Cap Dump

[John_Koorn]

Hi Chris,

I use an analog DC volt meter on the cap to see what voltage it dumps at.

John K.

[John_Koorn]

Hi Mike,

Where are the scope probes in that shot?

Nice looking setup. Just be careful if you're using welding rod for connections, make sure they are really well soldered or they will come loose.

John K.

[Catrinisin]

Thanks John. I think I figured out my issue with the scope reading. Yeeeaah, when I said I know how to read the output, umm, oops I had the variable knob twisted the wrong way.
So now I am reading what I expect; About a 15-18 volt drop across the cap.

I had used a DC meter, but it seemed to only produce an average voltage, going up and down too rapidly to get a decent reading. So I tried unhooking the primary battery from the machine and pulsed it on manually by touching the wire to the machine to slowly bring up the voltage in the cap and watching the meter. When I do this I see it get all the way up to about 29 volts and then drops down to about 14 or so volts. Maybe less but I can't quite catch it perfectly with this method. This now matches what I see on the scope so I feel a lot better now.

Here is a shot of my test setup with scope at 5v/div. (Camera doesn't pick up the entire trace, but I got the dump in there.) Cap is 1000uF 100v, zener is 16V. I may go down to a 12V so that the dump voltage is closer to 24-26V which is double the battery. This size cap seems to do the best with these smaller 9AH batts so far. You can see where I have disconnected the negative charge lead and clamped it to the anode of the SCR. The cathode goes to the source negative, and the gate to the anode of the zener just as the diagram above indicates. The zener's cathode is clamped to the SCR anode via the bolt/nut.

[Catrinisin]

Yes many combinations for the right dump to the right battery.
Let me say that I think??? a cap dump is a way of measuring the output of your sg circuit to see if it is properly tuned.

I really need validation on that statement.

For instance with JB lab machine he uses the alum battery at 11.6vdc and 1 ampere only for his input.
Then on the output he is using the cap dump and states that the cap is dumping once every second at 31vdc and 2.25 amps.

So I am thinking that his input is 11.6 watts and his output is 69 watts each one is per second to get joules.

Is this right thinking?

Here is the most recent box I am working on. Also a scope shot wondering it looks right??

[ATTACH=CONFIG]1657[/ATTACH][ATTACH=CONFIG]1658[/ATTACH][ATTACH=CONFIG]1659[/ATTACH]

Hi Mike,

What you are saying sounds right, getting more watts out than what goes in.

As far as your scope shot, that does not look right. I have seen a similar signal if I connect the leads across the charge positive and primary positive. My scope shot in the previous post was connected across the cap only.

-Chris

[min2oly]

Thanks Bob,

This is exactly what I want from the sound of it. I saw min2oly's video with his snazzy looking cap dump box. Does anyone have a circuit diagram of that one?

I just started a separate thread on it here
-KR,
Patrick

[min2oly]

Thanks Chris

It sounds right to me also, yet when I use the calculators for capacitor joules I find something different.
It sounds like a pulse of 31vdc X 2.25 amps every second would come out to 69watt/seconds.

This is in regard to John Bedini's LAB MACHINE youtube video.


Mike

Hi Mike,
you're talking about this vid right:

At about 6:20 John talks about the joules...
the way I understand it is that the cap reaches 31 volts and then dumps into a 13 volt battery. So that's 18 volts x 2.25 amps per second according to his amp meter. Still very nice charging.

[Catrinisin]

Ah yes, I also forgot to account for the actual voltage drop vs the total voltage in the cap.

So JB is dumping 18 volts to a 12 v battery huh... Hmmmm.

Hi Mike,
you're talking about this vid right:

At about 6:20 John talks about the joules...
the way I understand it is that the cap reaches 31 volts and then dumps into a 13 volt battery. So that's 18 volts x 2.25 amps per second according to his amp meter. Still very nice charging.

[Catrinisin]

I've had good success using a heavy duty SCR and one zener diode. The sch is below. All I do to adjust the voltage is swap out the zener for a different value. Right now I have a 16V zener on there. So 16V + about 2V that the SCR requires and that's roughly 18 volts over the battery voltage. I felt that this was better than using a 12 V zener because I wanted the battery to always have at a minimum of double the voltage hitting it. When the battery gets up to 15.5V, that's more than the 12V zener would produce on this circuit. I've never blown out one of either of the SCR's shown below either.

Schematic:


A couple different SCR's I've used. The larger one is a 2N1913 and the smaller one says R16RIA60 on it. Found these at my local surplus store. Skycraft Parts & Surplus, Inc.



-Chris

[romeo-kilo]

A question to the experts:
How can I stop the SCR after it dumped the cap?
From the SCR properties it doesn't stop until the main connection is disconnected.

Ralf

[Diverfun]

A question to the experts:
How can I stop the SCR after it dumped the cap?
From the SCR properties it doesn't stop until the main connection is disconnected.

Ralf

The SCR is designed to stop when the current stops, then it resets. As long as the current flows (ie... Cap voltage does not equal Battery voltage), it will not reset. If you keep pulsing the cap during the discharge cycle, you may never get it to stop without a disconnect. What is happening - as the cap discharges the current flow slows because the internal resistance of the battery - cap voltage = 12.5v and the battery is 12v - that .5v difference takes more time to discharge than the next incoming pulse. That next pulse slightly charges the cap and then you will get to a point where it will find a happy medium where you can never get it to equalize allowing the SCR to reset because you can't get the cap to fully discharge. If you are running into this problem, then that means your pulse design is very good, but you may have to go with another style dump circuit. I use op-amps to control the start/stop of dump with feedback to turn off pulses during discharge.

You might want to try decreasing the size of the charge cap. That will increase the frequency of the dump, but should decrease the amount of time needed to complete the discharge. The ideal frequency should be around 1 hertz, but a 3 or 4 hertz should still do the job.

[Faraday88]

It is called Resonant Commutation...Specially when a Pulse -Discharge Capacitor application is at work the device is under what is called as Under damped Oscillatory Discharge where in the a LC resonant tank circuit formed by the Discharging Capacitor along with the 'load' (the battery here) and the device (SCR), A Reverse current which will force the device below its Holding current will shut it off, hence only a Trigger to turn ON the device is needed while the device undergoes self turn OFF..!
Rgds,
Faraday88.

[Diverfun]

It is called Resonant Commutation...Specially when a Pulse -Discharge Capacitor application is at work the device is under what is called as Under damped Oscillatory Discharge where in the a LC resonant tank circuit formed by the Discharging Capacitor along with the 'load' (the battery here) and the device (SCR), A Reverse current which will force the device below its Holding current will shut it off, hence only a Trigger to turn ON the device is needed while the device undergoes self turn OFF..!
Rgds,
Faraday88.

Ralf
What he is suggesting is to induce some Reverse Current (or noise) into the circuit. You could do this by wrapping a wire around your bi-filer coil and connect the ends between the SCR and Negative side of the Charge Cap. The pulses from the coil should reset the SCR. How many turns and which end connects to the SCR will take some experimenting. Doing this will cause the SCR to reset at a unknown point (ie... 15v at cap instead of 12.5v), but removing or adding some turns will change the reset point. The reason for between the Charge Cap and SCR is to keep the noise from affecting the circuit when the cap is charging. (Hopefully not to cause the SCR to trigger on too soon.)

[min2oly]

Nice!
another thing I've done is to add an inductor in series w/ the Zener and LED that trigger the SCR. If you use a tunable inductor (air coil w/ movable rod in the core) This will help to adjust timing.
Nice thread here - Kind Regards,
Patrick

Ralf
What he is suggesting is to induce some Reverse Current (or noise) into the circuit. You could do this by wrapping a wire around your bi-filer coil and connect the ends between the SCR and Negative side of the Charge Cap. The pulses from the coil should reset the SCR. How many turns and which end connects to the SCR will take some experimenting. Doing this will cause the SCR to reset at a unknown point (ie... 15v at cap instead of 12.5v), but removing or adding some turns will change the reset point. The reason for between the Charge Cap and SCR is to keep the noise from affecting the circuit when the cap is charging. (Hopefully not to cause the SCR to trigger on too soon.)

[WAZ12]

How could be replaced the neon bulb in sg circuit with another equivalent part ?

[Faraday88]

You can use a High-Voltage Fast Recovery Diode say...BYV26E in reverse Polarization between Collector and the emitter to get the same function as the of course with no Glow!!!
Rgds,
Faraday88.