# Basic 7 segment display circuit

Discussion in 'The Projects Forum' started by ESSO, Mar 23, 2015.

1. ### ESSO Thread Starter New Member

Feb 14, 2015
15
0
Hi All, I am looking for a very simple 7 segment displays to do with my kids to "spark" interest in electronics.
I have some electronics components, (The displays(2), transistors, capacitors, some diodes and maybe some useful chip) I also have a Variable Power Supply. I tried to search but I need some something as simple as possible.. thanks..

2. ### GopherT AAC Fanatic!

Nov 23, 2012
6,305
4,029
You need a you need a way to pulse the circuit (push button)
- a 4-bit counter with binary-converted-to-decimal output
- a bcd-to-seven segment converter
- 7-segment display
- about 7 resistors (330 ohm)

A few 0.1 uF capacitors ,

A 330 uF capacitor

Some wires to go from power supply to breadboard.

This gets you one digit. More digits gets more complicated.

Jul 18, 2013
10,838
2,512
Electronic dice?

Max.

4. ### ESSO Thread Starter New Member

Feb 14, 2015
15
0
Thanks, I have the breadboard and jumping wires and all that stuff,

I found the 555 IC,

from the schematic above what are the following components

3K3 -?
4K7 -?
100R-I assume these are 100 ohms resistors

and what is the bar connected to the 1K resistor and the bottom transistor?

I will have to buy the transistors I have other ones ,but they did not matched the numbers
and the push bottom and diode

thanks

Gera

5. ### GopherT AAC Fanatic!

Nov 23, 2012
6,305
4,029
3K3 -?
4K7 -?
100R-I assume these are 100 ohms resistors

The 3k3 means 3.3k ohms (3300)
That way, no decimal point is needed. Old data books were not so clear and a missing little decimal screwed up a project. A little confusing until you get the hang of it.

2R2 would mean 2.2 ohm
2M2 is 2.2M ohm.

6. ### MrChips Moderator

Oct 2, 2009
12,625
3,451
FYI

1.
The TE555-4 is not the same as a 555 timer circuit. The TE555-4 is a preprogrammed Microchip PIC mircontroller.

2.
3k3 stands for 3.3kΩ resistor. This is an accepted way of documenting resistors since the decimal point could be easily missed in documentation, especially when documents have been copied repeatedly. Similarly 4k7 is 4.7k while 100R is 100Ω.

BTW R100 would be 0.100Ω, the same a R10, that is, 0.10Ω

3.
The dark line is a poor way of indicating that this is the same line as the power supply on pin 1 of TE555-4

4.
BC557 is a general purpose PNP transistor. You don't have to find exact components. 2N3906 would do, for example.

absf likes this.
7. ### GopherT AAC Fanatic!

Nov 23, 2012
6,305
4,029
That's not a typical 555.

It looks like a programed Microcontroller. TalkingElectronics.com made up a few different gimmic timers, one for stepper motors, one foe a 10 segment display, this one and one more (package name TE555 (plus one more digit).

Kind of a false expectation for someone with a real 555 timer looking for a project.

absf likes this.
8. ### ESSO Thread Starter New Member

Feb 14, 2015
15
0
Good learning guys, I learned electronics long time ago, but i never seen that notation before (or dont remember) plus I did not continue in the field until now that i am taking classes again...

In this case, I will order the TE-555-4, the push button and
will double check on resistors from my previous kit.

Thanks again..

Gera