1301Views15Replies

Author Options:

How to transform pozitive signal into negative? Answered

This may be not clear but let me explain.
If you got postive signal(a power, coming from battery, but its positive = + ) and you want to make it negative ( like coming from negative of battery, = - ) how you can do it. Some kind of tranzistor?
I wanted to use it in LPT port. i getting signal from pin 1(its +) and i want to change it to negative.

Please use picture as example(it's paint drawed, sorry).
picture(mirror 1) (mirror 2)

Comments

The forums are retiring in 2021 and are now closed for new topics and comments.
0
rickharris
rickharris

Best Answer 10 years ago

If you just need to drive an LED then a transistor will invert the input signal. So if you drive an NPN transistor on with the positive input the collector will go negative.

0
dava_2
dava_2

Answer 10 years ago

It's actually led matrix. No, your way dosen't work.

0
frollard
frollard

Answer 10 years ago

Rick is correct. You can drive the rows with one (pnp or npn) and the columns with the other. It would work.

0
dava_2
dava_2

Answer 10 years ago

Here's way I tried which didn't worked: http://i25.tinypic.com/148jgbs.jpg

0
steveastrouk
steveastrouk

Answer 10 years ago

There are no current limiting resistors on either the transistor base or the LEDs.

.So basically you want to turn ON your LEDs when the logic is 0V and OFF when its +5 ?

0
dava_2
dava_2

Answer 10 years ago

No, opposite. I want it on when is 5+, and off when nothing of power.

0
steveastrouk
steveastrouk

Answer 10 years ago

Then wire them as collector loads on the transistor.
LED Anode to resistor, resistor to supply +ve.
LED cathod to transistor collector
Transistor emitter to 0V
Transistor base to 4K7 Ohm resistor, resistor to +Ve supply.
Connect logic pin to transistor base

0
dava_2
dava_2

Answer 10 years ago

On this you said, of coruse, led lits up. What do you think at "logic pin"?

0
steveastrouk
steveastrouk

Answer 10 years ago

Connection to the computer that controls the matrix

0
dava_2
dava_2

Answer 10 years ago

Hmm. Yes, on some logics it should light up. Thanks for support ! I'm marking this as a best answer. I this dosen't working, I will start a question again. Thanks everyone !

0
steveastrouk
steveastrouk

10 years ago

Then wire them as collector loads on the transistor. LED Anode to resistor, resistor to supply +ve. LED cathod to transistor collector Transistor emitter to 0V Transistor base to 4K7 Ohm resistor, resistor to +Ve supply. Connect logic pin to transistor base

0
Re-design
Re-design

10 years ago

He's not changing it to negative. He's using the transistors as switches to turn on an odd the leds.

0
dava_2
dava_2

Answer 10 years ago

Example? Some sketch or something..

0
steveastrouk
steveastrouk

10 years ago

To literally turn say +5 into -5 relative to the same ground, you need to use something like an ICL 7660

0
dava_2
dava_2

Answer 10 years ago

Something simplier? I would need 8 of those then.. For example: some guy here(http://www.jbprojects.net/projects/led/) done it with some tranzistors...