Leaderboard


Popular Content

Showing most liked content since 10/21/2017 in all areas

  1. 1 point
    audioguru

    0-30 Vdc Stabilized Power Supply

    Since it was years ago I do not remember which page of which thread has version 6 or 7. I have the schematic and parts list of version 6 here:
  2. 1 point
    elctro123

    0-30 Vdc Stabilized Power Supply

    So Finally which version of schematic is correct / flawless to build the PSU ?
  3. 1 point
    Fliptron

    Help Under standing Schematic PSU

    Hi Islam, I'm a new user here (just signed up to answer your question), so I hope this helps. There seems to be several things that need to be understood about the overall topology of this PSU to get to answering your questions The power supply has two main parts: 1) The control section with the GHI outputs from the transformer, generates +12, -6, and -15. The ground of the control section (center point, more or less) is connected to the Positive side of the output. See ground below C4, and on the far right of the page (has the number 15 near by). (I think these numbers scattered through the schematic are test point numbers). So all of the control circuitry (anything using +12, -6 and -15) Is referenced to this ground. What is a little surprising, is that means that as the power supply output goes up/down, the control ground is doing the same. Also on this signal, is one end of the each of the six Load-Balance/Current-Sense resistors (6 x 0.36 Ohms). 2) The second part is the power section, which includes the lower half of the transformer (ABCDEF), the relays that select between the 4 voltages you listed (15-20-30-50), the bridge rectifier D7..10. The Negative side of the bridge is directly connected to the negative side of the output. (the line at the bottom of the page with label 14.) The Positive side of this bridge rectifier goes to the 6 collectors of the 2N3055s, then the 6 resistors mentioned above, then to the Positive side of the output, which as described above is also the ground of the control electronics. Since the maximum current is 3 Amps, and it will be shared evenly between the 6 resistors (with very minor differences depending on the exact characteristics of the six 2N3055s), the maximum current for each resistor is 0.5 Amp. So the max voltage across these resistors is 0.18 Volts , which gives about 90 mW , so these resistors are grossly over-sized at 5W, and will run cold (unless they are mounted on the heatsink). This also means the voltage on the 6 emitters is 0.00 to 0.18, which is averaged by the six 100 Ohm resistors and then sensed by U2 which implements the current limit circuit. U3 implements voltage control, follow pin 2 to the right which goes to the ground symbol, which we have established is power supply's positive output, and pin 3 which is connected to a voltage divider (including the front panel control) which connects to the negative side of the power supply, marked with the label 14. So now to get to your question. Regardless of what the output voltage is, the six emitters are no more than 0.18 volts above the ground of the control circuits, which tracks the positive output of the supply. The bases of these transistors will be 0.6 to maybe 0.75 volts above that. So the base voltage is always in range of the control circuit driving it. For the same reason, the 2.5V reference is an offset from the control section ground, and the power section's positive output. Yes, the six resistors also carry the base current, but this is minimal, compared to the collector current, due to the gain of the transistors. At DC, 25 deg C, and collector current of 0.5 Amps, the gain is over 100. I just did a Science (see picture below) to make sure I wasn't lying: With 15 volts on the collector, I got the following results: Vbe Ib Ic Volts mA mA 0.5 .05 3 0.56 .15 22 0.6 .36 82 0.61 .5 122 0.63 .7 190 0.65 1.0 280 0.67 1.26 370 0.7 2.2 600 (Note, Vbe is using the voltmeter in the PSU, which is not very accurate, and the transistor heated up on the last few measurements, and needed to be cooled) Anyway, the measurements I made show a gain on my test 2N3055 of about 300 when the collector current is around 0.5 amps which is the high end of what is expected in this power supply, and would contribute about 0.3% of the emitter current. Thinking a bit further, it doesn't really matter since it is sensed along with the collector current, and it all goes out through the positive output of the supply. Cheers
  4. 1 point
    repairman2be

    0-30 Vdc Stabilized Power Supply

    @Jeremy You may have 2 PCB's for AU$5 plus shipping in an envelope. Two boards weigh about 44grams. Email me if you would like some to: weigenmann@mannix4mail.com Cheere, William PS. Seems your Kit has a problem to start with. Before I found this Forum I ordered two Banggood Kits. It is still not assembled and probably never will be. Anyway, over at this page there is a lengthy description on how to improve the Banggood kit. "www.paulvdiyblogs.net/2015/05/tuning-030v-dc-with-03a-psu-diy-kit.html"
  5. 1 point
    Jeremy

    0-30 Vdc Stabilized Power Supply

    Ok, skip the voltage and current LCD panel With R18 = 33 kOhm I have got 4,7 A on out... U3 was replaced for another .
  6. 1 point
    tripped

    Solar Powered Water Pump

    I have some questions I was hoping someone would help me work through. I am building an outdoor fountain that I want powered by a solar cell. Can I run the solar cell wires directly into the BLDC motor and have it operate only when sun is shining? The brighter the sun the faster the motor turns. Or do I need more circuitry to make it work? If I do hook up a small 3.7 v 2000 mAh Li Ion battery, I need a charge controller? And what? Pump Voltage VDC - 6.0 Nominal Current Draw: 0.27 Amps Power Usage: 7.0 Watts Solar cell Output Voltage: 0.5 volts (Vmax) Output Current: 3.5 Amps (Imax) Average Power: 1.75 Watts Is there any way to turn the motor on for 1 minute every hour on the hour? Miniature controller or driver of some sort? System as compact and concealable as possible. Any help out there For this one? Oh one more thing, is there a micro charge controller out there that would protect the battery when it was full by dumping the load into some LED’s or something of that nature?
  7. 1 point
    stuee

    12v lamp Dimmer lamp ideas?

    I have a 12v transformer for interior lights and a few lights for it, but want to make it a dimmer light. the working amps are 250mA. I would like to know how to wire up these three ways, so i can try each one and see if its any good and use the best.... Touch lamp. touch the metal to turn on dimmest. press again for brighter and again for brighter and again for off. Manual pot adjuster. and digital potentimeter. press up to turn up and make brighter and down for darker / off, and a reset button to turn instant off. Any help and sche... will be helpfull. Thanks in advance
  8. 1 point
    Check this out! Awesome Project!
  9. 1 point
    hg70

    Electronic Gun !!!!!!!!!

    http://www.metalstorm.com/
  10. 1 point
    Silent Jack

    Electronic Gun !!!!!!!!!

    [i would not encourage children to develop high tech weaponry and would firmly discourage them from using them on themselves or others.] I saw a project online once that took a page from the XREF taser shotgun rounds, concept. It used pressurized air to propel a charged disposable camera capacitor, prongs first out of a simple barrel. Interesting concept, though from what I read, the 330V would be far to little to achieve the taser effect. That and I understand a specific waveform is needed to affect strictly skeletal muscle and not cardiac muscle. Seems like a safety concern to me.
  11. 1 point
    gogo2520

    Electronic suplus stores

    Hello RFamateur and welcome to the form. Here are a few. These have stuff some good lot outdated. http://www.goldmine-elec.com/default.htm http://unicornelectronics.com/prod.htm http://www.mpja.com/category/LEDs/LEDs.asp http://www.futurlec.com/index.shtml http://www.allelectronics.com/ http://www.danssmallpartsandkits.net/ http://www.alltronics.com/assortments.htm These are good suppliers http://www.mouser.com/index.cfm?handler=home http://www.futureelectronics.com/en/Pages/index.aspx http://www.web-tronics.com/ http://www.jameco.com/webapp/wcs/stores/servlet/StoreCatalogDisplay?storeId=10001&catalogId=10001&langId=-1 That should get you going. gogo
  12. 1 point
    audioguru

    Electronic Gun !!!!!!!!!

    Hi Shantanu, Electrolytic capacitors have a vent on top to slowly release gasses that build up when the capacitor is connected with backwards polarity then has a high current. With a very high current, the vent cannot release the gasses slowly so the capacitor explodes. A 9V battery cannot provide a very high current. Maybe a battery made with series-connected AA Ni-Cad or Ni-MH cells would provide enough current for a backwards electrolytic capacitor to explode. Bad-smelling "fluff" comes out.
  13. 1 point
    Here is the book in pdf for you all. You can press the free button and you have to wait about a minute then it gives you the links. Just pick one. http://rapidshare.com/files/3372603/Practical_Electronics_for_Inventors.pdf
  14. 1 point
    grsparks

    An excellent electronics manual

    After running across this at the public library in town, I just had to order my own copy: "Practical Electronics for Inventors" by Paul Scherz It covers just about everything from DC to Microcontrollers and is well illustrated.
  15. 1 point
    You are breaking the hearts of all the hobbysts who can not afford the cost of buying the books from amazon. most of us are ametures using the books for refrences or some other information. i dont think someone is making millions using these ebooks.
  16. 1 point
    Calm down people. It is not Mixos's fault, if it is against the law he has to remove the content. This site is very good for asking electronic related questions, I have yet to find a better one.
  17. 1 point
    juanpmoron

    0-30 Vdc Stabilized Power Supply

    R16 is 1K and is OK ???
  18. 1 point
    MP

    0-30 Vdc Stabilized Power Supply

    Think of the commas as periods or the periods as commas. These are used differently in different continents. It means the same. MP