# MicroFlash Schematic

Posted on Feb 5, 2014

These two resistors have two functions. One, if I touch the circuit by accident, they limit the current to a lower value. Two, when the flash fires, the main capacitor looks like a short circuit to the power supply. These two resistors limit the short circuit current. I just found myself a 10kV @ 23mA oil burner tranfsormer in the garage. Ya think

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running a single doubling stage for 20kV will be enough for the tube or would it be better to get a 50kV cap and double the voltage twice for 40kV Excellent drawing, thanks! Is there any reason why you went for high voltage & small cap (35kV. 03 µF = 1. 05mC i. e. 18. 38J stored), rather than small voltage and much larger capacitance (for instance a 450V 1mF = 450mC i. e. 101. 3J stored) Is it only because you do not require much energy since your subject is pretty close Does it have an impact on the flash duration The limiting factor for pulse width is the capacitance. Edgerton found out that the resistance of the spark flash is about 10 ohms. From this is follows that the RC time constant limits the pulse width. For example, your 1microfrad cap would give a pulse of about 10usec, all other things being equal. A. 03uF cap gives a pulse width of 10ohms*. 03uF or 300nsec. And I am not sure how you could get a good spark off of a 450V cap. These voltages use low pressure xenon to get a flash and the xenon light is very long lived, further increasing the flash length. So the small capacitance, high voltage combination is used to get a short pulse. All the microsecond flash units that I know about use this technique. It is a pain because of the high voltage, but it works. ...

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