Successful TPU-ECD replication !

[giantleap]

In relation to my previous post, think in the eye of the hurricain!

God Bless
Tim.

[chrisC]

@Rob & @Hoppy:
Thanks again for the chip references. Yes, I did try to find a distributor who carries the DDS board in the US but without success. It's not that expensive but adds up when you need 3! Other thing I'm not sure if it still needed an output buffer to get the critical rise times? And also whether it had the logic to vary duty cycle?

cheers
chrisC

[Hoppy]

I think this is a good time to remind people of something SM said.

"I ask you, what are these guys thinking about when they let their
ego's force them to ignore things i have said in the beginning and go off
trying to design and develop their own control devices using SS units.
SS units which are OUTBOARD of the collector ring i might add?
Some of them have gotten results and some of them have gotten big
power surges and dissipation of heat... all of which is wonderful and
certainly proves the point that there is truly something going on here.
BUT, i guarantee you that their SS control devices are all sitting right
beside the collector... aren't they?
They will probably never start the coil and get to catalyst.
I am not saying it is impossible, but it will Damn difficult for these guys to
get more then a big bang once in a while.
And just like me, that big bang will excite them enough to continue for a
while longer.
Maybe one of them will read back and see where I said the SS control
device must be placed inside the collector coil.
then they will explode with, MY GOD, maybe that is the reason why......
and off they will go. in the right direction at least.

God Bless
Tim.

OK good point Tim. Otto, Roberto and all who have so far tested, did you place your control circuitry inside the loop when you took the data published?

[MeggerMan]

@ZPE,
I am translating the German DDS 20 manual at the moment and plan to send a copy to ELV. Most of it done, just not the theory about the sine wave details.

@Giantleap,
Yes, I know about that and that is a problem, but the best we can do is to put the mosfet driver and mosfet inside the TPU and shield the rest.  The DDS 20 has a metal can shield around all of the high frequency circuitry.

@Chrisc,
The TL494 would benefit from an external mosfet driver at frequencies over 300KHz as it is only really meant to operate up to 300KHz.
The TL494 has the ability to vary the duty, but the DDS 20 will need an external op-amp connected to the sine wave output.

@Hoppy,
Yep, there are loads of other PWM chips. 
I also have the UC28025 (bought for my MEG project - JLNs MEG reproduction) that is good to 1MHz and 1.5A direct drive output.
(I'll take your 200mA @ 500KHz  and raise it to 1500mA @ 1MHz!)
http://focus.ti.com/lit/ds/symlink/uc28025.pdf

Regards
Rob

[Bruce_TPU]

@ giantleap

Otto had his mosfets and drivers in the center and on an aluminum heat sink.  Watching Cam's lab, it did not look like he had anything in the center.  As for Jason, I do no know.

Cheers and God bless,
Bruce  (P.S.  Good quote... LOL)