Electronic – Binary coded decimal ICs

7segmentdisplaydigital-logic

Is there any IC that can be use to convert 9 bit binary code to seven segment display?
EX:
100101100->300
I want to display 300 in seven segment display when 100101100 binary code applied to input.I want to do this only using ICs not using microcontrollers.

Best Answer

I can think of three ways to do this. I'll start from the most expensive and complicated and work my way down.

  1. All Logic IC's: Use a parallel-load 9-bit up/down binary counter (such as 3x 74hc190) and a 3-digit resettable BCD counter (3x 74hc163). Load the binary counter with your 9-bit number, and clear the BCD counter to 0. Clock both counters until the binary counter reaches zero. Load the output of the BCD counter into a latch, and then feed it to a BCD-7seg decoder. Repeat.
    • Pros:
      • Meets requirement of only using standard logic IC's
      • Requires no programming
    • Cons:
      • Expensive (The counter chips are about $1-2 each)
      • Prone to wiring failure
      • Requires a clock signal of 31kHz for 60Hz refresh
      • Requires 8-12 Logic IC's (I'll draw a schematic later)

  2. ROM Look-Up Table: Use a small parallel asynchronous FLASH memory (such as this one) to take all data inputs as an address, and then program the ROM to generate BCD outputs for 2 digits. Feed the result into a BCD-to-7seg decoder. Alternatively, use one ROM to generate a single decimal digit decoded into 7-segment pins.
    • Pros:
      • Fairly cheap price per digit
      • Scales better
      • Fast (but speed doesn't really matter)
      • Simple to wire/design
    • Cons:
      • Each ROM requires different programming
      • Need to buy a much larger ROM than needed
      • Programming requires computer automation.

  3. Microcontroller: A simple microcontroller with enough inputs and outputs can convert the binary number into BCD, and then encode it into 7-segment control signals. The cheapest solution (My digikey search picked out this PIC) will multiplex the output digits. You may need transistors to drive the common anode/cathode of your 7-segment displays, but those can be cheap transistors.
    • Pros:
      • The cheapest solution at $1.50 - $2.00 total
      • Simple Wiring
      • Ease of implementing Binary->BCD algorithm in software
      • Easy to add more functionality
      • Least expensive system for driving the display
    • Cons:
      • A chip programmer is required
      • You need to write software (not just a hardware problem)
      • The cheapest solution requires digit multiplexing, which is more complicated than direct drive.

I'll draw up some schematics later

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