Two Lead BiColor LED protection ?

[Delchi]

Reading at scitoys.com/scitoys/scitoys/light/light.html#laser_communicator I noted this little bit of interesting from a parts list for a laser experiment :

"A two-lead bicolor light emitting diode, to protect the laser from high voltage spikes."

After reading up here, I'm not sure this really works as to protecting the laser. Any thoughts?

 

[rog8811]

As far as I remember 2 lead bicolours change colour when you change polarity....like you I don't see how that would protect the LD.

Green led = LD working (and you can see it's beam)
Red led = you have connected your power supply the wrong way round and your LD is knackered


Regards rog8811

 

[Greyfox]

Here's an option for it. Create a parallel circuit in this manner:


X-----+----------+
| _|_
| _\_/_ D1
/ |
\ |
/ R1 |
| [LD]
[LED] |
| |
X-----+----------+


R1: used to limit current through the bi-color LED. (Value depends on LED's operating voltage
D1: IN4001 or equivalent for protecting the LD

 

[rog8811]

I still don't see how that is "using a bicolour LED to protect against high voltage spikes" though :-/

My explanation was just me trying to be funny.

Regards rog8811

 

[Greyfox]

It in itself won't protect a thing. All it does is warn you if you've made a mistake.