Thinking_J

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Design products for many industries


Thinking_J

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  • 05.23.2016
  • Teardown: A tiny drone and its controller
  • instructions on these are typically.. dismal. The pushing in of the joysticks typically changes the sensitivity of the controls and sometime the range of control (sometimes the same thing). The video subsystems I have seen on these very small products are often extracted from rejects in cell phone manufacturing. camera, video encoder, micro SD card interface in one piece. Like used in the video key fobs .. ( $5 each) Large percentage of these units are broken from the start. Binding motors is the most common issue. Who is going to bother to demand a replacement? We ended up buying a bag of replacement motors..
  • 12.15.2009
  • Burn-in, burn-in: dc inferno
  • Still, to be fair, I remember a number of projects with crazy schedules that were put in place for this "a time of war", and we were all ready to commit to what ever it took to get the job done. Sad that it takes a war to get that level of unity and commitment.
  • 12.15.2009
  • Burn-in, burn-in: dc inferno
  • The moral of the story? I can think of a couple: - No substitute for extended testing of the final product in critical applications. (We used 8 weeks at elevated temps on samples from every production lot) - "haste makes waste" (3 months of 80 hour weeks?!).. that is just asking for trouble. This story was as much a management failure, as a engineering one.
  • 12.15.2009
  • Burn-in, burn-in: dc inferno
  • Manufacturer didn't specify exclusively for AC applications either..... or short duration DC applications..
  • 12.15.2009
  • Burn-in, burn-in: dc inferno
  • Ouch. I haven't seen a spec on optocoupler for addressing this issue either. Isolation resistance.. is often spec'd.. with a given test voltage. From there you can determine some level of leakage - that may help/apply. With each component there are often dozens (if not more) characteristics that are not spec'd. If anyone thinks they can eliminate ALL assumptions .. they are only fooling themselves. Spec sheets are a starting point... sure.. and one shouldn't make any assumptions beyond the specs. But often one cannot get the additional info regardless of the effort applied. I often come across the need to specify a characteristic .. with no one at the factory aware of their product's performance on the item in question. Even if you go to the trouble of characterizing the component. The manufacturer will not guarantee the characteristic in question will not change dramatically with the next production lot. Result: All of us are forced to make assumptions ...... And sometimes they bite us. Ever try to spec the level of piezoelectric effect created by your ceramic capacitors during vibration of the product? ( creating another noise source in the signal chain). Or try to get specs on the expected value shifts created by ESD discharges..on your resistors? Unless you have no budgetary and time restrictions.. you will be making some assumptions. Still, it possible .. we should try - if possible - to allow failures to be less catastrophic (loss of feed back - leading to smoke)? yikes!
  • 05.18.2016
  • Wet and dry switching
  • I have wondered about this.. the vague threshold defining "wet" and "dry". I was under the impression .. contacts designed for inductive or capacitive (not resistive) loading also played a part in the definition. A bit redundant , generally larger loads are AC and have some inductive component. These terms appears to be kinda .. mmm.... anachronistic? So many issues that an engineer needs to be aware of .. thermal noise of contacts (an issue for switching thermocouples) , intended type of loading, level of loading , etc.. Too many variables to be addressed with any simplified term. A relay story: When I first got out of school , I was performing maintenance on a test panel used for testing very large AC motors ( 5,000 hp, 4160v 3ph... 15 feet tall -vertical mounting- .. used for pumping - flooding valleys) You could drive a small car through these motors when the rotor was removed. We had to perform full voltage @ rated speed (generally 4 pole=1760 rpm) REVERSALS! All the testing had to be performed at night.. .only time it the electrical consumption costs were reasonable.. and the grid could handle it (we had our own substation for just the test rig). The relays used? WWII submarine units .. 12 contacts, each @ 1.5 inch in diam with the entire assembly submerged in oil (contained the arcing and provided cooling of the contacts I assumed). I was asked to replace the contacts (~$500 each in the early 1970s) after a modest level of testing cycles. And sometimes replacing the oil ( ~30 gallons?). I did this multiple times. "wet" ? I think so... under every possible definition applied to relays (physically and loading) Side note: if things went "wrong" during testing .. we could take out the power for hundreds of miles around us. If (when) the motor broke loose during the tremendous forces being applied... well, everyone could break their own sprinting records getting out of the building! Very exciting... seeing one of these monsters run amok!
  • 05.04.2016
  • What is the aspect ratio for 50Ω microstrip?: Rule of Thumb #27
  • Michael, back to rule 0.. I haven't seen anything about the impact of silkscreened images on "impedance" of a high speed signalling line. But I have seen some silkscreening impact leakage currents on very sensitive/high impedance lines. This is rare. And often indicates other issues with your pcb house. The missing item .. for those trying to control impedance and signal quality on high speed signal lines ... is the impact of plating choices (or lack of plating). Not just because of changing thickness .. but because of gradients created and differences in conductivity (copper vs gold vs silver). Keep coming back to rule 0.... Often the best choice is: document what impedance you WANT on given traces and ask the pcb fab house to adjust / test accordingly. So many variations on FR4..
  • 05.02.2016
  • Reduce your prejudice to innovation
  • Jim, I think many (most?) of the larger corporations .. prefer to "buy" their innovative solutions today. ie: purchase IP or smaller companies with the innovations already demonstrated to some degree. I , like you , question the wisdom of "out-sourced" innovation. I understand why it popular. I understand why it is favored (Big corps can apply economies of marketing scale - aka: deep pockets- to the least risky / already demonstrated ideas). But , as with the scales of mass manufacturing changing (cheaper automation), so too the assumptions of resources required for mass marketing are changing (internet). Regardless, I think the message of innovative thinking is being directed at individuals - not corporate policies.
  • 05.02.2016
  • Reduce your prejudice to innovation
  • Appears to be a good read (Ransom's book). I couldn't agree more with the phrase .. "Prejudice: the ultimate form laziness" The laziness of thought.. (valued for it's speed in decision making, nothing more) Still .. sadly .. I understand why it would be so prevalent. Doesn't change the facts .. prejudging (simplifying one's thoughts to only a few options - good/bad/love/hate) always creates... "Prejudice". This form of laziness doesn't lead to any improvements beyond basic survival. Likely why it is so hard for us to evolve past it. Most of mankind's history is exclusively about simply surviving. Only relatively recently has a significant percentage of the population had the ability to live in modest level of prosperity. Effectively creating a conditions for a "new version of man" to evolve in. I don't expect us to change quickly, but I do expect us to change. Creativity, beauty, understanding, often comes from bothering to discern the shadings of truth in this world. Without exploring these distinctions (applying effort), nothing changes. In science or society. Creative endeavors, discovery, exploration... will always involve risk taking. Having enough additional resources to survive taking risks.. that is what has changed. If you discover the risks you take in meeting your needs rarely (instead of "often") lead to your own demise (or the demise of your loved ones) .. you will become more comfortable with taking risk. (risk has changed from eminent death to loss of time and/or resources) We can never eliminate risk. Not taking a "risk" ...becomes another from of risk (missed opportunity) But we can apply a modest amount of logic to understanding it. As stated earlier, I don't expect us to change quickly.