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Topic: Common Cathode Large 7 Segment Driver (Read 93 times) previous topic - next topic

engineerdk

I am trying to build a Driver circuit for a Large common cathode 7 segment driving circuit.

I am using Proteus simulator to simulate the circuit beforehand, but after lots of adjustments, I am not getting the results.

Can anyone please tell me if I remove the pullups from both UDN1981 AND ULN2803(as per datasheet standard) will the circuit run in actual Hardware.

Please see the attachment.

Grumpy_Mike

Why do you need those inverters? Simply invert the output in software.

Quote
if I remove the pullups from both UDN1981 AND ULN2803(as per datasheet standard) will the circuit run in actual Hardware.
The 2803 will only sink current so the pull up resistors are irrelevant.

MarkT

#2
Oct 10, 2019, 12:50 am Last Edit: Oct 10, 2019, 12:51 am by MarkT
UDN1981 doesn't exist.  Perhaps you mean UDN2981 ?   You certainly don't use pull-up resistors on the output of drivers like this as they are providing current or no current.

[BTW please check the text is legible before posting images containing text!!]

You haven't provided details of the LED display - voltage, current, and whether it has built in current limiting (usually not).  I suspect you'll need to add suitable current limiting resistors on the UDN2981 outputs to the segments.
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

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