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Recent content by treitmey

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    High freq EMC filter.

    My latest product went to EMC testing and failed miserably. I run the circuit from 115VAC and a long cord. I will test soon, but my gut says that the noise is comming in on the 115. Has anyone built a circuit(filter) for such a problem? The EMC high freq test is a steel plate driven by a...
  2. T

    capacitors - cant understand !

    You may ultimately be looking for something like this estimating time of a supercap. https://www.maxim-ic.com/app-notes/index.mvp/id/3517
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    pull-down for FDV301N N-FET

    OK. Got it. Just a current limit for protection of PIC pin. as for the diode. Got it. D5 see download image.
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    pull-down for FDV301N N-FET

    I see what you mean. Can you tell me how you calculate the 100 ohm gate resistor. That is what I'm have trouble with. btw unrelated I did find a note about how to calc the power of the gate resistor see below >The gate resistors are in series with the gates but they are all driven >from a...
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    pull-down for FDV301N N-FET

    I see that the FET is fully on with Vgs = 2.7 V
  6. T

    pull-down for FDV301N N-FET

    I have a relay that is driven from a PIC 18F452. It is driven with a FDV301N N-FET. I've put a 10k in series with the uC pin to limit current to the FET. NOW I want to put a pull-down on the pin for when the micro-controller is in reset and the pin is set as input. so I don't want the input to...
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    Externally powered light/dark switch

    Re: Light/dark switch try something like this (Last page is schematic) https://www.electronickits.com/kit/complete/elec/ck1602.pdf or this https://www.discovercircuits.com/H-Corner/12LightDarkSw1.htm
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    working with 24 bit registers

    I don't think the mode has anything to do with it. If you want to read 24 bits at a time you will need 24 free input pins. If you don't have 24 available input pins, then you could latch the results and read say 8 bits at a time, and mux to the next 8 and so on. The 8 and 16 mode you refer to...
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    what does PPm/deg celcius denoted when mentioned in spec.

    Re: what does PPm/deg celcius denoted when mentioned in spec PPM is parts per million. I've seen it used in oscillators. https://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=X062-ND where its rated at 20MHz ±30ppm/deg C So your value(20MHz) can be off by +-30 hertz per million...
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    Why LM7805 get very very hot

    very very hot I don't know who wrote this,... but it works and it is very handy. https://www.nomad.ee/micros/mc34063a/index.shtml the cooool thing is you get to see how changing a parameter changes the parts.:D p.s. i start with 10mV ripple and 40kHz
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    74LV244 buffer output current

    uln2803 mosfet output ..
  12. T

    Issues with interfacing two boards via I2C through cable

    i2c cable If you need to go farther, or are having problems, take a look at this https://www.ccsinfo.com/forum/viewtopic.php?t=39938 He is a great poster. He knows what he is talking about. Follow what he says and use that chip P82B96L...
  13. T

    protel 2004 - interactive routing question

    If blue is the color of your bottom traces(it is for me) then it sound to me like your trying to route net A through traces already routed on bottom for net B. Net A and B can't touch, that a short. Its just may be that you didn't see them (refresh screen) problem. Sometimes when I change...
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    magnetic card reader to pic micro

    homemade post pc card you may be able to get the parts needed here. https://www.barcode-manufacturer.com/magnetic_card/magstripe.html#OEM_Modules
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    magnetic card reader to pic micro

    homemade credit card reader I've made one of these. I bought the reader, that outputs wiegand. ((it doesn't make sense to build the reader/head unless your making millions of these)) Then the PIC reads the wiegand and outputs to the PC. Some readers are shown here...

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