# Capacitor charging

Discussion in 'General Electronics Discussion' started by Mark34, Sep 29, 2016.

1. ### Mark34

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Sep 23, 2016
Hello !
I have the circuit from the picture below and a 400v 1000uF capacitor, the problem is from 200V up the charging is going very slow and it stopes at 230V, any ideas? I want to charge it at least to 350V. Thanks!

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2. ### davennModerator

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Sep 5, 2009
then you need a psu of at least 350V. If it stops at 230V, that is telling you that that is the max voltage of your PSU

show us a schematic of that circuit you have displayed

Dave

3. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Also, energy storage in a capacitor I'd proportional to the square of the voltage. When charging from a power supply capable of constant power (like a fly back inverter) the rate of charge will fall as the capacitor charges. If you have a voltage source and a resistor, the charging rate falls even faster.

As Dave suggests, if it stops, you've run out of voltage.

4. ### Mark34

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Sep 23, 2016
I can't run out of psu i am using 4x 1,5v batteries, my guess is I need to replace the transformer or a resistor.

5. ### HellasTechn

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Apr 14, 2013
are you sure ? the cap in the picture does not look big enough to be a 1000uf 400V to me.
I would expect a capacitor of at least double or triple that size (compared to the led display and battery pack)

6. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
But there certainly may be a maximum voltage the inverter can generate.

davenn likes this.
7. ### Mark34

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Sep 23, 2016
Its a old picture with the 250V Capacitor but now i have a 400V one, so how can I increase the inverter voltage with the same 4x 1,5V batteries?

8. ### duke37

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Jan 9, 2011
If you show a schematic as previously requested we might be able to help.
There could be two possibilities
1. The invertor cannot supply the voltage. Higher voltage components may be required.
2. The invertor cannot supply the leakage current of the high voltage capacitor.

Try a disc ceramic capacitor and see what voltage you can get.

9. ### Mark34

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Sep 23, 2016
I don't have a schematic I received that kit, is the red pointed component a transformer? it has 4 pins.

10. ### CDRIVEHauling 10' pipe on a Trek Shift3

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May 8, 2012
I recognize that little transformer because they're used to drive Piezos. I have them in my two uC based bike horns. Even if yours has a greater turns ratio than mine they're wire gauge will be small. They're not intended to deliver a lot of current.

Chris

11. ### Mark34

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Sep 23, 2016
So that transformer might be the cause why I can't charge the 400V capacitor to more than 220V.

12. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
It could be lots of things.

Do you have a circuit diagram?

Do you have evidence that the inverter can produce voltages as high as 400V AND supply power at that point?

13. ### Mark34

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Sep 23, 2016
I don't have a circuit diagram, i bought that kit and it was working with a 250V capacitor and I switched to 400V, when you say inverter that's the transformer + transistor + resistor ? I have no idea how much voltage produces the invertor I am a novice in electronic circuits.

14. ### CDRIVEHauling 10' pipe on a Trek Shift3

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May 8, 2012
Mark did you read this post from Duke? Try a disc ceramic cap as he suggested. They're not hard to find rated >= 500V. They won't leak at all so it'll be a good test to see if the inverter can supply the voltage you want.

By the way while posting this I took note that you have made 6 posts which all have been in this topic. I also noted that not a single member welcomed you to EP.

Mark, Welcome To Electronics Point!

Chris

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15. ### (*steve*)¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥdModerator

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Jan 21, 2010
Ok if it was supplied with a 250V cap then that indicates the max voltage.

Adding a higher voltage rated capacitor and expecting it to charge it to the higher voltage is a bit like placing higher speed rated tyres on your car and expecting it to go faster.

Tha fios agaibh and CDRIVE like this.
16. ### CDRIVEHauling 10' pipe on a Trek Shift3

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May 8, 2012
OMG! Is that what's happening here? I have to admit ... That's funny!!

Chris

17. ### davennModerator

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Sep 5, 2009
the type of capacitor is irrelevant
the voltage supplied by the PSU is the only relevant thing to see if required voltage is reached across the cap

18. ### 73's de Edd

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Aug 21, 2015
.

Sir Mark34 . . . . . . .

Hoping that your English to Romanian translation skills are now working flawlessly . . . .

Well here goes. . . I will tell you what I think that I sees . . . and then you feed back what you see . . . and think that you saw, that you thought that you would think as being what I should have seen.

Looks like we have a battery capability of a series of cells, all strung together to output up to 12 VDC.

Looks like the left GREEN terminal strip is supporting the build of a blocking oscillator.circuit.
It is utilizing one small signal transistor , one resistor, one step up transformer /wound on a ferrite bobbin core .
The transformer secondary outputs its upped high voltage output into one rectifier diode that then passes up
and dumps its cathode lead to the + of your electrolytic storage capacitor
Now on the right terminal strips 4 screw connectors, just about all there is being a mystery.
Excluding that right bottom terminal . . . . . which is common power negative ground.
HOPING that panel meter has its series range divider resistors to be able to read up to 500 volts DC with its YELLOW lead..
Also, the right terminal strips top right connection is having the digital panel meter + connection, and being the high voltage connection which feeds into the + of the electrolytic storage capacitor.
NOW the weirdness fully onsets with the last connection to that same top connector also connecting to what looks like a larger R1 resistor that is going down to the 2nd terminal and there to connect to yet another smaller R2 resistor in series to ground.
That added series resistance , would be pulling that available supply voltage down, all in accordance of them not being on up into the megohm ranges.

Furthering the mystery is what looks like a D-pak surface mount power transistor of the TO-220 family with three attached flying wire leads .
The top collector tab wire ? goes up to a dormant screw connector, at the second screw position down.
Another lead (Base or emitter in accordance to the front/back orientated view of the transistor.) goes to common ground. . . .only emitter connectivity makes any sense.
The third connection is going to a momentary contact ORANGE "tact" switch that would momentarily make a connect to the 12VDC supply.
That makes no sense in that connection going to either a base or emitter.
That lastly leaves the YELLOW momentary contact "tact" switch that would momentarily transfer the 12VDC battery pack supply to the top left screw connector of the left terminal strip.
BUT that THEN leaves the mystery RED wire on that terminal exiting top left and going into hiding, unless it is looping back and coming down, and thereby effectively bypassing the YELLOW tact switch, to have that HV oscillator circuitry activated at all times, if there is being a 12VDC presence.

TEST PROCEDURE:

Lift the POSITIVE / cathode / banded diode lead completely away from right terminal block- top connection and connect it to a paper / polyester or disc ceramic capacitor with a break down voltage of of greater than 400.

VDC breakdown rating . . . minimum of 0.1 ufd capacitance and ground the other lead of that capacitor.
Utilize the LOW loading that a common DVM will provide and set it to DC Voltage function and scaled to a range of 500VDC.
Fire up the unit and THEN you will be able to see exactly the max DC voltage that unit will be able to supply.

THEN you will have to further deal with the hidden leakage resistance in that electrolytic that you are wanting to use and how FAST it will then be able to charge up IF-IF-IF-IF-IF its even being able to overcome the electrolytics internal leakage.

Back when we noted that larger R1 resistor ? of the series pair, if that just happens to be a DIODE, instead , its being wired in wrong, with its cathode needing to go back to the anode of the existing small HV rectifier diode and a 0.1 ufd capacitor inserted between its anode and ground . THEN you would have yourself a voltage DOUBLER circuit . . . . .BUT still, possibly with not enough OOOOOPH to overcome that electrolytics internal leakage.

FINALLY . . . . . . just exactly WHY do we need a 1000 ufd capacitor charged up to a 350VDC level ?

And whats a RISS bay . . . . . .does it have anything to do with those racy photos that are on your image storage support site ?

YOUR MAGGED UP and now LABELED PHOTO :

73's de Edd

Last edited: Sep 30, 2016
19. ### CDRIVEHauling 10' pipe on a Trek Shift3

4,960
652
May 8, 2012
I'm afraid I'll have to disagree. It's not irrelevant if the cap leaks faster than the supply can charge it. That said the point would seem moot since Steve seems to have read between the lines...... https://www.electronicspoint.com/threads/capacitor-charging.280653/#post-1708062

Chris

20. ### Mark34

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Sep 23, 2016
Thank you for the info, I checked the cap voltage with a second voltmeter with 1000V setting, it charges very slow above 200V I usually stop it at 230V because it takes ages for 1 volt, the yellow button starts the charging process you have to press it continuously to charge, the red one discharges the capacitor into a flash or coil not shown in the picture, I have a slight variation of that kit the flying transistor is a BTA16 800B thyristor the rest is the same, left resistor 510 ohms, right one 2K ohms left transistor is a SS8550 and 2 diodes. So the right side diode should be upside down? it has the cathode up right now .
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Last edited: Sep 30, 2016