Continue to Site

Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Seven Segment Circuit Design

Status
Not open for further replies.

patelvimal20

Junior Member level 3
Joined
Oct 11, 2010
Messages
27
Helped
2
Reputation
4
Reaction score
2
Trophy points
1,283
Activity points
1,463
Is it possible to interfacing 8 seven segment with Micro controller using only 16 transistors???

If yes , then please give the idea of this circuit.:roll:



Thanks,


Vimal Patel
 

Here is example for you..........................

HARDWARE FOR EIGHT SEVEN SEGMENT DIGITS INTERFACE

**broken link removed**

Regards
KAK
 

Yes you can using multiplexing

DI217Fig01.gif

you connect one transistor to each input line shown above

Alex
 

And here is the common anode version, using pnp transistors.

 

As you saw on other's reply, only 8 transistors are enough.
Assuming the display is common anode (positive terminal), the solution would become:

Each segment cathode would need just a limiting current resistor.
And each digit would need a pnp transistor (and a resistor or two at its base) to drive the 7 segments (actually 8 with the dot) at each each period of time.

The price of this method is that the uC should update the digits at a higher frequency say 1000 Hz (1ms interval) to get 125 frames/sec.
Also for the same driving current the LED brightness becomes lower because the duty cycle decreases with the number of digits.

But it works... I used it a lot.
 

As you saw on other's reply, only 8 transistors are enough.

You can't be sure of that, you assume that each mcu pin can provide about 10mA and that the mcu can provide a total of 80mA (8 pins combined) when number 8 and the dot is turned on.
Not all MCU can provide that current, an AVR or a PIC can but many others can't like for example NXP LPC2xxx or LPC17xx (ARM based).
So it depends on the capability of the device that drives the displays.

Alex
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Back
Top