Electronic Design

What's All This Reflex Response Stuff, Anyhow?

I must have been quite small when I learned that if I dropped something heavy, I should jump so as to pull my feet out of the way of the falling object. For example, if I dropped a brick that fell toward my right foot, I didn't have to worry about my left foot, but my right foot had better clear out quickly. Obviously, just about everybody learns this early enough that you have no recollection or memory of how you learned it.

At a somewhat later age, I learned that if I dropped my glasses, or my watch, or any delicate object, it was pretty easy to swing one foot underneath that object. Even if I could not entirely prevent my glasses from hitting the floor, I could deflect them so it would only be a glancing blow. And I have developed that knack, so it's pretty automatic for me.

Then, the other day - in the summer of 1990 - I dropped something, and I did not move my foot either to catch nor to avoid the object. Well, I asked my leg, what is this that you're so blasé about? I reached down and picked up - a stick of butter. My leg had apparently made a decision that a 4-ounce stick of butter was not worth worrying about, one way or the other. Smart leg!

I mentioned this at work, and a friend (who has a lot of experience as an auto mechanic) said, "Okay, here's the fourth situation - the fourth quadrant. Let's say you are working on a Porsche, and you leave the starter motor up on a bench. Suddenly you notice that the starter has just rolled off the bench and is on its way to the floor. It weighs 30 pounds. It costs $900. NOW, what do you do with your leg?"

After some consideration, I figured that I would try to kick the starter with my toe, pretty hard, about 16 inches off the ground, so my toe would not get crushed, but it would have a chance of slowing down that heavy object. But I haven't gone to try it out.

Now, there's a very good and very serious application for this kind of pre-planning, pre-judging what kind of a reflex reaction you will make, instantly, in a particular situation. Let's say you're driving along a freeway, and suddenly you spot a dog in front of you. You may blow your horn, but some dogs really don't pay much attention (some of them are deaf, and others are stupid enough, they might as well be deaf). Okay. What do you do? You might hit the brakes, but if there were a truck on your tail, he could do lots of damage to you. You might swerve. That's a better way to avoid the dog (unless the dog dodges in the same directions as you do - I've seen that happen). But what if there's a car passing you? You could easily wreck your car and any number of other cars, too, depending on how many cars are around you. Or, if you dodge really hard, you could go off the road and cause additional trouble. A woman was observed trying to dodge a dog on Route 93 in Medford, Mass., about 20 years ago. She missed the dog but went off the road, down an embankment, and was killed. Bad move.

Now, I'm not suggesting that you just hit the dog. In many states, if you hit a dog, you have to file a report with the police, and you might have to cart in an injured animal to the vet - no fun at all. Nobody really wants to cause pain to the dog, even if the dog is out where it shouldn't be. So, it's worth some effort to try to avoid the dog. But, what is the right answer?

The answer, I'm convinced, is to keep aware at all times of how much traffic there is behind you and beside you. If you're convinced there's nobody beside you, you can cut the wheel hard and avoid the dog. If the road is empty, you can also brake. Just try to avoid losing control. You might damage your car if you hit a big dog, but you might wreck it if you lose control completely.

And if you know there's heavy traffic all around you, well, you can try squeezing to one side of your lane to give the dog a chance to miss you. And all of the time you must have your thumb on the horn. Maybe the dog isn't deaf, just a little hard of hearing. And, after all that, if you do hit the dog, you have tried your darnedest to avoid hitting it. You did your best. But you can't do your best without being aware of traffic, and without planning in advance.

Now, if you're really aware of what's around you, you will also be prepared to dodge a deer, or a concrete block, or a loose wheel - or a child. Obviously, it's worth a lot to try to avoid a deer, because at 50 mph, almost every car will have several thousand dollars of damage if you nail that deer. And you'll be lucky if you don't wind up with the deer in the front seat with you. As for dodging a child - I hope you never have to do it. But just in case, I hope this column helps you to plan what to do. I know that in Massachusetts there's a truck line (the Crystal Freight Co., Wakefield, Mass.), and on every truck they have painted a scene with the caption: "Crystal says: After the bouncing ball... comes a running child." The scene shows a kid about to chase a bouncing ball out into a busy street. I used to laugh at that because it seemed so far-fetched. Then one day, two times, a bouncing ball sprang out from behind a parked car, into the street, right in front of me, In each case, a kid stood hesitantly by the car, wise enough not to run into the street. But I stopped laughing at Crystal and her silly saying after that.

Here's another angle on safe driving. Suppose you think you see something up ahead in your lane, and you're not sure if it's a blob of cardboard, or a dog, or whatever. As soon as you get at all suspicious, bring your foot over and give the brakes a tiny tap and start looking around for a clear lane behind you or on one side. If there's somebody behind you, it will catch their attention pretty quickly, so if you do have to hit the brakes hard, the driver behind you will be alert, too. Sometimes this is called defensive driving, and it sounds a little silly, but if you can use these techniques on the rare occasion there really is a dog or large object blocking your lane, you won't feel so foolish about tapping your brakes a little early, before you get all your plans made up.

When the N.Y. Giants played the S.F. 49ers in December 1990, the football experts said that Giants quarterback Phil Simms was playing much better that year. He had learned to throw the ball away or take a sack, rather throw into a crowd. Now that's a sensible reflex reaction. But on the game's last play, with the Giants losing 7-3, Mr. Simms could not find an open receiver and wound up getting sacked. The wisdom of refusing to throw into a crowd is imperfect if there's only one play, and you don't have any other chance to win. Every habit should be accompanied by an awareness that there are times when it doesn't apply.

Now, at this point, I wanted to give you some sage advice on how to use pre-planning and reflex response to help you in the electronics business. I had written this far, and could not think of a good example. But Frank Goodenough read my first draft and came to the rescue. He pointed out an old saying, "Never try to catch a falling knife." No matter how fast you think you are, it's very unlikely that you can grab for a falling knife 10 times without getting your hand seriously sliced at least once. Even if the knife isn't moving very fast, your hand is coming over rapidly, and it's astonishing how deep a cut you can make in that situation. In other words, it ain't worth it, and you had best plan your reflex response in advance so your head will automatically tell your hand, "Don't try it."

In the electronics business (see, I told you I would get there eventually) there's a good analogy: "Never try to catch a failing soldering iron." The odds are about as poor as trying to catch a falling knife, and the payback is equally painful. So, it's worthwhile to have a holster where the iron can be kept safely without likelihood of falling. Then drill the idea into your head, that if the soldering iron does fall, well, let it.

Frank related the story of the technician who was kneeling on the floor in front of his bench, looking for a part he had dropped. When he found it, he reached up and set it on the bench. Then, being an agile and sprightly fellow, he decided to spring to his feet. He put his hands on the bench, and gave a great LEAP - followed by roars of pain. He had inadvertently put one of his hands down really hard on the business end of his soldering iron, which was not in any holster. He was lucky to get out of the heavy bandages in a few weeks, but he got a very painful lesson about leaving hot items where they can be contacted accidentally.

Frank also proposed that I extend the analogy to a stack of lab equipment - pulse generator on top of three power supplies on top of a scope on a cart. If you live in California, you know there's always a 0.05% chance of having your set-up topple in case of a 'quake. Even if you don't work out here, somebody could stumble and bump into the cart. And then you have the privilege of diving to see if you can intercept a couple of those valuable pieces of equipment before they hit the floor. It's a little outrageous, but valuable things do sometimes take a dive. Just make sure that your head automatically decides that if there is a soldering iron, that is not a good thing to try to grab. And perhaps you could set up your equipment so that the stack is unlikely to topple. Maybe you can wire it together, or tape or strap it up so it cannot fall.

Once upon a time, when virtually all electronic equipment ran on vacuum tubes, it was easy to remember that you could easily get a shock from almost any node of a circuit you were troubleshooting. So the rule developed: When probing or trouble-shooting a circuit, always keep one hand in your pocket rather than hold onto a chassis or rack. Then if you brush against a high voltage, it will not cause a lot of milliamperes to flow right past your heart. The odds of being electrocuted used to be greatly reduced by this simple precaution.

These days, the new transistorized circuits are all at low voltage - except when they aren't. There are line-operated switch-mode power supplies, and high-voltage boosters that can put out +/-80 volts - and suddenly that old precaution of keeping one hand in your pocket is beginning to look pretty smart again.

So, whenever I start work on a high-voltage circuit, I tack in a neon lamp in series with a 100k resistor across the high-voltage busses. Then when I see the neon's glow, I'm graphically reminded that this really is a high-voltage circuit, and that the power is still ON (I don't care what the power switch says) and I should revert to the mode of High-Voltage Cautions. If I grab onto a really hot wire, the shock might not injure me, but I might convulse and jerk backwards. That's not a good idea if I'm standing on top of a ladder, for instance. So, looking for the glow of a neon lamp is a way to remind me to be serious, and I recommend it for you, too.

Please do try to keep aware at all times while you're driving, whether there's anybody beside you or behind you, so if you do have to make an emergency swerve, you will know if it's safe. It may save your life, or it might save your car. Be careful out there! And, keep one hand in you pocket when working on high-voltage circuits.

TAGS: Components
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