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Topic: RC Sail Boat speed measurement and transmission (Read 489 times) previous topic - next topic

Pascalou31

Hi all,

I am looking for a telemetry solution for a Radio controlled Sailboat to measure and transmit on a PC or Smartphone, the speed of the boat, the angle and the speed of the wind, the onboard battery voltage.
Is the Arduino + Xbee pro could be the right solution ?
What kind of sensor could be suitable to measure boat speed with a 0,1 knot accurency ?
Is anybody already done this kind of application and could help me ?


GoForSmoke

1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

Robin2

What kind of sensor could be suitable to measure boat speed with a 0,1 knot accurency ?
I reckon you need a GPS for any sort of accurate speed measurements and I don't know if it could be that accurate or if it would work at all over the short distances moved by a model sailboat.

I speak from the experience of money wasted on a paddle-type speed log for a real sailboat.

I guess a model sailboat has the advantage that you could easily clean a speed-detecting paddle. You would probably get better info about speed measurement on a model boat website.


Separately, if you want to transmit data directly to a smartphone or PC you will either need Bluetooth or WiFi. I don't know if Bluetooth would have the range you require.

AFAIK if you want to use XBee you will need an XBee receiver to relay the data to your PC - but I have no experience of XBees.

If you are content to have a shore-based receiver then I reckon using a pair of nRF24L01+ transceivers would be a lot cheaper than XBees. If you need the range the shore-based module could be the high-power type (with the external antenna). This Simple nRF24L01+ Tutorial may be of interest.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

Pascalou31

@ GoForSmoke : OK thanks for this information, this is a beginning...

@Robin2 : GPS accuracy is not ok for model sailing boat to get a 0,1 knot accuracy then I've already visited a lot of model boat website and forum without finding the right informations.

Regarding the shore-based receiver I'm afraid the nRF24L01 doesn't have enought distance transmission power. We need at least 200 meters and as far as I can see  nRF24L0 offer only 100 meters max.

wildbill

Xbee pro has the range you need.

Full size sailboats can use ultrasonic transducers to measure speed. It might be viable for your model, depending on how big it is. Of course, being marine equipment, they are prodigiously expensive.

Pascalou31

@wildbill : I know about ultrasonic transducers for full size boat but this is not suitable for small 1 meter model (race) sailing boats regarding size and weight...

srnet

Regarding the shore-based receiver I'm afraid the nRF24L01 doesn't have enought distance transmission power. We need at least 200 meters and as far as I can see  nRF24L0 offer only 100 meters max.
Droping from 2.4Ghz modules to 434Mhz ones will give you around 5 times further range, all other things being equal.  

LoRa modules are not expensive, and whilst its often assumed they are good for low speed data only I have had 105km LOS from a LoRa module running @ 13.7kbps @7dBm.

http://www.50dollarsat.info/
http://www.loratracker.uk/

Robin2

I've already visited a lot of model boat website and forum without finding the right informations.
Maybe because what you want to do just isn't practicable on a small scale?

I don't think you have told us the size of your boat, the type of place you will be sailing it.


I have had a pair of low-power nRF24 devices working at 110m range. AFAIK a combination of a low-power nRF24 on the boat and a high-power nRF24 onshore will give a range of a hundreds of metres. I believe those devices are used in some of the off-the-shelf 2.4GHz RC systems.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

GoForSmoke

The water pressure under a moving hull will be less relative to the hull than pressure under a stationary hull. That's what makes a pitot work. A sensitive pressure sensor might be easier to read than the water level in a tube.

If you point a tube out of the stern, it will pull even stronger as long as the hull moves forward.

I have one other idea, not sure how good.
If I put 2 contacts in water and pulsed a very short weak current from one to the other there should be a little time for the pulse to cross between. If the water is moving so one contact is in front then the time for the pulse to cross should vary depending on which makes the pulse and which senses it.

This is like the sonic except with electrons and it will likely corrode the contacts over time but if the pulses are 1ms out of every 500ms (to measure both ways in 1 second) and INPUT_PULLUP weak the corrosion will be very slow.
1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

wvmarle

If I put 2 contacts in water and pulsed a very short weak current from one to the other there should be a little time for the pulse to cross between.
I don't think an Arduino is fast enough to measure this delay by several orders of magnitude. The difference (if any) in moving vs. stationery water will need another few orders of magnitude faster measurements.
Quality of answers is related to the quality of questions. Good questions will get good answers. Useless answers are a sign of a poor question.

Pascalou31

@Robin2 : The boat I'm talking about are IOM sailing boat (International One Meter).
The speed to measure is between 0 and 4 or 5 knots (Miles per hour) and we sale mainly on small Lac ==> 30 to 50 000 square meter (not on sea)...


Wawa

#12
Jun 21, 2019, 06:58 am Last Edit: Jun 21, 2019, 07:03 am by Wawa
we sale mainly on small Lac ==> 30 to 50 000 square meter (not on sea)...
I assume you're only interrested then in SOG (speed over ground) and not STW (speed through water).
A GPS should be fine for SOG.
Leo..

Smajdalf

I have one other idea, not sure how good.
If I put 2 contacts in water and pulsed a very short weak current from one to the other there should be a little time for the pulse to cross between. If the water is moving so one contact is in front then the time for the pulse to cross should vary depending on which makes the pulse and which senses it.
I don't think it will be such easy. "Normal" lumped circuit model assumes infinite speed of light. Your signal will be more like RF, not classic circuit. Also relativistic physics consider speed of light constant. What it means for this application?
How to insert images: https://forum.arduino.cc/index.php?topic=519037.0

Robin2

#14
Jun 21, 2019, 08:08 am Last Edit: Jun 21, 2019, 08:10 am by Robin2
@Robin2 : The boat I'm talking about are IOM sailing boat (International One Meter).
I presume this is a racing boat so you won't want things poked into the water that would reduce the speed.

Do you want to measure the speed during a competition or only when practising?

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

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