see this post for latest I would like a little help with the following: I want to power one LED to half-brightness when the PC is on, and full when it's on and there is HDD-activity. (I have to use just one LED since it is hidden away in a vandal resistant switch.) After much circling, and some help from Jani Pönkkö of metku mods I have come up with the following: (ph34r my paint skills etc) should/could this work? also what voltages come from the mobo headers, and does anyone know the usual spec's for the LED in a vandal-resistant switch? Apologies for all the questions, just hoping someone can confirm the viability of this idea...
I think I see what you're doing in that schematic, but I would think you'd need some sort of amplifier after the HDD indicator... but I guess it would depend on your LED (like, what voltages cause it to be full and half brightness). Hmm, you know, with an amp and two diodes, this might be easier. If you make the amp (with input of the HDD indicator) put out whatever voltage you need for full LED brightness, then put a diode so you can't get a voltage coming the wrong way down that line. Then have a power line that gives the LED half power and a diode so that power can't come the wrong way down that line. Then, when the HDD indicator goes high, the signal gets amplified to give the LED full power. When the HDD indicator is off, just a half brightness power is being driven to the LED. But hell, I'd probably just test what you have on a proto board to see if it works. If not, it shouldn't be too hard to do PS, what is the line labeled "PUR"? Just straight voltage? PSS, n/m, just noticed it's PWR not PUR... man, I need to lower my resolution PSSS, damn, why do I always notice things AFTER I finish talking: what you have should work. What's happening is the HDD indicator is alowing more of the PWR to flow through the transistor. The hardest part would be figuring out what resistors give your LED the luminence you want
I wish I had some kind of proto board, and a cupboard of components... I remember at school we had a program which simulated circuits, think it was called crocodile (clips) or something - can someone tell me of a program I could use now?
well, you can get small protoboards from radio shack for like 10-20 bux. I have a pretty good sized one that set me back 50 or so. I also have a really nice electronics store that sells pretty much everything (I didn't think they sold EVERYTHING until I went there and bought some very specialized parts for a project last year including ribbon cable and specialized ICs) so if I ever need a part, I just go there. The parts you need for your thing are pretty general and you could probably get them at radio shack. As for simulating circuits, I suggested PSpice earlier in another thread but it doesn't simulate in the way you wanna simulate I think. You could put in a pulse on the HDD indicator and read the output at the other side of the LED and if you get the same pulse you entered with a DC offset, then you know it works. But basically it simulates by you making a graph out of, say the voltage output of a test point you create. It does have a visual function (like, you can choose from a part list) but I usually wrote it out as a program (which isn't hard to do). They have a student version for download I think.
found it: http://www.crocodile-clips.com/crocodile/technology/index.htm and I've aquired a working copy - will play with some numbers for a bit, then maybe order some components (and a soldering iron!)
Now I have: (2 Yellow LEDs used to simulate 1 Blue) The transistor on the far right is to ensure current only goes back into HDD mobo header when it's supposed to. Prob not necessary, as it's probably just a common zero-rail, but want to be safe, and not fry my mobo. Since I'm not a electronics whiz, I'm asking for confirmation that this could work... So, can anyone help me?
hmmm, I might be wrong, but from analyzing zapwizards hd and power one at a time circuit I came away pretty convinced that it is the minus that is disconnected, so the above wont work at all..... the following is a bit simpler, and I have no idea how big the resistor should be ... put a variable on and tweak it ...
Moved to electronics....if you want to make it a mod guide when its done, ask here and I can move the guide part back, or make another thread...cheers
bo.v i didn't realise that it's the 'minus' that's switched, but that's easy to over come if true. the reason my circuit is so complicated is that i don't want stray current to flow where it's not meant to. will thanks - i shoulda posted there in the first place. zap i hope you're watching...
I helped Bard a while ago, and he came up with just using a diode. Works great for me. You connect the diode between the PWR LED +POS side (After the resistor) and the -NEG side of the IDE Header. /Edit: DOH, I noticed you want a LED on all the time, with it Off during IDE activlity? That is easy, just use the above circuit and don't put in the IDE LED
uhm, you might want to read the first post again ... half brightness w/o hd activity .... full brightness with hd activity ...
Ah, in that case, all you need is to change the resistors a little. In which case the circuit you made above should work.
thanks ... btw, if I wanted to drive an array of led's from the 12v or 5v rail , would I still be able to ground to the hd minus pin on the motherboard for this effect .... or would that somehow damage the motherboard?
In that case us a transistor. (Switched by the IDE -NEG signal) BTW, it won't damage your motherboard, but your harddrives. As IDE- is wired to Pin39 on a IDE cable.
I'm assuming it's only a logic switch on pin#39, if so I wouldn't risk going over 15-20mA. Easy way is to use pin#39 low to switch on a PNP transistor, about 1k resistor to the base.
