Anybody know how to make a sync separator?
Nigel Kendrick
>Hi,
>I was just wondering if anybody knows or has some circuit diagrams of
>sync separators. I have a standard plain video signal (PAL) and I want to
>get the vertical and horizontal (or csync) from it. I know there exist
>chips that do this - problem is in Australia they are not so easy to find.
Alex,
There is a delightful 8-pin Sync Separator chip from national Semiconductor
- the LM1881 - which can decode the sync signals from a PAL or NTSC
composite video signal - UK cost is around £3.00. The input is composite
video and the chip outputs and odd/even field signal, Vsync, Csync and
colour burst/back porch.
LM1881:
<- CSync 1 8 Vcc
-> Composite 2 7 Odd/Even (hi/lo) ->
<- VSync 3 6 Reset
GND 4 5 Burst/back porch ->
R1 620R to pin 2 in series with C1: Composite >--R1--C1--Pin 2
R2 Join pins 4-6 via 680K
R3 Join pins 8-5 via 2K7
C1 0.1uf polyester pin 2 to R1
C2 Ceramic 330pF + Ceramic 180pF in parallel
From pin 4 to Junction of R1/C1
C3 0.1uF polyester in parallel with R2 (pin 4 to pin 6)
C4 0.001uF mylar film on pin 3: <- Vsync--C4--Pin 3
C5 Ceramic 0.1uF 16v Supply decoupling - between pins 4 and 8
Supply voltage 5-12v
Supply current 5.5mA
DC signal in 1.5v Max
Outputs are TTL compatible eg:
Sync 1&3 : Vin = 5v: Logic high = 3.6v. Lo = 0.2v
Signal 5&7 : Vin = 5v: logic high = 4.5v. Lo = 0.2v
Changing R2 affects timing and can allow faster signals to be stripped
Coupled to this could be a 1-chip (74LS123) circuit from Elektor '303
Circuits' that strips Hsync and Vsync from a Csync signal:
IC1 = 74LS123
R1 12K Pin 15 to Vcc (+5v)
R2 10K Pin 7 to Vcc
Link pins 2+3+11
R3 10K from linked pins 2+3+11 to Vcc
C1 18nF from pin 15 to pin 14
C2 27nF from pin 6 to pin 7
Pin 16 to Vcc
Link pins 13+9
Link pins 10+12
Pin 8 to Gnd
/Csync input on Pin 1 also used as /Hsync output:
'it is possible to feed the /Csync as line sync pulses direct to the
monitor...'
/Vsync output from linked pins 12+10
Good luck - if you can't decode the about I could fax/email you a GIF etc!!!
If you can't get hold of the LM1881, let me know and I will mail you two in
return for 10 x RG58 BNC crimp connectors - I can use these for my work and
it would be simpler than arranging a cash transfer - hey a new world
currency - the BNC!!
Regards
NK
** I understood every word you said...
...but not many of the sentences **
Alexander W. Chin
I was just wondering if anybody knows or has some circuit diagrams of
sync separators. I have a standard plain video signal (PAL) and I want to
get the vertical and horizontal (or csync) from it. I know there exist
chips that do this - problem is in Australia they are not so easy to find.
I have tried transistor circuits and I have managed to get csync but
vsync is not very stable. I would very much appreciate some help.
It is very convenient to just use an IC (if somebody could buy one for me).
I want to get it working soon. If anybody can offer help - please mail.
Thanks
Alex