Questions for Bob with no images attached

[Earl]

this is an almost carbon copy of a reply that I made in Ward's thread,
I repost here so Bob has an opportunity to reply without image loading problems.

Hi Ward,

I assume this choke is to keep the radiant energy from shorting to ground via the HV supply.
Two comments:

1- you can always use a resistor is series with the choke.
2- I believe you could also use only a resistor to achieve the same isolation.  A 22 Megohm resistor should provide enough isolation.
My suggestion would be to use only several [chip ?] resistors in series.  The reasons being that if one should short or get too dusty or dirty or humid, you would still have electrocution protection in case of something stupid happening.  The current should be essentially zero, so resistance does not matter.  I would use a couple of 1M or 10M SMD chips in series.  The distance between total resistance ends should be sufficient to satisfy safety concerns of eventual arc-over.  An additional plus is that if the resistance drops any voltage, then you know you have a current leakage somewhere.  A series connection of resistors also drops any residual capacitance across the R, 3 Rs in series has 1/3 the capacity of just one resistor.

the choke shown is real nice, but very big.  A couple of series SMD resistors has much less volume and will fit into the center of the toroid.
Do not forget that such big chokes while effective at lower frequencies might present a short-circuit at higher frequencies due to inter-turn capacity.  There is no such thing as one choke being effective over a broad range of frequencies.

My gut feeling is that series resistors are preferable over an inductance for the following reasons:
1- current limiting against electrocution hazard
2- wider frequency range
3- much smaller volume

One time I had a 220V to 24 VDC switching power supply that had arcing problems because of too close spacing, especially in boat motor rooms (salt vapor in the air).  I coated the corresponding area with 5 min epoxy 2-component glue and that solved the problem.  A solution, but not really the correct one.

Anything over 50 Volts and 10mA can cause fatal heart fillibration, so safety first.  As a teenager, I took 500V between the hands (young brains are not that cautious) and believe me it was not pleasant to have muscle contraction and know I was going to die from electrocution.  Only quickly standing up and moving backwards saved my life by pulling the vacuum tube power supply from table onto the floor where it smashed to pieces.

Regards, Earl

[eldarion]

All,

I'm rather embarrassed--seems I grew way too trusting with regards to the pulse generator's correctness:
http://www.falconir.com/pics/channel_phasing_OOPS.jpg
I will try to fix this ASAP...

On the bright side, my PCBs came!  So I will be stuffing one with parts.
Here is a pic:
http://www.falconir.com/pics/DSC02299.jpg

Eldarion

[eldarion]

Further updates on my build will be posted on my thread where they belong, so as not to pollute this thread any further...

Eldarion

[Bob Boyce]

Hey there everyone... Sorry, been busy here.

I wrote some simple code for the HexController+ Deluxe. It runs with trouble up to 60 Khz (primarry) with all 8 channels in use. If I drop back to 4 channels then it runs solid up to 90 Khz (primary). The secondary and tertiary are running at precisely 1/2 and 1/4 of the primary frequency, as expected. A little timing glitch pops up on channels 1a and 1b when running in 8 channel mode. I am getting double pulses only on those channels every other pulse, regardless of the frequency setting. I have double, triple, and quadruple checked my code, seems to be a compiler bug. Channels 2a, 2b, 3a,3b,4a, and 4b do not have this pulse anomoly, no matter what frequency I run it at. The double pulses are so close together that it just looks like a pulse that is twice the pulse width of the other pulses. That is until you really open the pulse up on a scope and examine it closely. At first I thought I had a short between channels somewhere, but if that were the case, it would be there when I run other code that pulses all of the channels

The hydroxy gas mode code runs rock solid, but that is at a lot lower in frequency than I would like to get this puppy up to. I really think I'm going to need a faster uC in order to get this up to where I want it, but at least I'm having fun ;-)

I am still seeing a tiny amount of ringing on the unloaded driver outputs. The driver to FET traces are nearly 0.400" long. Longer than I really wanted, but I also wanted to put my MUR410s right at the FET locations. The drivers are bypassed like crazy, with 12 SMD bypass caps surrounding each driver. They are shared where each driver meets the next. I have not installed FETs on this board yet, wanting to get the speed up there first before I waste any FETs.

The HP8116A arrived DOA and smashed control panel. From the packing material and box condition (excellent) it was determined that it had been dropped by some idiot in the shipping dept of Silicon Salvage in CA. They did a partial refund, but I'm still not able to use it yet. I about had a heart attack when the eBay auction for my old hydroxy version HexController closed today at over $1000! Looks like I'll be able to get some better test EQ from eBay ;-)

@eldarion
I was wondering if the waveforms being produced by your board were actually coming out like it was reporting. I know in the case of my new HexController+ Deluxe, measured waveforms were slightly different from what code calculations were predicting. I had to add compensation code to correct it. For example, if set for 42.800 Khz primary, measured output was rock solid, but at 42.794 Khz. the older HexController was even more off, as it would read 42.774 Khz. It required more compensation. Be sure to let us know how it works out.

Bob