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Type: Posts; User: prairiedog

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  1. Closed: Re: What is meant by "coating" when PCB track spacing is concerned?

    Coatings mean conformal coating (UL/CSA/EN/BS approved) to keep dust and moisture off the PCB and allows you closer spacings. PC board solder-mask is not a suitable insulator towards safety, as the...
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    [SOLVED]Closed: Re: HEI primary current duration

    You have to shut off the IGBT at precisely the right (spark) time, so you are always calculating backwards when to start the next dwell period.

    If you have reached max. dwell time before spark...
  3. Closed: Re: Beckman Industrial 9020 - Poor focus with no adjustment

    Service manual (in French): The Boat Anchor Manual Archive (BAMA), Beckman 9020 has schematics
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    [SOLVED]Closed: Re: HEI primary current duration

    Yes but you need to allow extra time- for the spark to finish, which can vary a bit due to plug gap and plug+cable resistance, misfires etc. Also, dwell varies with system voltage so assume 11V say,...
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    [SOLVED]Closed: Re: 12 vdc led running very hot

    The resistor and LED are around 23mA so the 0.25W resistor dissipates 0.28W and will get quite hot. I find this typical with LED stuff from china, they drive things a little past their max.
    I used...
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    Closed: Re: Residential Wiring Offset Voltage

    Electrical codes require neutral to be bonded to earth ground, after any (distribution) transformer and at the service entrance, breaker panel. A distribution transformer is step-down from say 15kV...
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    Closed: Re: Residential Wiring Offset Voltage

    It's specified as a total voltage drop, for both of the hot and neutral conductors, from the point of view of efficiency. You don't want large voltage drops due to thin wire. Residential mains cable...
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    Closed: Re: About Separating Supplies on PCB.

    Note the MAX5875 Eval board used three PCB ground sections: AGND, DGND, CLKGND. Maxim also used DAC output common-mode chokes and output transformer.
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    Closed: Re: Residential Wiring Offset Voltage

    NEC 210.19 has a limit of 5% total voltage drop for sizing conductors on branch circuits. 5% of 120VAC is 6V or 3V then for neutral. At the load (outlet), neutral goes above ground because it's 1/2...
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    [PIC]Closed: Re: 7Amp Heater and PWM using MOSFET

    Heaters (and their wiring, cables) have parasitic inductance, so the mosfet will see overvoltage spikes at switch-off, which can damage it. A fast-recovery diode across the heating element or a RC...
  11. Closed: Re: Conducted EMC equipment for 60W offline PSU

    I don't know of any company offering such a facility- you're asking for EMC lab benefits without the cost. EMC labs have calibrated equipment and shielded rooms, accreditation, operations staff etc....
  12. Closed: Re: Power Supply for M95 GSM module to be compatible with ATEX limitations.

    I did a Zone 0, IS cell modem design. Main power is a 6V lead-acid battery. 60079-11 does not allow active current-limiters. I used an LDO for 3.7V 2A power to the modem module. I thought a...
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    Closed: Re: Differential probe build

    Pintek DP-15K is rated 35MHz and 15kVpp differential, and 7.5kV common-mode, 100mV 50MEG input. From 15kV down to 1kV at 30MHz.
    It uses two THS4631 for their I/P stage op-amps 325MHz FET input. Many...
  14. Closed: Re: SOA of MOSFET....the meaning of "DC" in the graph

    Power MOSFETS are optimized for switching and high-power use in their linear region is fraught with peril.
    It's like walking into a cas ino, the datasheet SOA curves could be conservative... or...
  15. [SOLVED]Closed: Re: measuring capacitance of a transformers primary coil

    What's wrong with measuring self-resonant frequency? I connect a signal generator with a volt or two sine wave and scope coil current. HEI is around 1:85 turns ratio.
    A decent SPICE model is...
  16. [SOLVED]Closed: Re: LM3914 - What might "dot/bar logic" be?

    LM3914 Dot/Bar logic was explained in old National Semiconductor datasheets. For some reason TI has butchered them, deleting essential knowledge.
    The logic actually has three functions:...
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    Closed: Re: line level to signal level

    Best to find out where the overload distortion is coming from. There are two possible places and you are probably overloading at both.

    Guitar into a soundcard... MIC input or line input? You would...
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    Closed: Re: Safety of specific LEDs

    I use 3528 SMT LED's for indicators as they are large and popular in car dashboards. I find Digikey has nothing special, aside from the expensive Cree parts.

    Kingbright has specialty colours, and...
  19. Closed: Re: IR remote-control receiver design - getting it stable

    Sorry, here are pictures of just what I built.

    Assembled PCB 148186
    Bottom Layer PCB 148187
    Top Layer PCB 148188
  20. Closed: Re: IR remote-control receiver design - getting it stable

    The original Hitachi design was split into two (single-sided) boards. "Photo Amp" with metal can shielding Q1-Q3 and then a connector & shielded cable to the second board with Q4-Q7. I measure about...
  21. Closed: IR remote-control receiver design - getting it stable

    The best (discrete) IR remote-control receiver I have ever used, a Hitachi design from an old JCTV-3100. Fantastic range over 50m and used in large halls, works with IR bouncing off many surfaces...
  22. Closed: Re: How can I implement Phase sequence detection in PIC12F508 ?

    Why are you doing this? Phase sequence does not change once you are wired up to the 3-phase power system.
    In real life, there are phase-phase shorts (wind on power lines) and loss of one phase that...
  23. Closed: Re: Doorbell needs to be stepped up to 24v for Ring, but what about solenoid in chime

    Note that a doorbell transformer is Class 2 energy limited, so do not substitute an ordinary power transformer.
    Class 2 will limit current if there is a short in the low voltage doorbell wiring, and...
  24. Closed: Re: Cheap ESD flooring for electronics assembly lab

    I've used ESD (conductive) floor wax on ordinary tile and concrete floors. You have to re-apply once or twice a year. It is expensive but less cost than a new floor, with the risk of using "ordinary"...
  25. Closed: Re: Max permitted short circuit current according to ATEX for low voltages

    The spark-tables end based on the limits of the spark-test apparatus. They actually make sparks and try to ignite the various gas mixtures at different voltages, currents, inductance, capacitance....
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