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    the finer points of electronics - II

    alright, continuing the series... another question i would like to as is on NPN BJTs, would it be better to put the load on the collector side or the emitter side?? in schematics, i almost always see it on the collector side (Ic = hfe * Ib), but the emitter side also works and when doing plain...
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    minimum reliable low currents

    i need to know what is the lowest current that is reliable for cases such as: a.) charging a capacitor b.) when the current is being read by an instrument such as an ammeter c.) logic signals what i mean is that even outside normal conditions -- exposed to hot summers and cold winters, being...
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    are BT2222 transistors the same as 2N2222

    are these NPN BJTs: http://pdf1.alldatasheet.com/datasheet-pdf/view/17918/PHILIPS/MMBT2222A.html the same as those 2N2222 that has been around for since forever? can i trust that the reverse active and avalanche breakdown profiles are the same??
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    RF - separate transmitter and transceiver antennas for half duplex

    i was wondering why is it, for just half duplex systems, don't we have a dedicated transceiver and a dedicated transmitter antenna. ok, just hear me out... assuming we are using grounded monopoles, we can have a resonator connected to a diode whose anode is connected to the transmitting...
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    the finer points of electronics - I

    ok so i have questions with electronics that doesn't seem to be covered by tutorials that i've scanned throughout different websites, or i just don't want to read through a lot of material to find that small footnote that i needed to find. i'm basically going to be posting a series of threads...
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    can an ammeter damage zeners??

    so i got this small circuit that plugs to the mains as power source. as for its DC converter, it's one of those transformer-less ones that drops the voltage with a resistors and filters before rectifying and smoothing it. the ones that can only deliver small currents. well, after that, it uses...
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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 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?

    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

    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

    ---- 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`m thinking of buying this ballast http://www.ebay.com/itm/200971855385 to power 2 of my 2pin 9W UV CFLs: http://www.ebay.com/itm/331138643631 it says it can drive two 9W CFLs at the same time.... but i wanna push it and probably drive more (maybe 4 in total??)... can it be cheaply done...
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    2 pin compact fluorescent lamp to 4 pin socket?

    so i got these 4 CFLs: http://www.ebay.com/itm/161173123039 they are 2 pin and i don`t wanna buy a ballast for each and i think we have a few busted screw-on CFL () in a box in our garage. so i thought i could just rip off the electronic ballast off the busted screw-on CFLs and then connect...
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    high frequency audio amplifiers

    i'm looking for schematics optimized for high frequency (2,000-20,000 Hz) audio amplification. or would most other "hi-fi" amplifiers would do the job as well?? i'm new to electronics.
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