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  1. MagicSmoker

    High Amperage Boost Converter Design

    The boost converter is a perfectly fine topology for very high power, but it becomes less attractive as the ratio of output voltage to input voltage rises. To boost 48V to 170V (sounds like the front end of a very large 120VAC inverter) you will need to run the switch at a duty cycle of 70-75%...
  2. MagicSmoker

    High Power High Frequency Supply

    Interesting specs you got there. This is one of those rare instances where a fully resonant switchmode topology makes sense, both because the sinusoidal voltages (and/or currents) will be easier to handle vis-a-vis EMI, corona, etc., and because you can use the resonant tank to do voltage...
  3. MagicSmoker

    How do I Design an Isolated High Voltage Analog Output controlled by a PWM input from 140V DC

    An "electrical braking system" that uses a variable DC current? That sounds a lot like an eddy current brake. If so, this rarely requires such precise control of voltage/current. I mean, I've seen eddy current brakes and clutches on production lines controlled by what is essentially an...
  4. MagicSmoker

    Which DMM can you recommend?

    @benta - I keep trying to find something which is better overall than my Fluke meters, but, well, I end up preferring my Flukes. I previously replaced a 20 year old model 77 DMM with a 179 and I *really* like my new 381 clamp meter with the removable wireless display which replaced a 337. I do...
  5. MagicSmoker

    Recommendations for contract board assembly needed.

    itsmoked & bradrs, you both bring up the primary motivation for using someone local. Fortunately, I've already gone through several design revisions for each board that needs to be manufactured so I know they work, but I'd still feel better using a local company. The only contract PCB...
  6. MagicSmoker

    Recommendations for contract board assembly needed.

    Thanks for the suggestions, guys. Advanced Assembly looks like a good choice to get the first few sets of boards done quickly, but the last suggestion, GIC, looks better suited to our expected production volumes for at least the next couple of years. I did find a couple of places in Melbourne so...
  7. MagicSmoker

    Recommendations for contract board assembly needed.

    Thanks, Dan. Yeah, I'm more concerned with poor quality/abuse with outsourcing to China rather than IP theft, and your experience with cooked parts is exactly the sort of thing I wish to avoid. We make custom motor drives for industrial/transportation applications so we are exempt from the evils...
  8. MagicSmoker

    Recommendations for contract board assembly needed.

    I'm looking to hear about experiences others here have had with contract PC board assembly (ie - solder paste printing, component placement, reflow soldering), particularly of relatively small production runs (say 100 of each board). We've been doing all of our pc board assembly in-house for the...
  9. MagicSmoker

    First Turn Failure on submersible pumps

    Marke - a common mode filter will have _no effect whatsoever_ on the "legitimate" output of the drive. That is to say, the common mode filter is essentially invisible to the current which exits the drive via one IGBT, then goes through a phase winding in the motor and returns to the drive via a...
  10. MagicSmoker

    Why are color LEDs so inefficient?

    geniusxie - that is actually a very good question. My guess is that most colored LEDs are used as indicators, not lighting sources, per se, and so don't need to be terribly bright or all that efficient. Now where you might find colored LEDs that are very bright and highly efficient is in...
  11. MagicSmoker

    First Turn Failure on submersible pumps

    Actually, long cables between a VFD and a motor can act as a pulse forming network, significantly increasing the dV/dt of the PWM waveform. This causes significant AC current to flow through the insulation, resulting in dielectric heating, sometimes to the point that the insulation softens and...
  12. MagicSmoker

    Drawing program for system-level wiring diagrams?

    IRstuff/MacGyverS2000 - okay, I thought it was just me doing something wrong with Visio; nope, apparently the weird snap behavior is an "undocumented feature"... So far EDdraw Max seems like a more-than-competent Visio alternative, particularly if, like me, you only have to draw a few...
  13. MagicSmoker

    Drawing program for system-level wiring diagrams?

    Ok, so I downloaded the trial versions of both Edraw Max and SmartDraw. Both of these programs are basically centered around connecting vector graphic symbols together with "snappable" lines (that is, lines that stay connected even if you move the symbols they are joined to around). Both...
  14. MagicSmoker

    Drawing program for system-level wiring diagrams?

    I'm not really looking for a *free* program (though that never hurts, right?), nor a CAD program. Rather, I am looking for something to draw system-level assembly/wiring schematics like this: SmartDraw - Auto wiring diagram Although I am familiar with the particular pathology VE1BLL speaks of...
  15. MagicSmoker

    Drawing program for system-level wiring diagrams?

    Thanks for the reply DRWeig, even if it was yet another vote to suffer Visio (I just looked at it again and remembered why I dislike it so much - the learning curve is way too steep for someone that uses it once a year or two or three). An informal poll of my colleagues at a couple of other...
  16. MagicSmoker

    Drawing program for system-level wiring diagrams?

    I'm curious as to what other engineers are using to draw system-level schematics (as compared to board-level). Like, for example, multiple VFDs and motors supplied by a genset showing individual wires between each, but otherwise representing each device with a generic, geometric shape. More...
  17. MagicSmoker

    Looking for ideas on electronically switching resistors.

    Nope... itsmoked said: So it's pretty clear he meant that he wants to use a power transistor to select a resistor Thus my original suggestion applies.
  18. MagicSmoker

    Looking for ideas on electronically switching resistors.

    Are the set point resistors floating? If so, then the only practical option is a relay. If one end of the resistors is returned to either the positive or negative supply rail, then you can use a P or N type switch (MOSFET *or* bipolar) to select the resistor and simply read the voltage drop...
  19. MagicSmoker

    Understanding My Crystal Oscillator

    Any possibility that the crystal is actually a SAW resonator? Granted, SAW resonators don't have nearly the frequency stability of a quartz crystal, but, then again, a 200MHz quartz crystal is going to be a rare bird... Try these guys for the latter: IQD Frequency Products (no affiliation).
  20. MagicSmoker

    Color Temperature Meter Recommendation

    Hmmm... it didn't post the link for some reason... Link

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