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Everything posted by CRE

  1. Hello everyone, I've been thinking for a while that I'd like to clean up my computer's power wiring... I know the usual methods of using loom, etc, and tying them out of the way, but what I'd like to do is make a box for each 3rd of my server case with one power in connector and 3 - 4 power out connectors. I realize the number one issue would be pulling too much power through too small of gauge wire, but would I also do well to put in some high capacity caps on each rail in each box? To act as a kind of buffer? Thanks.
  2. Well, after talking to my friend who asked about doing this, he's taken some time to think about it and decided to do the sensible thing..... buy a case big enough to fit a full ATX PSU.... Still, one of these days I might be inclined to experiment on this with a couple cheapie's.... just to find out what works best. ;) Thanks alot guys!
  3. :-\ whoa..... umm, yeah what that other guy said. :o Err, ok, well backing up a few posts, I'm sure the two 9v's in serial didn't fry the cap as I hadn't even used them when that prob occured. It may have fried one of the IC's granted, but as I said, I tested the voltages and they were putting out only about 15v combined, but admittedly I tested them without a load. I think it's more likely that I miplaced a jumper.... I tend to do that.... fortunately enough I only tend to do it on the first circuit and not any to follow. :P I'm gonna go through and trace the circuit tomorrow.... hopefully it is just a misplaced lead and not a fried IC or two. I am interested in the complementary pair suggestion though, if the output is higher it should be exactly what I'm looking for. One of these days I need to either find out how to read and understand the values of transformers that I've found at suppliers'..... or learn how to start wrapping them myself. At any rate thanks! and I'll be sure to post once I get this initial one debugged.
  4. Well, I had it running fine on my breadboard.... I think I burned one of the ICs..... seres me right for not keeping enough IC Sockets on hand. I was wondering, if I use a larger bypass cap will it reduce battery life?
  5. Good to know, AudioGuru, so would one of the other opamps I listed as having on hand work better than a 741? The 741 seems to run fine... but I haven't tried a different one... all my others are dual or quad.
  6. Ok, so far, so good (excellent actually ;D).... Now, how about an auto reset on the trigger? I imagine I could accomplish it myself using an opamp/comparator, but can it be done using fewer parts such as a transistor in combination with another cap and pullup resistor? Something which'll reset the trigger once the voltage across the two contacts returns to 0v or possibly once the resistance becomes great enough for it not to trigger the alarm.
  7. It was definitely shorted.... because the 555 was still getting the trigger pulses. That's pretty muvh how I thought it was working, but
  8. Horay! Well, I swapped the ceramic cap I had in there (I wasn't positive of the value) and put in a 10nf Met. Poly. with the second pull up resistor and it works like a charm! I understand the basics of most parts of this circuit, but the cap and pullups escape me... I kinda see some of the picture, but I'm not understanding the whole thing... care to break it down for this nooB?
  9. Hmmm...... not sure what I've done wrong, but if I keep the trigger grounded the circuit doesn't stop until the trigger is pulled from ground. I understand somewhat what you're saying about the op-amp, but as i said, right now 741's, 324's, 348's, and 1458's are all I have to work with.... the 741 being the only single. I went ahead and tried 2 9v batteries in series and got buetter volume results. I guess the thing which is on my priority list is the triggering. I need to find where I made the mistake that's keeping the trigger active beyond the specified time period.
  10. Hey, wow, talk about a quick response... As a matter of fact I am using a 741.... didn't have any other type of single op-amp on hand. So as for volume, I'm either being limited by the piezo element or the single 9v supply... right? I mean, it's loud right now as long as the freq. is perfectly tuned, but I don't wan't loud..... I want downright terrifying!!!!!! ;D No, I'm not looking for ear damaging volumes either, but given that treble is directional I want to make sure my dogs hear it clear as day even though it's sitting on top of the refridgerator (of doom!). You know what I mean?
  11. I keep getting this error whenever I try to use the spellcheck.
  12. Okay, I've built the circuit and it works well, I'll need to modify the trigger a bit, either a one-shot circuit or a long delay before resetting as the contacts may take a while to dry and stop conducting (if I'm not home). Also, am I correct in thinking that the gain is set by the 10K resistor between the op-amp's output and the inverting input? Not that I'm likely to get much more out of it while running on a battery. I did replace the 22K resistor in the R/C with a 100K pot... makes it alot easier to find the piezo's "sweet spot". Thanks a ton Alun and everyone. Do you guys think adding another 555 timer running astable would work alright if set with a cycle of something along the lines of: 5 sec. high, 10 min. low? I don't think it would work well, but if it's only gonna loose some precision I might be able to deal with it. If not, can anyone offer another suggestion?
  13. LOL... ;D Oh I've been there a few times.... then again I'm still a newbie.... but even I know that once I've "Mastered" something I'll always find more to learn. Thanks for going to the trouble Alun, I'll probably have time to breadboard this tonight. I'll post my results... well, I'll post whether it works or not... as for actual results... depends on my doggy. ;)
  14. Hey guys, thanks for all the responses. For the time being I've set up a small analog buzzer from RatShack which made for some VERY amusing moments last night.... so funny, so sad.... poor startled little doggy..... so funny!I think I'll give Alun's circuit a shot, but I was wondering if I could substitute the CA3130 with another op amp such as a LM740 or a LM1458? These I have on hand. :D
  15. I presume, this is for some sort of medicinal use? In which case the frequency probably needs to be quite accurate... do you know the frequency needed? As for the circuit, if the use of this appliance is going to be tethered to the computer via the wiring anyway, why not box the driver and just run the transducer out on a longer wire?
  16. Nope, no joke, one of my pugs is getting out of hand with his "marking" behavior..... It's driving us nuts. So, I plan on placing some alarm in every area he's "tagging". I've got bare copper tape (used in stained glass work) which I'll run in two horizontal lines with only about a millimeter gap. The part I'm having trouble with is the audible alarm. I'd like to build a piezo driver which'll push about 80-90 dB. I'm going to use a 555 monostable to only allow the sirem to scream for a few second when triggered, then reset. Anyone have a schematic for a good loud piezo driver? I've got a few different piezo transducers on hand but I'll probably use the larger ones I picked up at RatShack (273-073A). Thanks! Edit: One more thing, I do want this circuit to run at an audible frequency, so I know when something's been done. Also, the electric dog whistles I've found are too quiet.... any idea how make a louder version: http://www.zen22142.zen.co.uk/Circuits/Misc/whistle.htm That's one I've tried.
  17. Yeah, I was thinking something along the lines of that Alun, but is that sufficient? I need to aim for a minimal loss of voltage and the rectifiers seem like the best bet. Depending on how the PSUs are built, I may be able to up each of the rails to compensate for that small of a loss... but a 1v drop kills the project.
  18. Hi, thanks for the response.... Wattage, lol, well, that's what I get for posting while half asleep. Yes I actually meant higher amperage. What I want to do is connect them in parallel, but filter them both so they aren't subject to any feedback from one another. Thanks
  19. Hey guys, I've got a kind if odd one here. A friend asked me to help him take two computer PSUs and merge them into one... the goal: higher wattage. Input 270W per PSU output >500W. Now I know that simply tying the two rails together would do the trick, but I suspect it could also result in a severely shortened lifespan, so I was figuring that a diode coupled with a nice big cap as a buffer would help eliminate any interference should one push less than it's counterpart. This will be on all the rails (-12v, 3.3v, 5v and 12v). Will this arrangement work?
  20. Could someone please recommend a substitute transistor for the BC108 which DigiKey carries? Thanks!
  21. I agree that the narrow angle of projection can be a real PIA, but on occassion I don't mind if it gets me the color wavelength I want. I just ordered some blue 3mm LEDs which I hope come out nice and deep in color (430nm as 450nm is "true blue"). They're not the brightest only about 50mcd typ. and the angle is ~20º.... but, if the wavelength is as the datasheet says I'll be quite happy. And I know what you mean about the site being slow.... wow.... just that much holiday traffic? or is it always slow?
  22. CRE


    Well, first does the solenoid just turn on once? or is it on until the path is cleared? If it's the first a 555 timer setup as a monostable vibrator would work. Second, if sensed optically can the sensor/emitter be placed opposite eachother? If yes then I'd probably first experiment with a LDR and transistor opposite an LED. Use IR if visible light is a problem.
  23. Do keep in mind that while most DC motors will operate in either direction depending on the polarity of the voltage, that if it is not brushless or designed for such operation the brushes inside may be damaged... it's all a matter of how it's constructed of course.
  24. Well, my thoughts on the LEDs in an IC was that since the light isn't straight as in a laser passing it through an acrylic rod/lens should serve to blend the colors sufficiently. hmmm...... free string o' LEDs? :) Nice.... too bad about the flicker. When you post the info on the 16M projector let me know.... I wanna see how it's done!
  25. Well, that's kinda where my thoughts were heading... As I've said before I'm a newbie with only enough knowledge to be dangerous. ;D But I recalled that they weren't all rated for 1.5A. looking at National's datasheet packages TO-39, LCC and TO-252 are only rated for .5A. But I was just curious to see what make and look if the pinout might vary, or if it has thermal protection. I don't expect this to help you guys, I just wanted to look at it from another angle for a sec.
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