First of all, that inane remark you made that the LM317 wasn't necessary was the point at which I took an interest.

You said that laser diodes use current sources, rather than voltage sources. That's true. Nobody questions that. However, there was no prior mention of a laser diode, since what Chico was using was a commercial off-the-shelf module. If it needed a current source, "it's in there." Kai immediately pointed this out, but you chose to ignore him.

At that point you referred to the ST2221A LED driver. Whereas you, correctly, exhorted Chico to refer to the datasheet for his laser module, you proceeded blindly, relying on facts not in evidence, assuming that IC to be suitable for his purpose, which it might be, but which needed some explanation. Had you made any attempt to qualify that assertion, explaining how it was applicable, there would have been lots less wasted bandwidth. That particular IC requires a regulated Vcc supply. Chico's problem was that he believed he didn't have a well regulated supply, particularly in light of the fact he needed a 3-volt supply. There was no indication of how the SD2221A would have solved Chico's problem, nor is there to this day.

Your remark that the LM317 was "unnecessary" was not only wrong because he needed a current source, but completely unnecessary since the LM317 can be used as a very good and stabile current source. Moreover, it is inexpensive and ubiquitous. Chico would have no problem obtaining and applying it.

I'd guess that nobody who's read what's been said about this doubts that what you're after is a "food fight" and not simply to bring forth useful information. I don't know why this is. You could have explained yourself, but, instead, you did what you often do, namely to "stomp your feet" and insist things are as you say, which they may, in some way, be, but never to explain yourself.

When you make an assertion, you should be prepared to support it. I repeatedly invited you to show where my assertion that you couldn't generate a precisely constant current without a precisely regulated voltage was incorrect, but you refused to do that. I Why? I didn't say that a constant current source that incorporated an integrated voltage control or reference of some sort had to be fed by a precisely regulated voltage, and I knew that there were devices that used internal zener, bandgap reference, current mirror, or other ways of creating that voltage. Since their voltage control is internal, they often don't need an external voltage control. This distinction was apparently lost on you, as you were more interested in the "food fight" than in presenting useful information.

Again, I invite you to support your assertion that a constant regulated voltage is unnecessary in creating a constant regulated current. That is what you said, isn't it? Further, on the off-chance that you meant something else, I invite you to specify what it is that you did mean, and show us how that serial-input shift register would be applicable to Chico's problem with his laser module. Rather than going on about how any idiot can figure that out, show us! There's obviously at least one idiot who can't.

RE