Use a 5 volt regulator chip, something like a LM7805, or an adjustable regulator like the LM317. There is a way to connect them using a resistor between the output and the ground (or adjust) lead to make them into a current regulator. Look for the data sheet for the device which you should be able to find on the internet, usually at the place where you buy the part. Try Digikey.com for instance. The data sheet will show you the lead basing diagram for the package type you order (not always the same between different devices in the same package type) and will have a drawing for how to connect it up as a constant current source. You change the value of the resistor to change the current.
Dan -----Original Message----- From: M. G. Devour [mailto:[email protected]] Sent: Monday, October 16, 2006 6:18 AM To: [email protected] Subject: RE: CS>Diodes with 3 leads ( Question and Use ) So, to drag the discussion a little OT, is there an easy tutorial or design article about this FET current regulator somewhere? How do you set the current level? I need to prototype a 20/40/80 etc.... ma regulator to drive some LED's for another project. :) Mike D. > Didn't you guys read my post?... ;-) > > It's really a JFET with the gate and the source shorted together. If > you look at the picture in > > http://photoman.bizland.com/diode.jpg > > you'll see that it is a FET - not a diode. It's some kind of voodoo > electronic speak (thanks Ronald) to call it a diode...but they did. > It is listed under the diode designations (1Nxxxx). > > (Perhaps the gate to drain can be considered a diode junction?...) > > Non-electronics people please disregard the above discussion... ;-)) > > Dan > > > Constant current two-terminal devices can be made by shorting the gate > and the source of a JFET together. When the FET is forward biased, > this results in a nearly constant current for voltages ranging from > roughly 2V up to 300V (or the breakdown voltage of the device in > question). In reverse bias, this kind of constant current device > conducts as a junction diode (so one can oppose two such devices in > series to regulate AC current). > > > > -----Original Message----- > From: Malcolm Stebbins [mailto:[email protected]] > Sent: Saturday, September 30, 2006 10:18 AM > To: [email protected] > Subject: Re: CS>Diodes with 3 leads ( Question and Use ) > > I could be wrong, but suspect the "three legged diodes" are actually a > reference to three-terminal current regulators - or possibly to > voltage regulators. These were mentioned a while ago as a method of > getting simple current regulation for CS generator applications, and > in context with regular regulator (current) diodes with two legs, not > shortened (Eeww! Sorry, almost) Malcolm > > At 11:28 AM 10/15/06 -0500, you wrote: > > >Morning V and The List, > > > > >> At 05:53 PM 10/14/2006, you wrote: > > > >> tere is a spec sheet that comes with theu little diodes that > >> tells > > >> which leads to short together. > > > > I think you and others have used this term, "Which Leads to > > short together". > > > >It has been a bit confusing to me, raises some questions, and may be > >misleading to others. > > > >I have used many diodes over the years, likely numbering into the > >thousands. At one time, the systems in the field were not perfect, > >the > > >manufactures did not have all their ducks in a row, and we had to > >interface systems, build small circuits on the job site, and even > >piece > > >together a diode matrix now and then. I would buy them 50 and 100 at > >the time and felt I cold not hit the road without a bag of diodes. > > > >I thought I had used them in every imaginable fashion, but maybe not. > > > >Still, the term "which leads to short together" leave me in AWE and a > >state of confusion. > > > >Literally, shorting the leads together can mean only one thing. > That > >is, unless the mounting / support lead enters the picture. Short one > >lead to it ? > > > >Still, in my mind, Shorting the leads together can mean only one > thing. > > > >Possibly you are meaning, "Where to put the diode in the circuit" as > >it would appear to "short together" the two points, but in reality it > >does not. As you know, there is a forward voltage and near a > >constant current for reverse voltage use. > > > >Makes me wonder if several biased in reverse would not work as a > >current limiter. > > > >A short is a short is a short. How can anyone define it differently. > >Shorting the two leads together ( A two lead diode ) would render it > >useless and worthless. > > > >Not trying to muddy up the water that you and others have already > >cleared up, but don't want to see the beginner or the novice to > >proceed > with any > >confusion. Or ....... confusing terms. > > > >Here is a wonderful link for the person starting to learn about diodes. > >http://www.kpsec.freeuk.com/components/diode.htm > > > >There are many "not so normal uses" for diodes. In a bind, they can > >serve as a "Model Rocket Ignitor". > > > >Wayne > > > >======================= > > > > > -- > The Silver List is a moderated forum for discussing Colloidal Silver. > > Instructions for unsubscribing are posted at: http://silverlist.org > > To post, address your message to: [email protected] > > Address Off-Topic messages to: [email protected] > > The Silver List and Off Topic List archives are currently down... > > List maintainer: Mike Devour <[email protected]> > > [Mike Devour, Citizen, Patriot, Libertarian] [[email protected] ] [Speaking only for myself... ]
