Opinions on displaying COMPUTER on seven segment display

[lijehy03]

good day!!
any one who can help me with my design?
my design is to use a seven segment and to display the letters COMPUTER ,right now i investigate how to use 74LS47 as a decoder, but my proble is what IC should i use in order for me to have an output letters that once you turn on the circuit it will show the letter COMPUTER and after a few second it will fade little by little until it will dis appear and after about 3 seconds it will again visible and little by little show its maximum light, and repeat the process again and again......
can any one please help me...

 

[IanP]

Re: seven segment

I am not sure how are you going to address letters such as M and T with 7-segmanet display - maybe you should consider, say, 3 LED per segmant and build the display of discrete LEDs ..

Anyhow, I wouldn't use 7447 decoders at all ..
Instead, I would connect Anodes of segmants (or diodes) that you need to illuminate through current limiting resistors to + supply and Cathodes to one NPN power transistor ..
This transistor can be driven by a small microcontroller and to achieve the dimming effect you can implement PWM (pulse width modulation) procedure ..

Regards,
IanP

 

[the_risk_master]

Re: seven segment

Can you post the circuit, I can help you

but...

Im very sure, you cannot display all the letters using a 7-segment disp.
I advise you to use a dot matrix LCD (It is also cheap though)

 

[rkodaira]

Re: seven segment

Using 74LS47 as a decoder, ables you to show only numeric hexadecimal digits (i.e. from 0 to 9 and A B C D E and F letters). You cannot show the letter M (or m) with seven segments displays. Letter T can be done activating segments d, e, f and g (a "t") but it doesn´t solve your problem. There is a kind of led display with 16 or 20 (I´m not sure) segments (a square with a cross and x inside) that is suitable for you. The better option to decode it is using a microcontroller.

 

[Slemi]

Re: seven segment

You might even use 5x7 dot matrix LED display. Just as an option.

 

[Rainbow00]

Re: seven segment

about the dimming part, a simple direct way to do is to control the current passing through the led or whatever by multiple transistors. let say 10mA will make the led bright enough. then you can choose 10 transistors to source the current. when all transistors are on, it is at brightest. when one transistor is turned on, the led are least bright.

notice that human eyes judging the brightest of led is not leaner. so you can make the transistors source different current. try it out. it will be fun.

regards
gd

 

[bigaussie]

Re: seven segment

Hi there,

Firstly you will need alphanumeric displays having 14 segments.

to display computer you will need 8 such displays each showing a letter.

then for each character display, find out which segements are required to be turned on.

hardwire all segments (on) with each having a series resistor, connect other common terminal to a transistor. then controll transistor with a triangular wave to get you required effect.

big aussie

 

[dindeds]

Re: seven segment

If you want to turn the display the letters permanently its better and cheaper to use individual LEDs arranged as whatever letter you want. Power all through proper dropper resistors and drive them from transistors buffers.
You can hv a flip-flop (or 555 timer) to drive the transistors to get the effect you want.

 

[yogi]

seven segment

**broken link removed**

Bibin John
www.bibinjohn.tk

 

[jason99pan]

Re: seven segment

My thought about the fading problem is maybe you can increase the driving capability of the led.

For example, maybe you can use buffer ic for doing this.

Hope it can help you...

If I am wrong, please correct me...

 

[yogi]

seven segment

fading occurs due to variation in power supply. Use a good power supply like SMPS
http://www.geocities.com/njbibin/robo7b.html


see buffer also require a power supply and the amplification is just current amplification and everything depends on the main supply voltage


Bibin John
www.bibinjohn.tk

 

[electronXwork]

Re: seven segment

I think you dont need to use a decoder anymore. Each display represents only one letter of the word COMPUTER so there is no need for decoder just bias the corresponding LED of the display correctly. Unless u will use more than one character for each display then thatz the time to use decoder. Like for example if you want to make the word COMPUTER a looping or rotating string.

For the effects, if it is possible to make a sinusoidal power supply w/ very low frequecy will do. during the first half cycle as the voltage of the supply increases there will come a point that the LED will ON but w/ dim light but brighter n brighter as the voltage also increases.Then it will dim again as the voltage decreases. during the 2nd half cycle or negative cycle the LED will reverse bias so they will stay OFF. The off time depends on how long the neg cycle is plus the time on the pos cycle when the LED turned OFF.

This is jz my opinion please someone correct me if Im wrong.....

 

[rajeshbij]

Re: seven segment

For fading effect : vary the current to the 7 seg by varying resistance in the path. You may use a digital pot or simply if u r using a micro use a port to select/deselct various resistors. Hope u got my idea.

 

[nishal]

Re: seven segment

Hi,
You can try serial interfaced 8 digit led driver with pwm which can be used for controlling the brigtness.

Visit the webpage at
http://www.austriamicrosystems.com/03products/products_detail/AS1100/description_AS1100.htm

or for more at their products page

Hope this helps

Nishal