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Re: [TCML] Need help with my first driver board for DRSSTC1

Thanks that is very helpful. I grounded the negative to earth ground which fixed some of the sinusoidal noise issue which as you say is likely a function of probing technique and layout.
I connected to the Q instead of the Q bar. I could use pins 12 and 13 on the Schmitt inverter to correct the output of the active low fiber optical receiver and then connect to Qbar the way it is set up in Steve Wards schematic. In fact did try this (using pins 12 and 13 on the hex inverter and it worked fine. I found a bigger problem for no output from my UCC mosfet drivers - a bad batch of chips. I tested all of them in my old SSTC1 setup and they either did not work at all or gave CW output even though I was pulsing the logic circuit with CW continuing when the interrupter was turned off.  See video for failed chips:

I was a little surprised by this and consider myself lucky with my eBay purchases!


Sent from my iPhone

> On Jun 29, 2015, at 3:25 PM, Kramnik Daniel <daniel.kramnik@xxxxxxxxx> wrote:
> Hi Brian,
> If your fiber optic system outputs active-low pulses, why don't you just
> try adding an inverter after your receiver to get the correct logic
> polarity? You know that (if it's assembled correctly) the driver schematic
> you are using works, so if you minimize the number of modifications you add
> to it, you reduce the risk of introducing a mistake. You've also got plenty
> of extra inverters in your 74HC14, if I remember this circuit correctly.
> In general, inverting the output of the flip-flop by connecting to Q_BAR
> instead of Q will not get you the desired behavior (though I didn't trace
> out an entire logic table for this circuit to see if it would work in this
> case). I would also not trust what your multimeter is telling you when you
> probe the input signals to the gate drivers and see some DC offset. Try
> probing those signals with a scope instead to get a better idea of what's
> going on. Either way, adding diodes or "filter capacitors" to the input
> pins will only be fixing a symptom, not the actual problem that's causing
> you to see that symptom. If your logic is wired correctly and you are
> applying the correct test signals, there should be no DC offsets in your
> logic signals. Furthermore, the little bit of "noise" that looks like
> sinusoidal ringing that you're seeing in some places when you're probing
> your logic signals is probably more a function of your probing technique
> combined with your board layout than anything else (how much inductance is
> there in the return path through your scope probe's ground clip? probably
> quite a bit). Either way, it's not an issue at the moment because it
> appears to be far below the noise thresholds of the logic gates.
> I would also recommend either shorting out the CT inputs or applying test
> signals from a function generator when you're verifying that your circuit
> is working instead of leaving them floating. For example, the input node of
> the 74HC14 that's squaring up the feedback CT pulses is a floating high
> impedance node that could easily be picking up noise or crosstalk from
> other parts of your circuit.
> Good luck, and post some pictures!
> (imo flipping through flicker to see your schematic, scope shots,
> construction technique, etc. is a lot more efficient than watching a video
> and scrolling back to the details you want to see)
> Kramnik
> On Mon, Jun 29, 2015 at 10:41 AM, Brian D <briandecosta38305@xxxxxxxxx>
> wrote:
>> Hi everyone, I am new to this online community. I have enjoyed making my
>> first 3 SSTC coils, the last one with a full bridge of 60n60s worked great.
>> I wanted to try my hand at a DRSSTC. I am however having trouble getting
>> the driver board to work. I am getting good square waves off the 47HC109
>> pin 6 but I cannot get any square waves off the UCC373XX's. I have tested
>> all the connections and they all look great.  Any help would be welcome.
>> Here is the link for the youtube video showing the problem I am having-
>> https://www.youtube.com/watch?v=Ig7FHaoqyfU
>> thanks in advance for your help.
>> _______________________________________________
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