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Electrobrains

Jan 2, 2012
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This thread seems to develop into something quite different than originally intended. But as Steve points out, maybe something positive could come out in the end.
My intention is not to quarrel with Coca-Cola, but this discussion could really be helpful to many.

In his recommendation to MPdesign and the answer to myself, Coca-Cola describes well some of his principles for development, production and sales of his products. Summarized (please correct me if I'm wrong): It's recommended (or at least to be considered) to develop new products on the basis of practical experience, rather than on strict specifications in data sheets. If it brings an advantage (eg. not having to include step-up voltage), it's worth taking the effort of pre-sorting components, handle complaints, repairing for free and maybe redesigning in a second step.

I will try to explain the situation from my point of view.
There is something attractive in CC's approach: Test it, if it works - do it! After being active here now for a little while, I realize that many here are in the same line - very practical people. And in a way I think this attitude is a green house for new creative products. I think here in Europe we have (had) too many rules, regulations and expensive procedures, limiting down the innovativeness of this continent.

This was improved considerably through the introduction of the very sensible CE marking.
ce_mark.gif

CE made it easier to invent products, but brought a very high responsibility to developers and manufacturers, who have to fully conform to the valid standards (and have knowledge about them), for their products.
In case of inspection, or I suppose more commonly in case of suspicion of non-conformity, the manufacturer must be able to present his own test protocols and needed proof for that the product is complying with the standards (for instance EN60950, EN50081 etc.). If he cannot prove that, he will be considered guilty before the judge.

In case of an LED toy, there will probably not be many security issues or even valid standards to follow, but there could well come quality disputes with customers or distributors. Why doesn't this thing work with NiCd or NiMH batteries? Why is the blue light not as bright as the other two? etc.
For anybody building his own LED lamp, this is really not worth discussing, but I realized that the thread-owner (MPdesign) has an intention of making series production out of this product. He is free to make that the way he wants, but I feel morally obliged to at least warn for the attitude of CC when it comes to commercial products.

I give you an example from my own life: I have been developing many products containing isolation and security circuits, power supplies etc. I promise you that at my test bench and in almost all customer applications an isolation distance of 0.5mm to the lethal 230VAC circuitry would look totally fine. It would work perfectly and I would save space too! But I would violate the "data sheet for design" - the standard, that tells me I have to have a much larger distance. At some places, under some circumstances, the consequence for some of my customers and for myself would be devastating, if I followed that line!
Believe me, I have seen the consequences in one of my former working places in a very noticeable way. Poor (mechanical) engineering (too small security margins) combined with false handling (too high torque). The result was an electrician disabled for life, by 500V through his body!

Of course the objection immediately will come: "this project is not dangerous". No, but for me it's a question of attitude, more than a single LED. Expressed in one word called quality!

I had the privilege (or horror) of being the head of the electronic development department in a company that went through the process of attaining the ISO9001 certificate.
I don't know how many of you have worked with the ISO9001 quality management system, or even heard about it.
ISO9001.gif

Basically it's a large concept applied to different "processes" in a firm (management, development, production, sales etc.). The goal is to assure that the company itself has efficient, documented and well working processes and that quality awareness is an integrated concept. Concerning the produced products, the goal is to assure high "quality" towards customers and partners. "Quality" has a wide meaning, but contains for instance design according to valid standards and data sheets, complete documentation (kept up to 10 years after the discontinuation of a product), traceability of production batches, spare part concept, procedure when changes take place etc.

Worldwide, ISO9000 certification has become very important to many bigger companies and many companies simply don't consider buying products from non-certified firms. My former employer realized it was a question of survival to get the ISO9001 certificate, mainly because the competitors had it and the customers demanded it.
I was not at all enthusiastic about that system. It brought a lot of bureaucracy (planning, documenting, signing, check lists etc...). But after a while I realized that the system had some very good effects. It was a protection for me, my employer and our customers. After I quit my job and started my own company, I can not afford any ISO9001, but I try to pick out the useful and necessary parts from that concept.

In the area of development, the quality concept allows for no compromise with respect to important standards and data sheets (thus saith the Lord..). It means that if I had designed products based on "it works, although the spec sheet says it might not", I would simply have been fired from that working place.
I could do that now, because I have nobody to fire me, but I feel the moral obligation to still produce quality (according to ISO9001 definition). I also intend to protect my customers from problems and to protect myself and the name of my little company as good as I can. One way of doing that is to design for "worst case" and carefully staying within specified data.

If you design expecting the maximum (like using a 2-5 second grenade like it was 2 seconds) you'll be safe. But the wise designer will also see if the other limits have any impact.
Finally, Steve (you said it...cross fire;)), I disagree on this one. A wise designer does not waste valuable time with data or design options that are irrelevant or based on non professional concepts.
In the firm I worked for before, the general engineering cost was set to approx. 1000$/day.
(unfortunately or maybe luckily, I am far from that amount in my own company... makes me more competitive)
Under such circumstances, words like re-design, pre-selecting components or free repairing, are almost like curse words. When a product has been developed and produced, it's supposed never to appear in the sight of anybody in that company any more... That's the reality of true quality management.

Yes, I live differently now (and happier), waisting some time with you guys here, writing terribly long messages and enjoying the freedom I have in my own company.
I suppose at least on that spot I can find some common ground with CocaCola and agree about something! :)
 
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(*steve*)

¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd
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Jan 21, 2010
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Just make sure that you quote the CE mark

ce_mark.gif


and not the (arguably better looking) China Export mark.

CinaExportLogo.png

The differences are shown here:

CE_mark.png



Finally, Steve (you said it...cross fire;)), I disagree on this one. A wise designer does not waste valuable time with data or design options that are irrelevant or based on non professional concepts.

(I said it)

Perhaps you misunderstand me.

Let's say a designer is making a linear power supply and he notes the output from the rectifier and filter is 34V. He also notes that his regulator has a maximum input voltage of 35V.

Would he be wise or not to consider any effect that variation on mains voltage might have on his design?

Now, the wise designer would probably have rejected the regulator already because he/she would probably not want to run quite so close to maximum ratings, but that is essentially a heuristic which tries to take into account other typical variations.

I guess the "wise designer" knows a set of heuristics which allows him to avoid checking the datasheet in most cases (such as knowing approximate voltage ratings on resistors, reverse voltages on LEDs and base-emitter junctions, and a whole lot more), but it doesn't mean that they aren't taken into account where relevant.

And that wisdom is perhaps best not born in the pain of having designs fail in production :)

To get back onto the subject of this thread, there is a difference between what will work (the vast majority of the time, with variations in components due to tolerances etc), and what may work (possibly assuming some lucky combination of tolerance, temperature, and phase of the moon).
 

Electrobrains

Jan 2, 2012
259
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Hehe
That was really good!
Thank you Steve for showing this. I write half a page about the CE-sign and pick a China Export to illustrate it!
I would have liked to leave it, because it's really funny, but I changed it so that no-one falsely would copy it from my post!
I just googled on CE sign and didn't realize the difference.
(the Chinese are GREAT!)
funny-smiley.jpg


I think you made a good statement at the end by pointing out that the whole discussion here is about "may" or "will".

My position in this thread can be summarized: For a commercial product, it's wisdom to choose "will".
 
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CocaCola

Apr 7, 2012
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However, how do you current limit them?

Depending upon design parameters I wouldn't do anything additional as there won't be high enough voltage to pass a high enough current to cause major damage to the LED in anything but an extreme very unlikely case... And if you use a PWM driver the risk of damage is exponentially lower, to nothing... This is as I have stated something that has to be considered on a design to design basis while you balance cost and making the circuit rock solid... Slightly over driving the LED might diminish the 'life' from 100,000 to 10,000 or even 5000 hours but does it matter in your design? Under driving it might diminish output and shorten run times but again does it matter in that particular design? You see this effect with LEDs exploited all the time with key chain lights, LED flash lights and LED carnival toys, most of them don't have any extra limiting and many of them are over driving the LEDs, because overall the product performs as expected within at cost point...

Very few consumers will ever expect a LED key chain or LED flashlight, or LED twirly toy to last 100,000 hours or 11+ years of constant use when they picked it up for $1... Thus it can be engineered and over driven slightly to produce 10% more light (a feature that the customer will notice and likely be happy about) even if it shortens the overall life of the LEDs as few if any give a rats pooper if it doesn't last 11+ years...

And this is perfect example of that, regardless of the rock solid perfect performing way to design it, the question begs that necessary in this design? As I have stated would supplying a 3.6V lithium cell and charger that can be purchased in bulk for about $2 total be a better design change that offers a buyer perk than investing in a design that boost the voltage to 5V? Or will a rock bottom price of using an over the counter RGB auto cycling light suit the intended audience better? Does the audience care if it last 20 hours on a set of batteries, or 10 hours? As much as many people like to milk batteries for every ounce there are plenty of people that change them religiously between uses on a 'just because' reason... I believe CDRIVE? Stated a few weeks back that he gets a ton of AA out of medical equipment as they are a single use/patient item regardless of duration of use... I have a bunch of musician friend that change their guitar strings and 9V batteries in their effects peddles before every show as a proactive measure, to them swapping a battery/string is just the cost of insurance...
 
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