Okay - I am working on a little mod that could really use a nice little watt/hr meter. I'm sure I've seen circuits around but I can't find anything now that I'm looking - Can anyone point me in the right direction? Cheers!
what sort of features are you looking for? just a display of wattage used? or a running tally of watt-hours used? digital, analog?
Ideally I would like an analog display of just the wattage used. I would again ideally like to make my own analog display to match it in with the style (or rip something apart and change the facia).
Thats the idea but with an analog display so that I can mount it proper like (also has to be 240v AC). Anyone else got anything in mind?
There is a whole class of analog meters which measure wattage. These meters are called dynomometers. They attempt to take phase errors into account as well so you get a more accurate reading of true power. Watts only equals amps x volts in purely resistive loads. With anything else, there will be a decrease in the power factor, diminishing actual power consumed. You might wish to try a Simpson Electric panel mount wattmeter. Stu
Maplin sells a digital Watt-meter you could pull apart. It's on offer for half price too! It'll tell you the current wattage, volts, amps and kwh used too.
Okay - so after hours (and hours) of googling I'm not further. I'm hoping that someone here has an idea or suggestion. What I'm trying to do is make a external PSU case with two power supplies (future-proofing!). I will hook these up in tandum with one powering the CPU and one powering accessories. On the front of the case will be a neat little capacitance powered flip-flop switch w/ relay for a nice clean look along with two LED's - one for each PSU. I was hoping to integrate a nice analog display into the front. I was first hoping for a 1000W analog display (thinking that I would have about 600w+- of PSU in the box. But after not finding much I was then thinking an AC AMP meter would be good - but all I can find is a 0-10A AC which if I was only using up to 3A - pretty much pointless. I was also thinking of a Temp but the only thing I can find is some car ones. I'd pref to have a round'ish display no more then 40mm dia. I would love to find something either nice and modern (like some of the car tuning guages) but retro would be cool as well. If needed I can post a image of what I'm planning. Thanks in advance!
If you could get a 0-10k tachometer for a car, you could make your own metering circuit to control the tach. You would just need a simple shunt resistor to get a voltage that varies with current, rectify that, and then feed it into a voltage to frequency circuit. Setup the tachometer into 4-cylinder mode, and then feed it the frequency. Just remember the tach reads out Revolutions per Minute, and your feeding it cycles per Second.
fan sensor wires would need a pull up resistor to get a usable signal, but the tach will still be dividing by 4, 6, or 8 (depending on how you set up the tach) Plus I dont think you would be using much of the tach anyway, 3000 rpm at the most? Unless you have a nice fast (noisy) delta, or tornado Oh, and I cant believe I didnt think of this sooner, on the 0-10 A meter, you should just be able to change the shunt resistor, and change the range, the face will still say 0-10, but open it up and cover up the A and maybe print out a new face or something, so it will be 0-10 W x100 Very good point, the power factor on computer power supplies is generally assumed to be .7 or so, so no reason not to just use that if he were to print off a new face for an ammeter. Though DSP and trig with a microprocesor would be... interesting
<sigh> Still not found a solution yet. I've bought some nice retro look'n movable coil meters. Now I just need a way to make up the wattmeter. Anyone else have a few ideas?
One problem with measuring current on a supply is that the meter shunt drops a small voltage (that's what you actually measure on the meter and convert to amps or watts by Ohm's Law). Depending on the meter sensitivity it could take you into unstable territory if you try measuring power on the 12V or 5V lines, though there's no problem on the mains side of the PSU.
Use an ammeter rated for 10A+ just make a new scale which multiplies each value by 240. This will give you a rather acurate unit http://www.bluesea.com/product.asp?Product_Id=31489&d_Id=7367&l1=7958&l2=6613 for a volt meter if you please http://www.bluesea.com/product.asp?Product_Id=31486&d_Id=7367&l1=7958&l2=6613 just find a dist. Near you.
You could butcher one of theese. http://www.coolermaster-europe.com/...serial=LLC-U01&other_title=+LLC-U01+Musketeer
