LED X-Y plotter

The steady fall in the price of LEDs now makes it an economic pro- position to construct an X-Y display using a LED matrix. Two UAA I 70 I Cs are used to drive a I Ox I O matrix of LEDs. Since the UAA 170 is normally in tended to drive 16 LEDs arranged in a 4 x 4 matrix, the out- puts of the UAA 170s must first be decoded to give a I of I O output, using transistors T 1 to T 10 and Tl l to T30.