Maker Pro
Maker Pro

Where could I salvage an LM317 Voltage regulator?

Raser

Sep 10, 2019
1
Joined
Sep 10, 2019
Messages
1
I just joined so firstly, Hello. I am Ben from Cardiff South Wales. I have a question which is what led me to join up:

What everyday appliances (if any) would be likely to have an LM317 voltage regulator component fitted, that I might be able to salvage one from?

I am making a very simple laser diode driver, the circuit is basic and I have everything except for the LM317 voltage regulator. The end result will be a laser trip-wire alarm, and I am thinking of hooking it up to my Raspberry Pi and a camera set-up, for some sort of remote alert system via the internet and my other devices, so if I am out I can see when somebody enters my room and see exactly who it is. I am even looking into facial recognition with Python programming but that is another project on it's own! The laser diodes I have are very power hungry and will quickly burn themselves out if just connected to a power source, so I need to make a laser driver circuit for maximum efficiency seeing as the laser diodes may need to be left on for upto an hour at a time, maybe longer if it works well.

I know they are fairly cheap to buy, at the moment I am a student and will be able to order some in about 2 weeks when I get money in my account. I will definitely buy a few then for future projects, but for now, rather than put my project on hold for almost 2 weeks, I hoped there would be something that uses them which I might be able to salvage one from.

I am thinking that seeing as I am using mine for a laser driver then maybe things like DVD players or burners might use them too.

Any advice appreciated

[NOTE] The image I attached to this post is not mine, but it shows the type of circuit and component I am talking about
 

Attachments

  • Laser_Driver_01.gif
    Laser_Driver_01.gif
    10.8 KB · Views: 24

Audioguru

Sep 24, 2016
3,656
Joined
Sep 24, 2016
Messages
3,656
Modern electronic products use extremely small ICs and a robot is used to connect them to a circuit. Fairly old products used "normal" size ICs that are easy to connect to. I have not looked inside many products so I do not know which ones would have an old normal size LM317 IC.

I hope that your "power hungry" laser does not blind you or a friend. Why not use an LED instead?
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
13,719
Joined
Nov 17, 2011
Messages
13,719
You can use almost any 3 pin linear regulator for such a circuit as long as the current is sufficient for your project.
It will not be easy to find a specific componnet (whichever type) in salvaged appliances.The typical hobyyist does ist the other way round: salvage an appliance and see what's useable in there.
 

dave9

Mar 5, 2017
1,188
Joined
Mar 5, 2017
Messages
1,188
Everyday appliances, none that I can think of. You'd be far more likely to find an LM7805 in something with some semblance of logic control rather than manual switches and mechanical timers.

You seem to be going in the wrong direction with your project. Your laser driver is for 2.5W or higher output which is far too much. That will burn things. You don't even need 100mW.

If you need maximum efficiency then get a proper switchmode driver. Something meant for an LED would work, and probably wouldn't have to cost more than $2.

Two weeks wait to afford an LM317? I think you need a job and a lock on your door instead of this project. ;) You should always have some money set aside for an emergency, enough that dipping in for $2 wouldn't make much difference.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
4,880
Joined
Jun 21, 2012
Messages
4,880
Talk about going off half-cocked! The usual laser diode inside a DVD player has a built-in short focal-length lens optimally selected to focus the laser spot onto the rear surface of the plastic DVD, thereby allowing microscopic "pits" that encode the DVD content to reflect (or not) light back into a separate photo-sensor. A servomechanism inside the DVD player allows the laser/lens/detector combination to be moved a very small distance along the propagation path of the laser beam in order to obtain optimum focus and maximum signal-to-noise ratio. How are you going to modify the existing optics to collimate the laser beam and allow the beam to remain collimated over a significant distance, sufficient to allow intrusion detection? How much power will your photo-optical sensor require to detect the presence of the laser beam? How will you prevent "false positives" caused by brief variations in the laser beam intensity? Most "intrusion detectors" of this type, i.e. garage door obstruction detectors, use an expanded and collimated amplitude-modulated light-emitting-diode (LED) beam NOT a diode laser beam for this purpose. The amplitude modulation allows the detector electronics to "ignore" any received amplitude variations, such as shadows and ambient light fluctuations, that are not coherent with the modulation frequency. Why do you feel a laser diode will better suit your purpose? Are you planning to burn the ankles off of intruders? Do you have any experience with practical optics? Practical electronics? Any experience whatsoever?
 

Harald Kapp

Moderator
Moderator
Nov 17, 2011
13,719
Joined
Nov 17, 2011
Messages
13,719
@dave9 : I deleted the rant previous to your answer as it by no means followed netiquette.
 

dave9

Mar 5, 2017
1,188
Joined
Mar 5, 2017
Messages
1,188
Thanks Harald... Then I better delete mine so it doesn't look like I'm talking to hevans.
 

hevans1944

Hop - AC8NS
Jun 21, 2012
4,880
Joined
Jun 21, 2012
Messages
4,880
@dave9 : I deleted the rant previous to your answer as it by no means followed netiquette.
Thanks, Harald, but I saw it (I think) today in an e-mail by @zayman who posted automagically yesterday, May 6, 2021. It was a really nasty rant, posted on an almost two year-old orphan thread, by someone who joined EP yesterday.

The OP, @Raser, (Ben) posted just once and has not been seen since. Ben was a student with limited funds available for purchasing new parts, even inexpensive one like the LM317 voltage regulator. So, he was looking to "salvage" one from some discarded or defunct appliance. It was quite obvious that he didn't have any understanding of what he was attempting to do (with a laser diode) in his efforts to build a "trip wire" to detect intruders into his room while he was away.

There are dozens of inexpensive ways to accomplish Ben's objective. None of them involve a laser, but we never got a chance to explore any of those alternatives because Ben was a one-shot "drive-by poster" who never responded to comments by @Audioguru, @dave9, or me @hevans1944. Then along comes the troll, almost two years later, to add their useless rant. Oh, well... glad you caught it before I did @Harald Kapp.
 
Top