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New 505nm Diodes! | newb help

Peter Dodge

Peter Dodge

New member
Joined
Jul 7, 2019
Messages
18
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Hey guys! I recently noticed some cool looking 505nm diodes​

I have wanted to build a laser pointer for a while now, and when I came across this, I just had to do it! I already have two red 200mW pointers and a 405nm violet one (same power, also my first one), and so I have a bit of experience with lasers, but also Arduino and breadboard electronics in general (trying to build a modular synth). Since I don't really know what all the good things are to do to DIY a Laser, I thought what better place than here to discuss it. basically I just want to build a pointer with this diode, and I don't know how to do it, but have the skills to. where should I start?

Thanks!

ebay.com/itm/The-505nm30mw-Green-Laser-Diode-Module-Laser-Generator-For-Laser/264469304760?hash=item3d939955
 





The link is just going to ebay' front page.
If it's from DTR on ebay he's also seller here with a awsome rep.
DTR shows a Sh**p 505 diode but it is "case positive". This might cause issues as far as choosing a driver??
Look at his sight and click on that 505 and he has them as a complete module/driver/lens option.

Member "Lifetime17" is a great host builder and has pre wired hosts with very nice prices. You just connect the wires and slide the module down the host and done.
The only thing i'm not sure of is the "case positive" issues, but i'm guessing it's the host that becomes the positive now rather than the norm negative.

Which ever 505 your looking at make sure of its polarity.. All 505's are not the same.
 
Last edited:
What GSS said. To add to it:

Chances are, the 505 you're looking at is case positive. Only the very first batch of 505's a few years ago were cause neutral... I'm not sure you'll find anybody willing to part with one of those.

With the near certainty of the diode you're looking at will be case positive, it will probably not be as simple as turning the battery around in the host. That depends on the driver. Some drivers only work by limiting current before power is supplied to the diode. If it's case positive, you'll need a driver that can regulate current after power is supplied. I'm aware the lazereer nano drivers had this issue but I am not sure about the others available to us today... perhaps someone else can chime in on that end.

Edit: Or you'll need a host that isolates the diode from it.
 
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Hmmm so then I’m guessing that my best options are going to be to build an unconventional driver, and get the module from DTR’s (I actually have seen this diode in his shop before this) or pick a new diode or do a lot of learning
 
For a pointer now since the linear driver for case positive lasers are no longer available to us you'd be better off isolating the diode from the host. That way you can use whichever driver that meets your needs for current regulation.
 
Good idea, but I think I’ll still do what I can to research it and maybe I’ll try to ask DTR just to verify if they are case positive.

Say I do buy the module, and I find a non-destructive way to power it, what voltage am I going to be working with? Also I’ve heard that the AMC7135 is a good driver. Any of y’all used it? Should I get some?

Thanks for the help
Peter
 
These diodes have a fairly high forward voltage, so it depends on the driver used. All linear and buck drivers will need a voltage greater than the forward voltage of the diode. I would expect to use two Li-ion batteries if in a pointer.
 
I've got a good supply of 18650's salvaged from a couple vacuum battery packs, and only 3 pointers to maintain so far, but if the diode I'm looking at is only around 35mW, then one of them should do fine? Also I recently received a boost converter from one of my Aliexpress runs, so maybe I could use it to prototype the laser.

I did a google search for case positive drivers, and came up with this:
laserpointerforums.com/threads/how-to-wire-case-positive-diode.87011/

in the thread it says that the only thing different is that you have to either isolate the diode from the module or host, or just put in the battery backwards. also I have a DVD burner that has a red diode in it around 100mW, and was wondering how easy it would be to make it into a pointer instead?
 
I do not believe the information in that thread is accurate saying that you can just put the battery in backwards. Isolating it is fine, but you can't just skip powering part of the driver circuit and expect it to work the same.

crude driver.png

If the part of the driver that handles current regulation on the + end, you can't just use the case to skip over it.
 
paul1598419 said:
That generally won't work as the set screw will make electrical contact with the module, so you need to isolate the whole module from the host.
Click to expand...
Use your brain for once Paul. The set screw can be shortened. Gee wiz
 
What!? Maybe if you used a nonconductive set screw you might get by, but a shorter one won't help at all.
 
Seriously Paul? ... -_- I've used plenty of heatsinks with set screws that went well inside the heatsink. I have also seen a few builds on here (a few I can remember from lazeerer) that specifically used an anodized heatsink to insulate the diode module.
 
Seriously! The module would need insulation, otherwise the set screw who connect it to the host. How many of these have you built?
 
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