7-segment display with encoder

Posted on Jan 17, 2013

This design explains how to use an encoder to set the number shown by a 7-segment display. Turn the knob clockwise to increment the number, turn it counterclockwise to set it back. Encoders are the most practical (and handy) way to set a large number of digital devices. Think of an alarm clock, would'nt be easier to set the alarm time simply turning a knob, in place of frantically pressing a couple of buttons? By the way, grandma alarm clock works exactly in that way. The circuit counts four main parts (Nutchip, encoder, display driver and display), nonetheless should not be difficult to understand. Its a matter of connecting two Nutchip inputs to the two encoder pins, and all four Nutchip outputs to a 4511 7-segment display driver.

7-segment display with encoder
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We suggest you to read the counter project pages for a detailed description of the 4511 and 7-segment displays. Here we note how all of the display connections are handled by the 4511 itself. The display, a common-cathode part, has been selected because it fits nicely a breadboard, but you can replace it with another brand or model provided it is a common-cathode type. Also, different parts can have different pinouts, therefore require a different board wiring to suit the new layout. To pinpoint all of the pins, try to power the display with a 5V source connected in series with a 390 ohm resistor (for limiting the current). Try powering different pin pairs until the whole pin/segment pattern is discovered. A good puzzling game for a rainy day, if nothing else... The incremental-type (also known as quadrature-type ) encoder connects directly to a couple of input pins (IN1 and IN2). We can think of an encoder in terms of a pair of switches (namely A and B encoder pins) with one of their pins connected together (COM pin). We connected this common pin to GND; therefore, from Nutchip's perpective, the A and B switches acts like any other pair of common-or-garden switches. The Nutchip reads an "1" on the input when the switch is open, and a "0" when the switch is closed. No other parts are required, as Nutchips include an internal pullup resistor which makes the input positive (a logic "1") whenever the pin is not connected to...

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