Bridge the two postive pins on the LPC-815?

[YAG]

I really have no idea what's going on in this thing, but it looks like the little rectangular crystal is being pumped by the two little electrodes on either side... I notice that as long as the case pin is negative I can connect either of the positive pins and it'll lase.


But why don't I power both positive pins at the same time? Would it be better to do that?

 

[lasersbee]

Jerry

 

[YAG]

An image I found on google, shows the two pins capable of energizing the crystal gain medium thing.

Another image says to power the diode through only one pin.


SO.... does anyone power their LPC-815 using both pins? Would it improve the diodes performance or anything? It looks to me as though this diode is meant to be powered through both, but it's not like I have a degree in photonics or anything.

 

[lasersbee]

If you look at the closeup of the LD you will notice that there are
2 wires coming off the die... One goes to the left and is attached
to the pin that is identified as positive (+) on the pinout drawing
(that is a rear view).

The other wire comes out towards the right and down and is attached
to the main housing/heatsink which is the center pin identified as
Negative (-)..

I don't see any connections to the pin on the right in the closeup...
so therefore it would not need to be connected... IMO...

Jerry

 

[YAG]

The right side connection in that picture must be different or broken, I have seen diodes where both pins have a lead that comes off and contacts the die, you can power it through either pin. I haven't checked to see if powering it using both increases the max current or anything.

EDIT: I'll have to take a picture sometime soon. Maybe I'm wrong.

 

[jayrob]

Haven't heard of that, but even so, it's best to just stick to the diagram:

 

[Benm]

If you have some oddball diode that has 2 positive leads that power the die, regardless of which one you connect, i would recommend connecting them both: in such case its likely that there are 2 bond wires going to the die, and using both would distribute the current.

Personally i have never seen any laser diode that uses such a contruction though. For red lasers the standard is that the case is negative and one of the leads (as in the diagram) is positive. The other lead is not connected to anything, or sometimes to a feedback photodiode, and has no use with the typical driver circuit.

In an assembled laser, it often IS soldered to the circuit board, but only to provide additional mechanical stability.

 

[lasersbee]

I suppose you could use a DMM set at ohms to see if the "2 positive pins"
are showing zero resistance (both pins tied to the die at the same potential)
or an open circuit (one of the pins floating) like in your closeup photo..

Jerry

 

[GreenLaser]

i thought on my red diode that the case is positive??
pls confirm.
cheers

 

[lasersbee]

i thought on my red diode that the case is positive??
pls confirm.
cheers

Confirm what.....:thinking:
We have no clue as to what LD you have...:undecided:

If you have a red LPC-815 LD then it would be VERY wise to use the
pinouts shown in the above drawings....


Jerry

 

[GreenLaser]

o yeah sorry i forgot most diodes are different. feeww. well if u connect the diode the wrong way to find wich is + and wich is - will it kill ur diode?
cheers

 

[lasersbee]

There is a good chance you may kill your LD if a high enough
voltage/current is applied in reverse...

Jerry

 

[Benm]

You might kill it, but i dont think it's that likely.

Most LD are rated for 5 volts reverse voltage in their datasheet, so with a bit of care you should be able to test polarity without going even out of the specs. But i suspect in practice they will take a bit more than 5 volts reverse before actually breaking down.

Note: the diode-test function on multimeters isnt suitable, as many will have problems with the higher forward voltage of laser diodes (compared to 'normal' silicon diodes).