I have had two setups showing very promising results, which has me staring accusingly at my frequency generator. The Zaev circuit I was playing with charged the battery, albeit slowly. And a second circuit, which was just random craziness playing with the freq gen and an amorphous toroid transformer, at around 31Mhz showed reverse current on my ammeter. For giggles I let it run for a bit (its touchy, only certain frequencies result in the reverse reading) and took the battery out of the circuit, and sure enough its voltage had increased. All in all from 12.4v to 13.9v in about 45 minutes.
There's nothing special about the circuit, I'm not even routing the output back to the battery. Therefore, I must be charging it via the frequency generator. When the voltmeter is hooked up to the battery, when I tune it to reverse current, I'm reading 50 volts on the battery and around -900mA on the ammeter. That seems like a lot to be pulling from the frequency generator.
Would an opto-coupler be a good solution to decouple the freq gen? I've seen them mentioned, but I've never used one before.
I'll post pictures and the circuit in a bit just on the off-chance I won the free-energy lottery and The Man is on his way to 'clip' me.
What is obvious for you (because you build it) it is foggy and obscure for an outsider, yet you expect help.
Again, you do not provide clear and enough info for a meaningful answer...
I agree. I think we need to see a schematic of your set-up. I am not sure if you have a scope but if you do. Get the circuit running and then disconnect the freq. generator and hook it up to the scope to see what voltage you are sending to your circuit.
The easiest way is to use a capacitor between the Generator Output and your circuit. I recommend a 1 microfared at a minimum of 100 V.
You still need a common ground between the Gen & your circuit, but the Cap will give you the ISOLATION that you want.
.
Quote from: void109 on June 02, 2010, 01:05:17 PM
All in all from 12.4v to 13.9v in about 45 minutes.
At 12.4v, am I right that there is very little power left in the battery?
So, you appear to have fully charged it from almost flat. Good going.
Quote from: gyulasun on June 02, 2010, 05:22:41 PM
What is obvious for you (because you build it) it is foggy and obscure for an outsider, yet you expect help.
Again, you do not provide clear and enough info for a meaningful answer...
I apologize, I've had some work related emergencies pop up and I've been coding every waking moment and haven't had time to get around to schematics. That said, I thought that my question was sufficient - how should you isolate a freq gen from your circuit. That seems like a pretty generic question - I should not have mentioned anything else.
I'll be certain to not post again unless the thread already contains an up to date schematic of whatever it is I'm asking about :)
The above posted schematic is what was left after I threw out everything in the circuit that didn't affect the result. The secondary is open. Looking around online, it seems like its a hassle to make a circuit to pulse at those frequencies, meaning, I don't think a 555 will do.
And again, sorry for posting insufficient information, I know I've been sloppy, I'll do better.
Quote from: void109 on June 03, 2010, 12:18:08 PM
The above posted schematic is what was left after I threw out everything in the circuit that didn't affect the result. The secondary is open. Looking around online, it seems like its a hassle to make a circuit to pulse at those frequencies, meaning, I don't think a 555 will do.
And again, sorry for posting insufficient information, I know I've been sloppy, I'll do better.
No problem. Nice drawing. I agree with Fatbird, use a cap to isolate the generator.
Another thing I always do is bust off the ground lug on all the power cables on my test equipment. Not sure if it's the smartest thing to do but I was told to do this from a guy who was into OU for quite some time. It's just a habit now.
Like this? (Added cap after freq gen).
BTW the Freq Gen is a Wavetek 166. Forgot to put that in the schematic.
That's it.
I just took a good look at your schematic. Once the induction coil is charged up from the battery, it has nowhere to go but back into the battery. Does your MOSFET get hot or is it on a heat sink?
Quote from: MrMag on June 03, 2010, 12:39:06 PM
That's it.
I just took a good look at your schematic. Once the induction coil is charged up from the battery, it has nowhere to go but back into the battery. Does your MOSFET get hot or is it on a heat sink?
Unfortunately it got very hot yesterday, I left it running with everything hooked up and melted the ground from my scope probe into the mosfet case. Oops.
Yeah, it's like a direct short across the battery. The only thing different is the coil. You might have to hook the secondary up to something to help take away some of the energy.
As the voltage was rising the frequency for "optimal charging" kept shifting, and if it wasnt just right, it would swap from -50mA to 1A. It was during one of these switches to 1A (my back was to it while I was working so I didnt notice) that it melted the probe ground wire.
When its just right, it doesn't get hot.
I put that cap in and have it running - showing -40mA on the ammeter. I put a yellow led with a 1K resistor across the battery leads and the voltage was slowly dropping, removed the led, its charging again. Have to get some work done, I'll look at it more later.
Quote from: void109 on June 03, 2010, 01:30:17 PM
As the voltage was rising the frequency for "optimal charging" kept shifting, and if it wasnt just right, it would swap from -50mA to 1A. It was during one of these switches to 1A (my back was to it while I was working so I didnt notice) that it melted the probe ground wire.
When its just right, it doesn't get hot.
I put that cap in and have it running - showing -40mA on the ammeter. I put a yellow led with a 1K resistor across the battery leads and the voltage was slowly dropping, removed the led, its charging again. Have to get some work done, I'll look at it more later.
I wonder if you hit the resonant frequency or one of it's harmonics? I would think that if it was timed just right, the load may not reach the MOSFET. This would keep it running cool and you would definitely see -mA going to the battery. Do you have a scope?
Hi void109,
Thanks for the schematics and further info.
Using opto coupler is expensive at 30MHz, much simpler to use transformer or capacitive coupling.
Re on capacitive coupling: as you do not use a resistor between the gate and source in your modified capacitive coupled version, the gate electrode is floating and has no DC return, (the gate capacitance has no real resistive path to discharge) you may wish to place a 51 Ohm 1/2W or 1W resistor directly between the gate and source. (Earlier your generator output resistance (50 Ohm) insured the DC return of the gate.)
However, to completely isolate your circuit from the generator, I suggest either using a series 100nF or 1uF coupling capacitor in the ground line too (just connect the ground point of the gen output (this is usually the coax cable outer shield) to the source electrode of the FET via a 2nd coupling capacitor, this way you get rid of the generator completely. Of course the gate coupling 1st capacitor and the 51 Ohm resistor between the gate-source also remains there.
Or alternatively you could use a 1:1 wideband transformer, just make a 10 turn bifilar coil on any ferrite torod core at hand (not critical) and connect it as I shown in the attached modified schematics. Some theory on wideband transformers is here:
http://www.minicircuits.com/pages/pdfs/tran14-2.pdf
Use a 0.5-0.6mm OD enameled copper wire and twist two wires (7-8 twists /inch) together for a length that is enough to make 8-10 turns on the toroid. It will surely work between 25-35MHz.
What I think now on you circuit is that it somehow oscillates at either the input or some other frequency and in this oscillator the battery is included as a nonlinear component (mainly as a capacitor but it may also behave as a low Q LC circuit too) and takes up "pseudo charge", though you may run the setup for a much longer time to see if the charge taken is really stored or not. IT is possible when you use the 51 Ohm resistor between the gate-source to terminate it from DC point of view too, and you use either the double capacitor or the transformer input isolation, the tuning for the "sweet point" will maybe be more difficult, though it shouldn't because in your circuit shown in your first schematic the gate-source was terminated by the generator for DC return too.
IT would better to see some scope shots both on the gate and the drain with respect to the source electrode, and also separately across the battery, use DC coupling and indicate the zero line.
Maybe you wish to use a second MOSFET to check the "toasted" one if it is all right... ;)
rgds, Gyula
Erm. So while tinkering further and taking photos to post, I finally ended up with the freq gen DISCONNECTED from the circuit, and the battery was still showing negative current draw.
Perplexed, I began sweeping the frequency on the disconnected frequency generator, and saw the coil's waveform changing accordingly. And finally powering off the freq gen, the coils voltage dropped to 0.
So is the coil acting as an antenna and the freq gen is broadcasting? (This was after putting in 50 ohm resistor and winding a small bifilar coil and modifying the circuit to match the one posted by Gy).
It is possible. Do you use a coaxial cable with BNC connector at its ends to take the output of the generator and lead it to the circuit or you use an unshielded wire pair?
The generator's own shielding may also be pure, and it if it is able to make 15V peak to peak voltage to its 50 Ohm output impedance, it is at least 0.56W output power.
Yes, I do use a BNC coaxial cable to carry the signal generator signal to the circuit.