fast horses

Thread Starter

barrelracerdad

Joined Jan 29, 2010
92
Would this type of sensor be more forgiving as to collection? It seems a little larger (about 1/8"x1/8") with the focusing lens already attached.
 

BMorse

Joined Sep 26, 2009
2,675
You mean a laser detector for vehicles? If that's the case, it would depend on the type of laser they are using and what band.....
 

Thread Starter

barrelracerdad

Joined Jan 29, 2010
92
Yes, a vehicle detector. Are they sensitive to visible laser light? How do you know what band they detect? Did you have any other ideas about a different sensor? Maybe a larger CDS? The cone thing didn't work very well (but my cone was pretty crude, maybe with some refinement?)
 

BMorse

Joined Sep 26, 2009
2,675
Yes, a vehicle detector. Are they sensitive to visible laser light? How do you know what band they detect? Did you have any other ideas about a different sensor? Maybe a larger CDS? The cone thing didn't work very well (but my cone was pretty crude, maybe with some refinement?)

I would try to find a replacement CDS first, possibly with a much larger surface, but not too large, cause then you might run into an issue of not enough light to cover the CDS detection area to trigger it.... unfortunately this is one of those "Goldilocks and the 3 bears" type of thing ;), where you just have to keep trying each bowl until you find the right one for you.....

B. Morse
 

BMorse

Joined Sep 26, 2009
2,675
We weere discussing a photvoltaic sensor earlier, did you have any further revelations pertaining to that?
Yes we were, you could use a PV, but like I had mentioned, we would have to use some kind of amplifier for it to be to get any usable signal out of it to switch the transistor.... We could try to utilize the 741 op amp amplifier I posted earlier in this thread, but then the power supply becomes an issue since a 741 works best with 12 to 14 volts as a power source........ Let me dig around my "lab" this weekend and see what I can find to use with your battery supply now....
 

Thread Starter

barrelracerdad

Joined Jan 29, 2010
92
Did you happen to look at the spec sheet for the silicone photodiode, I know you said they were pretty small also, but the casing and shell may serve to reflect and contain the laser light better than a cds (maybe?) and the is a package of 8 on e-bay for 20 bucks and free shipping. I would like to try one first to see if they work better, but from digikey they are about 11 dollars a piece. I was also wondering about arraying 4 or 5 sensors in a patter, but maybe there would be too much resistance? Your thoughts?
 

Thread Starter

barrelracerdad

Joined Jan 29, 2010
92
As I was searching for sensors, I cam across a laser tag set. Did they actually use laser energy or were they just an IR detector (for safety reasons) Back in days of old (but not too long ago) we had the MILES laser systems for our M-16/M-4s for training. That was not a visible beam laser, but the sensors could pick up laser energy very easily from 300-400 meters. What do they use for sensors/detectors?:confused:
 

BMorse

Joined Sep 26, 2009
2,675
by the way, what is the housing of the sensor made off? Does it have a lens? (Can't really tell from the pics).... I was just noticing how the red laser seems to make the inside light up.... what if you used something like white in the inside to help illuminate it more, or some kind of diffuser on the opening to disperse the light around more in the hole evenly.....hhmmmm.... do you have any thin Plexiglas laying around? (the transparent plastic they usually use for screen doors and such)

If you can find a piece of it, just enough to cover the sensor with some overlap (basically we want to increase the surface for you to aim the laser on to with less precision to get it to trigger, hopefully), and get some sandpaper (80 to 100 grit would work) sand one side of the Plexiglas, make sure you sand it evenly all over the surface, but sand it with a circular motion.... sand it until it looks opaque and you can not see through it..... now take some foil (aluminum foil), just a small strip of it to wrap around the piece of Plexiglas, make sure the shiniest side of the foil is facing towards the piece, tape it in place. (this will serve as a reflector to reflect the scattered light beam back across the diffuser (piece of Plexiglas)).... now mount this in front of the CDS, about 1/32" to 1/16" from it. now when you shine the laser beam onto the piece of Plexiglas, it should diffuse it and scatter it "evenly", with any luck the diffuser will be lit evenly across no matter where on the plexi you aim the beam, (although it will still be brighter where the beam hits, but it should be bright enough accross to trigger the CDS....)


My .02
 

BMorse

Joined Sep 26, 2009
2,675
As I was searching for sensors, I cam across a laser tag set. Did they actually use laser energy or were they just an IR detector (for safety reasons) Back in days of old (but not too long ago) we had the MILES laser systems for our M-16/M-4s for training. That was not a visible beam laser, but the sensors could pick up laser energy very easily from 300-400 meters. What do they use for sensors/detectors?:confused:

Those laser tag systems worked off of a modulate IR emitter/detector pair....

Those Miles systems I believe worked off of some type of high ouput IR, or a type of laser not visible to the naked eye.... but those also used some pretty fancy circuitry and optics......

and here... I tried that Plexiglas thing I mentioned earlier during our cross posting, and it seemed to stabilize my CDS output a little more, I did not notice as much jitter from the same distance as before... and here are a couple of pics of what it looked like with the Plexiglas diffuser in action ;)

this is before I diffused (sanded) the Plexiglas...

Laser Non Diffused.jpg

this is after.... you can see the triangular pattern I sanded into the plexi being illuminated by the laser beam, this was not sanded very rough either, the deeper the "scratches" in the plexi, the more light it will capture.....
Laser Diffused.jpg
 

Thread Starter

barrelracerdad

Joined Jan 29, 2010
92
I will give it a try, my housing is a plastic IR sensor shell from a garage door opener. It does have a lens on it, I think it is a colimating lens, when you shine light at it it makes the laser spot larger. (conversly, when you shine light from the inside out it makes a more focused beam. Back on subject, how thick should the diffuser be? I have some 1/8" polycarbonate sheeting laying around, and I think I may have some 1/16" lexan somewhere? And the outside diameter should be about 1/2" or so?
 

BMorse

Joined Sep 26, 2009
2,675
I will give it a try, my housing is a plastic IR sensor shell from a garage door opener. It does have a lens on it, I think it is a colimating lens, when you shine light at it it makes the laser spot larger. (conversly, when you shine light from the inside out it makes a more focused beam. Back on subject, how thick should the diffuser be? I have some 1/8" polycarbonate sheeting laying around, and I think I may have some 1/16" lexan somewhere? And the outside diameter should be about 1/2" or so?

Can you flip the lens over to see if this makes a difference? you might be able to focus the beam onto the sensor more..... just something else to try....


As for the lexan, polycarbonate or whatever you have, 1/8" sounds perfect. make the size roughly 2 to 3 times larger than the surface of the sensor.

B. Morse
 

Thread Starter

barrelracerdad

Joined Jan 29, 2010
92
Pretty catchy title, no? This has been a fun project and I couldn't have done it without all your help.:) I am going to try to line the inside of the detector shell with foil and install the diffuser, I will let you know.:D
 

Thread Starter

barrelracerdad

Joined Jan 29, 2010
92
Another question I have concerns IR lasers (which I only now just saw on ebay) Would a garage door detector (IR) pick up the laser IR? Then I wouldn't have to rewire the detector side at all. I have lots of old garage door openers laying around for parts and stuff. (my wife calls this junk, by the way) Aside, I do a lot of door installation including garage door openers, mostly because I own a big scissorlift. Anyway, the sensor output and input of most door openers is about 3 volts. And the detectors don't need to be aimed so precisely and aren't affected by vibration(jitter) They may have a diffuser behind the lens or the lens focuses the light onto the IR detector. It would seem that such a detector would not be subject to ambient light, and be easier to aim at and it has a cool LED on the side that says when it it recieving a good signal. They also trigger when the beam is broken, which is the result I am looking for. What do you think?
 

BMorse

Joined Sep 26, 2009
2,675
Is the range for something like that going to be suitable for your needs?? How far apart do you need the laser and receiver?
 
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