Successful TPU-ECD replication !

[Earl]

Hi All,

if you do not need a stand-alone DDS oscillator, for the same price you can buy a MUCH higher frequency DDS oscillator for the USB port, controlled by software.  See my post:

http://www.overunity.com/index.php/topic,2535.msg35477.html#msg35477

Regards, Earl

@Chrisc

Thank you for posting the DDS-20 kit. I sure would love to see your kit running. Please let us know if the output driver will drive the Control Coils directly or do you still need special fast switching output drivers?

Also, are you in Europe or the UK where you can buy these parts. Apparently there is no distributor in the US.

No, it needs to drive a mosfet driver then mosfet.
I tried to drive the mosfet directly but I think it overloads the output stage and it shuts down at the higher frequencies, say 5MHz.

Yes, I am in the UK, the kit was purchased from ELV in Germany, you should be able to order it for the US too.
http://shop.elv.de
Search for DDS 20 or 6847138
The kit does not include the AD811 so you can buy that from them or like I am doing, buy it from somewhere cheaper.
Its an easy kit to build and if you do decide to go for it I can help out if you get problems.
I have translated most of the manual now in English.
Rob

[chrisC]

Rob:
Thanks for the pointers on the DDS-20. I'll keep that in mind.

Earl:
Thanks too for the USB software DDS generator. Is there any 'protection' from spurious reverse electrical discharge back into the laptop, especially when we are trying to create these potentially high voltages?

I remembered seeing something from Jason about his USB ports 'froze' under certain conditions. can't remember exactly. Otherwise, I think this USB solution is great. I presume that little board takes in a secondary voltage from an external source. Will read the specs. later today.

Regards
chrisC

[Earl]

Chris,

will draw up a schematic to protect DDS from external spikes, maybe I have time tonight?

Regards, Earl

[MeggerMan]

@Chrisc,
Earl's device costs the equivalent of 75 EUR and the one from ELV is 61 EUR and is self contained.
I suspect the 85MHz is way over what you are going to need and even 5MHz is probably overkill.
There is something to be said about having individual bits of isolated test equipment.

One idea  have been toying with is to have the dds generator inside the TPU and have an infra-red link to a controller board some many feet away.
Because I could be here for ever more designing a DDS function generator to work with a PIC chip I have opted to buy kits instead.
Why re-invent the wheel yet, that can come once the TPU is up and self running.

Regards
Rob

[ronotte]

Hello Otto,

I've connected my already existing second secundary to 60W bulb as you suggested. Well I did obtained light but not so much and at lower freq than you suggested: about 60-70 KHz and anyway little effect for the third freq.

Then I thought to implement  the second CC  exactly as per your new specs and tried to connect it to 120 degree tap on collector. I did it but found only impulsive kind of waveforms, no way to get sinus. So I disconnected the tap and reconnected it to standard ZERO & PHASE. OK this time I found exactly what you said:

- good light on bulb

- F1 = 165KHz, F2=160 KHz, F3 variable from 20-34 KHz

- sinus present, about 50% completed


Anyway I noted that:

1 - the sinus is very good only with 2 freqs

2 - inserting the 3rd freq you obtain some more power but the waveform does deteriorate a lot

3 - the amper meter on PS read about 2A @ 9V. The P.S. itself is less tampered by the ECD. On sweet point the voltage analog meter doe shoe the correct voltage ...same for current.

4- As I've used copper enameled wire of 0.5 and 0.165 mm, the CC gets hot especially when outside the proper freq range...and it takes a lot of time to cool again.

Final note.
As you have noted the sweet point 160 and 165 KHz gives exactly the famous or infamous SM 5Khz. And maximum output is exactly when the F2-F1=5KHz! + - 0.5Hz.

The comparison with the first CC still in his first place (near the Mobius beginning) is difficult as the standard design does permit:

-  much more accurate sinus formation control

- quality of sinus is much more better!

- the input current required is higher (about 4A)


On the other side the isolated connection of the bulb is highly reccomended...so I think that there is still much unexplorated ground. I hope that also the other that are replicating the ECD will contribute to clear the way.

Ciao

Roberto