Running led using positive and negative voltage

[renzen]

Is it possible running led using positive and negative voltage?
example: 1.5v and -1.5v running 3v led

If possible, both current from 1.5v and -1.5v must same?
example: 1.5v 1A and -1.5v 1A running 3v 1A led.
What happen if the current not same?

and is it possible running led using positive and negative voltage with constant current?

 

[ronsimpson]

Why?
It is possible to connect the LED from +1.5V to -1.5V, using constant or not using constant current. The current will be the same! If you put 1A in to the (+) lead then you will have 1A in the (-) lead. No choice.
Why?

 

[audioguru]

If you connect a 2V red LED to +1.5V and -1.5V in series (3V total) then the LED will blow up since nothing will limit the current.

 

[alec_t]

..... and there is no such thing as a '3V LED'. LEDs have manufacturing tolerances; so the Vf of a LED which is nominally 3V may in fact be 2.8V, or 3.2V, or ....... That's why it's important always to use a controlled current source or a current-limiting resistor in series with a LED to prevent it cooking.

 

[renzen]

audioguru
In bridged amplifier, both amplifier must identical.
In led, both power supply must identical too?

 

[audioguru]

audioguru
In bridged amplifier, both amplifier must identical.
In led, both power supply must identical too?

The LED does not know that you have two power supplies. It sees only 3V. It does not see +1.5V and -1.5V.

Maybe you have two alkaline AA cells in series to total 3V. It might be +3V and 0V or +1.5V and -1.5V or 0V and -3V and the LED works exactly the same.

 

[Ratchit]

Is it possible running led using positive and negative voltage?
example: 1.5v and -1.5v running 3v led

Do you mean AC?

If possible, both current from 1.5v and -1.5v must same?
example: 1.5v 1A and -1.5v 1A running 3v 1A led.
What happen if the current not same?

Oh oh, I don't think you know how a LED works. First and foremost, a LED is a diode, so current exists in only the forward direction. Very little charge will flow in the reverse direction.

and is it possible running led using positive and negative voltage with constant current?

Read what I said above.

Ratch

 

[renzen]

Do you mean AC?



Oh oh, I don't think you know how a LED works. First and foremost, a LED is a diode, so current exists in only the forward direction. Very little charge will flow in the reverse direction.



Read what I said above.

Ratch

Yes, I only know a bit about electronic
I don't know if it's call AC or DC.
I have a 3A led with typ 18V (min 17V and max 19v) and will put into my motorbike for off road. And I have a -5V 1A power supply.
If it's possible running led with positive and negative voltage, I don't have to buy expensive 3A boost switching led driver.
The motorbike produce around 13V when engine on. With -5V, total 18V. Now the problem my -5V power supply is only 1A.
That's the reason I'm ask a noob electronic question.

So... will it work?

 

[alec_t]

So... will it work?

No, it won't. If the LED assembly needs 3A at a nominal 18V then your -5V supply won't be able to provide 3A. The LED current would have to flow through both the 13V and -5V supplies.

 

[Ratchit]

Yes, I only know a bit about electronic
I don't know if it's call AC or DC.
I have a 3A led with typ 18V (min 17V and max 19v) and will put into my motorbike for off road. And I have a -5V 1A power supply.
If it's possible running led with positive and negative voltage, I don't have to buy expensive 3A boost switching led driver.
The motorbike produce around 13V when engine on. With -5V, total 18V. Now the problem my -5V power supply is only 1A.
That's the reason I'm ask a noob electronic question.

So... will it work?

OK, so the "LED" is actually a LED assembly that takes 18 volts at 3 amps. And you want to connect the two voltage sources in series? You should be more specific in your description. A problem well defined is a problem half solved. The 3 amps will need to be present in both voltage sources, so that disqualifies the -5 volt supply for consideration. And don't forget that the voltage sources have other current loads also.

Ratch

 

[audioguru]

I have never seen a 54W LED searchlight. Maybe they are used on jetliners.