ICL7107 LED Display Settings

The diagram above shows a typical 7-segment LED display with the pin designations. The documentation recommends 0.3-inch or 0.4-inch red LED, however, almost any standard 0.56-inch LED will work with this IC; providing it is a common anode type. For more information, see the following article.

7 Segment LED Display

Connecting a LED Display to ICL7107

The ICL7107 is capable of providing 8 mA of sink current per segment. In the main circuit diagram of my design, I am not connecting the common anodes directly to Vcc, but instead, through a pair of 1N4148 diodes D1 and D2 in series to form a small voltage drop, thereby preventing the LED segments from being driven hard and burning out.

The link below will show an example of how to wire a single 7-Segment LED panel to the ICL7107 chip. This is very useful reference information that you should bookmark if you are planning to design or build this circuit.

Connecting a 7 Segment LED Display to ICL7107

Lamp Test Mode

Pin 37 provides a diagnostic test of all the segments to check if they all light up. When this pin is high to V+ all the segments should light up. When all the segments light up you should obviously see "1888" on the display, which indicates that the connections to the display are correct. If you see anything else, then chances are that you have wired the display incorrectly. Since the test pin can sink 15 mA, it can also provide a negative supply for driving the decimal point (dp) segment of a display. NOTE: In the lamp test mode, the segments receive a constant DC voltage. This may burn the segments if this mode is active for too long, hence use it sparingly for diagnostic purposes only.

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