YAPP idea - MOB alert system

Could you consider doing the same for NMEA, if I can figure out how it does it?
Click to expand...

May be in the future, but I need to limit the features if it's ever going to see the light of day. I'm not aware of a MOB NMEA-0183 message.


The sleep mode power consumption of the processor seems quite variable between different samples of the same type - 13uA to 18uA. These are the power calculations I have done using those figures for the victim unit...

Victim unit sleep mode varies between 13uA and 18uA.

In transmit mode takes 8.4mA.
Transmit takes 7ms every 4000ms.
Proportion of time transmitting=7/4000=0.00175.
Proportion of time not transmitting=1-0.00175=0.99825

Total Amps = (18/1000000)*0.99825 + (8.4/1000)*0.00175
33uA

Charge storage in CR2450 570 mAh
Estimated life 1.9 years

Charge storage in CR2032 210 mAh
Estimated life 0.7 years

Charge storage in AAA alkaline cell 1000 mAh
Estimated life 3.5 years

There are 2 problems I envisage if I went the CR2032 route...


1) It won't make my target 1 year life

2) My calculations are just that - estimates. I won't have the time before completion to leave one running for a year, so I want a good redundancy in my power calculations.

I really don't want to have to start drilling holes in boxes, because it is difficult to get right and the inevitable cock-ups cost me dearly. Maybe a later version could be smaller and neater, but to start with I want to keep it cheap and simple. As it will be open source, anyone else could have a go at a better victim unit.
 
I think that one of the (many) beauties in your design of the victim unit is that it gets a set of batteries in the spring and runs all season.
Holes, switches and lights are disproportionately difficult and expensive and I think you are very wise to avoid them.
 
nigelmercier said:
...Is the AAA battery and "no switch" set in stone? Have you considered a CR2032? These have about 1/3 the capacity of an AAA, but would allow the unit to be considerably smaller. Perhaps it could incorporate a flashing LED to indicate transmit, then a magnetic switch could be used to make the PIC go into sleep mode, and power the whole thing down.
Click to expand...

I was thinking the same about the battery, could use multiple CR2032's to get the capacity and maybe have a victim unit that was made from rod/tube so that it could be 100% waterproof and similar in size to a personal marker strobe. Making sealed circular units is way easier than non-circular ones and some of my dive torch canisters are rated to 100m+ so sensible priced housings rated to IP68 should be possible and I've seen battery canisters made from standard plumbing fittings that would be completely sealed and cheap

One thing I like about no switch is that its always on and nothing to forget

I am working on some divers toys and have been playing with using Bluetooth to talk to and control sealed units as any Android 'phone could be used to "wake up" or just control & configure a sealed unit

Also just like to say thanks for putting together the YAPPs
 
If anyone wishes to be able to disconnect the battery of the victim unit when not in use could fit a N/C read relay in the battery line and then place a magnet over the read relay site or have a rack with magnets to disconnect the battery when the victim unit is stored in the rack, like how the battery in and EPIRB in disconnected when the EPIRB is in its storage rack.

IMHO a transmit LED would be nice but would reduce the battery life considerably.
 
flat1 said:
I think that one of the (many) beauties in your design of the victim unit is that it gets a set of batteries in the spring and runs all season.
Holes, switches and lights are disproportionately difficult and expensive and I think you are very wise to avoid them.
Click to expand...

+1 I really like the KISS principle of the project and would prefer simple cheap and easy to operate over complex. Great idea and looking forward to seeing it make the light of day.
 
First attempt at the main board layout...

73u2.jpg


Updated victim unit board which now includes Nigel's LED and ability to set the transmitter power with jumpers...

409y.jpg


Having a go at modelling the lid to the box...

jft4.jpg


3D modelling is a lot more tricky than I expected!
 
Rum Run said:
On the "nice features to have" note. If possible, a relay output or facility to drive one would be useful for us Billy Nomates sailors: To trigger an engine shut-off device and/or put the helm over on those occasions when prancing about the boat when not hooked on goes wrong.
Also, can the trigger range be shortened? 25m is fine if the remaining crew will come back to get you, however it's a bit of a swim in the above situation.

Cheers
Rum Run
Click to expand...

Now your talking :encouragement:
 
Hello Angus, I have just posted a thread asking for just what you are offering, however I was looking for a system like yours but for a MOB situation for a single hander, would it be possible for your system to stop the engine my Beta engine as an electrical stop button, and also if under sail the same device to turn the boat head to wind. The reason I suggest stopping the engine is because if your system can bring the boat back to me it most likely would run be down, I think it would be much easier to just stop the engine and maybe turn head to wind.
Sorry if this has been already asked but it's way past my bed time.
Regards Mike.
 
Pagetslady said:
Hello Angus, I have just posted a thread asking for just what you are offering, however I was looking for a system like yours but for a MOB situation for a single hander, would it be possible for your system to stop the engine my Beta engine as an electrical stop button, and also if under sail the same device to turn the boat head to wind.
Click to expand...

The system as designed at the moment has a 12 Volt 2.5 Amp output which is switched on when an alarm is raised. I expect you could use that to stop the engine if you have a stop solenoid. As for turning into the wind - that's not in the current design. However, as I have the option of Seatalk output it would be a software change to do that, assuming you had a Seatalk controlled autopilot.
 
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AngusMcDoon said:
However, as I have the option of Seatalk output it would be a software change to do that, assuming you had a Seatalk controlled autopilot.
Click to expand...

Despite being a firm believer in staying on the boat rather than inventing gadgets to get you back onto it, I've always rather liked the idea of a MOB receiver that used the autopilot to (try to) keep the boat's nose up to windward. Obviously without forward drive it's not going to succeed in that aim, but the constant attempting should prevent the boat ever getting going and sailing away.

Two things spring to mind if you were to try it. First we need to ensure that the turn is to the side that brings the boat round to the wind "the short way", ie turning through the fewest degrees - this should minimise the likelihood of a gybe (worth also noting that Raymarine pilots have a "gybe inhibit" function that won't turn the stern through the wind, but I don't think this would interfere if we turn the right way. Or just be aware and turn it off.) Secondly, the pilot requires you to manually confirm before changing course at a waypoint - so the way you tell it to steer into the wind shouldn't look like setting off on the next leg of a route.

I guess you can put it into "steer to wind" mode via Seatalk? That and a relative wind angle of 0º ought to do the trick...

Pete
 
Maybe I'm showing the depth of my software knowledge here, but my pet idea for going any distance singlehanded is to have a light, strong line ( codline ) trailing aft say at least 100' long, led over the pushpit and tied to the outer end of the autohelm ram; then with a bit of luck the MOB could reach the line and grab it, pulling the autohelm from the tiller and the boat rounding up.

Of course ( pardon the pun ) this might not be so easy with wheel steering.
 
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