2 inch 7segment display.

[D.A.(Tony)Stewart]

THe exact part number is essential for the LEDs

 

[tapu]

Dear all,
Again problom in project.I designed as attached below.two mcu 89S52 have damaged.anode driver pins shorted.how to design perfect circuit.

 

[KlausST]

Hi,

It is quite obvious:
1) The transistor emitters are connected to 9V. So the voltage at the base is about 8.4V. Way too much for the microcontroller.
2) current limiting resistors at the base are missing.
3) depending on display type the voltage on the segment controlling pins of the microcontroller may be pulled higher than VCC.
4) current limiting resistors in the segment lines are missing

Klaus

- - - Updated - - -

Hi again,

You could avoid about 25 crossings in the segment lines just by shifting them...

Klaus

 

[tapu]

dear sir, large voltage on controller can avoid by base resistor?? Here display is 2.3" inch size.it requires 7.5v.

 

[KlausST]

Hi,

dear sir, large voltage on controller can avoid by base resistor??

No, you should not solve only one issue, but you should solve all the issues.

Klaus

 

[tapu]

Hi,
I am using330 ohm current limiting resistor in segment port.& 1 k ohm base resistor.is it right?

 

[KlausST]

Hi,

I am using330 ohm current limiting resistor in segment port.& 1 k ohm base resistor.is it right?

I don´t know if the values are correct...
But this may only solve issue 2 and issue 4.
Issues 1 and 3 still exist.

Klaus

 

[tapu]

Then how to solve these issues.any hints.

 

[KlausST]

Hi,

there are dedicated high side (power) switches. They can switch higher voltage than 5V, but are controlled with TTL levels.
Sometimes they are solw. Check speed.

Klaus

 

[tapu]

Can I use TIP122 for switching?

 

[KlausST]

Hi,

Can I use TIP122 for switching?

Yes you can.

But what of the above issues does it solve?
--> None.

Klaus

 

[MrCarlos]

Hello tapu

Repeatedly it mentioned they are required electrical characteristics of your 2 Inches 7-Seg. Display.
What has the identification number Display. ??.
If you do not find data sheets we will have to experiment to get what current required to turn ON these Display and the Voltage drop per segment when it is crossed by the current.

Why ?
Because current limiting resistors for the segments is calculated as:
Rx = (VCC - VF) / IF.
Your VCC Is 9V, According The Las image attached in Your Message #22.
VF, according Your message #24 You Say: Here display is 2.3" inch size.it requires 7.5v.
VF I Assumed to be 7.5V.
IF completely unknown.
So we can not move forward with help.

For these calculations You have to take into account the voltage drop across the collector-emitter junction of transistor you are using, when it is saturated. This parameter is called VCE(Sat).

Some questions for you:
Why you remove the ULN2803 IC that look in your original design ??
Who guarantees that the port3 of the AT89C52 can manage your display directly ??
You know that power can provide that port3 ??
Check, please data sheets AT89C52.
you will see that even says, in them, Not Recommended for New Designs.

Check out the PDF document that I attached (5623852400_1447828368.PDF).
In it you will see the missing resistances.
On the buttons, you must put resistors, called Pull-Up.
Or through your program, you program them.
Externally they could have a value of 10K.
These pull-up resistors are required for, when the button is open, a high level feel port1

 

[tapu]

Dear sir , I will use uln2803 again.but here the problem 8v is observed on base.how to avoid it.

 

[MrCarlos]

Hello tapu

Oh you will use again the ULN2803, Good.
But: on which Base you observed 8V ??. . . on Q1, Q2 or Q3 ??
Probably with a resistor in series with the base.

I've noticed that you do not like answering my questions. but would you like I answer yours. Any way.

May I see Your actual code for AT89C52 and also your actual circuit ??

 

[KlausST]

Hi,

I apologise for the folowing words. They won´t solve the technical problems.
But I think they can help to speed it up.

I've noticed that you do not like answering my questions. but would you like I answer yours. Any way.

Good point.

--> Giving feed back tell us you you appreciate our help.
This motivates other users to help you too.

--> Please give complete informations.
A one line post often is simply not enough to describe a circuit or a problem.
Tell us where and how you want to use the TIP122..a picture is always a good way to do this.
Else we have to ask and ask..

Klaus