This is a circuit converter from VGA in TV SCART connection. Basically it is a circuit that accepts the signals from the exit of card VGA, him it then changes in combination RGB+composite sync and it leads to fastener SCART. The elements of picture from her exit card VGA, RED, BLUE and GREEN are already ready, bring right tendency the 0.the 7 vpp and right resistance of 75W for direct connection with fastener SCART,
for depiction in the TV. What should it changes it is the right
combination the horizontal and vertical synchronization signals from the
VGA in a complex signal that will be led to the entry VIDEO in pin SCART. This transformation him they undertake electronic elements of circuit.
That It Functions:
This circuit has been drawn in order to it changes regular signals VGA, standard RGB and the complex signal of timing. circuit is simple because signal RGB from the VGA
is ready in standard level 0,7 Vpp and in 75W charge. For the signals
of timing exists a circuit that changes the horizontal and vertical in
complex. The circuit is simple based on a TTL completed with four gates XOR, two resistances and two capacitors. His choice completed TTL it is reasonable because the signals of timing of VGA they are signals TTL.
The converter of signals of timing is system that regulates the
difference of polarity of signals, so complex signal it is always right.
Card VGA uses different polarities in the
signals of timing in order to it informs the Monitor anymore analysis it
uses. This circuit regulates the changes polarity the signals in least
from 200 mSec, that are faster and from the time of regulation of common
Monitor VGA. The circuit in order to function need stabilized tendency + 5V (+/- 5%) and current 120mA.
Converter VGA in TV is easy in the
manufacture to him it is enough exists a relative experience in the
manufactures electronic. The circuit can be manufactured on one small EPOXY
board. Remember only to connect also the completed circuit with the
catering of 5V (in the drawing it does not appear). The circuit in order
to it rightly functions it needs without fail stabilized tendency
consequently it should you use also a REGULATOR LM7805.
In the entry the 7805 the tendency should be from 9 until 16V so
that it accomplishes us it gives the desirable stabilized tendency of 5V
in his exit. Tendency from 9 until 16V we can him take also from our
computer or from exterior small power supply’s socket. From the computer
we can we take from the following points: from door RS232, from the
parallel door , from the PS2 and finally from a gambling chip of
catering by his interior computer.
Big attention should be given in him you stick that you will make
and in the wiring of circuit, you avoid the chills you stick why the
circuit functions in big frequency and sure will be created
instabilities in the circuit with result bad quality of picture or even
lack timing in the screen of TV. Be careful in order that the soldering
is clean and glazing thus you will only be sure that the soldering has
become right. For the wiring you are used shielded cables blentaz and
ground the thorax of cables in the board’s chassis. Good it is
manufacture it is placed in a plastic box and it is placed and a
connector EURO/scart female for placement in chassis.
C2: 2,2 mF
R1, r2: 2k2
R3, r4, r5: 2k2
R6, r7, r9: 47k
T1, t2: 2N2222
Cable of connection VGA male 15pin sub D (DE 15)
Output connector 21pin EURO/scart female