Article
Mini Test Chart Generator
A video test chart for less than a tenner
Recognise this? You have to adjust a television or monitor but do not have access to the required tools… This small test chart generator for less than a tenner is then just the bee’s knees.The circuit described here is actually just a standard video signal generator that can be used to synchronise a television or monitor, provided that the equipment being tested is fitted with a composite video signal (CVBS) input. All the timing and corresponding signal levels are generated by a PIC12C508 microcontroller. This circuit also has a second function. Many video recorders can record stereo sound. It is interesting to exploit this property to make a good quality recording from a radio broadcast, potentially using the recorder’s built-in timer. Unfortunately, modern video recorders switch to a background colour when they do not sense a proper video signal at their input. This prevents noise from being recorded, but at the same time the audio signal is also ignored!
Materials
Gerber file
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.
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PCB
Component list
Resistors:
R1-R4= 1kOhm2
R5= 120Ohm
R6= 75Ohm
Capacitors:
C1= 100nF
Semiconductors:
T1= 2N2222
IC1= PIC12C508C (Microchip)
Miscellaneous:
X1= 4MHz quartz crystal
Disk, PIC program, order code 020403-11 or Free Download
R1-R4= 1kOhm2
R5= 120Ohm
R6= 75Ohm
Capacitors:
C1= 100nF
Semiconductors:
T1= 2N2222
IC1= PIC12C508C (Microchip)
Miscellaneous:
X1= 4MHz quartz crystal
Disk, PIC program, order code 020403-11 or Free Download
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