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Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
I am laying the last hand on my drsstc and was for the first time running the driver with a signal generator at 70 KHz sine wave connected to the feedback input and my interruptor connected to the opto input.
It seemed to be running in CW so I was worried the opto was fried due to it having experienced reversed polarity when I first built the driver, but it was fine, so I scoped the interruptor signal throughout the driver and got what I attached...
It seems that the signal either get inverted one time too many or one too less.... but I can not find any errors in my driver as its built to spec of Wards universal driver schematic
Any ideas of what is wrong? Should I just add/remove a inverter?
note to the pictures notes: where it says that pin 11 is the inverted of pin 8, it is only the "signal", the dead time is low on both.
Registered Member #2292
Joined: Fri Aug 14 2009, 05:33PM
Location: The Wild West AKA Arizona
Posts: 795
Keep in mind that the fiber optic receiver inverts the signal, and the driver is designed to re-Invert the signal. So if you send a non-inverted signal (without going though the Fiber RX) the driver will invert the signal and you will get exactly what you are experiencing.
Just so you know that first Buffer/Inverter after the Fiber RX is there to correct the signal after it comes out of the fiber RX.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Goodchild wrote ...
Keep in mind that the fiber optic receiver inverts the signal, and the driver is designed to re-Invert the signal. So if you send a non-inverted signal (without going though the Fiber RX) the driver will invert the signal and you will get exactly what you are experiencing.
Just so you know that first Buffer/Inverter after the Fiber RX is there to correct the signal after it comes out of the fiber RX.
Eric
I do use the fiber RX and its also Wards interruptor schematic for my interruptor.
The Fiber RX ( ) Ward is using is a photodiode, op-amp and a schottky output transistor The Fiber RX ( ) I am using is a photodiode, op-amp and a schmitt trigger
There is plenty of lacking information about the RX I am using, but it could be that it works inverted compared to the one Ward originally used...
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
Goodchild wrote ...
Then you must have the Fiber TX connected incorrectly, try inverting the signal to the fiber TX.
I know both work as I use that interrupter with my DRs and they all use that driver.
(edit) I just took a look at your pic again, it looks like that's the correct output to the GDT to me.
The TX is just a "LED", connected to the pin 3 output from the interruptor through a resistor
I would have thought the GDT output should be on for like 5% and off 95%, its very close at running in CW mode as it is now, the dead time areas are much more spread out than I could draw by hand its more like: |||||||||||||||||||||||||||||||||_|||||||||||||||||||||||||||||||||_|||||||||||||||||||||||||||||||||_|||||||||||||||||||||||||||||||||
And I think it should be like this, which is obtained by using the inverted output from IC3A, pin 6 instead of pin 5: ________________________||||_________________________||||_________________________||||_________________________||||
Registered Member #15
Joined: Thu Feb 02 2006, 01:11PM
Location:
Posts: 3068
Also keep in mind the fiber optic connector you are using. If i'm not mistaken, he specifies the HFBR 1412/2412 series which is fairly common. However, in recent years (perhaps the past 8 years), Avago uses an all plastic fiber optic connector vs. the original ones HP used awhile back that used an all metal (including the barrel) construction. The Avago ones now are prone to noise issues. I've seen this in both Tesla coil use as well as in high voltage radar transmitters where we use fiber optics extensively.
Registered Member #1403
Joined: Tue Mar 18 2008, 06:05PM
Location: Denmark, Odense C
Posts: 1968
EastVoltResearch wrote ...
Also keep in mind the fiber optic connector you are using. If i'm not mistaken, he specifies the HFBR 1412/2412 begin_of_the_skype_highlighting         Â
    1412/
2412      end_of_the_skype_highlighting begin_of_the_skype_highlighting         Â
    1412/
2412Â Â Â Â Â Â end_of_the_skype_highlighting series which is fairly common. However, in recent years (perhaps the past 8 years), Avago uses an all plastic fiber optic connector vs. the original ones HP used awhile back that used an all metal (including the barrel) construction. The Avago ones now are prone to noise issues. I've seen this in both Tesla coil use as well as in high voltage radar transmitters where we use fiber optics extensively.
I have the fiber receiver inside the drivers metal casing, as they are all plastic, so it should be shielded properly.
Registered Member #1334
Joined: Tue Feb 19 2008, 04:37PM
Location: Nr. London, UK
Posts: 615
Mads Barnkob wrote ...
Any ideas of what is wrong?
The fibre receiver Steve uses inverts the signal (it has an OC output), so IC1F makes it positive logic again.
If you are using a non-inverting receiver (though I note that inverting versions of your receiver are available) then bypass IC1F.
I made this mistake once using the HFBR-2412 after having had boards made up, so ended up inverting my interrupter instead as a work-round as I couldn't easily modify the main board. Its a mistake you make once only...
Edit: Note that if you invert the output of the interrupter as a workround then remember to turn it off between uses as the battery drains fast with the xmit laser diode on so much...
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Wards universal driver, inverted signal problem (solved)
