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Ignition coil voltage question

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dandy1
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2019/03/17 14:46:58 (permalink)
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Ignition coil voltage question

Does anybody know what voltage the ignition coil reaches in a generic cheap chinese generator.  Its 6.5hp chonda engine and i want to know the voltage of the primary side (kill switch wire) to make an RPM counter.
 
thanks in advance
post edited by dandy1 - 2019/03/17 14:53:46

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    AVB
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    Re: Ignition coil voltage question 2019/03/17 17:32:02 (permalink)
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    Due to the design of the electronics in the ignition coil you can not pick-up an signal on the primary without ignition trigger problem as the kill circuit is primary grounding the coil to kill it; otherwise it triggers the coil. The high voltage (secondary) is where you pick-up the impulses for you tach. This high voltage is btween 10KV to 16KV depending the coil internal turn ratio and how the magnets are that introduces voltage in the primary.
     
    Most tachs like the Tiny Tach only needs a couple turns to work but I have seen as many as 4 turns for the pickup lead on several mowers.
    dandy1
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    Re: Ignition coil voltage question 2019/03/18 11:26:09 (permalink)
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    Thank you for your reply AVB
     
     
    I have designed a circuit on the primary side that does allow for connection to the kill wire.  I did learn the mistakes of grounding the ignition through the circuit (and hence the micro controller) but nonetheless its an accurate circuit.
    The reason for this approach is because it is part of another circuit that allows for killing the engine (see link below if interested) and it avoids the higher voltages produced by the secondary.  However, as i do not have any accurate way(scope) to determine the true voltage on the primary i have over egged the components used and probably could use more efficient components and reduce the complexity of it.
     
    Is there any reference you could point me at to determine the peak primary voltage on these ignitions.
     
    TIA
     



    post edited by dandy1 - 2019/03/18 11:27:20
    AVB
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    Re: Ignition coil voltage question 2019/03/18 13:09:53 (permalink)
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    Okay then the turns ratio is approximately 18:1 so if you can check the high voltage output, you should get a fairly close estimate of the primary induced voltage. Or you use very high input resistance DDVM and check across the primary; Ground (coil metal core) to Kill terminal. Also you can check the specs on the D13003 transistor which has a BVceo minimum breakdown voltage of 400V and BVcbo of 700v minimum. Note: This is the main transistor in the Briggs newer coils, the rest are SMDs.
     
    I have never needed to check the actually voltage. I just know the newer Briggs coils are using an SMD circuit board One side grounded all the time the kill terminal is floating except when grounded which shorts the primary winding so it doesn't produce any voltage.
    dandy1
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    Re: Ignition coil voltage question 2019/03/18 14:13:43 (permalink)
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    Nice info AVB thanks
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