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how to make a DVA adapter for multimeter

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  • Re: how to make a DVA adapter for multimeter

    can anyone clue me in on what might be wrong? 1st of all let me say that I'm testing this adapter on a running 1974 85hp evinrude. I built adapter per schematic," 1n4004 diode 2.2 uf cap., 1mohm 1/4w resistor." When tested on house current meter reads 167 vdc as it should, or so I am told, but when I check voltage between the brown and brown/yellow wire for 150vdc I only get 16vdc.

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    • Re: how to make a DVA adapter for multimeter

      Originally posted by ferman View Post
      can anyone clue me in on what might be wrong? 1st of all let me say that I'm testing this adapter on a running 1974 85hp evinrude. I built adapter per schematic," 1n4004 diode 2.2 uf cap., 1mohm 1/4w resistor." When tested on house current meter reads 167 vdc as it should, or so I am told, but when I check voltage between the brown and brown/yellow wire for 150vdc I only get 16vdc.
      Hi Ferman,
      Looks like your DVA is working as it should as it is reading peak AC line voltage correctly. As far as troubleshooting your specific engine issue, I suggest opening a specific thread on that.

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      • Re: how to make a DVA adapter for multimeter

        Originally posted by ncpi View Post
        Hi Ferman,
        Looks like your DVA is working as it should as it is reading peak AC line voltage correctly. As far as troubleshooting your specific engine issue, I suggest opening a specific thread on that.
        thanks ncpi. I'm using outboardignition.com's testing procedures for my specific model, but i can take another look.

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        • I realize this is an old thread but I am confused about the value of the capacitor. Is it 2.2uf or 22uf? I've seen both values posted.
          Bill

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          • Originally posted by ko4nrbs View Post
            I realize this is an old thread but I am confused about the value of the capacitor. Is it 2.2uf or 22uf? I've seen both values posted.
            Bill
            It is 2.2 uF The design was published by Bill Rogers on the ScreamandFly forum in Dec 2003:
            He says Re: a different capacitance value, you could go up to maybe 4.7uF, but it will take a little longer for the reading to stabilize (which means more wear on your starter). If you go much less than 2.2uF, it might fail to hold the peak value constant between input pulses.

            Last edited by Vic.S; July 7th, 2014, 05:16 PM.

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            • I got it built and tested in a wall socket and it works. Read about 170 volts on the meter using the DVA.

              I used a 3.3 volt electrolytic capacitor rated at 400 volts. It's all I had available for now.
              Thanks,
              Bill

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              • Hi, I made this device and decided to check the network 220-240 volts 50 Hz. The device burned! Why?
                Click image for larger version

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                • Originally posted by Dmitriy Balenko View Post
                  Hi, I made this device and decided to check the network 220-240 volts 50 Hz. The device burned! Why?
                  [ATTACH=JSON]{"data-align":"none","data-size":"thumb","data-attachmentid":10693882**[/ATTACH]
                  What part or parts actually smoked?
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                  • Cap too big? I thought it was supposed to be 2.2uF.
                    '83 Springbok 16' with Franken Xflow, in Southern Alberta. If it ain't smokin', it must be broken.
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                    • Originally posted by interalian View Post
                      Cap too big? I thought it was supposed to be 2.2uF.
                      The 300 ohm resistor limits the charging current when a 22 μF capacitor is used. Otherwise the diode may be damaged.

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                        I calculated the power consumed by the 300 Ohm resistor and 22 uFD cap to be 30 Watts, with 18 Watts for the resistor. That circuit was not designed to be used with that high a voltage with a 22 uFD cap. Unless the resistor is 20 Watts or more, it will smoke. So will the cap. It should be 2.2 uFD. Even then with 240v applied, the resistor must be 2 watts or larger if this is to be used for more than a few seconds.

                        Don't forget that the power is squared with a doubling of the voltage So those who got this to work at 120v with small components and 2.2 uFD were experiencing only 1/4 the power that is created at 240v..
                        Last edited by DouglasW; January 9th, 2019, 09:02 PM.
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