XO controlled 480Hz Oscillator

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I would certainly like to see them again, i liked the architecture, = though many did not.

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Maybe, the many analogous properties between tuning forks and crystals=20 make that a potentially shaky proposition. Consider the old Bouleva=20 accutron watches, about 4 ppm on your wrist, better than chronometer=20 grade of the day, done with a tuning fork.

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If you liked the 1802, I assume you also like wacking your thumb with a hammer.

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Well, I already ordered the crystal. I will keep that in mind. I need to make a 60Hz VCXO in a PLL slaved to a 24Hz pulse. That is for later though.

Regards, Chris Maness

If your camera's drive motor is sync'd to 60 cycles, then you could extract the 8th harmonic of 60 cycles to end up with 480 hz. There would be some value in having both the deck and camera speed controlled by the same reference frequency (line frequency). For that matter, you could install an alternator or optical disk somewhere on one of the camera's rotating parts to generate 480hz. In the long run, I don't see how you are going to sync the two without time code on the film and the tape. Tape will slip, that's guaranteed, and the error accumulates no matter how accurate the capstan speed

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Well I didn't want to get into all the nitty gritty of the project. The tape deck is a fullcoat recorder. Fullcoat is perforated tape. Therefore the capstans have sprokets, and the sprockets don't slip (if you threaded it right). The deck has two time references. A 480Hz (a

960Hz fork with a divide by two in the can) tuning fork in a can that is almost impossible to open without destroying it, and a sync line in from the camera. The fork standard is putting out 960Hz. I would imagine the divide by two in the can is fried. There is also a jack for 60Hz pulses with a 12V swing from the camera. The deck contains a three stage binary divider (divide by 8), that provides a 60Hz pulse to a 12VDC-to-120VAC inverter. The inverter drives a 120VAC sync motor at a constant speed. The cameras I intend on using with the deck have a flash sync on the camera (think super 8). This sync closes a switch for 5ms 24 times/s. I plan on making a box or installing a PCB in the deck that can convert these pulses to 60Hz pulses. Since the camera speed is not controlled by a crystal reference the deck will keep speed with the camera. Yes, I do realize that if the camera varies in speed it will produce noticeable fluctuations in audio pitch. However, since my projectors don't sync either, it is better to have the deck be the sync slave.

I want to keep the thread on the design topic, but I would be happy to discuss sync issues on the yahoo group:

Regards, Chris Maness

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=A0 =A0 ...Jim Thompson

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Unfortunately, while the mains frequency it held at precisely 50Hz (or

60Hz) over the long term, it can vary by a few percent in the short term, so it wouldn't be a good idea for Chris to lock his 480Hz to the mains.

-- Bill Sloman, Nijmegen

Not that many fewer. 16 words of program memory and one RAM location.

The load caps are not optimal because it's in a solderless breadboard, but still the accuracy is within about 0.004%. Not too shabby.

Best regards, Spehro Pefhany

--
"it's the network..."                          "The Journey is the reward"
speff@interlog.com             Info for manufacturers: http://www.trexon.com
Embedded software/hardware/analog  Info for designers:  http://www.speff.com

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"The Journey is the reward"

eff.com

That is really nice. I strayed away from this one because I have never programed a PIC before. I was also wondering about caveats of using a proto board before I solder the final product. I am getting

25 CD4060B's to play with so I would have to worry about screwing up. I will probably get a socket for the crystal. I am anxious about getting my parts in the mail. I am anxious to see if my solution fixes my fullcoat deck. It all looks good on paper, but the proof is in the pudding.

Regards, Chris Maness

:What is the simplest way to get 480Hz from a crystal controlled :oscillator? Looks like most of the pre-packaged XO's and VCXO, seem :to put out much higher frequencies. Would a series of dividers be the :best way? : :Thanks, :Chris KQ6UP

You might be able to still pick up this surplus item

With a bit of trimming I'm sure it could be pulled to 3.360kHz and then you can use a divide by 7 counter using the HCF4018 to get 480Hz.

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Hmm I've never looked that closely at line frequency. Do you have any idea how long you'd have to average for to 'clean things up'? A few second time constant is not too bad for an oscillator.

George H.

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I don't really know. As I understand it, if the load on the network gets heavier, the first effect is to slow down the generators and drop the frequency, and the control loop then turns up the power in the steam generator or the gas turbine driving the generator to restore the frequency and push it back above 50Hz (60Hz) for a bit so that all the mains-driven synchronous clocks go back to reading the right time.

This is all fairly heay machinery, so a few seconds probably isn't long enough.

-- Bill Sloman, Nijmegen

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I have looked closely. Over 24 hours there are exactly the right number of cycles. Over shorter time frames, the number of cycles per unit time gets worse the shorter the time.

When a heavy load is suddenly applied, the phase can jump in either direction by something like 10 degrees. It depends on where in the phase the load arrived and the nature of the load. The system very quickly comes back to normal phase and amplitude. If you live near an industrial area, you may even see periodic modulations of the phase of the mains. Things like punch presses draw surges of power for the electric motors.

A few percent seems way high to me for the North American power grid.

0.03Hz = 0.05% will apparently affect power transfer by 1 GW. IIRC, HP wrote a report many years ago in which short term stability was of the order of a tenth or two tenths of a percent.

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So you say the 1802 is less ugly than its 3 ugly sisters. Still:

LD LOW(ValueA) PLO R3 LD HIGH(ValueA) PHI R3 LD LOW(ValueB) PLO R4 LD HIGH(ValueB) PHI R4 LD LOW(ValueC) PLO R5 LD HIGH(ValueC) PHI R5 LDN R3 SEX R4 ADD STN R5

Thats 16 instructions to do C=3DA+B where the 3 are all in random places. Way back when, the boss designed in the 1802 to save power. The need for a lot of instructs meant that we had to put 3 EEPROM chips on it to hold the code. It was in a "power up - do it - power off" sort of application. I tried to explain at the time that a Z80L would draw more power while it was on but it would be powered on for so much less time that it wouldn't matter. As it was we couldn't keep the display going while we did RS-232 or anything like that. It had to a purely one thing at a time program.

Spehro Pefhany a écrit :

Know zilch about that stuff but all the generator are interconnected through the power grid. This means that they all have to be at the exact same frequency or a gigantic firework will start, and only a phase shift can be tolerated between them. Also having a network of long transmission lines with servoed sources here or there and varying loads might be a nightmare to design and get stable.

--
Thanks,
Fred.

Qn DIV BY

-----|--------- Q0 2 Q1 4 Q2 8 Q3 16 Q4 32 Q5 64 Q6 128 Q7 256 Q8 512 Q9 1024 Q10 2048 Q11 4096 Q12 8192 Q13 16384

:-)

JF

Hey guys. I was able to finally get my simulation of the speed control of my fullcoat deck to work correctly. I found two missing parts that I had not included in the simulation. Also, earlier on, Charles helped me find a couple of errors, it now works correctly. There is no mystery on how this thing works any more. It takes a 60 Hz square wave pulse to sync from the camera (with a +12V swing). It uses the 480Hz tuning fork with a divide by 8 circuit to produce this same 60Hz square wave to drive the sync motor at speed.

I still have to replace the tuning fork with a crystal oscillator as it is running at 960Hz instead of 480Hz. I like the idea of running it on quartz to keep the start up time down, and I believe the crystal would be more accurate. I could not crack open the tuning fork can to fix a divide by two in the can. The actual tuning fork runs at 960 to keep the size down, but the can is marked 480Hz, and the design of the deck requires the output of the fork to be 480Hz. Therefore, there has to be a divide by two in the can. This is not working, and it is causing the motor not to run very well at all. It runs fine off of the mains, but due to the nature of the deck, it needs to be portable, and sync to the camera not the mains.

The circuit simulation was done in LTSpice, an awesome free circuit simulation program. If you guys ever need to proto or reverse engineer something without frying real hardware, it is the way to go.

Regards, Chris Maness

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Really. Abusing the instruction set like that to attempt to make a = point?