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    comparator for DC voltage

    or do we have to have wheatstone bridge and more complex ones for the general cases??
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    comparator for DC voltage

    ok, i need a simple DC comparator. so would the attached pic do the job?? all resistors are equal EDIT from above ^: my mistake, R1 and R2 (not labelled below) are the only ones that have to be equal. R3 (not labelled below) ideally has high impedance.
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    a circuit that cuts off current when voltage drops from a given level.

    i thought i had a solution, but it wasn't doing the right voltage comparison... good thing there's a "remove post" option here in this forum.
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    a circuit that cuts off current when voltage drops from a given level.

    i need a component or circuit that cuts off current when voltage drops from a certain level... or basically an SCR (which are usually designed to have a low holding voltage) that instead has a high holding current/voltage (cuts off earlier).
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    making sure the under-watt-ed resistor survives

    a simple question... so i have to create 8A DC for a very simple section of a circuit for 2-3 seconds. it draws it's power from the 120 VAC mains. i will rectify the AC and condition it witha capacitor, but i cannot use a voltage regulator and/or a transformer before or after the rectification...
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    a circuit that closes when power is cutoff

    i need a circuit design that closes a secondary circuit, when power is cut from a primary circuit (@ typically 6V). i don't need extremely fast switching. this isn't also going to be a backup power supply (so the secondary circuit WILL NOT be providing a continuous power to the primary). so...
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    advantages/disadvantages of auto-ranging DMMs

    are there any advantages/disadvantages to using an auto-ranging DMM such as this? http://www.multimeterwarehouse.com/my69.htm i would expect that they are not as responsive as regular DMMs... but then again if you need to measure rapidly changing signals, you might as use other means or...
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    replace my multimeter?

    how do i  make sure that the multimeter i buy have safeguards against mismatching the probes again??
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    replace my multimeter?

    so i got this multimeter (the only one i have now), which i purchased about 8 years ago or so. i think WAS pretty good quality back then. throughout the years, every now and then, i would mismatch the probes to the multimeter function (volts, current, resistance). sometimes, i would first be...
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    soaked capacitor

    i left this capacitor (http://www.digikey.ca/product-search/en?vendor=0&keywords=382LX123M100N082) outside and it rained. it was in an upside down position (as shown in the picture). it was like that as i soldered big gauge wires to it, as i sometimes use it to rectify high currents. there...
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    parallel bridge rectifiers

    not to mention harder to machine those wee small fins.
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    parallel bridge rectifiers

    also, i will screw them together in just one thick copper plate that will serve as the heat sink. would that also help?
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    parallel bridge rectifiers

    alright, i've set out almost exactly a year ago to build the 0-30V power supply in the project section (or at least a slightly modified version of it). well, a year afterwards i'm finally getting on with it (took me long enough, but i was preoccupied with other things). anyways, i'm building it...
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    turning my old arc welder into a mini spot welder

    i'm trying to find more uses for my current arc welder which has the specs of mode 1: 25V @ 50A and mode 2: 23V @ 70A (i forgot the cycles for each, but it's less than 60 secs or so) so i figure i'd modify it to also function as a mini spot welder... i'm targeting about 1.5-3V @ 750A max...
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    6V lead acid battery

    i've got a 6V lead acid battery that i ripped off a portable CFL. i tried charging it with the old circuitry that it came with, but it won't get past the ~4V mark. then i tried charging it from a wall wart of 12V  with a max current of 1A. it was exceeding 1.5A when charging the lead battery...
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    wrecked my Epson R280

    yeah, already have a copy of that manual before i went here. i first checked the PSU and it SEEMS like it's in good condition. when i measure the output (if you  could cross reference it with the manual, pg 124), from ground (CP52), CP51 is 42.7V and CP53 is 41.7V. i'm not completely sure if...
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    wrecked my Epson R280

    ---- PROLOGUE ---- so i purchased a second hand Epson R280 for direct to PCB etch resist printing. it needs no modification at all, as you can simply put the pcb on the CD printing tray. eezy peezy... well, it's color balance is always off, but other than that i have no complaints. well, i was...
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    extending an CFL electronic ballast

    i ripped an electronic ballast from a portable desk lamp that was going to be thrown away. i posted a question in yahoo answers where i mentioned measuring a voltage that goes up to thousand of volts (most likely AC, since it registers for both DC and AC, but goes higher than what my multimeter...
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    extending an CFL electronic ballast

    i`m going with your suggestion, hero999. btw, i`m using this for a UV exposure box.
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    2 pin compact fluorescent lamp to 4 pin socket?

    UV-curing solder masks, i've read somewhere, cures at ~365nm, which is right in the middle of UV-A (black light) wavelength, so this should work just fine. but i'm thinking of also using it in the future for making perchlorate salts by exposing chloride salts.
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