Power supply for marine environment

E

edmunds

Senior Member
Dear all,

I have a project (one taking me away from the little line follower for a while, but I will be back :)) where I'm designing a system that will be running on a sailing boat. Some sensors, data logging and maybe a display later if the first part of the project proves successful.

Because of the sensors, I would like to run the system on 5V. 3.3V is possible, but it seems 3.3V would be the lower possible margin for some sensors and maybe it is not such a good idea. The power will come from a 12V car like battery some 10m away from the picaxe+sensors. I think it makes sense to send 12V down to sensor location and convert there for lower power line losses. The circuit would require 20mA at most, but designing for at least 100mA would be a good idea (and maybe even more if it does not cost anything) for future functions like the aforementioned display. While the environment is 'harsh', it does not have the automotive problem of starting the engine or even running it - the boat has electric propulsion running from electrically isolated battery bank. So the power source in question is running some LED lights, VHF, charging phones onboard and the like. Relatively clean power.

It would not be me, if I would not be trying to design something small, so size matters :). With that said, the design of enclosures and some mechanics is still totally up to me, so strange form factors of purpose built modules could be acceptable, for an example. SMD is preferred over TH.

I have browsed various solutions for a while now and I really feel puzzled. It is not like there are no solutions out there - it is rather the other way around. Farnell returns roughly 28.000 parts for voltage regulator. I can narrow it down to a few hundred, of course, but that is still a lot to choose from.

Maybe there are proven parts/designs out there that have already worked well for some folks?


Thank you for your time,

Edmunds
 
S

stan74

Senior Member
I've got a 12 to 5 and 5 to 12 device some where. Came from RS. size of a 741 with the legs cut off. solid plastic tiny block. There's a tiny coil in it but can't be looking for it now. So they are out there. Sorry I can't provide more info. I'll root through some drawers and see if I can find them.
 
N

nekomatic

Member
A plain old 7805 would do perfectly well for this application, wouldn't it? Or even a 78L05, if the average current draw is less than 50-60 mA or so (I'm guessing that 7 V drop x 0.05 A = 0.35 W is a comfortable sort of dissipation for a 78L05; do check the datasheet to make sure).

You don't need low dropout or high efficiency as far as I can see.
 
E

edmunds

Senior Member
Thanks, that was all that was needed. There are even some water proof modules on fleabay with just wires sticking out. That could be even better.

Edmunds
 
E

edmunds

Senior Member
Well, the boat is 4.10 metres long, so you could say it is a very small boat, but not as small as the one in the other thread I'm following with great interest. I'm designing a masthead unit for anemometer that combines navigation lights and anchor light in a single housing, would meet regulatory requirements and be produceable at reasonable cost. These things start at 500USD these days and apart from the outrageous price for two reed switch and magnet setup are fine for 40-footers, but for a boat with 5-10 metres of mast the units are just elephants. LED nav lights start at 400USD themselves and both units require separate wiring. I'm designing something that might change this for my boat at least and maybe for the small boat market at some point in time if I'm lucky.

Edmunds
 
S

stan74

Senior Member
I thought it was like the car you made :) With you're mechanical skills an anemometer would be easy,just stick it out the car window at 20 mph to calibrate it. I suppose the lights come on at night automatically. There's probably a thriving boat stuff market and normal things cost more because they've got boat in the name.
 
You must log in or register to reply here.
Top