In the world of Electronics, as in the Real World, there are those who try to manipulate the truth to take advantage of those who have a limited understanding of its underlying principles. We will call these manipulators scammers.
One scam that I often see is when an experimenter tries to get a LED circuit running and tells everyone that it’s brighter than before. The presenter says that it’s brighter, but gives no quantitative measurement, only that it looks brighter. Without a measurement, his brightness claim is nothing more than an opinion, with no basis in fact. It is up ti the person making the claim to provide evidence that what he is claiming is true and more than just an opinion without any factual basis.
If a project has claims of a certain performance, then it is logical that the performance should be documented. A measurement of light output of the LED would give a relative indication of performance. Light meters, or luxmeters, are inexpensive, less than $50 with shipping. Provided that the LED is kept the same distance from the sensor, the luxmeter will give a reasonably accurate indication of the light output of the LED as the circuit is adjusted.
Those who have little experience in this field should always remember that what people say and what the actual truth is have little relation to each other. If someone makes a claim, the first thing that the viewer should ask is what is the claim based on? Is it just a statement of opinion, with no evidence that is proof? If so, then do not accept it as being true.
In this case of the claim that “it’s brighter”, the guesstimate is being made by the claimant’s eyes. The eye can be very deceptive. When the person is in a bright area, a fairly bright LED can look dim. One good example is when you try to view your cell phone screen outside and it looks so dim you can barely read it. You have to go inside to let your eyes open up so that more of the cell phone’s light gets in. What this means is that your eye is a very poor judge of brightness because the pupil of your eye adjusts automatically and you have no indication of how it’s limiting the light. In one bright area you would make a judgment that the LED is dim, but in a darker area you might judge the LED as bright. So the Number 1 Rule is to never trust your eye’s judgment on how bright something is.
Parts – They’re important Do you understand what your components are doing, and do you know if you are subjecting them to stresses outside of their rated limits? If you are, do you have a way to test them to see if their performance is still normal? A mountain climber doesn’t use a frayed rope. But in the case of an electronic component, one may seldom see the effects of use and abuse. If you don’t have a way to test them, then you should be stocking new and unused ones that have not yet been through the mill. Transistors are cheap, only a few pennies apiece. It’s foolish and futile to try to get a circuit working when a 4 cent transistor that has been abused is the problem causing the trouble.
I must say a word about the parts and their suppliers.
If you get parts from a reputable distributor you can be reasonably certain that the parts are new, prime parts without any “seconds” that may be out of tolerance. If you buy from some distributors, you may not have a choice of selecting a better grade of component. For instance, if you buy a BC337-25 transistor from Digi-Key or Mouser, you are ordering that exact transistor with the gain range of -25 specified. If you order a BC337 from Futurlec, they may not have any gain range suffix, so you will not know what the gain of the transistors you receive are. They could be evenly distributed throughout the gain ranges, which means you could measure the gain and select the higher ones for your use. This could save you some small amount of money, but when Avnet charges $2.28 for a hundred BC337-40s, and Futurlec charges $7.00 for the plain BC337, it really makes no economic sense.
Surplus dealers are a whole ‘nother story and run the gamut from new, never used parts in their unopened packages, to cannibalized parts removed from old equipment. The cannibalized parts at first seem to be the worst choice, but that may not be true, I’ll explain. With cannibalized parts, you are not deceived: you know ahead of time that you’re getting used parts. In some cases, the part may have a lifetime associated with its use so the older it is, the less life it may have left. But if you can’t find it in better condition, this may be the only choice. In other cases, when the part such as a transistor has been used within its rated maximums, can continue to be used with full performance and no degradation for decades to come.
On the other hand, there are those parts that may have made it through the production line, but my be out of tolerance or what they call ‘seconds’. Here is a part that may look new, and may be sold as new, but is not capable of performing as a new part. The new look allows the seller to deceive the buyer and get premium prices for an inferior part. This often happens with electronic parts because the electrical and electronic qualities of the part may only be found with test equipment that the average buyer does not have. Thus the average buyer may never know that he or she has bought substandard parts.
There is another category of parts that has been found, counterfeit parts. With transistors, especially power transistors, the counterfeiter rubs off the original markings and puts on the markings of a higher performing power transistor. The buyer gets stuck with a substandard part that may fail due to its inadequacy. And you might think these don’t get into the mainstream market, but you could be wrong. Some otherwise reputable distributors get stuck with these dud parts even when they believe they are getting prime parts. But the chances are far less than if the buyer were to get the parts from a shady dealer.
All together, the parts that buyers receive can determine the fate of the product they go into. If the experimenter buys a low grade part, it may not effect the outcome of the equipment as much. Yhe experimenter may find that the part is not giving the performance that was expected. A high volume producer may have hundreds or thousands of the product sold and in service when it is discovered that the product has defective parts. This happened several years ago when, among other PC makers, Dell made GX-270 computers with electrolytic capacitors that were defective, and started to fail after a year or so. It cost the company a lot of money – $300 million US – and hurt their reputation.