Generating 15.7KHZ Horiz signal pulse from 60HZ reference pulse?
Jim Chandler
We have a need to synchronize our Visual Flight Simulator system
to the flight simulation computer. The flight computer supplies
a 60HZ reference pulse only. Our Visual Flight Simulator system is
synced to a 15.75KHZ external horizontal reference pulse. We were going
to design a phase locked loop circuit to accomplish this, but were
wondering if maybe a commercially available product might do this?
Perhaps, some of the new genlock systems for VGA to TV converter
or those available for Video or Camcorder system editing? The equipment
would have to have the ability to sync on 60HZ only.
Also, is anyone familiar with building a VCO locked to a 60HZ signal?
We were thinking of using a Fo of 31.5KHZ, dividing by 2 to get the
required 15,750 and dividing the 31.5KHZ by 525 to get a 60HZ feedback
for the phase comparator. Is anyone familiar with what stability we
could expect from this?
Jim Chandler | Daytona Beach/Ponce Inlet
chan...@enterprise.america.com | Florida
904-767-8838 |
henk buisman
>Greeting:
(...)
>Also, is anyone familiar with building a VCO locked to a 60HZ signal?
>We were thinking of using a Fo of 31.5KHZ, dividing by 2 to get the
>required 15,750 and dividing the 31.5KHZ by 525 to get a 60HZ feedback
>for the phase comparator. Is anyone familiar with what stability we
>could expect from this?
Your problem is almost identical to a design example desribed in
Horowitz and Hill's The Art of Electronics (Cambridge Univ. Press). In
the example is based on a 4046 with a passive phase lead/lag filter.
The example also includes design equations. I think that the only
thing you need to do is to adjust the divider in the feedback loop of
the PLL (divide by 525 instead of 1024 used in the example).
Good luck,
Henk Buisman
Henk Buisman
Organic Instruments
The Hague, The Netherlands
PDRUNEN
signal. I used a 74HCT4046 PLL along with a MM5321 veritica/horiz sync
driver.
If all you want is the 15.7Khz output, I have a program which will
calculate the values of the loop filter for the 74HCT4046, the program is
from Signetics and is centered around the 74HC4046 PLL chip.
PDRUNEN
val...@ibm.net
>Greeting:
>
>We have a need to synchronize our Visual Flight Simulator system
>to the flight simulation computer. The flight computer supplies
>a 60HZ reference pulse only. Our Visual Flight Simulator system is
>synced to a 15.75KHZ external horizontal reference pulse.
Is the 15.75khz input labled "comp sync", "black" or "reference"? is the current
ref. pulse coming from a video ref. genorator? If so, you may have luck just
sending the 60hz ref to the input. If all else fails, consider buying a cheap
video ref. gen. and modify it's VCO to lock to your 60hz ref. Also keep in
mind that there is NTSC interlace going on. Make sure field 1 of both systems line up.
Glenn Valenta
Richard Cave
>Greeting:
>We have a need to synchronize our Visual Flight Simulator system
>to the flight simulation computer. The flight computer supplies
>a 60HZ reference pulse only. Our Visual Flight Simulator system is
>synced to a 15.75KHZ external horizontal reference pulse. We were going
>to design a phase locked loop circuit to accomplish this, but were
>wondering if maybe a commercially available product might do this?
-snip-
>Also, is anyone familiar with building a VCO locked to a 60HZ signal?
>We were thinking of using a Fo of 31.5KHZ, dividing by 2 to get the
>required 15,750 and dividing the 31.5KHZ by 525 to get a 60HZ feedback
>for the phase comparator. Is anyone familiar with what stability we
>could expect from this?
Security cameras are often synchronised to the 60Hz mains (Those with
a 'Line Locked' setting) and pull the horizontal frequency with a VCO
to achieve this. I guess this means stability shouldn't be a problem.
Your PLL solution is the obvious one; Maybe you could use a camera
timing chip such as the Phillips SAA1043 which gives you the VCO drive
and dividers to Hsync and Vsync rate. Then you just need to add the
phase detector to pull the VCO until Vsync = reference, and Hsync can
go to your system.
Rich
Richard Cave
ri...@adam.com.au