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Thread ID: 28946	2003-01-05 22:19:00	anyone who knows much about electronics...	tango (2697)	Press F1

Post ID	Timestamp	Content	User
111321	2003-01-06 09:07:00	> > I tried that, except the voltage coming out of it > isn't enough to run the big LED :P Ah, so you want your neighbours to know that your HDD is being defragged and working hard :p :D *Chilling_Silence realizes he should not give up his day-job*	Chilling_Silence (9)
111322	2003-01-06 09:08:00	The case LED will be a "normal" one with about Vf~2v. The current limiting resistor will be ~ 470 or 1k depending on the voltage (5 or 12) for the case LED The current through the blue LED (Vf~10.5v) would be ~ 1.5 ~ 3 mA, not enough for a glow-worm	godfather (25)
111323	2003-01-06 19:25:00	I tried the link and got this: SCR C106D / TYN404 400V 4Amps T0202/T0126 Sensitive Gate Cat No. Z4320 NZ$2.70 Add to Basket Me thinks your cat number might be wrong.... What is this LED? Something designed for a car or something? .Clueless	Clueless (181)
111324	2003-01-06 19:36:00	oh geeze..I'm really losing it today :P it's actually Z4230, sorry :)	tango (2697)
111325	2003-01-06 20:00:00	Cool LED! I noted in th description: "Blue LED that uses only 2 leads for simplicity of connection instead of the usual 12 found in LEDs of such sizes." My suggestion is to just get a blue led with "the usual 12 found in LEDs of such sizes", which i would assume is 2 wires for each component LED, and then wire them up in 3 pairs so that the voltage is an adequate match... .Clueless	Clueless (181)
111326	2003-01-07 01:38:00	Many of the component values in electronic designs are arbitrary . As godfather says, 10k or 1k for driving a transistor from logic will saturate (turn on fully) the transistor . I would normally use 10k or 4k7, depending on which bin was fullest . I actually calculated (with envelope and pencil), the 47 ohm value (godfather left out the voltage across the saturated transistor ;-) --- so his value is high --- I got "about 50" so went to the nearest preferred value . From his value of "~60", we'd go to either 68 (or 47 . . . depending on the stocks) . I don't see the point of using a optocoupler . . . the circuit is all in the same box and using the same supplies . I spent this morning working on a dead 600W inverter (60A from a 12V battery to make 230VAC) . The clever manufacturers had polished off the type numbers on the transistors . X-( I drew the circuit a while ago for a friend who also had a non-working one . Mine half works . After desoldering the shorted transistors and looking at them a bit harder I have finally identified the type number . . . they're $50 each:_| . There are four of them . I think I will change from these transistors --- BUR50S (120V 70A) --- to power Mosfets at $5 each . Amazing the difference in modern technology: the dissipation will be reduced by a factor of 50 . But the change in design will need some proper calculations . I think I'll use my sliderule for technical things like that . :D	Graham L (2)
111327	2003-01-07 06:51:00	ok change of plan...I'm going to run the big 10.5v LED off a 12 volt supply now. I know I'll need to lower the voltage, but what about the current? how can I tell if it's less than 25mA? And I'll get one of them superbrights and hook it up to the HDD light output. I think need another resistor for that but should I worry about current overload?	tango (2697)
111328	2003-01-07 07:14:00	> ok change of plan...I'm going to run the big 10.5v > LED off a 12 volt supply now. I know I'll need to > lower the voltage, but what about the current? how > can I tell if it's less than 25mA? Use your multimeter If its more than 25 mA, you will tell as it will go for a few milliseconds only. Remember 25 mA is the MAXIMUM. Best to run slightly below. 12 volts - 10.5 volts = 1.5 volts for 25 mA to flow with a drop of 1.5 volts across the resistor, its: 1.5 divided by .025 = 60 ohms (nearest should be higher to protect the LED, use two 33 ohm resistors in series) If they have the resistor range that has 62 ohms, then use it otherwise 2 x 33. Deja Vu...I can remember doing this before? > And I'll get one of them superbrights and hook it up > to the HDD light output. I think need another > resistor for that but should I worry about current > overload? In place of the existing LED or ?	godfather (25)
111329	2003-01-07 07:30:00	oh sorry, in place of the existing one thats there.	tango (2697)
111330	2003-01-07 08:10:00	Well, the standard HDD LED will probably have a lower Vf than a superbright. Superbrights are around 3.6v Vf, 20 mA, a tad higher than the standard. Nowhere near the extreme of the blue one though. You will be flat out trying to replace the resistor though, its bound to be a SMC (surface Mount Component) on the IDE electronics printed circuit board on the drive. Case one ditto, but on the motherboard. Just use the resistor thats there, it means the new LED won't be quite as bright as it could be. Simply replace it with the superbright. As with all these LED's take care to get them round the right way, first time.	godfather (25)
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