Drive 4digit 7Segment by PIC16F84A

[myzx]

Can anyone help me how to code to displaying simple multiplex 4x7 segment by using PIC16F84A. Simple, just display 1234 then delay 2second display 5678. Then it loop itself. Sorry i really noob in PIC. Plz.. Thanks

[Brian Griffin]

To multiplex (or "time-share") you must display one digit one at the time, very quickly until your eyes perceive it as looking at all the digits.

Have you started to light up one digit first, and get the segments lighted up correctly?

Also - if you have the chance - use a PIC16F628A which is an improved version of PIC16F84A.

[ZaM]

1. first you must try to ON at least 1 7-seg.
2. then try display 1234 using delay and loop to ON 1 segment on one time with speed that cannot be detect by human eye(blinking if using camera)
3. delay 2 second
4. display 5678 same as step 2
5. loop

[ABSF]

You need 4x PNP transistors for the digit drive (assuming LED is common anode) or else your PIC can get spolied.

Take a look at my board here:
http://forum.cytron.com.my/viewtopic.php?f=5&t=11348

Allen

[myzx]

ZaM:
Only one digit at a time is active, but they change their state so quickly that one gets impression that all digits of a number are active simultaneously. Oh i see.
1.Thanks for the flows. Now i can code it easier.
2.Delay=10ms is it okay to make it blink of d'eye? What you prefer?

ABSF:
1.What you prefer d value for d Transistor the resistor if i'm using PNP Common Anode Transistor?
2.So if im using NPN Transistor so i must use Common Cathode(my output must 1 to enable digit)? While if i using PNP Transistor i should use Common Anode (my output must 0 to enable digit)? Is that right?

[shahrul]

If using Common Cathode 7-segment, you can NPN transistor ex 2N2222 or you can use ULN2803 (transistor array).
Give the transistor high, will activate that 7-segment.
Related video
1. Electronic Dice
2. Timer and Stopwatch

[ABSF]

ABSF:
1.What you prefer d value for d Transistor the resistor if i'm using PNP Common Anode Transistor?
2.So if im using NPN Transistor so i must use Common Cathode(my output must 1 to enable digit)? While if i using PNP Transistor i should use Common Anode (my output must 0 to enable digit)? Is that right?

Exactly. Follow Shahrul's connections and you'll be OK. If you want to use 16F84A or 16F628A, just connect the RB0-RB7 to the segment a-g &dp of the 7-segment LED. Connect RA0-RA3 to the digit driver. Put a 10K resistor on MCLR to Vcc. Dont forget to set CMCON=7; in your program.

Allen

[takao21203]

Hello I saw your post.

It is possible to drive 4digit LED display with some PIC directly, no resistors or transistors.

For instance I made one LED display with serial interface, based on 16f54, no extra parts are used.
The multiplex is 8x, every second phase is blank, and this is also used to clock in data.
However I'd rather recommend hardware serial port for this.

Lately I rather use C, not so much RISC assembly, because poor maintainability.
There is more information in this thread on picvietnam.com
http://www.picvietnam.com/forum/showthread.php?t=9976

Some attachments need login to see them but there are also pictures visible without login.

If you have worry about burnout of PIC, use lower voltage for instance 3 volts.

By the way I clicked the links and saw the stop watch. I started this morning with new circuit which actually, also is a stopwatch. It is based on the new 12f1822, and serial display. Circuit board can be much smaller, and it's faster to build.
I have not yet worked the master interface in Hitech C, only RISC assembly exists
And I want to try some new idea with this circuit. It has 1.2v battery supply.

[ABSF]

May be putting resistors between PIC and 7-segment LEDs are just good practice. I would put them in unless my PCB is short of space. It all depends on indivisuals. I have notice some beginners never bother to put in resistors when blinking LEDs on the SK40C. But as PICs are getting cheaper each day, so who cares...

As a hobbyist, I dont mind to burn a 16F628a or 12F629 but I wont risk the more expensive 40 pin or 68 pin PLCC PICs on this.

Allen

[Brian Griffin]

May be putting resistors between PIC and 7-segment LEDs are just good practice. I would put them in unless my PCB is short of space. It all depends on indivisuals. I have notice some beginners never bother to put in resistors when blinking LEDs on the SK40C. But as PICs are getting cheaper each day, so who cares...

As a hobbyist, I dont mind to burn a 16F628a or 12F629 but I wont risk the more expensive 40 pin or 68 pin PLCC PICs on this.

Allen

Putting resistors between things with lights and microcontrollers is my habit already.

Burning these lower end PICs are not fun - sometimes they are not even cheap! Last time I seen a 16F628a cost like RM8 something...