This may be a stupid question, but I have looked everywhere and everything is a bit more complicated that I need to get.
I am simply trying to establish a simple one bit on/off radio link. One arduino will continuously listen for a pulse while the other will occasionally transmit.
I figure this can be done with an oscillator and a simple circuit but I cannot find a simple example. I would appreciate any insight.
Thanks.
-Jon
I figure this can be done with an oscillator and a simple circuit but I cannot find a simple example.
You could probably do it with a simple tuned AM oscillator, turned on/off via a transistor or mosfet controlled by the Arduino. In fact, there is a circuit in one of Forrest M. Mims III Mini-Engineer's Notebooks (Communication Circuits, IIRC) that would probably work with some simple modification. On the receiving end, you would need an AM radio, of course (and a few other parts).
Your problem is going to be distance; the device above could probably be used legally up to about 50-100 feet (possibly less, going by US FCC rules here, which I haven't read lately). Anything beyond that would require a license (and likely a change to the circuit).
You could also hook up a couple of cheap toy walkie-talkies (if they're still made?), and transmit using the key-coding morse switch (to transmits beeps and such). It might also be possible to do something similar with family radios (you would need to add your own oscillator, of course) - maybe using 2-tone? Not sure if that is legal on family radios or not (I know it wasn't legal to transmit data using CB radio).
You might look through that Swiss link-list, but I think you will consider most of them (or all) as "too complex"..
http://senderbau.egyptportal.ch/schaltungen.htm
OTAH you can use any Arduino pin as radio transmitter by toggling it as fast as you can, just connecting an "antenna" to it (which can be any wire of appropriate length).
Or just this?
50 feet should be quite sufficient, I am building a ultrasonic trilateration system for accurate indoor navigation, I just need to have an instantaneous radio signal so the robot is able to determine when the pulse left the beacon.
I will try these solutions.
Thanks all
If it's indoor, within 50 feet - does it need to be radio (ie, non-line-of-sight)? An IR beacon could be a simpler solution. You might also look into some of those low-power RF transmitter/receiver modules - similar to:
I have developed a system using infrared that works quite flawlessly at transmitting data over a very very short distance, however I find that at more than a foot or two the signal is not strong enough, another problem i ran into with infrared was directionality, the infrared led's i was using had a very narrow beam of light, as did the infrared photo transistors I was using to detect the signal, I tried using reflectors however I found this did not work well at all, i suspect because it diminishes the light hitting the photo transistor too much.
If these problems could be solved infrared might work, however after running into these problems I thought a radio connection might be easier, since i only need to send a one bit on/off signal. Perhaps i was wrong. :-?
What if you used a flash bulb behind an IR filter?
Maybe I am being unclear, I am not actually trying to send information, simply an instantaneous signal to the other arduino to start counting. There must be no delay as accurate timing is essential for a correct position reading.
I ordered a transmitter and reciever from sparkfun to experiment with, I have a feeling the IR filtered flash bulb is what I am going to end up using ;D
I will post an update when i get the system working.
thanks for the suggestions guys.
I ordered a transmitter and reciever from sparkfun to experiment with,
The thing about those transmitters/receivers I posted is that they are considered something akin to a "virtual wire" (in fact, there's an Arduino library called this, IIRC - to allow serial comms over such a link).
Basically, a logic-level HIGH at one end produces a logic-level HIGH at the other end (your "one-bit" value you are looking to transmit). If you do a series of HIGH-LOW bit transitions (aka. serial data!), you can do communications.
You just need an "on/off" HIGH/LOW value - which is what they provide, so they should work for your needs.
These are pretty cheap:
http://www.satistronics.com/mini-24ghz-wireless-nrf24l01-nrf24l01-transceiver-module_p2450.html
Infrared can work 30 ft plus. Try a better led and receiver. For 360 degree support, you may want multiple leds and receivers. There are several threads on this forum discussing this.
Have you made any progress on the ultrasound portion? What parts were you thinking of using?
Check out www.moderndevice.com
They sell the Jee-Node which is a tiny radio tx/rx unit.