A simple capacitor charging circuit.

Discussion in 'The Projects Forum' started by primus_285, Nov 26, 2007.

  1. primus_285

    Thread Starter Member

    Nov 26, 2007
    11
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    Ok, I'm pretty bed with circuts, but I know electricity. (I have built a tesla coil and am not dead. yet...) This is not about tesla coils though.

    I have been trying to find a simple circut to completely charge several large capicitors from (one or several) 1.5 or 9 volt battery(s), and then light up an LED when their "full nuff". This is more difficult than it sounds with so many "battery chargers" and other crap out there on google.

    Something similar to a disposible camera circut would work.
    Plus or minus the 300 volts output...

    I need this circut as a power source for a solenoid. The solenoid is going to be a trigger of sorts. It needs to have enough power to give one sharp (and unfortunately, somewhat long, maybe as much as a 1/2 inch, probably more like 1/4) pull every time I press a button. I have already decided to use a relay button switch thing circut. When you press a button it triggers a relay. This will discharge the capicitors into the solenoid actuating the rod. I'll probably have to build my own solenoid, but I already have brass tubing and steel avalible. Magnet wire is also avalible. I have built crappy coil guns and as stated above tesla coils, so solenoids should not be too much of a problem.

    Plans that only use parts avalible from radio shack would be nice.

    I'll probably use the large 4700µF 35V Electrolytic Capacitor from radio shack.

    Maybe several if the solenoid needs more power.

    Let me know if you need more info, and thanks for any help.
     
  2. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    We need more info. Absolutely.


    How 'bout we start with your solenoid. What is it supposed to do? (IE: how much power will it need?) 1/4 to 1/2 inch (8 to 13mm) we got, but how much force? 1 or 2 grams? 3 or 4 pounds? 5 or 6 stone?

    Solenoid power required, along with size of wire it will be wound from, will give ballpark indication of current and voltage. This in turn will dictate size of capacitor bank. Then we can talk about a charger and an LED.
     
  3. cumesoftware

    Senior Member

    Apr 27, 2007
    1,330
    10
    A comparator with the desired voltage reference will indicate the fullnuffness of a capacitor.

    But indeed, we need more detail.
     
  4. primus_285

    Thread Starter Member

    Nov 26, 2007
    11
    0
    more... ok

    Well, 2-3 pounds of pull for the solenoid should be enough.

    but really, for a capicitor charging circut, all I really need to be able to do is charge an electrolytic capicitor to 30 - 35 volts. (then a light would come on indicating charged to 30 volts this might be able to be done using a transistor, resistor or something similar along with a standard LED, correct?)

    am I correct in believing that if I have a capicitor charging circut, and the solinoid needs more power, that all I would have to do to the circut would be sodder on another capicitor? and if that still wasnt enough, I could keep going until I had a whole bank of capicitors? And the only real difference would be that it would take longer and longer to reach a full charge?

    Well, assuming this theroy is incorrect, and to add another capicitor would require major change to the charging circut, what would need to be changed?


    Well, for starters, how about some hints on how to kick up 1.5 or 9 dc (from a 9 or 1.5 volt battery) volts to 35 volts. Transformers would be the obvious choice, BUT finding the exact one I want will be difficult. Would it just be a better option to take a whole bunch of 9 volt batteries and wire them together (this should add the voltage, correct? I'm no good with DC power. heck, I'm no good with voltages less than 10,000. Because up there, it really dosnt matter too much. ) assuming that the voltage of the batteries adds, I could just take, well 3 or 4, 9 volt batteries and connect them to the capicitor.

    Well, if you still need more, (and you probably will, because all of what I am assuming above is probably wrong) I'm here till I get a decent answer. One that will allow me to start soddering. I may load some crappy sketches to this page later.
     
  5. GS3

    Senior Member

    Sep 21, 2007
    408
    35
    It's CAPACITOR. Just seeing it spelled capicitor is giving me a dandruff attack.
     
  6. primus_285

    Thread Starter Member

    Nov 26, 2007
    11
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    Yeah, my spellings is about as good as my knowledge about circutry...


    here is a quick video of an animated cad sketch.

    The pull should be 1/2 inch

    the overall rod lenght is 3 inches

    the lenght of the coil wraping is 1 inch

    that is a brass tube that is 3 inches long.

    there is a return spring.


    http://www.youtube.com/watch?v=nAcCbTiX0FY


    BUT BACK TO THE TRANSFORMER. Is a transfromer a good idea.

    Is there better ways to build up voltage?

    remember, I'm basicly trying to emulate a disposible camera circut.
    Except all I need this one to do is charge the capacitor(s) from a battery.

    Any ideas. Any good sample circuts? I really have no real good starting point. I'll probably start on that fancy relay switch to dischage the capicitors into the solenoid.


    One more thought.

    Would it just be easier to connect a wholelotta batteries together and run them to the solenoid? But then I would need a new fancy relay switch that only remained on for about a half second. Plus, wouldnt there be more heat? due to the higher amperage?
     
  7. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    The transformer is not a good idea. Not a good idea at all. Transformers don't work with DC.

    Try a DC/DC converter instead.
     
  8. primus_285

    Thread Starter Member

    Nov 26, 2007
    11
    0
    dc/dc convertor. thanks. thats a start. I'll look up some wiring diagrams and find something. More to come
     
  9. primus_285

    Thread Starter Member

    Nov 26, 2007
    11
    0
    ahhh. here looks like a good simple one.

    [​IMG]

    so, looks like a couple of resistors, capicitors, doides, one fancy (not rly) transistor and one 12.6 vac 450ma power transformer. looks like it is avalible at radio shack.

    quick question though. that +3 up there. What does it mean? What does it go to? dead end?

    what should everything be grounded to? the case? a sodder bead along the side of the chip?


    once you all give me some answeres, I'll post another cad of the acutal circut layout. That way you can all give it a look over.
     
  10. omnispace

    Member

    Jul 25, 2007
    27
    0
    That means +3 volts DC. You would connect a 3V battery / power supply with the + side connected to the arrow, and the - side to ground.

    3V battery = 2 AA batteries in series
     
  11. primus_285

    Thread Starter Member

    Nov 26, 2007
    11
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    Ahhhh. That would... make sense. And the ground goes to the negitive treminal. ITS ALL STARTING TO MAKE SENSE.

    Now, just a guess on the output on this beast with 3 volts?

    I know you can change the output by adjusting the resistance ov the 4.7K resistor.

    How would I wire up a varible resistor? it has three terminals, right?

    Would I wire one up to a side terminal, and one to the middle? sounds right to me.

    Well, this should work well.

    And if I attach this circut to a capicitor, it should charge it, right?

    And if I discharge said capacitor into a soleinoid, the force from this would be greater than just attaching a battery, and more importantly, easier to build than a circut that takes a crapload of batteries, and building a circut that just "taps" a relay for a half second?

    And just one more quick question (stupid, I know)
    If I put batteries like "|=|" as opposed to |--|, the voltage would be 3 in each, right (wrong, I know fix me someone)
     
  12. primus_285

    Thread Starter Member

    Nov 26, 2007
    11
    0
    [​IMG]
    ok, more questions. I'm starting actual sketches of the circut as it will appear on the board.

    Does the +3 (where the battery will attach) also attach to the case of the transformer? That line kinda dead ends.

    I assume all of the 0.1 uF capicitors should be rated for at least 100volts, and more wouldnt hurt?

    And for the restifier, which way does it go, there is a line on it. I'm assuming that it should be put on in a peticular direction.
     
  13. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Case goes to ground. Its a safety thing. You learned about safety things when you built that TC, yes? Your +3 ties only to the resistor and to the primary center-tap.

    There is only 1 each 0.1uF cap. The 1 uF caps need the 100V or higher rating. The 0.1 uF and 2 uF can be much smaller.

    There's no such thing as a "restifier.". A rectifier is a type of circuit. It is your diode which has a mark on the cathode end.
     
  14. primus_285

    Thread Starter Member

    Nov 26, 2007
    11
    0
    Ok, so this circiut is now real. I have double checkedd everything. I couldnt find a 2n3053 transistor at radio shack. So I bought the frist one that "looked good" (unfortunately it is not good enough, I think its switching voltage is too high) IE this one didnt work.

    The good news is that upon letting off of button, I get a good DC (higher voltage) charge from the other end. But it only lasts a second. If I press the button quickly... I get a bigger charge. Its almost like the transistor is not switching. Any ideas?

    I found another transistor that is "similar" its a TIP120. Will that work? I have soddered it in and same problems as before.

    And one more thing, the transistors get very hot when the circut is on. Does this mean anything to you?

    Suggested fix?
     
  15. primus_285

    Thread Starter Member

    Nov 26, 2007
    11
    0
    Does any one know how to build a circut that could "press the button" for me? I've never used 555 timers or like chips of any kind. But I am willing to learn.

    Lets see, a circut that completes the circut about, say 50-60 times a second? Thats the fix I have come up with.

    Unless one of you sees something else that could go wrong aroung the transistor area? other than the wrong transistor...

    Well the only other thing I would consider would be that I put the rectifiers on backwards.

    One more symptom for you to ponder. When I press the button repeditly, there is a charge that builds up. When you touch the output terminals there is a spark that is correspondingly large to the number of times the button was pressed.

    I'll post a video of the whole thing some time soon showing the symptoms.
     
  16. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    What does the word "button" mean in this context?:confused: What kind of button? Where is it? What does it do? (What do you want it to do?) What the heck are you talking about?:confused:
     
  17. primus_285

    Thread Starter Member

    Nov 26, 2007
    11
    0
    Well, neermind about the above. The button is wired into the circut so that I can turn it on and off. (kinda hard to pull batteries out of this circut) Not listed on diagram. I figured out what was wrong. The potentiometer (my variable resistor) has to be in a certain range for the circut to work. I'll still post a video so that the world will know, but I started sweeping the resistor all the way from bottom to top, and somewhere in between I started hearing buzzing. And I could control the buzzing from about 20hz up to 100hz. And upon trying to tell the voltage, I got around 400 volts DC (max 600, but thats at a very low pitched buzz).

    I 'll also list other changes to the circut. for the 2uF capicitor, I used 2 1uF electrolytic capicitors. For the 1uF 100 volt capicitors, I used 1uF 250 volt capicitors. For the transistor, I used a TIP120. For the 4.7K resistor, I used a 5K potentiometer.

    I also made a heatsink for the transistor out of that foil ducting tape.

    I'll probably redraw the circut, and post a video of the working circut. Thanks for everything so far. Now I need a capicitor that can handle 400 volts.....


    And one more question. What do you think the maximum input voltage this circut could handle?
     
  18. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    3V battery = 2 "AA" batteries in series.
    Or 2 "A" batteries in series.
    Or 2 "C" batteries in series.
    Or 2 "D" batteries in series.
    The bigger the batteries, the fewer trips to the battery store.
    Or if you have a cordless phone, the handset batteries are generally 3.6v - and the phone base generally recharges them.

    Of course, if you use that circuit to charge 35V capacitors, be prepared when the smoke gets let out of them to go buy more 35V capacitors; that is unless you manage to turn off the supply prior to exceeding 35V across the caps.
     
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