Help with circuit involving old composite video. (Experienced needed)

[rickey1990]

Okay so my problem is iv come across a circuit that takes a video signal and maps that signal onto a LED array. I am wanting to use the circuit as a micro-controller-less eye for a robot. There's a description and simplified circuit diagram but i am not sure how they go together.





Written information,

BEAM circuits are very similar to the older analog type video technology, still used in simple B/W TVs and 20 years ago all televisions used analog beam like circuits for decoding video signal. So it's not surprising that it is fairly simple to use BEAM circuit blocks to convert video into digital or analog signal suitable for interfacing with other beam circuits. In the example suggested by Dennison below, The video signal is converted into a 2x2 matrix which corresponds to the average light level of a quadrant of a video frame. The attached block diagram shows the general concept of such BEAM video decoder.

A composite video signal (ie a sugar cube camera output) is processed by a sync separator to produce Horizontal and Vertical sync pulses as well as a DC restored video signal. This circuit requires some 2N3904s and a few passive components. The H and V sync signals each trigger a Hsync Nv and Vsync Nv (74HC14) respectively which are adjusted to time out at a point corresponding to the horizontal and vertical midpoint of the screen. The signals are connected to one half of a 74HC139 (Z bridge) which generates 4 control signals corresponding to each screen quadrant. These 4 Q signals are used with four 4066 analog gates to route the video signal to one of 4 Nu (74HC14). The analog voltage on each Nu cap corresponds to the average video signal of that quadrant This can be used to "influence" a central pattern generator like a microcore. A digital signal can be generated with a one bit A/D converter also know as a comparator or Schmitt trigger. If the video level on the Nu cap is above the trigger level of the comparator, a LED turns on. A bright light moving from one quadrant to the next, will turn on the corresponding LEDs indicating the relative position of the light.

This concept can be scaled up to a low resolution "gray scale" (or red scale) monitor (ie 8 by 8 LED matrix) which can also be easily made with a V and H chains of 8Nvs each buffered with HC240 LED drivers which can drive 64 LEDs in real time. The video signal is "sliced" by a comparator the output of which drives the HC240 tristate enable lines. No Nu stages are needed to measure the average video since your eyes will do a visual integration of the LED light level. Any old video signals can be used for experimenting with this concept including a camcorder or VCR video output.

regards

wilf