How do you make one of these? I know you need a gauge (like a speedometer) of course, and wire connecting to where the LED light normally would, but what else? I've heard capacitors, potentiometers, PCB, solder, and have no idea how this all forms into one little gauge measuring my HDD activity, so does anyone actually no know how and would be willing to explain how to make it work?
Is this the kind of thing you are looking for? Or for ATA (IDE ribbon cable type) drives just use pin 39, SATA however is more difficult and you will need to ask someone with more skill.
Sort of.. it's got circuitry, that's good, but that seems to be lighting LEDs, I mean like an actual gauge, with the little 'finger' moving left to right.. it doesn't quite seem to cover that, but thanks for the link, it's a start at least, lol
You could modify the circuit slightly to give an analouge output. cpemma is the one who would know how to do an analouge meter for HDD activity.
The circuit ratchet linked sends a ramping wave-form to the LM3914 chip so when there's any blinking on & off drive activity the bargraph more gradually moves up & down between about 2V and 10V. The signal at the wiper of VR2 would drive any analogue voltmeter from 1V FSD up to 10V FSD using VR2 to set the maximum AFAICS if you just want the needle to move about. Just miss out all the parts to the right of VR2. If you get a current meter like the 50uA or 100uA here it's easy to turn them into any range voltmeter with a series resistor (and the non-RoHS ones are half-price while they last ). The LM4558 op-amp may be hard to find, LM1458 or MC1458 is the same thing and any other dual op-amp would probably work. It's very much harder to measure an actual bytes/second speed.
Something told me this wasn't gonna be easy... While asking around in real life since I posted last I came to the general consensus that I could just take the two wires that normally light an LED, add a resistor that will make the current fit the sensitivity of the needle, then wire the resistor the the gauge, then wire that back to the other wire connecting to the mobo. Also a capacitor could be added in after the resistor to make a smoother motion. Does that actually work or would I be better off following the schematics in the link, minus everything past VR2? I don't care about bytes/per second though, just the effect of the needle moving is good
Yes, with a suitable meter. The HDD LED header has one pin going to 5V through a current-limit resistor on the motherboard, the other pin through a transistor switch to ground. Best way would be to find a 100uA meter like the ones linked and convert it to a 3V voltmeter. Put it across the LED, when the LED is on it will measure the LED forward voltage (around 2V). To re-scale that meter to 3V FSD, it's just Ohms Law. 3V/100uA = 30k, subtract the resistance of the meter (which may be printed on it but it won't be much so ignore if you can't find it) so that resistor in series with the meter should give you a good ghetto flicker. You can't really damage anything as you aren't using an external voltage supply, so the opto-isolator safety system isn't needed.
I'm not very experienced with wiring, so as a visual representation, I'd just attach the meter right onto the lines going to the LED, and add a resistor also? A drawing is attached of how I see it working, the black boxes are resistors.. I'm not too good with MSpaint, lol. Thanks for helping with this
Looks OK, you'll only need to add a resistor to the meter, the LED resistor is already on the motherboard if you're putting the meter across the existing HDD Activity LED. If you find the meter needle is moving too fast, damp it with a small capacitor, also across the LED. Try 47nF (0.047uF) or 100nF (0.1uF)
Ah, that I can do, thanks! Also, went hunting for a gauge and came across an old voltmeter that will work for my plans, only thing is it doesn't quite work with 5 volts, only 15 volts, is there anyway I could get that 5v signal into 15 on the gauge? It'd be so perfect if I could, either that or a setting (multiple settings for multiple volts) called "RX1K*omega*" that flat lines with a 1.5 battery, I think .5-1 volt would make it work, so a simple resistor would work I guess.
Better damping is to split the resistor to give both a slower response and a fade, and my maths was out by a few decimal places on the capacitor size. You can turn a 5V meter into a 15V meter but not the other way round.
I think I'll just stay with a crazy flickering needle, but do you know what RX1K with an omega sign after it means?
correct me if i'm wrong (and I probably am), but bearing in mind the omega sign mean ohms, which I THINK is used for resistance, probably a 1k resistor.. Like I said, i'm probably wrong...
Thanks Cpemma, I have been looking for a way to do this myself I was going to hack up the LED HDD activity meter but this looks so K.I.S.S. If I am reading this right I wont getting an 'accurate' response showing differing amounts of load but it will move smoothly instead of flopping from off to on. On a related note do you foresee a problem using this to route my Nic activity light to a gauge? well other then getting voiding the warrenty to get to the onboard NIC led.
All you're doing is making a suitably-scaled analogue voltmeter and measuring the voltage across an LED. Nothing should go wrong...touch wood... See Titanic
I wudnt add anything other than a case led onto the hdd output pins on the mobo while a VDu mtere wnt draw much current. useing a resistors and captiors will pull extra current from the mobo it may not have been designed to give. use an opto isolator. ima sure someone on here can tell you which one to use iam quite sure. its too late for my brain to work
First up, punctuation, secondly, spelling, thirdly it is basically a voltmeter, and voltmeters drawn very little current. V=IR, so I=V/R so the higher R is the less current is drawn. Anyways, thanks cpemma for stepping in were my knowledge is lacking.
If you read my thread i said that voltmeters dnt draw much current but by teh time you start to added resistors and capaitor into the sytem you'll will draw current.I would risk my motherbaord for the sake of a few pounds worth of eletrical compents. sorry for my abd grammer and spelling its late and iam also dyslexic if anyone could point me in teh direction of a built in spellign checker for firefox i wudnt complain.
Don't worry about it, your English is better than your Electronics. Firefox 2 has a built-in spell-checker.
