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  1. I

    a regular transformer

    Ferrite core transformers sometimes do have a very small gap to prevent saturation and help in reset. In general, the idea with transformers is to NOT store any energy in the core. Leakage inductance, which all transformers have, will store energy in the core, so you want to minimize that with...
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    How to make an audio console's power supply better?

    More is not always better. There are dangers in making your cap's too large..... i.e. how would you limit inrush current? For the most part, the ripple is "more" a function of ESR. Most times cap's are put in parallel to get ESR down instead of capacitance up. Lower voltage cap will give you a...
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    Variable DC Power Supply

    Are you SURE you want to go with “that” (collector – emitter) or stick with the base - emitter  junction?
  4. I

    Want to make Auto Range Power Supply.

    If I understand correctly, you want to make a "universal input" (85 - 250 VAC ) adjustable switch mode power supply (0 to 30VDC @ 3A)… correct? This can be done, but the control loop is very, very tricky because of the wide swing in duty cycle and potential variation of the load!!! Take a look...
  5. I

    Constructing an inductor

    You want to make a 4.6H air core inductor???
  6. I

    15A Lead Acide Battery Charger!

    It's really ohms law at work. You have to consider the battery's internal resistance. You can hold the current constant and the voltage will go to whatever it has to, or hold the voltage constant and the current will be whatever it has to. Once you have defined 2 of the 3 terms, that's it...
  7. I

    15A Lead Acide Battery Charger!

    Since the "battery experts" themselves can't agree as to what is best, how can we determine which camp is "right"? I suppose one could argue that if the "pure DC" camp is correct, and since the vast majority of battery chargers are of the peak-pulse variety as opposed to the multi-stage DC type...
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    15A Lead Acide Battery Charger!

    Greetings Ante, From the www: Charging the lead-acid battery The charge algorithm for lead-acid batteries is similar to lithium-ion but differs from nickel-based chemistries in that voltage rather than current limiting is used. The charge time of a sealed lead-acid battery is 12-16 hours (up...
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    DC/DC Converter

    A buck converter would be VERY hard to do!!! With a 5 volt output, and a nominal input of 110VDC that's a 4.5% duty cycle (plus a little for losses) and at 160VDC in it's 3.1%. Such small duty cycles are hard because of the speed at which you'd have to switch the swtching elements to keep the...
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    How to Use a 555 Timer for PWM

    One thing that will happen when using a 555 as PWM is that the switching frequency will change with line and load.
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    15A Lead Acide Battery Charger!

    No, you can't current limit the ATX power supply by pulling on the standby pin, as was already stated. Pure DC is BEST for charging, it is too expensive to build/sell 20 or 30A pure DC chargers!!
  12. I

    15A Lead Acide Battery Charger!

    None of those circuits can do 15A. If you look at the 1.2A & 2.5A chargers, there is a current sense resitor that turns on the NPN transistor connected to the "adj" pin. As the current goes up, the voltage across the resistor will increase until the NPN starts to turn on and pull down the...
  13. I

    DC/DC Converter

    Can you be a little more specific about the 110VDC input voltage? Is it a "nominal" 100VDC with
  14. I

    15A Lead Acide Battery Charger!

    What you just said is pretty much what I meant. You need circuit that can operate in voltage mode and current mode, basically voltage foldback. Under certain conditions you want the output voltage to control the output current, and under other conditions you want the output current to be able...
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    Low-pass Filter?

    OK...... so what your "saying" is that, in a second order Butterworth low pass filter, there is gain just prior to the corner frequency due to "positive feedback"??? The transfer function only has poles and NO zeros, how can that be???
  16. I

    Low-pass Filter?

    John I know the math...... for a second order, the transfer function solution is quadratic, but you're the "theory expert", so can you explain, in technical terms why the gain doesn't start to roll off a decade before the corner frequency?
  17. I

    Low-pass Filter?

    That doesn't show me the math or answer the question.
  18. I

    Low-pass Filter?

    Show me the math................. A Butterworth filter, irregardless of order, only has poles in it's transfer function, so could you explain.... "A Butterworth two-pole active filter uses a form of positive feedback to hold the output up just before the cutoff frequency."
  19. I

    Glaringly obvious errors

    Varying the duty cycle will change the speed, and a fixed duty cycle will cause the speed to remain constant, but that will ONLY work if you have a constant load on the motor. If the load can change, then you'll need feedback (like a tachometer) if you want to maintain the constant speed. Why...
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    15A Lead Acide Battery Charger!

    Not really. If the battery you were charging was trying to draw more than 15A, the charger would just bounce on and off. You don't want to limit the current to  15A, but regulate it to no more than 15A. Take a look at some of the apps notes from National on 5A adjustable regulators. You should...
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