How to display dot on 7-seg , 4 digit

[paul borgmeier]

Chai98a,

Soory! for circuit not clear for you.. , we used 7 seg COM Cathode..

It is clear to me as presented. Is it wrong? I did not assume Common Anode – you told me it was Common Anode (see your third post). The transistors shown in your schematic and the code line Digits=~DCD i also imply Common Anode.

Your code is largely not commented
Your schematic is not complete

I spent considerable time sorting all this out and now I will not offer more until you give more detail.

1) Is the the schematic fragment correct?
2)What is the P/N of Q1-Q4 are they really PNP?
3)What troubles are you having (i.e., does the display light up (at all)? wrong temp? junk? just missing DP?)
4) Are pins 1 and 19 tied low on U2?
5) With the code you posted in #17, how does temp get set? (I don't believe it ever does)

From post #7

I can read data temp from ds1820 and send to RS232 -->OK but canot to diplay to 7 Seg. Ex 29.5C

and from post #17

This circuit i have test with time counter alredly done no problem

it appears to me you have everything you need – your circuit works and you must have code to drive it; your temperature sensor reads temperature correctly.

I am not sure how to help you until you provide more information

[sayzer]

Paul, let me help you here a little.

I see you are trying to help; all of us went through the same process that Chai98a is now going through.
I am sure when Chai98a gets more experienced, he will also help others on this forum as much as he can.


Chai98a, are you using standard 4x7 segments LED display? or it is one of those LARGE ones?

Also, why are you using 74HC ?

Based on your answer, I will post a schematic for you.

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[ardhuru]

With this talk of CC and CA displays, I'd like to share a technique I've used and found very useful.

I like to design PCBs that would work with CA as well as CC displays; the only hardware difference between the two is whether to tie the emitters of the driver transistors to +5 or ground, depending on the display.

So, provide for a jumper that lets you select between the two.

AND, use this signal as an input to the PIC to tell it what kind of display is being used. Keep 2 lookup tables in the code, one for CA and the other for CC; depending on the state of the jumpered signal, the code uses the corresponding lookup.

During production time, then, it becomes easier as one could use either CA or CC, without having to change the code; just connect the common line to +5 or Gnd, and it will work.

Regards,

Anand

[paul borgmeier]

Paul, let me help you here a little.

I do not need help ... the OP does Anyone is welcome to contribute and chime in.

[paul borgmeier]

I do not need help ... the OP does Anyone is welcome to contribute and chime in.

Maybe I do need help - I need to sharpen/review my PNP circuit abilites a bit and will comment soon.

Others welcome to comment.

EDIT:
based on an offlist conversation with another member

[paul borgmeier]

Sayzer - where did you go ... I thought you were helping me here? .

Chai98a,
As Sayzer was hinting at in his "Large" post, if you are using a "standard" common-sized common anode display, you might want to simplify your circuit and follow something like figure 6 of the below link. Your schematic as draw is not correct and makes little sense (to me).

http://picbasic.com/resources/articles/ledart.htm

Is this an option or are you locked into your hardware as shown in your earlier post?

[sayzer]

We had a long holiday here in Turkey.

Sorry Paul. I was busy with my .... (fill in the blank).


I will post some concept schematics, using PNP, NPN and ULN type of drivers.

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[chai98a]

Hi sayzer and paul borgmeier
# Is the the schematic fragment correct?
-see attached
# What is the P/N of Q1-Q4 are they really PNP?
-TR # BC557
# What troubles are you having (i.e., does the display light up (at all)? wrong temp? junk? just missing DP?)
-found Junk display,flash ,missing dp
# Are pins 1 and 19 tied low on U2?
- yes
# are you using standard 4x7 segments LED display?
- we used standard 7 seg.
# why are you using 74HC ?
- I did follow some sample on web