Infrared blink to Photoresistor

[koossa]

I want to send a single blink, over a distance of about 100m, from one PIC to another, using Infrared LED on the one a photo resistor on the other side (just 1 single blink)
Will I be able to receive this blink from the Infrared LED on the Photo resistor, if not what alternatives are there or how could I accomplish something similar?

What I want to do is just send an alert from one pic to another as cheap as possible.

[mackrackit]

Laser

A LED will never make 100m.

[Jumper]

Well...

A LED can easily go 100 m if you put an external lens infront of it. Use an old magnify glass and move it away or closer to the led and you will see where it is in focus. (use a red LED and it is really simple to see where you get a nice beam)

The lower mangnify the further away from the led the lens will be.. and the more narrow the beam will be.

Big and bulky? Yes, definatly

Easy to build the receiver since you can use a normal IR receiver that is built to detect modulated IR light.

Laser, for getting a reliable signal you will need to modulate the laser (same as for the led). Some laser modules have soft-start chips and are not that easily modulated.

If you really want to use laser and dont want to modulate it, put the receiver in the bottom of a longer pipe where is it always in the shadow.

[koossa]

Hi Jumper, thank you very very much!!!!

So I have to modulate an IR LED and IR Receiver?

There isn't a way to just use an IR LED, through a magnifying glass in a pipe, put it high for a couple of milliseconds and monitor a photo resistor on the receiver side, also in a pipe?

[Jumper]

I think you have missunderstood me a little.

Pipes are great to use to build this kind of things. You should be aware that normal coloured PVC is transparent for IR so you will need to have either black PVC or paint the pipe.

Of course you can try using a LED and a photo resistor. If it works in a reliable way good for you, if it doesnt there are a few options down the road that can help. Modulation is really simple to do if you have a HPWM and a mosfet transistor or just do the modulation in SW on any pin. The receiver for modulation you can usually harvest from any old remotecontrolled device. Look for a black little component with 3 legs.. TSOP48xx or 41xx or anything.. they will all detect a pulse if IR.

Maybe your family has a DVD player that needs to be replaced with a Blueray ...

Build the transmitter tube first and then you can see how far and big the beam becomes. If size is not a problem you can easily get more than 300m transmission range but then you need a proper lense. Big diameter and low magnification.

[koossa]

Thank you very much for your help Jumper!!!