How to convert a 4 bit binary to decimal and display it in two 7-seg led display?

Question

i need a circuit design to convert 4 bit binary into decimal and display it in a two7-seg led display

Answer 1

Check out the TTL 7447 and 7448 DIP's.
They take a four bit binary and drive a seven segment display. One is for the common cathode and one is for the common anode 7-segment displays.

I built a two digit timer with them years ago.

The links below provide an overview as well as circuit diagrams.

Answer 2

My first reaction is that there ought to be a multi-digit 7-segment display with an onboard convertor accepting binary, so that no additional parts are needed. I'm too lazy to look for one, but probably there's no need for a 2-digit display like that.

Ref 1 shows a datasheet for the 74C912 that accepts 4-bit binary and drives up to a 6-digit 7-segment display. This IC is meant to be a part of a microprocesser system, so it has bus address inputs, etc. that are not needed. So a simpler (cheaper) IC may be more suitable.

Ref 2 shows the 4015 that accepts binary and drives ONE digit. Ref 3 is a nice write-up of how to actually build this, except it uses a 4511, the main difference seeming to be that it has a latch to hold the input values so that the display keeps its number displayed steadily even when the input is changing around to the new value. (That feature is of no value if the inputs remain steady while the display is to be read.) If you are new to circuit building, this article would be a definite read even though it's only one digit.

Since you need two digits, you can use the above to drive the least significant digit (the ones digit) and not use a second digit 7-segment display at all; instead you substitute an LED that feeds a clear plastic piece in the shape of a 1 or a row of LEDs wired together in the shape of a one, either of which I shall call the tens bar. After all, humans don't need or like a leading zero in front of their numbers. The tens bar would be driven by the most-significant bit of the input (bit 8), because that bit will be on only when the input is in the range of 10-15, which is when you need the tens bar to light up.

The above addresses just the logic involved. You may need a few transistors after the IC to drive the display/bar. If you can't do that or get help locally (school, amateur radio club, PC club, etc. [ASK!]), you will have to search the Web for a complete, ready-made circuit so that you can just "paint by numbers."

You have not mentioned the voltage or power available from your inputs or the method by which the inputs change (manual switches, etc.), which will influence the design.

I have not even looked at the zillions of pages of the IC manufacturer's online catalogs, a tremendous resource; the above has been excerpted by people teaching/learning like you. Also there are many forums probably more suited to posing your question to, as they eat and breath electronics and inhale rosin fumes even if they don't smoke.

Answer 3

Unlike above answerers, I am taking your question literally.
You want to decode binary into Decimal (0....9) first, and then take that decimal signal and convert it for a 7-segment display.
The problem is that there doesn't seem to be a decimal (0...9) to 7-segment decoder on the market.
There are 2 possible methods:
A) use your BCD signal, and feed it into two decoder chips in parallel (yes you can do that), one is a BCD-to-Decimal decoder like the 74HC42 or 74HCT42, the other one is a 4511 or 74LS48 BCD-to-7segment decoder.
B) Only use a 74HC42 or 74HCT42 to get the decimal numbers, and then make a "home-made" diode matrix to light up the correct segments of the display corresponding to each number 0...9

Answer 4

There's probably many ways you can do this. A straightforward approach would be to start with the 5-bit binary number (ranging from 0 to 31), and convert this number into its decimal representation. Then, you can split the decimal into its two digits (the left digit is just num / 10, and the right digit is num % 10). Then convert each individual digit back to binary. Alternatively, you can just brute force each of the cases. There's only 32 possible inputs.

Answer 5

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You need to use Binary Coded Decimal which is an encoding for decimal numbers in which each digit is represented by its own binary sequence. Decimal:___0____1____2____3____4____5 etc BCD:___0000_0001_0010_0011_0100_0101 etc Thus 127 would be encoded as :- 0001 0010 0111 The following code will convert 2 digit decimal numbers and is easily modified for larger. int num=23; int tens=num/10; int units=num%10; int bcd=units|(tens<<4); alternatively you could use :- int bcd=(num%10)|((num/10)<<4); I use this kind of code regularly for displaying numbers on 7 segment LEDS

Answer 6

Use two of these:
http://engineering.dartmouth.edu/courses/engs031/databook/sn74ls47.pdf
or you can produce the circuit using basic logic gates and the schematic.

There may be better sources in the reference search.