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[Pease Porridge]

Bob's Mailbox



Bob Pease  |   ED Online ID #8187  |   June 21, 2004

Article Rating: Not Rated

Dear Bob: I enjoyed (well, as much as experiences of the sort would let me) a few months ago when you were discussing the convenience of modern credit-card billing shenanigans*—relating to my own protection and my typical spending patterns. My mother expounded to me a tale of this as it relates to a company that does this "service" in-house. I thought that was a bit odd. I wanted to forward it because it is more of the same. But my mother seems to have handled it well. I know she did better than I probably would have, but it may be a true "mother thing." (Note, mothers usually have learned how to handle idiots. But I think your mother handled it better than usual! /rap) Here is verbiage she sent me, knowing I was going to forward it along to you. The name of the business is blotted out.

"I purchased several books three times in 10 days at XXXX. When attempting to purchase additional books within two weeks, XXXX informed me that I had a 'bad check' alert on their register and they could not accept my check. Bad move on their part! I had the manager come to the register and he said that it must be the case ('bad check'), and I said absolutely not and that we would call my bank to verify the balance. The bank substantiated my statement of more than adequate funds.

"I suggested the manager contact the XXXX head office to verify their practice—which SEEMS to consist of stopping business if a person places orders for more than three items in less than 10 days. (THAT certainly would seem a special DIS-incentive to discourage repeat customers. Like, sorta the opposite of "Frequent Flyer Miles." /rap) He called back to tell me that no such practice existed. I got the name and number of the head office and contact person and called. Finally, I reached someone that confirmed that XXXX does use this practice 'to protect' their franchises.

"I talked with the local manager again and gave him the name and phone number of my head-office contact. He called and learned this is a practice. The manager apologized profusely and I requested that he send a letter of error to my bank and credit agencies, which he did. He also gave me a $50 gift certificate for the trouble and embarrassment. I very seldom shop at any XXXX after that experience."

I just thought this was great and that it spoke more along the lines of the topic that you brought up. Although it's regarding checks, it is an important note since it is so typical to verify based on routing and checking account numbers scanned from the checks these days.

Colin Shaw (via e-mail)
Pease: It sure does seem these guys are screwed up, and their right hand does not know what their left hand is doing. I think I know what kind of business they should be in: They should hold a big GOING OUT OF BUSINESS SALE! And, I'm glad your mother knows how to handle mistreatment of her credit.

Hi Bob: Your "Analog PowerPoint Stuff" article was great (Electronic Design, March 29, p. 18). I wish I had a nickel for every idiotic, substance-less PowerPoint presentation I have ever been forced to soak up. It also reminded me of the view graph competition that took place a few years ago between Dave Middlebrook and Slobodan Cûk of Caltech. They and their respective students were always trying to outdo each other with Analog PowerPoint overlapped sheets. Movement of the sheets resulted in some very clever animation effects and were always great to break up the formality. I wish I could remember some of the specifics, but the details are lost in the mists of Machhapuchhre!

Nicholas John Tsacoumangos (via e-mail)
Pease: Those are great mists! I saw those mists on the evening of June 15, 2002, at 7:00 p.m., from NauDanda! Then we bicycled down to Pokhara, in about one hour flat, ALL downhill. Thanks for writing.

Comments invited!
rap@galaxy.nsc.com —or:

Mail Stop D2597A, National Semiconductor
P.O. Box 58090, Santa Clara, CA 95052-8090

*Electronic Design, Oct. 13, 2003, p. 20




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    Reader Comments

    What about calibrating circuits when you don't want to pay top dollar for calibrated sources? If you have any general comments, please share them. More specificly, I am trying to calibrate a UV meter. It works fine but I wish I could help the faith of the biologists in my lab with an appropriately labeled scale. We do have a source that thinks it is calibrated. And it probably does pretty well when the bulb doesn't flicker for the first few seconds. Can you shed any light on the topic? (No pun intended.) -- Kevin Neff

    Hello, Kevin. It's HARD to calibrate a kilovolt meter, but easy to calibrate a UV meter. Is your meter an ac or dc meter? Take a good signal source, dc or ac as needed. Take some SUITABLE 1% resistors. Design a good attenuator, to get a volt attenuated down to X UVolts. Use 2 or 3 stages, cascaded. Measure all the resistors with a good meter with full resolution, better than 0.1%. Compute the actual attenuation. Put in a good calibrated signal, dc +, and then reversed using a reversing switch, for dc-. (If ac, establish the input amplitude). Compare this to the output reading. Adjust or trim the gain of the METER until the calibration is right. You can probably prove the accuracy is well within 2%. Put on a calibration sticker and sign it, and date it. Keep this calibrator so you can do it every year, or as required. NOT rocket science. Okay? Best regards. /rap

    Kevin Neff -July 06, 2004

    Dear Bob, I'm a sincere enthusiast of LEDs. I would like to make a nice LED flash lamp for my daughter.

    (In the U.S. a "flash lamp" puts out "flashes" of light, little bursts. A " flashlight " is what you use for light to walk around in the dark. Is that what you want? /rap)

    Perhaps 6 arrays of white LEDs. I have heard about low-volt designs (3 V) using a step-up volt design. If it is not a big effort, please send me a circuit diagram. Thank you and regards, KJ Kumar

    Hello to Mr. Kumar. THIS is not perfectly difficult, nor perfectly easy.

    Let's say you can find a group of white LEDs that are not too expensive, but are efficient in lumens/ watt. Get them and measure them. If you put 20 mA through each one, are they bright enough?? A stack of 6 would be perhaps 24 V x 20 mA or 1/2 W.

    NOTE that the eye is logarithmic in its sensitivity. More watts does not give much better lighting.

    There are several NSC IC's that will convert (1.5 V to 4.4 V) to enough current AND voltage to light up LEDs at 10 or 20 or 40 mA, in switching mode. THIS may take me a few days to find the circuit that is appropriate.

    The LEDs might take the 10 or 40 mA in series, or in parallel. YOU might make one for her and one for yourself. If it is a good design, you'll make at least 3.

    Do you want a low beam and a high beam? This is wise, I think, as we do not always need full "high beam" brightness. That's what I do.

    NOTE, there are more than 2 dozen kinds of LED flashlight on the Web. Search around. Some are inexpensive, some are very expensive, some are in-between. Most have NO SPECS on overall brightness or battery life. The "PALIGHT" is not bad. Why not just buy 3 of those for $60? That will get you GOOD packaging, which is not easy to engineer on your own, for a quantity of 3... OR, buy ONE of them, to compare with your best design.

    I often walk around at night with one LED running at 8 UA. It's surprising how much light that can give. I can read my watch; I can get out the door and back. C cells are much more efficient at this than AA cells. D cells are 2 x cheaper, as a D-cell that has 2 x the energy, costs no more than a C cell.

    Will she have to carry this many miles? Those D-cells get heavy. I just hiked UP 35,000 feet in Nepal, and 35,000 feet DOWN. Carrying my flashlight that was no heavier than a 9-V battery.

    As you can see, there are no easy answers. Hell, the questions are not even easy!! Right? Your comments are invited. Best regards. /rap / Robert A. Pease

    KJ Kumar -June 24, 2004

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