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Competition #1: High/Low Pulse Indicator

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Project: [FONT=Verdana,Verdana][FONT=Verdana,Verdana]High/Low Pulse Indicator[/FONT][/FONT]

The purpose of this circuit is to indicate the status of a present pulse.
When a high pulse present it will display the letter "H" & when a low pulse present it will display the letter” L” in the seven segment.

Parts List

2N 2222 NPN Transistor 1
1N 4148 Diodes 8
1K Resister 1
470R Resister 1
Common Cathode SSD 1

Circuit Diagram



Operation

When there is low pulse, there’s no any current flow through collector & emitter, so the first three diodes will forward biased & the other five diodes won’t get any current from the input, this allows current flow to d, e, and f segments via the first three diodes. Then it will display the letter “L” on the SSD.

When there is high pulse, current starts flow through collector & emitter. So the first three diodes will not get any current & the same time the other five diodes will get current through input so they starts to forward biased & pass current to the b, c, e, f, g segments. This allows to display the letter “H” on the SSD.

Note that the diodes going to e & f segments are combined together because those segments are common to both letters.

Construction

Construction is simple, it may take few minutes to assemble in a vero or in a breadboard. The circuit needs a 5V supply. The display brightness will vary if you change the value of R1.


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