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Everything posted by flippityflop

  1. 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 needless to say, what i need is very simple.
  2. 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 equipments, like say a low bandwidth oscilloscope would do. also, the hobby electronics i'm into have signals that are pretty constant, except on audio applications... i've also gathered (not sure about this) that auto-ranging DMMs don't get overvolt-ed or overcurrent-ed, unless the very maximum limit is re
  3. how do i make sure that the multimeter i buy have safeguards against mismatching the probes again??
  4. 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 measuring voltage, then current afterwards (properly switching the selector to the correct function), but leaving the red probe at voltage/resistance socket. ok... this could be harmless. but sometimes i would accidentally leave the red probe on the Amps socket when i would be measuring the voltage or r
  5. 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 was very little white tarnish/oxides around the boundaries where the rubber and metal can meet. looks a bit of the metal oxidized due to the 1.5V difference. they happen to trace a path from the negative to positive. i took it back in as soon as i got out of bed. tested it with 1.5VAC again then +40VAC
  6. not to mention harder to machine those wee small fins.
  7. also, i will screw them together in just one thick copper plate that will serve as the heat sink. would that also help?
  8. 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 in modular units so i can mix match and borrow sections for other projects. i'm assembling the dead easy rectifier unit (the diode bridge, capacitor and a small LC filter -- the filter just for kicks). as for the diode bridge i have 3 of these: https://www.digikey.ca/product-search/en?vendor=0&keyw
  9. 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 since my welder already ramps down the AC to above voltages, i figure it that there are other taps in the transformer that might go down pretty close to 3V.... well i opened the thing for the first time (and confirming my hunch that it's just one big transformer, as implied by it's low price 4 years ago), a
  10. 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, so i used some a voltage divider from some spare high wattage resistor that i got to lower the charging to around 7V @ 800-900mA. it got the lead acid battery to 4.83V. but after that it plateaus, no matter if i leave it charging for extended periods of time. i've never heard of lead acid batteries havi
  11. 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 CP53 is ok, as i don't know even what's "PSC" is supposed to be. but these are the measurements. no burning components. then i unscrewed the main board, inspected it (visually seems ok), then plugged it all back in (with the aforementioned FFC that got disconnected when i first disassembled, then connecte
  12. ---- 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 doing some adjustments. i had the copper clad piece taped down and the tape gets caught in the ink head and there were smudges. didn`t worry about it since it`s happened before. so, to make sure that smudges have been cleared out, i tried printing on paper sheets. on the 3rd or so print, the paper wasn
  13. 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 can take) ... it's most likely because i used an incompatible DC power supply. see, the old portable lamp had a wall wart providing 9V @ 1A. i have long burned that out in my electrochemical experiments... so when i tested the said ballast from the portable lamp with the 9W that i got from ebay, i used
  14. i`m going with your suggestion, hero999. btw, i`m using this for a UV exposure box.
  15. 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.
  16. i'm trying to make a cheap UV exposure box... this time, only for curing solder mask.
  17. i don't think you read through the listing page description: Lamp Configurations (2/1) CFQ/M13W/G24q (2/1) CFQ/M13/GX24q (2/1) CFS16W/GR10q (2D) (2/1) CFS10W/GR10q (2D) 4-pin lamp (2/1) CFT9W/2G7 (2) CFT7W/2G7 - it lists CFT9W and 2G7 together. google'd it and found CFT9W are 2-pins, while 2G7 are 4 pins. maybe it can accommodate (2/2) same types or two CFT9W and one 2G7 (2/1), so it has a total of 8 wires??
  18. you mean to say i should've gotten these ??: http://www.ebay.com/itm/321293131731 (36W) about $~28 total (price + shipping) -- hardly inexpensive. i wasn't just buying any CFL (which are around $~7 or so), these are UV lamps. well, the four 9W "old" UV CFLs that i bought were practically just a dollar each ($~6 total) and i thought finding the appropriate ballast was just easy peezy.
  19. 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? maybe a separate starter for each new lamp added and then have them parallel for each output. i have a feeling the answer would be no, hey, i still gotta ask.
  20. you probably thought i bought these: these are what i got (CFLs): http://www.ebay.com/itm/331138643631
  21. 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 the 2 pin lamps there. just so happens, as i`ve read more into screw-on CFLs and what i saw as i opened one of them, is that they have 4 connectors that connect to the raw fluorescent tube itself... wired that way because integrated to it`s ballast is also a starter. i`ve read that the 2 pin CFLs that i
  22. 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.
  23. so for the past 5 years i've been putting up with my lousy PC speakers that i bought from a thrift store. i've always wanted to replace them, both for reasons of better music listening and that it doesn't match with my overall black PC. i also want a long term device so i've always had my eye on high end speakers. the problem is, the good ones come in hundreds of dollars. so to save money and since i've always wanted to design my own sound system, i'm think i'm gonna build myself one step by step. i don't need a surround sound, quadraphonic must the most i'm gonna be stretching with the syst
  24. so i bought this cheap portable device and it worked ok for the first week. then i started noticing it would get discharged more and more quickly, until it doesn't even power up. i reckoned that it was a battery problem. so i wanna replace it. i don't have any more spare li-po battery, but what i do have are a couple of AA-sized lithium ion batteries (3.7V). i want to solder an AA-battery holder, so i can simply swap the lithium ion batteries whenever they get discharged. my question is, if i where to leave the AA-batteries in and plug in the recharging cord, which is USB, rated 5V, would it
  25. if the solder mask says it's UV curable, is there any other way of curing it? i don't suppose you can just wait and let the solvent evaporate out... would leaving it on a high temperature, say in an oven or hot air work??
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