So just yesterday i got my hands on two 75 volt 10000 uF capacitors. What would you do with these?
I'm also looking for a not so sparky way of charging these (tried a 30 volt dc wall transformer with tons of sparks.)
Also currently building a magnet shooter, we'll see how that turns out.
I'll see if I can get some images up, looking forward to ideas.
-ssdd12AX7 - 18-8-2007 at 11:02
I would use them for filtering a solid state amplifier in the +/-60VDC, 200W output (into 8 ohms) range.
Which I'm willing to bet is exactly what they were originally doing.
Timhalogen - 18-8-2007 at 12:13
Magnet shooter? Usually railguns are more efficient, or is that what you meant?ssdd - 18-8-2007 at 18:48
Quote:
I would use them for filtering a solid state amplifier in the +/-60VDC, 200W output (into 8 ohms) range.
Yea thats what they were doing... good call
Not a rail gun but rather something like this: (Hmmm, under physics on woelen's site you'll find "launching of a magnet.")
Rail guns look like they could be a bit much to build and I'm not sure if those capacitors have enough power to make a decent one.
Now I attempted the "magnet shooter" and it seems I need a better magnet for the job, I tried using a chunk of a old ceramic magnet and it failed me.
-ssdd
[Edited on 19-8-2007 by ssdd]chemrox - 18-8-2007 at 23:11
The webpage cannot be found (@ssdd)Mr. Wizard - 19-8-2007 at 05:44
The reason they are 'sparking' while you are charging them up from your wall transformer is they represent a dead short to the source while they are
uncharged. Once they become charged up that will change. As an experiment, try putting a light bulb in series with the capacitor while you charge it.
The bulb will be bright as you start, and then get dim, and should finally be dark. Then the cap will be charged. The voltage on the light bulb should
be at or over the voltage of your charging source. The amperage of the bub should not exceed the amperage of the charger. In other words, you should
match them so hooking up the bulb across the charger will safely light the bulb. How many milliamps or amps is your wall source? Once we have that
number I can suggest a suitable resistor or light bulb.YT2095 - 19-8-2007 at 06:45
and remember also that not ALL electrolytic caps are designed for instant discharge either!
some will get warm after a few tries and some can even explode on the 1`st go.
Filter caps aren`t normally rated for dead short discharges.Xenoid - 19-8-2007 at 13:37
For a "magnetic shooter" you will be better off using the 300V / 120uF "photo flash" capacitors from disposable cameras (do they still make them). My
son has a large bag of these capacitors, and they cost nothing. There are plenty of websites describing their use for this application. They are
specially designed for rapid discharge. Be careful, two or more of these in parallel can kill you.
As for a magnetic shooter (don't let me put you off, as it is an interesting experiment, and good physics learning) but prepare to be underwhelmed. A
"slug" or "BB" air gun has far more power.
As Tim suggested, I would use your capacitors for a power supply. Can you get the transformer and bridge rectifier or diodes from the original
amplifier? You can never have enough power supplies of different voltages, for experimenting with. Again, there are innumerable circuits on the web.
Xenoid
[Edited on 19-8-2007 by Xenoid]ssdd - 19-8-2007 at 15:13
Ok so the wall transformer is 30 volts @ 400 mA. I thought about using a voltmeter (one with a needle) to do this, I have a few laying around that
should work.
I should have a few flash capacitors laying around, if not heck it's easy enough to get them. (After they have been discharged that is.) But if I can
pull it off with these big ones I'd like to use them.
I should be able to pull all the other stuff from the amp, still have the heap of leftovers in my electronics graveyard somewhere, time for a trip
with the screw driver...
-ssddXenoid - 19-8-2007 at 17:15
Your capacitors should be OK for the experiment on Woelen's site.
Check that your wall transformer is actually a DC supply and not just AC, some are simply transformers with no rectification or filtering.
If it's a DC supply you could charge your capacitor up with a 100 ohm resistor in series, that would limit the initial current to a maximum of 300mA
(Ohms law). Put your voltmeter across the capacitor terminals, and watch the voltage rise to 30V, then it will be fully charged. Be aware that
electrolytics are polarised, note the + and - terminals.
You should really discharge it using an SCR (Thyristor)..... but thats another story!
Xenoid
[Edited on 19-8-2007 by Xenoid]ssdd - 19-8-2007 at 17:51
Yea I have been carfull to only use DC, using AC would probably not be so good for the capacitor. (or me after the fact!)
The positive on the cap is pretty clearly marked.
Still have to go rumage into the piles for the transformers, though I did find this really fun magnetic switch. (Works with 12vdc from a computer
power supply in my tests.)
Thanks Xenoid
-ssdd12AX7 - 19-8-2007 at 19:36
You mean a...relay?
Timssdd - 19-8-2007 at 20:14
Sorry yes a relay.
One electrical component I wasn't terribly familiar with until now, but at least now I have a name for it.
