how can i make a cheap/efficient/lightweight laser receiver

[Josh Inouye]

hi,
I am currently working on a project with some friends and i was wondering if you could help. we want to make a laser tag game for RC planes. we in vision that if you flip a switch you fire a laser. If you hit the plane in the right wing then the right wing would not work on if it is hit enough this same concept wold apply to the other parts of the plane as well. so i guess my question is is their a way to use a laser and make a laser receiver that is relatively cheap, efficient and lightweight. thanks.

 

[chuckey]

To get maximum range you must switch your laser on and off rapidly (100 - 40,000 times a second), this is so the detected signal can be amplified more easily and light from the sun ignored. This also gives you the choice of different channels.
In the aircraft, you need a photo diode then an amplifier with a suitable filter tuned to your transmission frequecy. The out put from the amplifier can be turned into DC to operate a relay.
I do not know what sort of range you can expect.
Frank

 

[Josh Inouye]

Thanks this was very helpful.
Josh

 

[Josh Inouye]

Where can I buy or how do I make a small photodiode laser sensor. Thanks.
Josh

 

[G4BCH]

You could try starting here https://modulatedlight.org/optical_comms/optical_index.html
and here https://sites.google.com/site/g3xbmqrp3/optical for some ideas

 

[Josh Inouye]

I was wondering about photodiode laser receiver that is small, lightweight, and cheap to make or buy. Thanks any way.
Josh

 

[G4BCH]

You do not need ll the lenses that are needed for long range communication. Some of the receiver circuits are failry simple just low oise amplifiers connected to photo diodes.
You could also try looking at TV remote control circuits for ideas. They are simple enough. What ever you do you will need to use quite a lot of power at the transmitter end to overcome ambient light levels and the distance between the aircaft. The photo diode is a small target so if you use a laser it will need a beam expander first to make it eye safe and second to get the beam wide enough that it will be possible to hit the photo diode.
Peter

 

[Josh Inouye]

Thank you for the info and do you think I could have multiple photo diodes acting as one. So it is easyer to hit with a laser?
Thaks for all the help,
Josh

 

[G4BCH]

I'm not sure it would help much to increase the area that can be hit by the laser. If you pointed them in different directions so that they covered a larger area of sky, that would help. I would not wire them all directly together, that would loose sensitivity, each one would be better off with its own amplifier.
The size of the laser beam at the target needs to be quite large when you consider the relative movement of the aircraft and the accuracy that you could point from a radio controlled model. To make a game you do need to have a reasonable chance of hiting the target.
Peter

 

[Josh Inouye]

Would it be easyer just to have one large photo diode instead of multiple ones and a single laser because all of this has to fit on a RC airplane.
Josh

 

[G4BCH]

You will need to check the directivity of the photo diodes to determine how many you will need, they do not cover a 180 deg hemisphere. You will also need a sensor on each side of the wing.
Peter

 

[Josh Inouye]

Thanks
Josh