Big 7-Segment Countdown Timer

Paul Stoffregen of PJRC created this big 7-segment countdown timer for DorkBot PDX meetings:


Big 7-Segment Countdown Timer

A few months ago I was feeling inspired to create a nice countdown timer.  With the next Dorkbot open mic only days away, I finally had the motivation to actually put it together.

The main challenge was driving the LEDs with a constant current, because they need about 10.5 volts across the several series LEDs.  I wanted to run from 12 volts, so there wasn’t much voltage left over for the normal current limiting resistors.  Instead, I used this opamp circuit.

The project runs from a Teensy 2.0.  The code is very simple, using the SPI and Bounce libraries for the hardware interfacing.


PaulStoffregen has shared his board design on OSH Park:

Shared Project: big7seg i.png

Big 7-Segment driver. A ‘595 shift register lets you chain any number of these to build a large display.

Perfect for keeping Open Mic talks at hackerspaces on time!

Order from OSH Park


Big 7-Segment Countdown Timer

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