ed ro

's profile
image
President

Ed Rodriguez was founder/CEO of Theta-J Corp(now the Clare division of IXYS Corp). In that role he developed the optical MOSFET solid state relay, now a global defacto standard in the telecommunications industry. He is a veteran of the power semiconductor, power supply and LED lighting technology industries.Early on, before becoming an entrepreneur, he was a product manager with Unitrode (now part of Texas Instruments.) Keynote speaker at 1986 MIT national conference on advanced power electronic technology, he has published dozens of feature articles in the leading technical trade magazines. He also has been noted in Forbes and Wall St Journal. He holds 22 patents with 8 pending, virtually all involving successfully commercialized products. In 2005 , he formed OptoThermal Technologies to focus on thermal management technologies related to high-power LED lighting.


ed ro

's contributions
  • 10.08.2013
  • True or false: High-power LEDs don’t generate IR heat in the forward direction like a filament lamp
  • It is good to see continued comment. Some final thoughts. In my experiments, I was supported by several PhD’s with far more knowledge than I about radiated energy. I was first drawn into the efforts after observing some thermal “anomalies. Wth over 40 years experience as engineer, product mg and CEO in the power semiconductor and optoelectronics biz so I certainly had a “passing” awareness of all that goes on. Furthermore, I tend to focus on thermal management of power semi’s, so over the years got to believe I “knew it all”. Wrong! Very recently I’ve become involved in the high-power LED “grow light” area and observed that a 100W blue COB ...operating at less than 60C case temp, could make wax melt, and paper smoke--- and almost burn my hand if too close to emitting surface. I do not need to understand with certainty the physics of how this 440nm blue light, causes things to cook The point is that the energy, manifested as heat, does exist and can make “bad things happen”. My point was not to create a technical paper for endless debate, but to point out that these effects are real, quantifiable, and can be important to know (from an applications standpoint). That means that engineers need to be cautious when high-power emitters are in enclosed areas or close to heat-sensitive surfaces and components. Surfaces or enclosed air spaces on the emitter side can exhibit higher temps than assumed after one simply does the math for junction watts and the various thermal resistances in the path from junction to air. I have no interest in endlessly debating the physics of what is happening. There are plenty of smart readers available for that (some of whom may indeed be correct about certain aspects).But to paraphrase the last writer--- Actually going to the bench and doing things can sometimes be an eye opener. Ed Rodriguez
  • 10.30.2013
  • That 60W-equivalent LED: What you don’t know, and what no one will tell you…
  • I know you seem to have already answered your own question –but for the record-and for others who may have similar question—Let me provide some facts, based on certain specific projects I am now involved in regarding 40- and 60 watt-equivalent LED bulbs. I have mentioned that in last 18 months there has been rapid standardization of 40 & 60 watt types in industry in that all major suppliers—GE, Sylvania, TCP, Feit, Cree, and Philips now offer low-cost bulbs in the standard A-19 shape virtually identical to the familiar, smooth profile 60 watt incandescent. Except for Cree everybody now uses same curved-metal-shell heatsink approach. All are tested per UL 1993 and confirmation that internal capacitors do not exceed 90C. upside down or not. TCP, Cree and Philips OK for enclosed. GE and Sylvania do not allow use in enclosed fixtures. . To be approved for enclosed fixtures, UL tests in an enclosed steel "box" about 6” X 6” X 6”and confirms again that a bulb’s internal capacitors do not exceed 90C. This says -- unless specifically noted on packaging--- do not use in enclosed fixtures. A 40 watt LED bulb of today such as the Cree, Philips or TCP item(which is sold under Great Value label at Walmart) puts out a lot of perceived light when used in outside sconce-type fixture-in an otherwise pitch black area—and makes the enclosed fixture a non issue—more than enough light unless you are trying to play badminton or read a book in backyard at night. A lot of this is helped by fact that the newest 40 watt/450 lumen (I.e. high efficacy) equivalent LED bulbs only dissipate about 5 watts.
  • 10.30.2013
  • That 60W-equivalent LED: What you don’t know, and what no one will tell you…
  • First of all there is ZERO safety or fire hazard if you use any 100 or 150 watt “equivalent” LED bulb in a table or floor lamp. That is because the LED version will actually use only about use about 15% of the watts of an incandescent of that actual wattage—so really only 15-25 watts !! You will find that a 100 or 150 watt –equivalent LED bulbs are still much larger and more expensive than today’s most popular 40 and 60 watt types—but heat or safety not an issue. Separate commentary---. Since my first remarks few years ago-dramatic change-- prices of a 60-watt-equivalent have dropped from the $8-10 range to today’s pricinginUS of $1.50 to $2.50 each at almost every mass merchandiser—a far faster drop than ever imagined. Has ended the CFL-versus- LED bulb debate. Today It makes almost no sense to buy a CFL which, even if only half the LED bulb price a) takes up 60 seconds for full brightness b) only lasts only 1/6th as long in very best of situations and c) has poorly specified accuracy on color temperature temperature(warm white, cool white etc) Furthermore, after 10 years of dozens and dozens of mfrs producing every conceivable kind of configuration, the industry has now settled very firmly into an A-19 standard shape almost identical to the long familiar incandescent bulb. It is a certainty that not a manufacturer in the industry is making a cent of profit on today's 40 and 60 watt residential LED bulbs but the high volume is giving them a volume base which translates into profitability for all their much higher priced industrial or special purpose types, such as Par 30, 38, candelabra types etc Ed Rodriguez www.optothermal.com
  • 06.14.2016
  • LEDs in stores could leave a bad taste in your mouth
  • I would flunk the Cornell researchers ( rookie grad students conceiving/doing the experiment?) for sloppy science. For any regular transparent or translucent quart, half gallon or gallon container of milk, any outside LED lighting is greatly attenuated at only 1/4" from outside container surface---- and, at one inch inside, there is essentially zero light penetration. This is really easy to test in a couple minutes (which I did). So any poured glass of milk, from a new container, in the worst case, will contain a mixture of at least at least 95% "good" milk with a max of 5% "imperfect" milk. So this is a make-believe problem- -unless consumers buying their milk in Petri dish containers. I am unaware of any supermarkets who sell milk that way. Looks like our better engineering schools are losing something off their fastball. Ed Rodriguez OptoThermal Technologies Inc
  • 04.20.2016
  • What you don’t know about LED light intensity curves for grow light apps
  • The challenge is not just to achieve a result but to do it while meeting cost thresholds for commercial practicality.There are optical methods to create grow light 45, 60 or 90 degree beam angles with less than 10-15% "received" light level variation across an entire grow bed but the cost is prohibitive for 95% of growers. The real intent of the piece was to point out how misleading the "light intensity" curves can be for so many commercial lighting products (LEDs, optics and finished lamps), not just grow lights. Not sure an Abbe reflector approach for an LED array would address any of the issues here. (from one who worked with many kinds of military radar parabolic antennas early-on in my career before I moved over to the semiconductor industry)
  • 10.08.2013
  • True or false: High-power LEDs don’t generate IR heat in the forward direction like a filament lamp
  • good to see that folks still reading these things. However, in these LEDs, nor any other commercial LED the material is gallium based, "NOT" silicon, so silicon defects not the issue. Since originally writing this I have become more educated on the subject, which indeed is very complex and the subject for discussion among those whose careers have refleced an emphasis on radiated energy--- really into the physics of all this. When and how IR is secondarily generated and manifests itself as forward directed heat with high power blue LEDs-- phosphor coated or not-- would be a great grad student project. My only caution to designers is to not take literally the idea,common 12 years ago, that LED's run cool and send "no" heat forward . Heat sinking the back side is a given but convective heat removal, heat coming forward , and potential IR heating of nearby things is not to be ignored. Moral of the story? Make sure, before putting a higher power LED lighting product into production , that all surface temps near the LED are close to what one thinks they are, no matter what your math has predicted.
  • 10.30.2013
  • That 60W-equivalent LED: What you don’t know, and what no one will tell you…
  • The reason your bulb does not work in horizontal position is going to be EXTREMELY SIMPLE reasons--such as the socket depth is a little deeper so tip of bulb does not make contact and you have to screw it in a little tighter to make cntqact-- and hopefully not break it--but that sometines happens with socket depths.There really is no mystery here and if I had your chandelier and bulb I would figure it out in two seconds. I assume that 1) your previous bulb, or a rgu7alr ncadescent bulb works OK in that hariznatal socket or 2) that bulb which doesn't work, "does" work in another fixture. I assume, snce you bought oin Amazon, you bought because of lowest price and that 1) it is NOT UL listed. If you really want to know what;s going on, go to Lowes and buy a similar candelabra bulb from Feit, Sylvania or Lowes'"Utilitech" brand, make sure !!!!! package says "UL Listed" or has that little UL logo, and try it. Buying "no name" LED lighting products of Amazon, in my opinion, is risky. I oftent do it for experimental purpose but would never install an LED bulb in a fixture in my home unless from known firm and UL listed. I have spent over 40 years as engineer and CEO in related tech industries, especially LED lighting in last 8 years, so, as my wife well knows, I don't fool around or try to save a buck when it comes to electrical things. I have advised my three sons, for their homes, accordingly on LED lighting and dimming matters.
  • 11.04.2015
  • Can GE's new LED bulbs help you get to sleep?
  • This GE announcement "reminds" me.... With all the breathless commentary over the last 5 years about the validity of the so-called Haitz Law and the constant march toward 300 lumens per watts--along with he breathless announcemetns over last 24 monthsr ago of over 200-250 LPW for LEDs ,by Cree and others.--------- if readers go to Hmee Depot and Lowes. and pick up latest "state of the art" GE Bright Stik or latest from Cree and Philips ,you will see lumen per watt figures under 70-80 LPW. So much for Haitz Law and the American consumer, Consumer led bulbs have changed little in terms of efficacy over the last 3 years. Lower prices are synonymous with using the bottom end of LED mfg distribution with the "good stuff" only finding its way into commercial lumenaires. There's a method to the madness. Ed Rodriguez
  • 10.30.2013
  • That 60W-equivalent LED: What you don’t know, and what no one will tell you…
  • Reader mentions that COSTCO shop light works OK. Makes sense. Today, many low cost, relatively low wattage, simple LED "fluorescent-tube-replacement" type products use a simple series string of many LEDs . along with a 15 cent bridge rectifier and a one cent resistor as a "ballast" instead of an LED power supply (aka Led "driver" or even the AC LED circuit" I had alluded to. The simple LED string, with dozens of cheap LEDs, with a resistor and rectifier, has relatively lousy power factor(but still OK per industry min standard) ,loses some efficiency and other properties but is really cheap to make and perfectly adequate for a low cost "basic function" shop light . Having no need for a capacitor in it would make it immune to that flashing characteristic,
  • 10.30.2013
  • That 60W-equivalent LED: What you don’t know, and what no one will tell you…
  • There are no such things as lighted switches which can work for you--neon or led.. The problem of course is that a "lighted switch" is never really off. It is "cheating" and powering the neon . and the neon typically acts like a 47K ohm resistor connected across the switch contacts, allowing a small charging current to flow and charge up large capacitor in the lamp internal power supply.As soon as the capacitor charges, there is enough power to momentarily turn on the lamp.No big deal and perfectly safe but indeed you have discovered an interesting "anomaly". The problem will not exist if you control a lamp or LED fixture having what is now called an "AC LED" direct-drive circuit--no internal power supply and no charging capacitor. Home Depot now sells low profile 10 watt ceiling mounted LED fixtures(made by Lithonia/Acuity) --about $20--with this circuit ( I have one here) , but there are not yet ( I don't think) any lamps readily available with this circuitry (for reasons I won't go into here)--Ed Rodriguez