Early schematic

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Here is my initial design and draft of the circuit used to control the Digital Counter.
  • The counter will have a One's and Ten's digit which allows it to go from "00" to "99".
  • There will be three buttons: Reset, Up and Down
I've decided to start with a pair 74LS192 chips to which are Decade counters (count from 0 to 9). Upon reaching a value of "9", the counter jumps back to Zero and outputs a Carry signal. That Carry signal is used as the clock signal for the Decade counter that handles the Ten's digit.

Each 74LS192 is connected to it's on C4511 BCD-to-7 segment display decoder. As the name suggests, the 4511 converts the Binary number coming from the 74LS192 to signals that can drive a 7 segment display. There are blanking and lamp test inputs available, but I've no plans to use them for now.

The display LED's I plan to use are found here (www.sparkfun.com). The current draw of each LED segment is 20ma, a bit much for the 4511 chip to handle especially if all segments are lit up. So for each segment output of the 4511, I'll use a power transistor to help switch on the LED segment load. Much of this design is borrowed from these guys at Evil Scientist.

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