Help Needed with DC Transformer Pinout

Discussion in 'The Projects Forum' started by moocrow, Apr 3, 2011.

  1. moocrow

    Thread Starter New Member

    Apr 3, 2011
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    Hi,

    I hope somebody may be able to help me with the following query; I've tried looking online, including in this forum, but as yet to no avail.

    I am trying to build a xenon flash circuit, ultimately with the aim of achieving a very low flash duration. I'm hoping to base it on this: http://www.discovercircuits.com/DJ-Circuits/xen2xtr.htm

    I'd rather power it from a battery for safety and portability reasons and so have bought a handful of these transformers to step up a small battery voltage to the sort needed to charge a flash capacitor: http://www.produktinfo.conrad.com/datenblaetter/575000-599999/582263-da-01-en-Uebertrager.pdf

    I got them from Conrad (product code: 582263, www.conrad-uk.com, the site won't allow a direct link). For whatever reason, the specs listed on the site are different from those listed in the datasheet (which I got from the Conrad site, strangely). The transformer's webpage also incudes an image (2/3, can't direct link as above) which appears to be saying something different about the pins.

    I am unable to work out which pins I need to put a battery voltage into (around 6V) in order to get a much higher voltage (230V or 345V depending on whether you believe the site or the datasheet), and which are the output pins? Any help would be much appreciated.

    Finally, in searching for the part number on Google, I found this schematic: http://www.kronjaeger.com/hv-old/chauer/mobilehvgen/mobilehvgen2.htm. I don't understand the schematic, and in any case it looks like it's for something unpleasant, but may indicate to those with more knowledge what the various pins are for.

    Any help would be much appreciated,

    Jim.
     
  2. SgtWookie

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    Jul 17, 2007
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    I'd contact Conrad and ask them why the transformers they shipped to you did not match the datasheet and image that is on their website.
     
  3. moocrow

    Thread Starter New Member

    Apr 3, 2011
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    Thank you for the suggestion. However, the technical support question box is limited to only a few words in length and the issue over which schematics are correct is not (I don't think?) related to which pins are which.
     
  4. SgtWookie

    Expert

    Jul 17, 2007
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    Go to their Customer Service page.
    Under "Service and Returns", click on "What is the reason for your return"
    Then select "Wrong part received".
    Then you can give a more verbose description of the problem in the text box, along with your address, etc.

    Don't forget to include their part number.
     
  5. moocrow

    Thread Starter New Member

    Apr 3, 2011
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    Thank you. Apologies, I think I caused confusion about the intent of my original post with the comments about the accuracy of the data on Conrad's web page, which I included for completeness.

    I'm not seeking to make a return but rather to understand the device I have. I will assume that the datasheet is correct until I discover otherwise, as the quoted physical dimensions match my product.

    In any event, I have a transformer with five pins capable of taking a small DC voltage of the order produced by a battery and outputting the sort of DC voltage capable of firing a small xenon flash tube.

    Based on the datasheet, I assumed that the DC-in was pins 3 & 4 while the DC-out was either pins 1 & 4 or pins 1 & 6. Either combination gives me 6V out.

    I will try to find an alternative way of raising this as a technical support query with Conrad which doesn't involve, at this stage, trying to make a return.
     
  6. BillB3857

    Senior Member

    Feb 28, 2009
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    Can you post a schematic of your circuit. You are aware that the transformer shown in the discovercircuits link is for triggering the flash tube and not supplying the high voltage to the flash capacitor. In that circuit, the charge for the 6uF, 400V cap comes from the line power. To duplicate the circuit using batteries, you would need about 200V worth of batteries.
     
  7. SgtWookie

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    OK, I think you misunderstand what the transformer is.
    It doesn't convert DC voltage to high voltage. It needs to have the current through the primary coil varying in order to produce a voltage on the secondary.

    However, the pin numbers are different in the datasheet than the schematic.
    Here's how they go:
    Pin 1 in the schematic is pin 5 in the datasheet.
    Pin 2 in the schematic is pin 3 in the datasheet.
    Pin 3 in the schematic is pin 4 in the datasheet.
    Pin 4 in the schematic is pin 6 in the datasheet.
    Pin 5 in the schematic is pin 1 in the datasheet.
     
  8. moocrow

    Thread Starter New Member

    Apr 3, 2011
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    Guys - thank you very much for the advice so far, it's much appreciated.

    This is the schematic I'm working with at the moment:
    [​IMG]

    The transformer I referred to in my original post is *not* intended to trigger the flash tube. For this, I have a specialised trigger transformer which takes an input of 170VDC from a 0.033μF capacitor and outputs 4KV. The trigger transformer is the one on the bottom right of the schematic. It came from Maplin: http://www.maplin.co.uk/trigger-transformers-2298

    The transformer I was asking about is at the top-left of the schematic. The purpose is to get a high enough voltage out of a battery to charge the 6μF capacitor, which in turn discharges through the flash tube when the trigger transformer ionises the xenon inside.

    The flash tubes I have work within a wide range, 200V - 450V, so there's some latitude. However, I can't work out which pins in the transformer I referred to originally do what, and how I go about getting a high voltage out of it. I have tried all combinations of pins as the input pair and tested the voltage across each pair amongst the remaining three pins in each case. Every time, I either get 0V or 6V.

    Based on the configuration in the 'HV Generator II' schematic I linked to, it seems that the transformer needs a more complex input arrangement than a standard AC/AC step-up transformer. I don't understand this schematic well enough however to work out what the analagous arrangement would be in my own schematic.

    SgtWookie - thanks for the pinouts. When you say 'the schematic' are you referring to the discovercircuits flash schematic or the HV Generator II schematic, which I also linked to? Can you determine what each of the pins is used for - my assumptions (obviously!) haven't been right.

    PackratKing - thank you for the suggestion, which with a bit of advice I'm really keen to have a go at. Is there anything I need to be looking for in LEDs to make sure they can rise/fall quickly enough? I'm aiming for a light duration of under 20μs. What is 'PWM'?

    Cheers,

    Jim.
     
    Last edited: Apr 5, 2011
  9. BillB3857

    Senior Member

    Feb 28, 2009
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    Where does the AC that is need for the transformer coming from? I only see a 6V battery and switch. You are aware that transformers DO NOT work with DC. Only change in the current of the primary causes coupling to the secondary. Usually, if powered by a DC source, some kind of oscillator is required to generate the AC. Buzzer type devices can be used. In the old days, car radios used a device called a Vibrator that chopped up the car battery's 6 volts to drive a transformer. The output of the transformer then supplied the high voltage needed for the vacuum tube circuits in the radio.
     
  10. moocrow

    Thread Starter New Member

    Apr 3, 2011
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    BillB3857: The datasheet for the transformer I have ( http://www.produktinfo.conrad.com/da...ebertrager.pdf) states that it takes 6VDC as the input and the supplier website states, under 'Features': "Oscillator frequency: 15 kHz" suggesting that the oscillator required to convert the 6VDC into AC is part of the transformer.
     
  11. SgtWookie

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    Ahh, I think that's the frequency the transformer primary wants to see, and I don't think the transformer is anything BUT a transformer.

    Going back to this page: http://www.kronjaeger.com/hv-old/chauer/mobilehvgen/mobilehvgen2.htm
    You're going to need that circuit to drive the transformer, substituting the pin numbers that I gave you before.
     
  12. BillB3857

    Senior Member

    Feb 28, 2009
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    Last edited: Apr 5, 2011
  13. SgtWookie

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    I like the Zetex schematic BillB3857 found better than the one on the kronjaeger site, as it has a means of controlling the output voltage that's more than a spark gap.

    Unfortunately, the Zetex schematic can't be used with your transformer, as windings S (the HV winding, 3.3H, from pin 1 to 6) and F (the 300uH winding, pins 4 and 6) are connected together internally on pin 6.
     
  14. BillB3857

    Senior Member

    Feb 28, 2009
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    What if instead of using the resistive voltage divider to generate the base bias, just a single resistor to +6 were used, to balance the DC resistance of the winding with the common tie between the S and F winding grounded. The primary winding would then have to be reversed to provide proper regenerative feedback. Just my thoughts. What do you think, Sgt? Would that work, or not?

    On edit: Or even keep the resistive bias and capacitive couple the feedback.
     
    Last edited: Apr 5, 2011
  15. SgtWookie

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    Well, the transformer our OP has is quite different from what the Zetex schematic requires.

    His transformer:
    P: 1.3uH
    F: 300uH
    S: 3.3H

    Zetex schematic transformer
    P: 10T - 16uH
    F: 23T - 84.6uH
    S: 128 - 2.62mH
    Note that the uH/mH ratings are approximate; I had to dig around to find some RM 6 cores on the Web, and decided on using an AL value of 160. It could be 250 - or another value entirely, as the Zetex schematic didn't specify anything more than RM 6 and a 0.15mm gap
     
  16. BillB3857

    Senior Member

    Feb 28, 2009
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    The devil is in the details! I was looking at it only from the schematic and logical point of view without regard to component values.:( Glad you're around to keep me straight, Sgt.
     
  17. moocrow

    Thread Starter New Member

    Apr 3, 2011
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    Thanks again, for the help, though I have to admit that I got lost during the discussion over the inductance values of the two transformers.

    If I proceed along the lines of the kronjaeger site, which parts of the circuit do I need? I have to confess, I don't really understand what the capacitor/resistor combination and NPN transistor are doing, though presumably they're causing the current to oscillate in some way?

    In particular, do I need the two diodes? -

    [​IMG]
    Uploaded with ImageShack.us


    These are confusing me a bit as, between them, they seem to preclude current flowing in either direction, though obviously this can't be the case.

    Could a 555 timer be used to produce the right sort of oscillating current?

    Thanks,

    Jim.
     
  18. BillB3857

    Senior Member

    Feb 28, 2009
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    In simple flash tube designs like the OP is working on, the flash duration is a primary result of the storage capacitor size in uF and the voltage stored. The duration of the trigger pulse has little if any effect on flash duration. For controlled duration flash, the theory is explained here...... http://www.repairfaq.org/sam/strbfaq.htm#strbpoo in the section titled
    Automatic Exposure Control Electronic Flash Units



    It involves shunting the power away from the flash tube through a secondary device.
     
  19. moocrow

    Thread Starter New Member

    Apr 3, 2011
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    Thanks again guys, I feel like I'm beginning (slowly) to get a grip on this! At the risk of now disproving that, is my assumption here about the output of the transformer correct? -

    [​IMG]

    I'm still not sure which elements of the kronjaeger schematic are specific to the HV generator and which are necessary to get an output from T1.

    BillB3857, I hadn't really begun to think about how to shorten the flash duration beyond just using a smaller capacitor or perhaps closing the circuit with a JFET or JFET/optocoupler. The strobe site you linked to is really useful and seems to be the better option.

    Thanks.
     
  20. SgtWookie

    Expert

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    There are a couple of problems with the kronjaeger schematic.
    1) The diode on the output of T1 (pin 5) is backwards.
    2) 1N4007 diodes are much too slow to be used for this; they are only designed for frequencies up to around 500Hz or so. You need fast-recovery diodes rated for 600v or so.
     
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