Bedini Comparator Cap Dump

[adys15]

Thanks for reply Lman.I get what you are saying but when the led stays on longer the mosfets stay open more, more amps are being dumped into the battery,if i pulse faster less energy is being dumped taking longer for the batery to charge,shuffeling power from one point to another very fast without any gain..look at bedini's comparator its dumping 2.5A once per sec.and yes my caps discharge slower thats why i need a bit of longer on time.Cheers!

[Lman]

adys15,

You said in your previous post that you are charging the caps to 22V and discharge them to 15V. If it takes a whole second to do that ... there is something wrong and if it was my circuit I would not be satisfied with it. Are you sure the gate on the MOSFET opens fully ? Why do not you charge them to 24 volts by the way ? Check again the components in your circuit ! This is an opportunity for you to learn why it is behaving the way it does.

You are referring to John's video on Energenx channel where he is using a small comparator, right ? The analog Am meter is slow and showing 2.5 to 3 amps while the peak of the dump is probably like 10 times more. Do not focus on that though.
My circuit discharges as fast as the one in the video of John.

Hope that you will find an improve

Regards
Lman

[adys15]

it takes 2secounds to charge them to 22v and 1sec to discharge to 15v.I could charge them to whatever but then i have to pulse slower 3-4 secounds to charge past 25v.How do i know if my mosfets are fully opened?i'm not using irf's but more powerfull ones out of a pc powersuply,dont know the exact rating on them.
Yes the Energenx video.The ammeter is pulsing at same rate as the led not to fast...how do you know that there are 10x times amps?at 30A the battery would blow up or boil very fast
Note:I'm using just 2 power coils,maybe thats why the charge is slow,and i'm using the clasasic ssg setup without the fbwr,because i'm low on coils)....cheers

[Lman]

adys15,

I will leave the charging time for now, probably you could improve it there too. But you have it wrong with that Mosfet. The PC power supplies are Switch Mode Power Supply type. The Mosfet in them has different characteristics than what you need. They are designed for really fast switching and work with higher voltages but lower amperage, and they have higher internal resistance. While a Power Mosfet is designed for lower voltage and higher current.
I am giving you an example :

IRF840 is designed for fast switching applications and it is 500V; 8A; 0.850 Ohms, it can dissipate maximum of 125W
IRFP260 is designed for 200V; 46A; 0.055 Ohms, and can dissipate 280W

The dump from the cap is a high current pulse not high voltage.
I don't know how you decide that your Mosfet is more powerful but I am sure that it is not the correct device for what you use it.
You have to replace that Mosfet with the correct one. Right now it is the bottleneck in your circuit.
You can use oscilloscope to measure the voltage on the gate or good enough multimeter that can measure peaks. The cheap multimeters sample the measurment like every second and would not be helpful at all.

I told you about that Am Meter in John's video. It is an analog meter, they are slow in how they work. They just can not catch the high transient peak of the pulse. Until the needle start moving the transient is gone and we see average measurement. They work just like the VU meters on the old audio equipment. John has put that meter to show the pulse but it does not mean it is 3 amps.
Well, if you pulse an AA battery it will evaporate but a car battery has no problem with that pulse and will take it. It will blow only the sulphation out of the plates.
In this video John Koorn shows 10 amp pulses (on the analog meter) going to the batteries.
www.youtube.com/watch?v=XixyCaTegyY
And in this next video at around 4:25 you can see the current pulses on the oscilloscope when John K. switches to the current probe. It shows it all.
http://www.youtube.com/watch?v=YIzqgA3qI3I

You say you have 2 strands of power windings, but do you use the correct components for that, did you match your transistors ?
Everything counts. John is not saying take just some transistor, some diode, whatever wire and do it. He has told us the right components.
I used MJ15024 for my solid state after I watched Johns videos about the oscillator.

You can improve your circuit, just replace that Mosfet with a correct one.

Regards
Lman

[RS_]

Hi folks,

Sorry I have not been paying attention to the forums since i got back from the conference..... been busy trying to get my shop's ele Lab built so that i can install the solar system, etc.....

JB does not have a adjustment on the on time in his circuit... but adjusting the value of the C2 cap slightly will help increase the on time. I have also seen another way to do this before the conference on another forum, but cant find that reference at this time......
My micro power cap pulser Sch has the on time adjustment.......

[Lman]

Hi RS_,

Nothing to be sorry about. Everybody is busy with his things in life and other priorities.

JB knows his circuits, the components he uses and what to expect. But we always choose different components and that is why our circuits behave differently. I am not sure if the BD243C in my circuit is not chinese for example I used LM358 as comparator and my circuit would stop discharging too early at around 20 or 19 volts. That is why I began experimenting with that cap and as you said adjusting the value of it helps increasing a little the on time. Now that it discharges to 15 I am satisfied with that adjustment.
Something that caught my attention was when later I tried to charge some small rechargeable 9V NiMH batteries with the same circuit. It appeared as the LED was constantly ON at first when the battery is discharged. But I assume it was just pulsing so fast that the human eye can't catch it because after a minute or two the pulsing frequency was slowing down as the battery voltage raised. I was not sure if that was good for the battery and had like presets of different caps to choose for the different battery types. I was surprised by that behavior because I expected to change just the point to which the circuit charges and still have the same pulsing frequency. But it seems it was sensing the different impedance of the battery. Have not investigated it much as the batteries were charging normally. And that 9 volt rechargeable NiMH was dead like ... it was not used for 5 years and it was staying like 2 volts when I measured it before recharging it.


Regards
Lman

[adys15]

Hy Lman!I agree with what you say about mosfets.The circuit i build is just to see if it works and i was using recovered parts.I changed the mosfets to irf640 and the pulsing amps staid the same.Thanks for John K.'s videos,i saw the amps on the scope...i font know what to say...i put a 20w auto bulb in series with the - of the batt and the bulb lit half of its brightnes(2A)....And remember that the duty cycle was 1% on 99% off and the freq was 80hz,so the average power is much less.
Anyway,i repositioned the colector of the bd on after the 2,2k resistor and no diference this time,but with these mosfets my pulsing freq increases when i adjust the pot on the coils...

[Lman]

adys15,

I have checked the datasheet of IRF640 and it is again not correct one. It is for switching applications, it has inductances on the Drain and the Sorce and that gives you still higher internal resistance than we need.
Consider IRFP250 or IRFP260.
The video of John K shows you what happens when the circuit is correct. It shows how high that pulse goes and it shows how sharp it is.
Now you know that these 3 Amp on the analog meter are actually much higher and the Mosfet has to be able to handle that. Than the sharpness shows how quick the on time need to be. If we put too big cap on the voltage divider we start accumulate losses.

Regards
Lman

[adys15]

Thanks Lman!i looked at irf640 datasheet,i am aware that i have a high resistance,but thats what i have right now, I will have to order some irfp's.Maybe analog meters are inacurate but the bulb aint lieing

[alfinip2000]

Lman,
What value of the capacitor that you put on? So it can cut at 15v..
Thanks,
Alfin

Hi RS_,

Nothing to be sorry about. Everybody is busy with his things in life and other priorities.

JB knows his circuits, the components he uses and what to expect. But we always choose different components and that is why our circuits behave differently. I am not sure if the BD243C in my circuit is not chinese for example I used LM358 as comparator and my circuit would stop discharging too early at around 20 or 19 volts. That is why I began experimenting with that cap and as you said adjusting the value of it helps increasing a little the on time. Now that it discharges to 15 I am satisfied with that adjustment.
Something that caught my attention was when later I tried to charge some small rechargeable 9V NiMH batteries with the same circuit. It appeared as the LED was constantly ON at first when the battery is discharged. But I assume it was just pulsing so fast that the human eye can't catch it because after a minute or two the pulsing frequency was slowing down as the battery voltage raised. I was not sure if that was good for the battery and had like presets of different caps to choose for the different battery types. I was surprised by that behavior because I expected to change just the point to which the circuit charges and still have the same pulsing frequency. But it seems it was sensing the different impedance of the battery. Have not investigated it much as the batteries were charging normally. And that 9 volt rechargeable NiMH was dead like ... it was not used for 5 years and it was staying like 2 volts when I measured it before recharging it.


Regards
Lman

[Lman]

Hi alfinip2000,

In my case 100uF did it. We have been discussing that since post #68. If your circuit shows the same symptom first be sure that you are using the correct devices, check if the transistors are getting the correct triggering voltages.

P.S. That cap is not a panacea.

Lman

[sergejfa]

hi RS

what kind of capacitor i need for c2 and c3,ceramic or elektrolytic?

Thanks

[RS_]

C2 will be a ceramic or Mylar in most cases, can be a electrolytic for larger values if needed to tune the on time. the C3 will always be a electrolytic

[sergejfa]

RS thanks for your help

[adys15]

Hy guys does anybody know how to calculate pulsed power coming from the comparator?I'm getting the same voltage out as in but at 3A once 2 sec