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Another 813 Build




 
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w9jsw
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« Reply #125 on: August 03, 2019, 02:16:28 PM »

Hi Tom,

You have convinced me - again.

I plan to use the same unit you used - ACS712, I believe. It puts out an analog signal with it at VCC/2 for zero current. How did you hook this up to the latching relay? Did you use a comparator circuit like is described in the application note that allows you to tune the current trip points? Since I am using a Arduino for my sequencer, I am really tempted to use one of the analog inputs and monitor the voltage directly. I can do this in a loop while I am in PTT mode. If I see any of the currents go past normal, I can shut off PTT directly. I have a small TFT display so I plan to also display the data digitally.

My only concern is what happens if the Arduino messes up. Using the Arduino is an untested approach as I don't see anyone else doing it. If RF scrambles it's brain I may lose the whole rig. So I am tempted to also have a failsafe discrete system that watches the same sensors and drags PTT low outside of the sequencer.

I just don't know...

On Spark gaps. I was planning on gaps on the mod secondary tap 4, the other side of the mod reactor secondary tap 5 and the 2 primary connections that go to the mod tube plates taps 1 and 3. Does that sound correct?

John
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K1JJ
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« Reply #126 on: August 03, 2019, 06:37:56 PM »

Hi John,

If you put everything in an aluminum box and then bypass the input leads with .001's (and toroids if needed) , there should be no RF in the circuit.

This six relay latching board below for $9.37 should work FB.

https://www.ebay.com/itm/6-channel-12V-latching-relay-module-Switch-controls-the-high-voltage-H-current/121951095953?hash=item1c64da0c91:g:oVYAAOSwAvJXCcQQ


It will take a low level signal to trigger.


A sensor like you suggested  below may work OK -  or some other derivation. These are only $3.95 so worth the try.  Order the six relay board and then see what sensor works best with it. Play around.

https://www.ebay.com/itm/30A-range-Current-Sensor-Module-ACS712-Module-Arduino-module-NEW/382824575626?_trkparms=aid%3D555018%26algo%3DPL.SIM%26ao%3D1%26asc%3D57476%26meid%3Dec2b38a14a9541fd80c52ea43f41aaff%26pid%3D100005%26rk%3D1%26rkt%3D12%26sd%3D202681517336%26itm%3D382824575626%26pg%3D2047675&_trksid=p2047675.c100005.m1851

You can generally use a 0.5 to 2 ohm resistor in the negative DC lead for the grid, screen and plate to get a tiny DC current sample.  A pot across the resistor sampler can then adjust the trigger point. At least that's what I did here.  My particular current sampler has an opticoupler in it, but I cannot determine what kind it is due to no labeling of value on it.

I did not use a comparator, but that would work fine.

This really is a cool system once working. For example, I can tune my 4-1000A finals off resonace, drive it for too much grid current or load the final for more screen current and off goes the PTT. Even a bad antenna, forgetting to turn on the HV, etc etc, will trip it. Not to mention when I mess up and hit the audio too hard, the PTT drops out due to the modulator current(s) (grid, screen or plate).  I realize there is a slight delay due to using a relay and the PTT unlatching, but with tubes it is plenty fast enough without causing damage.  When the rig has been pretuned and turned on again, you don't even know the protecton circuit is there other than the trip lights are off.  When it trips, I know exactly what circuit (of six) tripped by the LED being lit. Just reset it and try again or adjust the current sensor a little until the rig runs flawlessly at normal parameters.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
K1JJ
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« Reply #127 on: August 03, 2019, 11:12:34 PM »


On Spark gaps. I was planning on gaps on the mod secondary tap 4, the other side of the mod reactor secondary tap 5 and the 2 primary connections that go to the mod tube plates taps 1 and 3. Does that sound correct?

John,

I think you have it, but just to be sure:    Four sets of gaps are used. Round ball gaps are best.  One set across pins 4-5 secondary.    One set across pins 3-2  primary.    One set across  pins 2-1 primary.    One set across the modulation reactor, L1.    I also put a small one across my screen choke as a precaution after having unkeying spark problems in general, but is probably not needed there.

Also remember that later on in testing if you have unkey sparking, a vacuum relay that puts a 5K 100 watt resistor across the mod reactor when unkeyed will quench the sparks. It solved all my sparking problems despite having a sequencing system.   No matter how we look at it, that energy stored in the mod choke has to go somewhere during shutdown and if it doesn't  eventually find its way out to the antenna in the form of RF, it will spark instead at the reactor. Bad sparking is what damages our iron in the form of internal insulation arc-overs.. (both mod xfmr and choke)   Normally commercial BC iron is safely turned on once a day or less. Hams beat the crap out of it with the rapid PTT. We gotta have it set up right or get your wallet out again.

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
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« Reply #128 on: August 04, 2019, 07:41:03 PM »

Ian's (G3SEK) has a tetrode protection board that does exactly what you're looking for.

Schematics are freely available for the googling.  Would give ideas in pictures on what is being discussed.

--Shane
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w9jsw
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« Reply #129 on: August 06, 2019, 05:05:58 PM »

What about using either 1 or two of these to regulate the grid current to 80ma - IXCP10M90S
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K1JJ
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« Reply #130 on: August 06, 2019, 09:54:06 PM »

What about using either 1 or two of these to regulate the grid current to 80ma - IXCP10M90S


An interesting thought... using a solid state current regulator device to limit the maximum current thru the screen to 80 mA. It should be invisible until current hits >80 mA.

I've never tried a current regulator so not sure if it makes sense in this application.  Maybe one of the guys with circuit modeling software can simulate it. Make sure it will handle 500V X2 if it is referenced to ground...

T
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Frank / WA1GFZ says when he's working near high voltage, as a warning he sings this song by Jay and the Americans: "Come a little bit closer, you're my kind of man, so big and so strong, come a little bit closer, I'm all alone and the night is so long."
w9jsw
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« Reply #131 on: August 07, 2019, 05:48:20 AM »

Here is the article - http://amfone.net/Amforum/index.php?topic=30947.0

I am also looking closely at the tetrode board. It has a lot of really nice features...
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DMOD
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« Reply #132 on: August 09, 2019, 11:18:38 PM »


Quote
An interesting thought... using a solid state current regulator device to limit the maximum current thru the screen to 80 mA. It should be invisible until current hits >80 mA.

I've never tried a current regulator so not sure if it makes sense in this application.  Maybe one of the guys with circuit modeling software can simulate it. Make sure it will handle 500V X2 if it is referenced to ground...

Tom, were you thinking of something like this?

R3 senses the Isg current and develops a voltage drop which switches Q1 on and startes to pull down the gate voltage. One trims R3 for the threshold sensitivity and current limit.


Phil - ACC0OB

* Regulator FET with Current Limit.pdf (106.87 KB - downloaded 13 times.)
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"What kind of Koolaid do they make you drink in the Physics Department?" Charlie Epps to Dr. Larry Fleinhardt, NUMB3RS   Smiley
w9jsw
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« Reply #133 on: August 12, 2019, 06:57:39 AM »

thanks Phil. I will breadboard this soon. Since it is very close to the regulator you designed for the mosfet board, I am going to take one of those PCBs to build it. With a few jumpers and some extra holes for the 2N3904 I think it will fit up nice.

I think I will scrap the 75V bias design using the VR tube as well and build up another regulator board for the -75V.

Thinking about all of the PCBs and silicon on this transmitter I think I have an idea for what I will call it. With these 2, the 2 for the mosfet board, the mosfet board itself, the RF driver that will be silicon based, the sequencer that will be an arduino with relay board -  it is adding up.

The name is The Borg...

If you are familiar with the Star Trek canon, this makes sense. Take technology from other species and craft it into a new being that is technologically superior to the prior beings. With the amount of silicon crafted on to a hollow state design it kind of makes sense, I hope...  Grin

John
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KB2WIG
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« Reply #134 on: August 12, 2019, 05:43:12 PM »



"     If you are familiar with the Star Trek canon  ... "
   

I worry about these 'hybrids'. You never know what they'll do.....   As Capt. Kirk would say, " whose your daddy, Nomad? "

klc
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What? Me worry?
DMOD
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« Reply #135 on: August 12, 2019, 07:45:52 PM »

thanks Phil. I will breadboard this soon. Since it is very close to the regulator you designed for the mosfet board, I am going to take one of those PCBs to build it. With a few jumpers and some extra holes for the 2N3904 I think it will fit up nice.

I think I will scrap the 75V bias design using the VR tube as well and build up another regulator board for the -75V.

Thinking about all of the PCBs and silicon on this transmitter I think I have an idea for what I will call it. With these 2, the 2 for the mosfet board, the mosfet board itself, the RF driver that will be silicon based, the sequencer that will be an arduino with relay board -  it is adding up.

The name is The Borg...

If you are familiar with the Star Trek canon, this makes sense. Take technology from other species and craft it into a new being that is technologically superior to the prior beings. With the amount of silicon crafted on to a hollow state design it kind of makes sense, I hope...  Grin

John


Or, how about "GLASSFET?"   Grin  The Borg is not only exhilarating but also assimilating! Cool


Phil
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"What kind of Koolaid do they make you drink in the Physics Department?" Charlie Epps to Dr. Larry Fleinhardt, NUMB3RS   Smiley
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