circuit with the lamp is OK except that when you press the button the light should be come on but when you release the button the light should stay on.

    To test the diac you need a DC supply of 40V to 50V, though a multimeter will verify that it is not shorted (it should read open circuit on the ohms or diode test setting).
     
  6. Vigge

    Thread Starter New Member

    Feb 5, 2018
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    C1 has been changed once before. Still seems fine it tests 472nF
    New resister still intact. The whole thing has not worked since it been changed.
    Before the old resister burned it would charge fine,and only burn when charging at max current.
    (apparently it has been changed more than once!!)

    Main Triac might be faulty. I have not testet it so far.
    Reason being it does not get a signal from the Diac ( Only 17VAC before the Diac)
    I will test these as soon as possible.
    I`m not sure but I think the main Triac gate -signal is 12V max !! Can you confirm?
    http://www.datasheetspdf.com/pdf/614055/TagSemiconductors/T2513BK/1
     
  7. AlbertHall

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    Jun 4, 2014
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    That 17V is why I suspect the diac may be damaged.
    In the table below, from the datasheet, the figure for gate trigger current is the current which is guaranteed to trigger the triac for each quadrant. The VD figure is the voltage between MT1 and MT2 at which those gate currents are specified. If you look at the next line it says that 2.5V on the gate will trigger the triac in all quadrants with that same VD.

    upload_2018-2-6_9-57-58.png
     
  8. Vigge

    Thread Starter New Member

    Feb 5, 2018
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    But MT1 and MT2 is 230VAC Sorry but I`m confused!!!

    And I need 30V to open the Diac. how can 17V be to much?
    There is a 22ohm resister between the Diac and Triac
     
  9. Dodgydave

    AAC Fanatic!

    Jun 22, 2012
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    I would say if it's burned the resistor then the diac and opto will need to be changed, also to check the Triac short the Gate to Mt2, to fire it. You can use two 27V zeners back to back as a diac.
     
  10. AlbertHall

    AAC Fanatic!

    Jun 4, 2014
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    No, that won't work. The diac has a negative resistance when triggered so it dumps the charge from the capacitor into the triac gate. The zeners would just gradually begin to conduct and leak away the capacitor charge.
     
  11. AlbertHall

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    The triac triggering is specified at 12V but that doesn't mean that is the voltage that must be used.
    If the diac and/or triac are now defective then they could be leaking away the charge from the capacitor.
     
  12. Vigge

    Thread Starter New Member

    Feb 5, 2018
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    Okay. Disconnected the triggwrwire.
    Messured the voltage triggerwire to N. = 208VAC
    Reconnected G..
    Turned om power and it startes charging and buzzing????
    Turnes on/off power sometimes it charges sometimes it wont.
    I guess I Will have to change the diac/triac. At least for the sake of it.

    Triac = NTE5679
    Diac = ??? Any suggestions ?
     
  13. Dodgydave

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    Jun 22, 2012
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    Triac spec sheet says 2.5V @100mA gate trigger. Any Diac that will give you 100mA will do. Try a Db3 type.
     
  14. Vigge

    Thread Starter New Member

    Feb 5, 2018
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    But it has a 5V output !! right
     
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