chicken

[POTM] dAISy - A Simple AIS Receiver

262 posts in this topic

I haven't tried any other modules, but I think the one above is about as easy as it gets.

 

I have a very cheap Hope-RF module on my bench that claims to be compatible with Si446x. But patching it up was a mess as there's a lot less space. And lack of 100 mil headers make for more work to break it out. Still have to wire it to a Launchpad to test.

 

But don't hold your breath. The weather is way to nice to spend time in the lab right now ;)

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Your module looks fantastic! I have bought a similar one from Radargadgets: http://www.radargadgets.com/

But doesn't show very good performance. It can only see 15 boats while the other standard AIS class A receiver can get 40!   

I love this module and looking forward to buying one for play. 

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hi,

 

dAISy USB has a solid and excellent sensitivity ...with a simple 1$ DIY electrical wire copper dipole it can receive ships exceeding 553 nm. - 1000 km !!!!

 

 

Esteban.

 

post-25037-0-05479800-1407403510_thumb.png

bluehash likes this

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I managed to buy modules that weren't in 2.54mm DIP config , actually 1.27mm SIL but didn't want bits of wire everywhere. I rummaged thru my boxes and found the perfect solution, 24 pin SOP adaptor boards. The pic is BEFORE soldering, looks great after soldering.IMG_20140824_090200.jpg

http://bit.ly/1p3sdEN

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I used the whole adaptor for each board as I had plenty and they are cheap in bulk but it should be possible to cut each in half and make two adaptors. I like the whole board as it provides more support and makes them easy to handle. Of course, if the board is too small to fit on the intact adaptor than bisection would definately be necessary.

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It would be really cool to see this data get pushed to data.sparkfun.com we could do some cool web interface on imp.guru. Here is a example of tracking adsb data for airplanes in Honolulu http://imp.guru/f1n

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Hi Everyone

 

This really is a great project.

I'd quite happily purchase this.

 

 

As an offshoot to this, what I'd like to see on the market is a small deivce I could plug dAISy into that alarms on detection of a signal.

i.e. a device that powers dAISy from the house batteries and is itself an audio alarm alerting signal detection.

This way I could leave it running 24/7, when a ship arrives on the horizon an alarm triggers, I power up my chart plotter, removing dAISy from the alarm/power supply and plugging it into the chart plotter.

The purpose being to save power, which is very precious in small sailboats.

 

Presumably dAISy and a powersupply/alarm would consume very little power in comparison to dAISy and a chart plotter.

 

Thanks

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Thanks for checking out my little project.

 

@@Lgbeno If going the IoT route, my first goal would be to submit messages to Marine Traffic or AISHub without a PC.

 

@@cowlum Interesting idea. If it's just about detection of something in range, one could easily change the software to turn on a pin when a message was received within the last 15 minutes or so. However, I'm not sure how useful that alone is. For a more intelligent warning system, dAISy would need to interpret the messages it receives. This way it can determine whether the message is from a ship or a base station, how far away the object is and what direction it moves (would require a GPS module).

 

There are lots of possibilities when processing AIS messages in an embedded device. That's why I consider to build the complete receiver (i.e. what today is dAISy USB) in a BoosterPack or Shield form factor. Combined with an Energia/Arduino library that spits out the decoded data it would be pretty straight forward to hack together these kind of projects.

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I completely agree that detection alone is not very usefull (or fun).. and im not suggesting detection alone is what we want.

 

Many small sailboats (your target market) only have 100-200ah charged by solar to run everythnig onboard, so running a chart plotter long periods (when its actually needed) is not an option. Most sailboats I go on dont bother with chartplotter AIS because in the harbour races keeping watch for 4-8 hours is easy. When sailing longer offshore races we get tired but the boat cant afford the energy to run a common ais chart plotter long periods. So we go without.

 

It would be great if there was a device that used little power on alert mode and then fed nmea to the power hungry chart plotter.

 

I guess my comment was more about a hole in the market than anything else..

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@@cowlum What criteria would you use for an alarm? Anything within reception (~5 nautical miles with a basic antenna at sea level)? Or something more specific?

 

What would you use as alarm? Piezo speaker?

 

And what is an acceptable power consumption? In its current form it draws a bit less than 20mA.

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I don't know the feasibility of it, but on ebay there are little micro wind power generators that output 0.01 - 15v, .2A max current. Seems ideal for a sailboat?

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How much power would be acceptable? As little as possble...

A better way to answer this question is to show you the competition.

 

1)VHF unit AIS (requires additional gps to work) in receive mode ~0.8A  (~$300)

 

2)AIS receiver + chart plotter ~0.4A  (~400+)

 

3)AIS receiver + Laptop  ~LargeA  (price really varies, I have a discriminator bypass on an old VHF)

 

**Laptops are ultimately too delicate for reliable navigation at sea.

 

All options are power hungry and overkill for the usual coastal passages on small vessels.

 

You could alarm on detection of signal, Aerial and location being the determining factor. 2-5nm would be about right.

If you wanted to intergrate gps and add a level of intellegnce that may be benificial.

Or possbily strength of signal determins volume of alarm?

 

I really had not thought much further than a small box that supplies power to daisy and sets off a peizo if a ship approaches. Power saving being the name of the game.

 

If its cheap enough and works well enough, I'd purchase it.

chicken likes this

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@@abecedarian Wind generators and solar panels work reasonably well on sailboats. But most race boats dont want the weight or wind drag and you cant always rely on the wind and/or sunny days.

 

Also, Even if you had the perfect conditions to claim and store the 0.2A you are not competing with the loss from most Nav systems.

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Hmm, signal strength is easy, I already have that information. Probably would need to be calibrated depending on the antenna, but it's a solution that avoids a GPS module and packet inspection. Not that they are expensive (starting at $15) or that power hungry (~ 50 mA), but certainly saves time in code development and system complexity.

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One consideration with strength of signal is I beleive there is Class-A and Class-B transievers. Class A being far more powerful so Class B may appear distant in comparison.

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http://www.bosunsmate.org/ais/ has some info on the NMEA packet structure.

As for the sailboat, checking every 5 minutes for 1-2minutes for a new vessel within a packet may be all that is required.

I can't test this yet as I'm still building mine, had to buy a hot air rework station, solder paste etc as the filter component changes are way too small for a soldering iron. Anyway it is about time I moved into the 21st century.

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Complete AIS protocol documentation can be found here: http://catb.org/gpsd/AIVDM.html

 

@@PaulTech my cheap hot air station saved my butt more than once, best investment ever.

 

In other news, as posted on other threads, I found a case for dAISy USB. It required redoing the board layout, but I really like the new form factor.

post-9974-0-23916100-1414199800_thumb.jpg

 

I also learned, that the LDO I use (MIC5205) does not like MLCCs as output capacitors. I had to go back to tantalum caps to get rid of a 200mVpp oscillation.

 

And I finally got a "real" AIS receiver off eBay. Turns out dAISy still has a long way to go to compete with these. :unsure: But then, this particular model costs $450 new ($400 without GPS) and is about 7x the size (volume) of dAISy.

post-9974-0-75229600-1414885941_thumb.jpg

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interesting that the commercial model doesn't support NMEA according to their site.

In what way does the dAISy have to catch up?

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Not sure what NMEA they refer to. It sends AIVDM messages over old-fashioned serial, plus addtional messages about its own position.

 

Compared to dAiSy it seems more sensitive. With the same antenna, about 5 times more messages are received and range is about double. The SR162 is much better at receiving targets that are not in direct sight, e.g. behind hills.

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double the range is aout a 6db better sensitivity, so a MMIC at the antenna end or FET amp would easily get this result. The MMIC have the advantage of being very easy to work with. Even if the was a bit of filtering before the amp it should still get about an extra 10db improvement.

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Thank you for your input @@PaulTech. My current suspicion is, that noise and/or selectivity play the bigger role than sensitivity:

  • @@gmtii's station typically covers around 50 NM, and up to 500 NM when weather cooperates
  • when adding a 162MHz, 14MHz bandpass filter, local reception improves (at the loss of fewer outliers beyond 100 NM, which I attribute to the 1.9dB insertion loss)
  • even for ships clearly within range of dAISy, the professional AIS receiver is much better at picking up the (2.5x longer) static and voyage related data messages

I already work on adding a bandpass filter to the PCB, so maybe I should just add an amplifier and see what happens. Any pointers to a suitable MMIC, and/or articles for beginners about the topic?

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Try the minicircuits site for MMICs as well, the filter looks like an easy solution as it would stop a lot of interference that the onboard filter just isn't designed to deal with.

http://www.minicircuits.com/products/Amplifiers_what_is_new.shtml

you really don't need much bandwidth so a MMIC that goes to 1GHz would work. I still have lots of the first gen MMICs as I had to buy a whole strip as they were special order way back. Even these old MMICs are very very handy, you can mount at antennas very easily. Just check the noise figure, as some can be a bit noisey and when you amplify the signal by 15db ,you also amplify the noise by 15db + amplifier noise.

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just had another quick read thru the Si4463 doc, and noticed the channel filter bandwidth is configurable from 850KHz to 1.5KHz wide. Too narrow or too wide will cause problems too.

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