Why are Diodes needed?

[TecHNooB]

photodiodes make your digital camera work

 

[Gibson486]

What is a transistor? Infrared? You can also use an infrared diode.

The on/off switch. If you shut a diode off, you burnt it.

 

[IndyColtsFan]

The on/off switch. If you shut a diode off, you burnt it.

You're talking about the receiver end. I'm talking about the emitter piece.

 

[brainhulk]

I heart my single ended triodes

 

[KMc]

If I recall, diodes can be used to sense temperature.

Yes, if you reverse bias a diode, you can correlate it's output to junction temperature. This was the old-school way to measure microprocessor core temperatures before dedicated temp-sensing circuitry was used.

 

[Gibson486]

You're talking about the receiver end. I'm talking about the emitter piece.

Diodes do not turn on/off on their own. You need something to control the voltage to it. In the instance of the emitter, you need to put a switch in series with to turn it on/off or it would constantly be on.

 

[Cogman]

Transistors (BJTs that is) are essentially two diodes slapped back to back.

 

[IndyColtsFan]

Diodes do not turn on/off on their own. You need something to control the voltage to it. In the instance of the emitter, you need to put a switch in series with to turn it on/off or it would constantly be on.

Exactly. And how do you suppose that is done with an infrared diode on the transmitter piece?

We're not discussing the entire circuit here, but specific applications of diodes. An IR transmitter in a remote is one such application:

Obviously you see a transistor in the circuit above. You also see a physical switch. That isn't the question though. The question was: what are diodes used for?

 

[TecHNooB]

Exactly. And how do you suppose that is done with an infrared diode on the transmitter piece?

We're not discussing the entire circuit here, but specific applications of diodes. An IR transmitter in a remote is one such application:

Obviously you see a transistor in the circuit above. You also see a physical switch. That isn't the question though. The question was: what are diodes used for?

are you asking how a diode emits light?

 

[IndyColtsFan]

the remote emitter is an infrared diode, the receiver is a transistor with the base exposed to light.

Exactly. That is what I've been trying to say.

 

[IndyColtsFan]

are you asking how a diode emits light?

No, the question was:

What are diodes used for?

I responded with two examples: LEDs and infrared remotes

Someone said "They aren't used in infrared remotes, transistors are."

I said "For the receiver piece, that's true. But I was talking about the emitter/transmitter piece."

 

[WhoBeDaPlaya]

Without diodes (parasitic or otherwise) for integrated ESD protection circuits (HBM, CDM, MM), there'd be no functional consumer electronics.

 

[PottedMeat]

Yes, if you reverse bias a diode, you can correlate it's output to junction temperature. This was the old-school way to measure microprocessor core temperatures before dedicated temp-sensing circuitry was used.

As far as I know this is the only way it's been done. I think they just feed one current, then 10x that current and the voltage difference between the two gives an indication to temperature. They just add to the thermal diode with additional circuitry like a simple a/d converter.

 

[Gibson486]

No, the question was:



I responded with two examples: LEDs and infrared remotes

Someone said "They aren't used in infrared remotes, transistors are."

I said "For the receiver piece, that's true. But I was talking about the emitter/transmitter piece."

NOt what I meant, it was geared more toward your comment that diodes are on/off devices. No need to discuss anymore because its moot now.

 

[WelshBloke]

 

[IndyColtsFan]

NOt what I meant, it was geared more toward your comment that diodes are on/off devices. No need to discuss anymore because its moot now.

Oh, OK, now I see what you mean. Probably poor wording on my part.

 

[thescreensavers]

I am still kinda on the I dont get exactly what they do other then, one way and Convert AC to DC but any how.

So if diodes are one way why is it needed in this rear brake light? You get power in and it goes to LED's theres no power coming back?

that diode9(1N4007) fails on that board and I need to replace it, so I was just wondering this whole thing. since I have no idea lol.

 

[PottedMeat]

I am still kinda on the I dont get exactly what they do other then, one way and Convert AC to DC but any how.

So if diodes are one way why is it needed in this rear brake light? You get power in and it goes to LED's theres no power coming back?

that diode9(1N4007) fails on that board and I need to replace it, so I was just wondering this whole thing. since I have no idea lol.

Guaranteed voltage drop maybe. When forward biased ( conducting current ) there will always be a ~0.6V drop across a regular silicon diode. But they put in resistors too and that would have done the job. Hmm.

 

[Eli]

I am still kinda on the I dont get exactly what they do other then, one way and Convert AC to DC but any how.

So if diodes are one way why is it needed in this rear brake light? You get power in and it goes to LED's theres no power coming back?

that diode9(1N4007) fails on that board and I need to replace it, so I was just wondering this whole thing. since I have no idea lol.

In that case, it is probably reverse polarity protection.

There's also a slight chance they could be using it for the 0.7V voltage drop.

 

[disappoint]

I am still kinda on the I dont get exactly what they do other then, one way and Convert AC to DC but any how.

So if diodes are one way why is it needed in this rear brake light? You get power in and it goes to LED's theres no power coming back?

that diode9(1N4007) fails on that board and I need to replace it, so I was just wondering this whole thing. since I have no idea lol.

Judging by the name Lumileds I'm guessing that's an LED light, the diode is probably there to prevent the LED from burning out if connected backwards accidentally.

 

[PottedMeat]

aren't vehicle light connectors polarized anyway?

 

[SagaLore]

I suppose there is a reason but why?

From what I read a Diode is a one way valve for electricity. Why not just hardwire it in?

Hardwire what in? What are you talking about?

 

[Eli]

aren't vehicle light connectors polarized anyway?

Yeah, but reverse polarity protection is never a bad thing. I hate it when circuits don't include it, especially if they're sensitive.

That said, I have never managed to kill an LED with reverse polarity... but I suppose it's possible.

 

[DrPizza]

IIRC from a trailer harness I had to install once, there was a diode for the brake lights because the turn signal lights and brake lights were "the same." When you hit the brakes, the brake lights would go on. But, without the diodes, when you hit the left or right turn signal, both sides would flash. The stupid little $75 wiring harness went bad once while on vacation. It took an entire pack of diodes from Radio Shack, wired in parallel, to be able to handle the job. Boy, did they get hot.