I want to place a transmitter of some sort on my boat. And as I get within a certain distance of pre-placed bouey I want LEDs to turn on. Lighting the way.
I was considering using cheap 433mhz rf, but from what I read theirs lots of noise and other issues
Does anyone have any thoughts or advice concerning this?
I'm thinking maybe a range of 300' and because I will be on the water their will be no obstructions
My first thoughts:
Everything electronic on/inside your bouy will have to be waterproof.
How are you going to power it? Batteries will have to be replaced occassionally. Access to a waterproof battery compartment will be difficult.
The range you require rules out IR control.
Have you thought about ultrasonics? SONAR (ultrasound) works quite well in water, although I don't know much about its range, other than from watching war films about U boats. 
Otherwise it only leaves radio. Someone who knows more about radio may be able to help you.
I don't understand why you'd want to turn lights on 300 feet away?
Can't you just have proximity sensors along the way, picking you up as you float near (within a couple of meters) and switching light on?
I was considering using cheap 433mhz rf, but from what I read theirs lots of noise and other issues
That might actually work to your advantage. Part of the noise issue is that the cheap receivers use a sort of auto squelch feature, so when there is no transmitter, it picks up random noise. Of course the way to get around that is to make sure that you can tell the noise from real data, which means sending more that one bit at a time. Fortunately, the VirtualWire library takes care of all that and makes it so you can pretty much ignore the noise issue. I have done this, so I am pretty sure it would work to some extent. You might want to use the 315 mHz modules for greater distance.
I don't know how you would calibrate it to turn on when you get a certain distance away. Maybe mess with rf propagation properties -- antenna length and placement or ground plane setup. You might have problems with propagation changing with different weather or time of day or sunspot activity or whatnot. Maybe on rainy days it wouldn't turn on until 100 feet, while on a clear night it might pick you up at 400 feet.
If you want it to be more accurate, and your boat doesn't make too much noise, you might be able to ping SONAR back and forth between your boat and the buoy. Sound travels slowly enough, even in water, that if you could get a good signal, you should be able to calculate the distance within a foot. That's only theoretical, though, since I have never worked with SONAR or even ultrasonic through air. I have no idea what the practical issues would be.
You might want to use the 315 mHz modules for greater distance.
With an antenna longer than the required range? XD
sp. "315MHz"
Bradshaw106:
I want to place a transmitter of some sort on my boat. And as I get within a certain distance of pre-placed bouey I want LEDs to turn on. Lighting the way.
I was considering using cheap 433mhz rf, but from what I read theirs lots of noise and other issues
Does anyone have any thoughts or advice concerning this?
I'm thinking maybe a range of 300' and because I will be on the water their will be no obstructions
As others have said waterproofing and rust will be big issues but assuming you can resolve those then one option (not tested) but i remember reading about someone doing something similar on another forum was to have two radios on your boat - one at the front and one at the rear (assuming a reasonable sized boat) - these were both aligned so that their sweet spot was (in your case 300) feet away from the boat - If i remember correctly - they used directional aerials (i think they used Pringle cans for the effect of restricting the "field of view" of each of the radios on the boat in the prototype)
Worth experimenting with to see if the solution would work
So it would go something like
- Buoy sends out a packet every 10s and then listens for a certain return signal
- If both of the aerials on the boat receive the signal with little separation then you know you are within the 300 foot limit so you send a return packet that the buoy is waiting for and it then turns on its light and leave it on for a set period
Craig
Could you use GPS and a database of buoy-positions ?
Or get a radar, but that is a bit expensive. I like Craig's idea. Do you have a marine radio on your boat?
Being a pilot, some airports that don't have a tower, fss, or fbo use a radio frequency to activate the runway lights. Dial the radio to a specific frequency, key the mike 3 times in quick succession, and the runway lights come on for 20 minutes or so.
Great responses! Little more info for you. My boat is a commercial fishing boat, the 300' was just a random number. I was thinking just as the boat came into to "range" the buoy would light up and as it got out of range it would shut off. So maybe a 100' ? I know where all my buoys are, I just want easier time during dusk and dawn finding them. I figured when I get a few hundred feet away a nice bright led would be nice
I read somewhere that the 315Mhz will mess with GPS, which I have several on the boat.
I thought that since I was just turning on a led that maybe a cheap rf setup would work versus sending lots of critical info like a rc plane..
craigcurtin:
As others have said waterproofing and rust will be big issues but assuming you can resolve those then one option (not tested) but i remember reading about someone doing something similar on another forum was to have two radios on your boat - one at the front and one at the rear (assuming a reasonable sized boat) - these were both aligned so that their sweet spot was (in your case 300) feet away from the boat - If i remember correctly - they used directional aerials (i think they used Pringle cans for the effect of restricting the "field of view" of each of the radios on the boat in the prototype)
Waterproofing, rust and particularly battery life are the problems. Transmitters use considerable power but are only keyed briefly. Receivers however must be on continuously to pick up a signal and even one milliamp on a continuous basis adds up. It is possible to use asymmetric operation where the receiver only listens briefly every twenty seconds or so and your transmitter, powered by the boat's main battery, can transmit for at least thirty seconds, and only when you wish the system to operate.
The "Pringle can antennae" only become usable in the order of 2.4GHz and above, not at 433 or 315 MHz.
craigcurtin:
- Buoy sends out a packet every 10s and then listens for a certain return signal
- If both of the aerials on the boat receive the signal with little separation then you know you are within the 300 foot limit so you send a return packet that the buoy is waiting for and it then turns on its light and leave it on for a set period
You are consuming a fair amount of power here running both the transmitter and receiver in the buoy, even if intermittently. You really do not want the buoy to transmit.
And you have not thought out the arrangement - the time separation of reception at both ends of the boat corresponds to the direction of the received signal, not its range.
If you were to use a radar arrangement, the distance of 300 metres, return 600 metres, corresponds to only two microseconds (and that, the maximum), difficult to measure in software to say nothing of the ability of the receiver at one end to effectively discriminate the transmitted pulse fast enough to respond and at the other, to recover from the transmitted pulse soon enough to discriminate the reply. This is beyond the capability of the simple RF modules by over two orders of magnitude, much more sophisticated radio systems are required.
However the simple continuous (modulated) beacon from the boat and intermittent receiver in the buoy should work - just completely forget about any sort of exact rangefinding.
An arduino solution could work with the cheap radios you mention. Just have the transmitting arduino on the boat sending 'A' continuously. Each buoy has an arduino listening for 'A'. Any that pick it up turn their LED on for a number of minutes. Simple, but a bit pricey - you might want to make up your own boards and just use the real arduino to get the chips for them programmed. Battery life and waterproofing look to be the major challenge in this case.
Presumably the buoy needs to have a substantial power supply to power the lamp, so the small additional drain of some electronics might not be a big issue. If it is, would there be any chance of adding a solar panel? I'm imagining something similar to those cheap solar powered garden lamps.
You could reduce the receiver power consumption by having the receiver power down for e.g. ten seconds at a time, and then arrange that the transmitter transmits continuously on approach - the receiver should pick up the signal within a few seconds when it is range.
You could save a lot of battery life by not powering the receiver and sleeping the processor during the daytime. It's pretty easy to put a photoresistor or phototransistor (or even an LED) on there and check it by watchdog every 8 seconds or so. If it's light out, go back to sleep. When it gets dark enough, power up the receiver.
My little 433 MHz receiver pulls 4 mA when it's listening. Using a battery-powered stripped down board you could probably get away with less than 15 mA when listening. At 12 hours a night, that would last 13 days on a set of 4 AA batteries at 2500mAh. That's listening full time. Using PeterH's idea you could get a lot more battery life out of it.
Can't you just wire up the whole thing and stick it in a ziploc for waterproofing? Or a nice waterproof plastic case with a clear cover for the LEDs?
Paul__B:
craigcurtin:
As others have said waterproofing and rust will be big issues but assuming you can resolve those then one option (not tested) but i remember reading about someone doing something similar on another forum was to have two radios on your boat - one at the front and one at the rear (assuming a reasonable sized boat) - these were both aligned so that their sweet spot was (in your case 300) feet away from the boat - If i remember correctly - they used directional aerials (i think they used Pringle cans for the effect of restricting the "field of view" of each of the radios on the boat in the prototype)Waterproofing, rust and particularly battery life are the problems. Transmitters use considerable power but are only keyed briefly. Receivers however must be on continuously to pick up a signal and even one milliamp on a continuous basis adds up. It is possible to use asymmetric operation where the receiver only listens briefly every twenty seconds or so and your transmitter, powered by the boat's main battery, can transmit for at least thirty seconds, and only when you wish the system to operate.
The "Pringle can antennae" only become usable in the order of 2.4GHz and above, not at 433 or 315 MHz.
craigcurtin:
- Buoy sends out a packet every 10s and then listens for a certain return signal
- If both of the aerials on the boat receive the signal with little separation then you know you are within the 300 foot limit so you send a return packet that the buoy is waiting for and it then turns on its light and leave it on for a set period
You are consuming a fair amount of power here running both the transmitter and receiver in the buoy, even if intermittently. You really do not want the buoy to transmit.
And you have not thought out the arrangement - the time separation of reception at both ends of the boat corresponds to the direction of the received signal, not its range.
If you were to use a radar arrangement, the distance of 300 metres, return 600 metres, corresponds to only two microseconds (and that, the maximum), difficult to measure in software to say nothing of the ability of the receiver at one end to effectively discriminate the transmitted pulse fast enough to respond and at the other, to recover from the transmitted pulse soon enough to discriminate the reply. This is beyond the capability of the simple RF modules by over two orders of magnitude, much more sophisticated radio systems are required.
However the simple continuous (modulated) beacon from the boat and intermittent receiver in the buoy should work - just completely forget about any sort of exact rangefinding.
It was not meant to be range finding - rather making the reception spot for the radio signal to be very directional by stopping off axis signals being received - if both antennas were aimed at the same spot and they had a lot of shielding so only on (or near) axis signals could reach them - this would provide a crude form of distance calibration
Craig
I've no idea if this would work or the possible range of it. Just 'blue sky' thinking.
How about an unpowered receiver?
Wind a large coil to fit inside your bouy, tuned to a fixed radio frequency. Transmit that frequency from your boat. As you approach the bouy, the coil will pick up the signal and the induced current can be used to light your LED. Like a giant RFID tag (without the ID part).
Channelling the dear departed, eh?
I did think that I might build a coil with a magnet in it that would go up and down with the waves to keep a small bat charged.. But now I'm getting to far ahead of myself
Paul__B:
Channelling the dear departed, eh?
I made no claim about the originality of the idea, nor did I know of Tesla's experiments in that area, but thanks for that link. It shows that the idea could work. How well is still in question.
No idea how realistic this may be....
Then maybe a 'booster' circuit/antenna on the transmitter part?
And if you want to get really fancy...use GPS to determine when in range of the receiver & only send signal at that time? This part might only be energy efficient if you can/will use the GPS for something else as well. Just another idea.