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FireFly

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Everything posted by FireFly

  1. I started collecting the parts for this project quite some time ago and then got sidetracked with other things.
  2. Anyone happen to have a pcb image for this project that they would like to share? Thanks.
  3. I was looking at the datasheets for the Maxim ICL7135 4 1/2 Digit ADC and the ICM7211 4 Digit LCD Decoder Driver: http://pdfserv.maxim-ic.com/en/ds/ICL7135.pdf http://pdfserv.maxim-ic.com/en/ds/ICM7211-ICM7212.pdf I'm still a little (actually alot!) baffled by the various display interfaces but I was wondering if 2 separate meters (a volt meter and an amp meter) were created using 2 each of the 7135/7211 chips, could they be connected to one LCD display such as a 1 line, 16 character display to show volts and amps at the same time? Or am I trying to put a square peg in a round whole? :-\
  4. Sorry about my 2 previous posts. Please ignore my stupidity. I'm going back to bed now!
  5. Sorry. My last post should have said 450v caps rather than 250V caps.
  6. I'm aware that the filter cap is recommended to be much larger uF wise but I'm wondering about the voltage rating. The original part list called for a 50V cap. I may have found some large-enough, 250V caps. Would using caps with much higher voltage ratings do anything good or bad to this power supply? Should they perform as well as the same size cap rated at 50V? There must be some kind of trade off. Perhaps physical size or cost?
  7. And one more substitution please: 2N2219 I can't seem to locate these in a form easily attachable to a heat sink. Can someone suggest another model(s) suitable for this circuit that would be easier to find in a "heat sink form" such as TO-220? Thanks again (for the umteenth time!)
  8. Could some one tell me if TI's 44V TLE214x op-amps would also be a good substitute for the TL081. I haven't got a complete handle on what all the specs mean yet. Thanks. Datasheet: http://focus.ti.com/lit/ds/symlink/tle2141a.pdf
  9. Thank you, MP. Sounds like 3/4 experience and 1/4 mathematical. The heat sink(?) I was referring to in the picture is the black "collar" towards the upper right of the board right beside where the 3 2N3055 connection wires attach to the board. Isn't that the Q2 = 2N2219 and a little, round, black heat sink or is it something else? That's what made me wonder in the first place about knowing when to use a sink especially if only working from schematics. As far as heat sink ratings, I guess I should pay more attention to what was attached to old heat sinks that I salvage to give me a hint of
  10. I was looking at various datasheets for bridge rectifiers for the "0-30 VDC STABILIZED POWER SUPPLY" project. I'm trying to understand when a heat sink is required. For example, the datasheet for the NTE5329, 6A bridge rectifier: http://www.nteinc.com/specs/5300to5399/pdf/nte5329_31.pdf ...states "Recommended mounting position is to bolt down on heatsink with silicone thermal compound for maximum heat transfer with #6 screw." But how big a heat sink does it need? Is there any way to tell from these spec sheets (bridges, transistors, etc.) if my usage is low enough to not require a sink?
  11. Does this NTE cross reference give you what you want: http://nte01.nteinc.com/nte/NTExRefSemiProd.nsf/$$Search?OpenForm It comes up with an NTE equivalent for each one you listed and maybe you can get the specs from the NTE part datasheets? Does that help? Sorry if this isn't what you wanted. I'm still learning this stuff.
  12. I've been looking into selecting a one-piece square bridge rectifier for the 30V/3A power supply project. There seems to be lots of these like every other component type! Generally, they seem to have rather heavy voltage/amperage handling abilities. What is the downside to using a bridge with significantly higher ratings than required besides slightly higher cost and larger physical size? Would a bridge with just adequate specs put out more heat than one with much greater than required specs?
  13. While looking over some big capacitor specs on the NTE site, I came across what they call Snap-in mount. Can these be used with a board I create myself? Is there some kind of connector that I would attach to the board and then the capacitor attaches to that? Or what...?
  14. I've almost collected all of the parts I need for the original 30V/3A project. A new, old-stock, Hammond 25V/5A transformer will be arriving any day now. I've got the presinsitized board, chemicals, etc. and have added extra points to drill to allow meter attachment (someday!). But I don't want to burn it until all of the components have been suitable "upgraded". Could someone suggest what part to use for the diode bridge upgrade? The PCB appears to have enough room on that corner to easily allow changes to the copper trails for this if needed. Can the 1N5402,3,4 diodes just be upgraded
  15. Thank you very much for your previous posts on the component sizes and issues. I just want to make the original 30V/3A supply reliably live up to its specs! Just so I understand would you please answer the following. For the original 30V/3A supply: Transformer should be about 4A to 5A, right? Do you feel that "C1 = 3300 uF/50V electrolytic" is suitable? If not, what would you recommend? Are the "1N5402,3,4" diodes adequate for the bridge? Any other substitutions you would recommend? Thanks alot.
  16. I have a heat sink from an old stereo receiver that I think is substantial enough for this project. The project page states: "...use the mica insulator between the transistor body and the heatsink..." I will be able to re-use the screws and plastic hole inserts but there was a piece of clear plastic between the sink and transistor that is too small. What should I use? Is there something around the house or hardware store I can use or do I have to hope :-\ my local electonics store guys will know what I am talking about? Also: "Use a little amount of Heat Transfer Compound between the tr
  17. I've been wondering about this too. Here's 3 more: http://www.mainelectronics.com/scope-ct.htm Has anyone used these? Are these a reasonable alternative to a "standalone" scope -- especially for someone just getting started? As usual, I suspect you get what you pay for but if it's a PC scope or nothing...
  18. Not sure if anyone cares about this but I did some digging and found another ESR capacitor meter. It's cheaper than the "Wizard" and has a digital display: http://members.ozemail.com.au/~bobpar/esrmeter.htm It's available in kit form or preassembled. Testing caps in-circuit sounds like a great idea. Anyone tried this meter? Comments anyone?
  19. Thanks from me also, everyone. Now, if I just had the schematic and PCB layout for the Capacitor Wizard listed at the bottom of the link that mixos gave... ;) http://xtronics.com/capacitor-wizard.htm Anyone have the plans for something similar?
  20. Thanks MP. This site has an LCD panel meter that seems cheap enough: http://www.circuittest.com/Default.asp?Main=/English/OnlineCat.asp?Menu=/English/Content/Categories/CatM_81.asp%26Detail=/English/Content/Items/DMD-3500B.asp Not sure about the quality. Any thoughts on that? The description states: "Note: Supply voltage must be independent of voltage being measured." I've seen something similar for some other meters. Any idea what that is about? Would this meter need a separate transformer or would it be good enough if it was on its own taps? TIA;
  21. If meters are to be added to this power supply, I believe they should powered by their own transformer. Am I right? So to add a cooling fan, should that be powered by the power supplies transformer, the meters' transformer or a third transformer of its own? ???
  22. No, I haven't built it yet. I haven't had enough free time lately. I also took a detour to try the laser toner/inkjet photo paper transfer method for making PCB's. IMHO, don't waste your time. Now I'm waiting to see what comes out of this discussion about the proper transformer to use as well as bumping it up to 5A. I'm relying on those who know something about this stuff. I'm not including me in that group yet! :)
  23. Staigen, thanks alot for the info. For 3A and 30V output, you believe the 24V/3A transformer is a little light. What transformer would you recommend to get the 99 VA you are suggesting? Maybe around 25V and 4A? What tranformer would you suggest if this power supply is converted to 30V and 5A? Thanks again.
  24. Thank you very much, mixos. I'll have to think on that for a while. You confirmed my suspicions: I'm just slightly in over my head! ie. This power supply does 30V/3A; the meter can do 20V/200V and 2A. Have a happy New Year!
  25. I think I understand how to add a voltmeter to this project though, I've been wrong before! It's the current part I'm a little confused about. An ammeter wouldn't show any reading until the power supply was connected to a load, right? So, can a meter (ammeter?) be added to this project to show where the current limiter is set? Should I add a couple of connection points to the pcb diagram to do this and if so, where? Thanks again!
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