Transmit/Detect Circuit Thoughts.....

[Factory]

Hi,

Can anyone suggest a good (ideally cheap and compact) way of doing this?...

I'm looking for a way of getting a circuit to turn an led on when it gets within 1-3meters of another identical circuit.

so, when the circuits get within range of each other they will both automatically light up and the switch off again when they go out of range of each other...

I can't use IR as they will probably not have line of sight.

(dont need a detailed circuit or anything - just need some good ideas of how to achive it)

cheers in advance....

 

[asi]

What is about using an inductive "transmitter" in the long- or medium-vawe range?

 

[Factory]

What kind of range would that have? - anything over 5meters is too far really

 

[akg]

Hi,

Can anyone suggest a good (ideally cheap and compact) way of doing this?...

I'm looking for a way of getting a circuit to turn an led on when it gets within 1-3meters of another identical circuit.

so, when the circuits get within range of each other they will both automatically light up and the switch off again when they go out of range of each other...

I can't use IR as they will probably not have line of sight.

(dont need a detailed circuit or anything - just need some good ideas of how to achive it)

cheers in advance....

just make a low power oscillating magnetic field . detect it with coil in the other ckt , range can be controlled by the strength of the transmitting magnetic field.

 

[mramos1]

What is about using an inductive "transmitter" in the long- or medium-vawe range?

Pickup loop would be large. I do ot see a cheap solution the way I would to it. Would br RF tx/rx.

 

[akg]

ohh..i just noticed .."when the circuits get within range of each other they will both automatically light up and the switch off again when they go out of range of each other... " .. hmm.. u requires a two way transmission.? .. well at first thought rf transivers comes into mind , just control their power(and pulsed) to control their range.

 

[mramos1]

Might want to search the fourms for "RF cost".

I thought someone mentioned some $5 range chips for transmitting and receiving out there.. Get a small 50 cent PIC to signal then and light the LED.
See Nigel's winchester tutorial and you should be good. You will requirre a PIC
programmer and know the PIC language to do it.

It is just seems non line of sight still seems to be something that required more than a transistor or two.

And if you try a simple FM transmitter, seems the reciever is never simple to make.

 

[Factory]

I'll do a search for that now - if there is a $5 transmitting/receiving out there does sound a very tidy way of doing it....

 

[mramos1]

It will be in CHAT, PROJECT, or MICROCONTROLLER, not sure which one or who posted it.

 

[Factory]

Had a look at the tutorial and then onto maplin....

**broken link removed**

- mentioned on the tutorial... costs £2.12

Cheers chaps you've been a great help

 

[philba]

uh, that's a max232. I think your range will be fairly, uh, short. not RF. and that's a pretty high price for that chip, too. It's possible you could get a loop to couple at higher data rates. not sure what kind of data you would see, though.

take a look at the RFID stuff. there is a 125 khz standard that uses 2"x3" loops. I recall seeing designs out there in the google-sphere. Not sure if you could make them for £2.12 but they wouldn't be that bad either.

 

[Factory]

ah... I do need a range of 2 meterish...

I thought the RFID recievers werent all that compact? + had a limited range on them - few cm's for the compact versions? - ill have a google about though, see if I can find anything out there!

 

[philba]

a lot depends on the device. they can be quite compact. the range is more a function of whether it's a passive or powered circuit. clearly, passive has a short range. Orrientation makes a difference, too.

 

[mramos1]

RFID is expensive though, at least what I have seen.