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Digital Thermometer Project.

e14 Contributor

I am building a simple Digital Thermometer. This is not strictly an Arduino project, I use Arduino to program 2 ATtiny84 that will run the 3-digit, 7-segment LCD.

 

My problem is two fold. First I'm not sure how to direct the current through the LCD: ground to common, or VCC to common. (will ATtiny provide enough power?). If VCC to common how do I program the pins - LOW to display or still HIGH.

 

Second problem is that the LCD fades after a while even it the current is still running through the port. Do I need to multiplex the display?

 

Thanks.

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  • Hello,

     

    About the current direction it depends on the specification of your LCD. Cathode common type is connected to ground and so anode common type to Vcc.

     

    If it's a common cathode type then the pin should be programmed HIGH to display etc....

     

    In concern of the fade problem i'm not sure that it can be solved by a multiplex circuit as the main problem is about current sinking from the LCD

    and that the tiny pin could not provide it. Try it with a transistor connected to those common cathode or anode it should be much easier !?

     

    Good luck.

Reply

  • Hello,

     

    About the current direction it depends on the specification of your LCD. Cathode common type is connected to ground and so anode common type to Vcc.

     

    If it's a common cathode type then the pin should be programmed HIGH to display etc....

     

    In concern of the fade problem i'm not sure that it can be solved by a multiplex circuit as the main problem is about current sinking from the LCD

    and that the tiny pin could not provide it. Try it with a transistor connected to those common cathode or anode it should be much easier !?

     

    Good luck.

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