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Digital clock problem

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Member level 4
Nov 28, 2005
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I made this clock but it have one mistake. Problem is that every single led that is currently on, have shadow wich is shifted eight times backwards. For example if 26-th second led is turned on, there is 18-th led also turned on but with aprox. 20% intensity. This is present in whole system.

On the picture you can see leds that have to be on: 10,20,30,39 and leds that must not be on: 2,12,22,31.

Here is schematic of the clock. I can send source too but comments are on serbian and I must translate it first.

maybe its the code

the circuit looks aok...

you could wire a frame update to all the !sclr pins
this way adding a blanking pulse

would rule out the led drivers and setup
and also a mute clock feature in hardware

ha maybe you need pullups enabled or not on port b?? just an after thought


Check out the buffer that you are using and see if you have any leackage voltage. i.e see the when you puls 0V from the PIC, you get 0 at the buffer and also at its output. Myaby you are geeting voltage from other pines or something. Dont forget that you are using Transistors ( link the 2003 buff ) that will output voltage relative to the input, and not gust 1 or 0.
Maybe you can find schmit trigger buffer with the same pinout as the 2003, and then you can be sure that they will be only on or only off.

I would start with the voltage on the pines, from the PIC up to the LED with simple voltmeter.

If you found my answer useful, click on the button that says Helped me. ( NO points will be taken from you! )

Good luck.

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