[Konvas] Kinor 35 conversion

[Peter Haas]

On Feb 6, 2010, at 11:22 AM, Bob Lipet wrote:

> Would you have aschematic of that circuit?

The schematic is proprietary to my electrical engineering company,  
Vanguard Engineering.


> I would guess it uses 555 clock IC?

Some years ago, I outlined everything which is required of a camera  
motor crystal control unit in a post to the USENET group,  
rec.arts.movies.tech.

I was unsuccessful in finding that post of quite a number of years  
ago, but I will attempt to reconstruct the outline here in this post  
to the Konvas List, from my possibly failing memories.

1) A very high frequency source is selected, usually 3.579545 MHz or  
14.31818 MHz.

Very accurate crystals are available in these frequencies, and it is  
customary, for the most accuracy, to use a TXCO ... a temperature- 
controlled crystal oscillator ... although a conventional oscillator,  
suitably "trimmed" at the time of manufacture, can also be quite good.

The better the oscillator design, and the more care which is employed  
during its manufacture, the closer other, similar units will behave  
when employed in multiple-camera shoots, or, most significantly, when  
employed in a sync-sound application with sound recorders, such as  
Nagras or Stellavoxes, which have an internal TXCO as their reference  
frequency.

So, the first choice is a TXCO, and the second choice is a crystal  
oscillator of a suitable design, employing a temperature-compensated  
crystal and a "trimmer" capacitor which is adjusted at  the time of  
manufacture, and is, thereafter, sealed to avoid tampering or mal- 
adjustment, for, in the last analysis, the accuracy of the camera  
control unit is only as accurate as its frequency reference.

2) The high frequency source is divided-down to an internal reference  
frequency, often in the 9600 Hz range. A CMOS divider IC, with a high  
division factor, is usually employed.

3) Connected to the motor, and driven by it, is an electro-optical  
tachometer. The output of this tachometer is a frequency which is  
directly related to the camera frame rate.

4) The reference frequency and the tachometer are input to a suitable  
phase detector, often of the XOR type. There are ICs which are  
capable of performing this function.

5) The output of the phase detector is passed through a low-pass  
filter. This is perhaps the most difficult part of the design.

6) The output of the low-pass filter is then sent to what is loosely  
called a "bang-bang" controller (which see), which either turns-on,  
or turns-off the series-pass regulator transistor, often a 2N3055,  
or, more recently, the "Darlington" equivalent of the same.

7) The series-pass regulator directly controls the speed of the  
camera motor. The source voltage is as required, and can be anything  
from 12 volts to 96 volts, or possibly more. 19 to 32 volts is  
somewhat standard, to the extent that anything in cinema technology  
is "standard".

8) However, the speed of the camera motor is constantly, and perhaps  
40 or 80 or more times per frame, compared to the reference frequency.

9) This comparison is fed-back to (4), and the cycle starts all over  
again, 40 or 80 or more times per frame, hence the appropriate term  
"phase locked".

10) As one output of this entire technical process is the presence or  
absence of a phase-locked condition, it becomes quite simple to  
reflect to the operator an indication of the status of this lock.  
Usually, a lamp or LED is illuminated when lock has been achieved,  
or, inversely, a lamp or LED is illuminated when the camera is out-of- 
lock. The achievement of camera lock is equivalent to the camera  
being up to sound speed, upon which occurrence the assistant might  
announce "SPEED!"

Perhaps the most suitable ICs are the RCA (now Harris) CD4046 and  
CD4060, but there may be others, depending largely upon what  
secondary and tertiary functions are desired, after the primary  
function has been satisfied. The CD series is most suitable where the  
camera motor is designed for 12 volts or less, certainly 15 volts or  
less, but, with the appropriate alterations to the circuitry, motors  
of up to 120 volts, dc, are possible.