标签: alarm

I tell you, I am not making this stuff up. Well, my chum Jay just sent me a link to an Oscar Mayers' sponsored website boasting an alarm clock that wakes you with the scent of bacon and the sound of it sizzling on the stove. This website has the rather tantalizing URL of WakeUpAndSmellTheBacon.com . This is not a cheap production by any stretch of the imagination. You start off by watching a video that is billed as "A Bacon Awakening Beyond Your Wildest Imagination." Now, I have a pretty wild imagination, but I have to admit that the video is really rather good. You now go to the "Get The Device" page, where you see the message "Transform Your iPhone into a Bacon Scent Alarm Clock." There's even a little animation showing you what this will look like.   From here you click a link that invites you to "Apply for a chance to get the device" (another link invites you to "Download the free app from the iTunes store"). Of course I couldn't resist! I tried applying and was informed that, unfortunately, this was not to be my day. In fact, I was presented with another video featuring Phil Roudenbusch, whose job title is Oscar Mayer Bacon Cut Design Chief (and I thought my job title was cool). In dulcet tones, Phil explained how deeply sorry he was personally that I hadn't won this time, but he reassured me that I was welcome to try again. (You really should take the tame to watch this video—it makes you feel good about losing.) All in all it was a lot of fun, but I am left wondering if the bacon scent attachment really does exist, or whether it's just a cunning ruse to gain my attention (in which case it worked admirably). What do you think? Is this real, or am I just a sucker for all things bacon?  

In a university chemistry department, there is a broad range of equipment, ranging from technologically recent equipment to old equipment, older equipment, and finally the "designers-have-been-grave-stoned for twenty years" equipment. One day a call came in from the Mass-Spec Lab: A quadrupole mass spectrometer, made in the UK, was alarming in standby mode but not in operate mode. Fortunately, we had a set of schematics for the instrument, but the folks across the pond draw things a little differently. Fortunately, deciphering the drawings didn't take long using my super secret decoder ring (a.k.a., paper, pencil, and pencil sharpener). The alarm was coming from a relay board that distributed 24Vdc power to three off-board circuits. On this particular machine, power for each circuit goes through a dedicated set of two (one operate and one interlock) SPDT relays rated to 5A. Both relays are energized to pass power in the operate mode and de-energized in standby mode. Any other relay combinations sounds an alarm. The NC contacts on each relay go to alarm logic, where they are XORed to each other. When the "operate" relay is de-energized, 24V (applied to the COM) passes through a 100kΩ to the NO contact, providing 24V low current signal to the second relay's COM. This is needed at the second relay so when it is de-energized there is a "high" logic signal to the alarm logic through the NC contact. A visual inspection while switching "standby" to "operate" showed that all of the relays were toggling. Using a low-power binocular microscope, the relay contacts where inspected. As expected, the NO contacts showed pitting for current switching. The NC contacts appeared clean and pristine, also as expected since they switched very low current. Measurements with an ohmmeter showed some relays having NC contact resistance ranging from half an ohm to tens of ohms on repetitive relay cycling using a bench power supply. One relay randomly measured higher resistance to megaohms. But continued cycling slowly reduced the resistance. After ordering an identical relay and replacing it, the alarm issue went away. But a few months later the problem was back. This time another relay had the resistance issue. We ordered several identical relays. But the real quandary began after we installed one of the new relays. The alarm issue persisted and was traced back to the new relay. Several of these new relays were tested and a few showed the same contact issue. A "good" relay was selected and installed, getting the instrument back in operation. But what was going on?   After some hypothesis, analysis, meditation, perusing of datasheets on different kinds of relays, a headache, shot o'wiskey, dinner, more shots o'whiskey, sleep, hangover, breakfast, I began to formulate a theory. The relay uses silver contact material, which is correct for switching moderate power currents. But the COM-NC circuit is a microamp (small-signal) circuit. Small-signal relay contacts always use gold plating. Why? Because gold doesn't oxidise. Silver is more durable and withstands arcing better than gold, but silver oxidizes. The arcing cuts through this oxidation. Microamp current at 24V does not arc and, therefore, does not clear the oxidation. Over time the oxidation builds up, causing contact resistance problems. Obviously a design goof or oversight by engineers on the big island. (This might be one of the reasons why in 1620 a small group of them left and started a colony called Plymouth.)     So what to do? One solution was to add a load resistor to the NC side to pull more current, thereby causing arcing to clear the oxidation. But this would not work on the second relay due to the 100k resistor. What we needed was a relay with silver on the COM-NO side and gold on the COM-NC side and also fit in place of the original relay. Right! What else? Re-designing the circuit was not an option due to down-time and budget constraints. Hum! What followed almost defies commonsense, but we are academia and the rules do not apply. Take a relay, remove the cover then disassemble (see picture). Go to the junk drawer and get an edge-card connector with gold contacts and remove a contact. Un-curl it. Use a rounded-end punch and piece of hardwood to make two bowl-like dimples. Cut out the dimpled areas forming small pieces for soldering over the NC contacts. File the NC contacts down to make room for the gold contacts. Tin the NC contacts. Using the old-school silicon heat-sink compound and wooden tooth-pick, carefully put heat-sink on the convex side of the dimpled contact. This will keep solder from flowing onto that surface (Ssshhh! This is a secret technique so don't tell anyone.) The heat-sink will also hold the small contact to the toothpick so it can be flipped over. Tin the concave side. Heat the relay contact to melt the tinning, then carefully place the concave side of the gold contact over the relay contact and wait for it to heat. Remove the heat and carefully hold until the solder cools. Repeat process for other relay contact. Clean off heat sink. Reassemble relay but leave the cover off. Use bench power supply to cycle the relay and verify the NC contact arm flexes slightly, bending the NC arm as needed. This insures there is contact pressure. Put on cover and store this "special" relay. Breath deeply, have a cup of coffee, and stretch. Move onto the next project—plastic membrane switch/label eaten off the hot plate... chemists!   About two years later, the instrument failed again, alarming in stand-by. Testing showed one "bad" relay and another following suit. Repeat above process on another relay. We installed these "special" relays and tested. No alarms! Yesss! It has been three months now, and only time will tell if these relays fail. The modification for one takes about an hour of delicate work. A second identical mass-spec has since arrived in the department, improving odds on opportunities for us to mod more relays. But, hey, America's got talent! Richard Bedell, electrical engineer, submitted this article as part of Frankenstein's Fix, a design contest hosted by EE Times (US).  

Several days ago, at about 3AM, I was awakened by a very annoying electronic "meep" sound. I'm sure it must be from a smoke detector or something of that ilk telling me that its battery needs replacing, but I couldn't work out which device was clamoring for my attention. Apart from anything else, I hadn't realised just how many "things" we have in our ceilings. When I actually started to pay attention in the wee hours of this morning, I discovered that we have white plastic enclosures with flashing LEDs all over the place... in our bedroom... in our bathroom... in the corridors... Good Grief! Even when I take things like motion detectors and smoke alarms into account, there seem to be an awful lot of other things up there and I have no idea what they are all doing. It's very, very strange. But back to my annoying "meep". First of all I attempted to use a low-tech approach... I tried to ignore it. I might have succeeded if the time between "meeps" had been just a tad longer, but another "meep" invariably came just as I was poised to slide back down into the land of nod. So after what seemed to be a year or two, I decided to find the offending unit and either (a) replace the battery or (b) reprogram it with a mallet. I couldn't turn on the light because I didn't want to wake my wife (Gina the Gorgeous), so how does one go about determining the origin of the sound? I don't know why, but for some reason the source of the "meeps" is not easy to pin down. Is it just my imagination, or are the duration of the "meeps" and the spacing between "meeps" designed to make it almost impossible to determine where the noise is actually coming from? Following a "meep" you take a few steps and then stand there for ages waiting for the next "meep" (it may be only 10 seconds or so, but it seems much longer), and then off you go again. This really is very annoying. Do the people who create these products ever actually "field test" them in any way? WHY is this so difficult? It would be much easier if the %^#$# thing went "meep ... meep ... meep ... meep ..." so you could hone in on it. Or how about augmenting the "meeps" with a rapidly flashing LED – would that really be so hard? And what about incorporating some sort of sensor or timer so that the thing only starts "meeping" around dawn or dusk, which would mean that there would be a good chance you are in the house to hear it along with a reasonable chance that you wouldn't be fast asleep when it goes off? But do you know what the really frustrating thing is? I couldn't track down the offending unit in the dark, so I ended up sticking cotton balls in my ears. Then, when I awoke this morning ... the #$%@# thing had stopped "meeping"!!! All I can say is that I did not wear my happy face that day...