Your problem is the segment driver transistors. To turn them off you need to raise the base voltage until it is at or close to 12V (the emitter voltage) and you can't do that with a 5V signal source. They are always conducting, that's why you see all segments turned on. The solution is to use a voltage translating buffer (CD4050 should work) or else another transistor between the MCU and TIP122 to rise it's base voltage when 'off'.
Brian.
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