Hello, i am new to the forum because i am looking for help. The general concept if my design is to detect a red dot laser (620-670nm wavelength). I have tried photo resistors, but the 5mm surface area is too small. I have considered using a raspberry pi, pi camera, and using recognition softwhere to identify the where the dot lands, but that costs more and requires a bit of coding. Anyone have any thoughts? I deal with AC voltage equipment so my knowledge bank with dc components is not great.

Thank you!

 

hi BOR,
Do you just want to detect the dot on the sensor or its position on a flat area sensor.?
E

 

The problem you face is a LASER diode emits a very narrow beam and detecting devices have a very narrow area of focus. Unlike a for example a TV or similar transmitter which emits a modulated IR signal over a wide beam with its receiver. I do not know of any LASER receiver module which can detect a beam in the general area.

Ron

 

hi BOR,
Do you just want to detect the dot on the sensor or its position on a flat area sensor.?
E

Well, with the camera i could detect its position, but id assume with a sensor I would have to detect if it just hits the sensor.
I wrote code for a 16 channel multiplexer to test 16 photo resistors, but I felt if 16 points of contact is combersom unless they can be larger than 5mm

 

Why are you doing this? What is the problem you are trying to solve by sensing the laser?

 

The problem you face is a LASER diode emits a very narrow beam and detecting devices have a very narrow area of focus. Unlike a for example a TV or similar transmitter which emits a modulated IR signal over a wide beam with its receiver. I do not know of any LASER receiver module which can detect a beam in the general area.

Ron

Given your user name, would be familiar with a product "Laser Ammo Interactive Multi Target Training System i-MTTS"? The use a green light to as a base and some how when the red dot hits the target, the sensor triggers a reaction. The only issue i have with this setup is that the position doesn't matter, but if I could understand the basics of what it is reading, maybe i could figure out a way to make something different.

 

Why are you doing this? What is the problem you are trying to solve by sensing the laser?

I'd like to make my own in home target practice system / game.

 

I'd like to make my own in home target practice system / game.

Are you looking to reproduce something like this? It uses an app running on a mobile phone and the phone's camera to spot the hits. Are you planning to make your own gun, or dry fire a real one?

 

Are you looking to reproduce something like this? It uses an app running on a mobile phone and the phone's camera to spot the hits. Are you planning to make your own gun, or dry fire a real one?

So im looking to dry fire, but i dont want to use my phone on a tripod to capture to hit. I'd like to be able to have everything on board i can hang or a stand i can place on a table. I think the camera is the better way to go for positioning.

 

So im looking to dry fire, but i dont want to use my phone on a tripod to capture to hit. I'd like to be able to have everything on board i can hang or a stand i can place on a table. I think the camera is the better way to go for positioning.

I do think that the camera is the best idea. The OpenCV framework for Python will make things much easier. There will still be a fair amount to learn, though.

I was thinking of a scheme where you use frosted lucite rings for the scoring zones and put detectors, probably more than one per ring, behind them. A hit anywhere on the ring will light the whole ring up. Adding opaque barriers between rings would prevent false activation of adjacent rings.

I still thing the camera is better. It would be kind of cool if the target was presented by the RPi on a small HDMI monitor so it could show the hits immediately on the target.

 

The lucite idea may not be bad if I want it stand alone.

I'll try messing around with the pi again. Maybe i will go that route. Then I could do so much more.

Thanks for the feedback.

 

Given your user name, would be familiar with a product "Laser Ammo Interactive Multi Target Training System i-MTTS"? The use a green light to as a base and some how when the red dot hits the target, the sensor triggers a reaction. The only issue i have with this setup is that the position doesn't matter, but if I could understand the basics of what it is reading, maybe i could figure out a way to make something different.

While I have seen the LASER sighting systems I have never played around with one. Just not sure how the targets work. I will be disappearing for several days but for those who may wish to help:

This is the target system.

This is an example of the cartridges used. Cartridges are chosen for the gun you wish to practice with.

Yes, you did get it right based on my username and avatar. Electronics was my long time living and the shooting sports have been my forever hobby. Retired now. Not from the range though!

Ron

 

actually for 'laser dot' detection, I've thought about such as scheme, if you control that laser (diode) after all, simply take a picture with the laser off and later on, the differences between these 2 images is probably that 'laser dot'. of course, this is just 'theory' and either way it requires a good camera (and optics) and image sensor.

 

If 5 mm is too small, what isn't? What are your minimum and maximum desired target sizes?

Also, is the laser beam modulated so it can be differentiated from background illumination?

Consider a small aluminum funnel with a phototransistor (not photoresistor) down in the hole. Or an array of such sensors. Long ago I did a project with a group of 2" diameter funnels, each bent into a hexagon shape. They fit together like a honeycomb, with very little space between the apertures, sorta like a phased-arrray radar.

ak

 

actually for 'laser dot' detection, I've thought about such as scheme, if you control that laser (diode) after all, simply take a picture with the laser off and later on, the differences between these 2 images is probably that 'laser dot'. of course, this is just 'theory' and either way it requires a good camera (and optics) and image sensor.

My idea was to simple live stream the image and have the code sense the appearance of the red dot and capture that moment for records.

 

If 5 mm is too small, what isn't? What are your minimum and maximum desired target sizes?

Also, is the laser beam modulated so it can be differentiated from background illumination?

Consider a small aluminum funnel with a phototransistor (not photoresistor) down in the hole. Or an array of such sensors. Long ago I did a project with a group of 2" diameter funnels, each bent into a hexagon shape. They fit together like a honeycomb, with very little space between the apertures, sorta like a phased-arrray radar.

ak

5mm is tiny when you are standing 15-20 feet away. You're accuracy to hit that small of target consistantly would be incredible.

I have thought about doing arrays, but like I discovered with the multiplexer, it requires far too many gpio pins on a microcontroller to build a large enough array.

 

Another sensor option is a small circular solar cell. They come in different diameters.
Something like this.

 

A large corner reflector panel would reflect the beam straight back to the gun. Place one photo transistor under the barrel. To protect your eyes, modulate the beam and reduce its power.

https://www.ebay.com/itm/132368552058?hash=item1ed1c7d07a:g:~ywAAOSwWLBZ6HST

ak