Large Seven Segment Display Project

Thread Starter

emporiumx

Joined Feb 16, 2007
12
Hi

I am building a rate counter that uses a photosensor/reflector type system to detect cans passing a point on a factory line.
I am using an ATMEGA8535 Micro to do most of the work and outputting to either 3 or 4 separate 4511 (BCD to 7 Segment) and through a ULN2003(per display) to the 2 inch (50mm ish) display segments. (Common Anode)

My Question is? Of course the ATMega and the 4511 will be working on 5v however the displays are on 12v (Each segment requires 8v to run). Is pin 9 on the uln2003's tied to the 5v or the 12v? Also is there any problem to tie the pin 9's from multiple displays together? (I am guessing it is ok to tie then together and to the 12v but why I ask is because I saw a design for such an application with the pin 9 floating so I want to make sure before having boards manufactured).

Also I have found a pretty reasonable pcb house in china to make my boards (all through hole components) but can anybody suggest any other reasonably priced placed to get small runs of pcb's done?

Thanks

Bruce
 

hgmjr

Joined Jan 28, 2005
9,029
Hi

I am building a rate counter that uses a photosensor/reflector type system to detect cans passing a point on a factory line.
I am using an ATMEGA8535 Micro to do most of the work and outputting to either 3 or 4 separate 4511 (BCD to 7 Segment) and through a ULN2003(per display) to the 2 inch (50mm ish) display segments. (Common Anode)

My Question is? Of course the ATMega and the 4511 will be working on 5v however the displays are on 12v (Each segment requires 8v to run). Is pin 9 on the uln2003's tied to the 5v or the 12v? Also is there any problem to tie the pin 9's from multiple displays together? (I am guessing it is ok to tie then together and to the 12v but why I ask is because I saw a design for such an application with the pin 9 floating so I want to make sure before having boards manufactured).
The best practice is to tie pin 9 of the ULN2003 to the positive supply to your LED displays. They will be tied together in this case and that is OK.
Also I have found a pretty reasonable pcb house in china to make my boards (all through hole components) but can anybody suggest any other reasonably priced placed to get small runs of pcb's done?

Thanks

Bruce
Check into SierraProtoExpress . I think they still have low pricing on low-volume 2-layer through-hole boards.

hgmjr
 
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