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  1. DHambley

    Residential structures - Code enforcement in Northwest Arkansas?

    Preface: I'm a retired PE from WA State, building a home in Benton County Arkansas. We found a builder who has built many homes in this area. I liked him as he personally performs all the tile and trim carpentry - really nice work. We picked a floor plan (I have no time nor desire to design...
  2. DHambley

    I am an aircraft and aerospace cont

    Robert, If the new NX10 software is the wave of the future you might consider that $5k a valid business expense and buy it. In my line of work (electrical) I used to use Cadence Orcad software. Many clients were using Mentor PADS instead. It cost me a total of $6k to buy the software and take...
  3. DHambley

    System Identification. Do not pass go, do not collect $200 until you learn how to do this

    Peter, I liked your first video (didn't have the time to watch all three). I've been "closing loops" for 30 years and it was nice to brush up on some basics as seen from another point of view. Yes, I cringe too when someone thinks that trial-and-error is engineering. NOT. Engineering is applied...
  4. DHambley

    PC board anchoring for Aircraft Vibration

    jgKRI, The attached single-sided board just might work. Are you thinking of flush headers or something to connect the two boards? Darrell Hambley P.E. SENTEK Engineering, LLC
  5. DHambley

    How to avoid damage to resume

    Engineers here posting on E-tips may have an idea what a resume should look like if they were the engineering lead looking for help but, often the gatekeepers (HR) have a different view. It's very enlightening to read HR blogs in LinkedIn to get an idea of what HR people are looking for in a...
  6. DHambley

    PC board anchoring for Aircraft Vibration

    I have a small, approx 1.25" x 2.5" PC board (called a daughter board) which I need to connect to a larger board. In our box there is only enough room to either, 1. Attached the smaller board at a 90d angle to the mother board with a 90d connector or, 2. Bolt the daughter board several inches...
  7. DHambley

    phase shift calculation

    MRSSPOCK, The sin(x) and sin(2x) waveforms you show remind me of the relationship between input voltage into a resistive load vs the power which the load sees (which is double the frequency of the fundamental) or, the voltage out of an inverter vs. the power delivered by that inverter (power is...
  8. DHambley

    Power Supply Not complying with the new DOE Level VI Performance Requirements

    EEMan, Interesting post. Thanks for the heads up. I just looked up the new 2016 DOE requirements. Yikes. The 100mW which you mentioned is 200mW less than the old 300mW standard. That in itself required everyone to redesign input stage filters. Let's see: 0.2 W savings x 24 hrs x 365 days =...
  9. DHambley

    Telecommuting...why is this so HARD TO FIND???

    Kevinas, In my 12 years of contracting I've only had one client who was OK with me designing from my home office. I'd fly to the plant location once a month to do the necessary hands-on work and 2/3rds of the time I was at home. They trusted me and I delivered. The new product line has sold in...
  10. DHambley

    Power Supply Smoothing without Capacitor?

    For a more realistic application the question might be: "How can I reduce the size of the filter capacitor in a AC/DC power converter?" Some in the industry use active filtering to smooth the ripple voltage of an output capacitor or a DC link cap. Instead of using a huge aluminum electrolytic to...
  11. DHambley

    Arizona at it Again

    I was surprised at the method which Warren Petersen (R-Gilbert) suggested for safety, "unhappy customers could write bad reviews... on Yelp". So, instead of a licensed landscape architect who ran calculations of the strength of a retaining wall, the state saved money by just hiring a guy with a...
  12. DHambley

    A SMPS transformer question

    SnubberRoger, Yep. I think Comcokid's answer is right on; Big noise suppression beads. hmmm....He might be one of these geniuses who just see's obvious things that many of us don't. Darrell Hambley P.E. SENTEK Engineering, LLC
  13. DHambley

    Understanding Core Loss Measurement

    Hi reson8or, There's a typo. You're right, it isn't Ipp. It's ipp for eq 3.1. Looking at figure 3.3 If you split up ipp into i+ and i- and also split Vpp up into V+ and V- then, do algebra for 2 minutes, you'll come up with: P=D*(1-D)*Vpp*ipp which is the correct eq 3.1. You will see...
  14. DHambley

    Failure of attachment points during RTCA DO-160 Vibration Testing

    rhlg, Could you explain a little more about what these "attachments points" are? Do you mean the bolts themselves which attach the UUT to the aircraft which are "representative of actual installation"? or is it the test equipment that these bolts (or rivets or whatever) are attached to...
  15. DHambley

    Electrical Power PE Exam study material

    While the code books are full of information, they make for very boring reading. Memorizing a bunch of codes may help with some questions on the PE exam but the exam mostly demands your mathematics and critical thinking. What I found is best are the study guides (They weren't called ppi2pass...
  16. DHambley

    High Amperage Boost Converter Design

    A boost is not a good topology for 17kW. Assuming you'll get about 95% efficiency, you're dealing with almost 400 Amps in the primary. I would spend some time performing some topology studies. Here are just a few suggestions for study: A single full-bridge using one of those Infineon...
  17. DHambley

    PCB reliability

    IRStuff, Thanks for those links. It was weird reading the reasoning in Weglinski's paper; He decides to only consider thermal effects even knowing that power supplies do fail often at turn on, and noting that the turn-on surges degrade components considerably. He wrote that the decision to not...
  18. DHambley

    Case grounding requirement of electronic equipment in composite aircraft.

    answering some of the questions: This is for commercial and general aviation for avionics in the cockpit as well as power for other LRUs. The goal is to save a few dollars by not supplying a grounding strap or spending additional money to remove anodizing from the case. This is very important to...
  19. DHambley

    Starting of Synchronous Gas Turbine Generator with Load Couumtated Inverter

    Rockman, I can't tell from your first post if this LCI topology which you are looking at is a separate circuit for start up than the normal generator circuit. As you most likely know, you can use the inverter for both a generator and motor starter. Starter/generators I have designed utilized a...
  20. DHambley

    Case grounding requirement of electronic equipment in composite aircraft.

    Berkshire, Good info about the conductive layer in composites. I went to hit the "Star it" button but hit the "Red Flag" by mistake. Then it went off the screen so I don't know what you'll see in your in-box. Sorry. Darrell Hambley P.E. SENTEK Engineering, LLC

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