Later, you can modify the input of this circuit to instead be the output of a counter that counts seconds, to create a stopwatch. This is a fun circuit to build as your first 7-segment display circuit. A 7-segment display (Must be common cathode.The CD4511 controls the 7-segment display so that it turns on the correct segments for displaying the number. Set this pin LOW for normal operation.īelow is an example circuit where you set the input number using switches. When HIGH, the last data is displayed regardless of the changes to the BCD inputs. The LE (Latch Enable) pin, also called store, is used to store the current value. You can use it to control the brightness of the display with pulse-width modulation (PWM).
The BL (Blanking Test) pin turns off all segments when LOW. The LT (Lamp Test) pin is there to test that all the segments of the display work. Pins a to g are the output pins that you connect to your 7-segment display. Pins D0, D1, D2, D3 are the BCD inputs through which you feed the number you want to show on the display in binary format. Check the datasheet of your version of the chip for exact values. Although, some versions of the 4511 chip support up to 20V. You can use a power supply voltage between 3V and 15V. To be able to use the BCD to 7-segment decoder in the chip, you need to first connect the VDD pin to the positive supply terminal and the GND pin to the negative supply terminal. The logic gates below convert the bits from the latches into 7-segment output. But when LE goes HIGH, the last data present on D0 to D3 is stored in the latches and the segment outputs stay unchanged. This means that when LE is LOW, the segment outputs ( a to g) are determined by the data on D0 to D3. But when EN goes low, the last input value is stored onto the output Q and cannot change. When the EN input of a D latch is HIGH, whatever is on the D input is transferred to the Q output. So, how exactly does this IC convert binary codes to decimal numbers? It does so by using a combination of logic gates and D flip-flops.įrom the HEX4511B datasheet, we can find the internal circuit of the 4511:įor each input bit (D0-D3), there is a D latch.
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