Discussion in 'Article Discussion' started by Koolvin, 25 Aug 2001.
Damn nice idea....I'd personally use 1 red and 4 blue LEDs I think...but then I really don't think I could do this myself...anything involving PCBs sounds tricky....
oh, and koolvin, couple of broken links at the end of the article
well, it's not that tricky
Basically it's all logic, you just have to take care not to lose that thin red line of logic...
Working on a PCB does not make any difference - it's just cleaner and imagine the Voltage Regulators (which get quite hot and have a certain current in their heatsinks) just loosely hanging around somewhere. besides everything is neatly fixed to the frontplate this way and does not hang loose somewhere in your 5 1/4" Slots...
If you use a red LED, don't forget to re-calculate the Resistance of the Resistor leading to your red LED (same thing if you use different blue LEDs):
Resistance = ( Voltage[Supply] - Voltage[LED-forward] ) / Current [LED]
f.ex. using the blue Maplin LEDs (NR85G) you have:
DC Forward Voltage: 3.6V
DC Forward Current: 30mA (=0.03 A)
At the Switch you get 12v Voltage[Supply] (for the Fan-LEDs it'S 10.75)
so for the switch:
Resistance = (12 - 3.6) / 0.03
which gives you: 280 Ohms
There's also +- 100 Ohms Tolerance and I chose to use 180 Ohm Resistors so that the LEDs that indicate the Fans respond as soon as possible (at lowest possible Voltage).
Hope you like it anyway
surely if you've got that much tolerance as far as resistance goes, any LED of the same size is going to be ok....
ah... but I suppose if you used a 180 ohm resistor and the red needed 350 +/- 100 you'd be screwed
yeah, that's exactly why you have to recalculate the Resistance because the specifications for LEDs do heavily differ and if the Resistor is too strong it will not light but only glow quite dimmed and if it's too weak, the LED will burn after switching it on some times.
ok, I got tons of mails and saw that everybody seems to be afraid of soldering PCBs, so here's some advice:
* PCB's don't bite
* PCB's are your friends
* PCB's are simple to make and help keep everything neat and tidy
there are several ways for making PCB's:
* The Professional way is to make a pic of the circuitry, print it on a laserprinter (or copy it on a copier), iron the circuitry onto a copper-plated pcb and put it into an acid-bath so that everything that is not covered with toner is eaten up by the acid.
* Another possibility is to connect everything by soldering from point to point of the PCB which is quite clean, but hell of a lot work
* Furthermore you can connect the holes with a silver conductive pen - this is quite good but the pens are expensive and you can quite easily make mistakes by connecting wrong things
* the last one is what I used - you can connect everything using small wire-bridges (form: |_____| ). This is quite cheap and easy too.
I'll show you how to do it:
First you'll need a Hole Raster Euro-PCB with a spacing of 2,54mm (look at the pics)
The copper-plated side is always the bottom!
bend the middle-foot forward 2 holes like this:
this makes soldering a lot easier! Then have a look at this pic:
The non-filled dots are where you stick the LM317T through the PCB and the filled ones are where you stick your wire-bridges through. Then solder them, so that you have little cones with the diameter of the copper covering the feet/wire-ends and use a wire cutter to cut off the ends that look out of the cones. When you've done this, put some more solder between the cones as I marked above to connect the wire-bridges to the feet of the LM317T. That's the whole magic about it. in this case the yellow wire is the one that comes in from the switch and the red and black wires lead to the feet of R1. from there the black one continues to Pot1 and the red one to R2 and then to the output.
You see, there's no magic about PCB's, but they make soldering easier and keep everthing neat and tidy and in place.
Two more for you:
It's all the same procedure as above:
stick the resistor through the holes marked non-filled, the red and black filled marks on top are thw wire-bridges coming from the LM317T, the black mark on the bottom is the wire leading to the center foot of the Potentiometer, the red one leads to R2 and from there to the output
"Splitting" aka hooking up the yellow wire from the switch to the 4 LM317T's:
The non-filled mark is where the yellow wire from the switch comes in, the filled ones are the wires that are connected to the right feet of the LM317T's.
Hope that helps and takes the fear of PCB's off you guys
some more tips:
* do not solder the switch onto the PCB, but leave it loose on cables, at least if you do not have a PCB-mountable switch (and they are hard to get)
* use heat-shrink tubing on the feet of the LEDs and the connectors of the switch
* take a lot of care not to shorten or misconnect anything
-lol- so does Koolvin!!
arghghg my mind. Even though its a great article i think i'll leightweight it and buy one...
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