7 Segment does not make sense

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#1
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Heu guys.

It's been a while since I worked on my electronics and posted on AVR freaks. Well, I'm back in the industry and I have an urge to build things again.

I'm building a digital temp meter with 3 x 7 segment displays. I've set up the Atmega8 to move the value to a 8 bit serial in || out shift register that feeds the data to the 7 segment display driver. I use 1 7447 driver and I just switch the 3 displays by using transistors. I haven't attached the temp sensor yet, just trying to get the displays up and running first.

The code is working fine, the displays can display what I send to the displays. 0, 3,5,6,7,8,9 displays fine but 1 displays a 7, 2 displays a swapped around 6 and 4 displays a 9.

Has anybody experienced this problem before? I've already swapped the driver with a new one and it did not solve the problem. If the lines were connected incorrectly then the other numbers would be wrong as well.

I am confused and I can't find out what's causing this problem.

Regards,

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You could have a short circuit to the bottom L/H segment. (Or the bit map could be wrong)

John Samperi

Ampertronics Pty. Ltd.

https://www.ampertronics.com.au

* Electronic Design * Custom Products * Contract Assembly

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a 74xxx47 is a BCD to 7 segment converter chips so there are not bitmaps that can be wrong.

Have you already implemented the multiplexing? What happens if you control the four binary inputs manually?

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I thought about it today and I think there might be a short somewhere, if there is no short, I'll do some mods to control in manually.

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Hey guys.

It was a short, between two pins.

Thank you for the help.

Regards,