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Powering projects from marine power circuit.

cramar

Aug 22, 2022
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I am fairly new to electronics as a hoby, so please bare with me.

I am building a project to run a bow thruster control system in a yacht which has a 12V battery bank. In essence the project has four substantial blocks
1) An MCU (ESP32) that controls logic of timing, relay switching delays and some bluetooth functionality.
2) A number of opto isolated signals to control the truster relays. These signals use very little current so can be driven directly off the MCU.
3) Power supply circuitry that protects, regulates and filters the potential noisey electrical environment due to the relay swithcing and inductive bow thruster motor.
4) A cntrol panel board with LED backlighting (expected 60mA max).

Up until now I have focused on a power supply using a DC/DC converter (XL1509-3.3) to provide a low noise supply for the MCU at 3.3V.

I now find that I also need a steady 12V rail for back lighting etc. The voltage from the battery bank can swing from something like 10 - 15 Volts - I guess)

So my question is - what is the best apprach to supply these two rails.

Should I,
1) Create a seperate 12V rail using another DC/DC converter (I guess would need to be Buck/Bost) and associated circuity.
2) Create a primary 12V rail using changing the existing DC/DC converter to a XL1509-12 and then use something like a 3.3V linear regulator to provide the logic level voltage.
3) Some other approach.

A couple of notes:
1) Board space is getting a little cramped due to some mechanical constraints of the project so I want to use as small footprints as is reasonably possible.
2) One of my mechanical constraints is depth of components so if possible I want to use SMD's
3) I am trying to keep as noise free as possible.


I would be interested in your thoughts as to how you would approach such power supply requirements.

Craig
 

Sunnysky

Jul 15, 2016
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Jul 15, 2016
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Common mode noise may become an issue for any analog sensors and feedback for servo control, so grounding, shielding and filtering and CMRR are of primary importance.

Power supply specs are often defined by tolerance to supply, load, step load, ambient temperature and temperature rise. Once you specify these requirements, I think you will know what is best to meet those requirements. TI and Analog Devices both have design tools to solve these requirements.
 

danadak

Feb 19, 2021
205
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Feb 19, 2021
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205
I would use the buck bost for the 10 - 15 and a linear for MCU as its inherently lower noise.

Also choose bypass caps wisely, lower esr better -

1663973747557.png

As far as data links, if wire needed low cost optical great for noise
immunity and other wire drop and induction issues.

ESP32, take care in packet drop and connection issues. Code appropriately
for safety concerns. ESP32 also has issues with its A/D accuracy, methods on
web to improve this.


Regards, Dana.
 

kellys_eye

Jun 25, 2010
5,134
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A lot of marine electronics is powered by dedicated (not built-in) power regulators that accept a 10-30V DC input and output a steady 12V. If you know of or can spec a manufacturer/model regulator to work with the device you're designing you could save yourself a lot of time/trouble.
 

Sunnysky

Jul 15, 2016
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It is better to drive heavy inductive loads from a battery with suitable switches and protection. This is because of the estimated 10x rated power surge accelerating the device. With CM chokes and shielded twisted pairs this will result in fewer EMI problems for everything else making it easy to choose.
 

cramar

Aug 22, 2022
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Aug 22, 2022
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Firstly, thank you for your replies. Sorry it has taken a while, but my real work has some downsides.

Kellys_eye you are absolutely correct that using a black box regulator would certainly save a lot of time/trouble. Dana, thanks for the info, I have used a small buck boost (one of the readily available ones from everywhere) to provide the 12v rail in my prototyping and then used a 3.3V LDO linear regulator to provide the 3.3V rail for the board. This works kind of ok up to about 600mA before it starts becoming less stable, which for now is OK but ultimately I would want a little more current in the power budget (around 18W) - However, one of my design goals is to learn (and keep my brain active), so despite the increased effort in terms of time and expense, I am keen to try and build the power supply, even though I will probably try and fail a few times. Simply learning for learning’s sake and if I get something useable at the end that’s a bonus.

Sunnysky, you have pointed out one of the things that I have been thinking a lot about, which is how to minimise noise on the board. I am spending a fair bit of time researching design approaches to assist in this space, and am focusing on board layout, isolated power and ground planes and opt isolation of the board from the boats 12V supply. Again, for my actual use case, a bow thruster controller, it would have been much quicker, easier, and cheaper to buy an off the shelf product - but where is the fun in that and I think I can add some nice features that are not available in the general market and learn some things at the same time. Am I over engineering/complicating this simple objective - absolutely! - But only for the objective of learning something new. Thank you for the design resources from TI and Analog Devices. I found this helpful.

One of the new things I am doing is 4-layer PCB design. This is my first 4-layer (and relatively busy) PCB with the added design goals being:

1) Tight board layout
2) Learning techniques to achieve some form of electrical compliance. I want the board to handle most power surges present on a marine 12V power system.
3) Learning techniques to reduce as much as possible EMF (to prevent disturbance from other sensitive devices such as VHF radios or GPS antennas and the board itself)
4) Learning techniques to protect against EMI (will not be disturbed by a VHF, SSB, or a radar or as we have been discussing inductive loads ever present on a Marine 12V power system.
5) Finally - have something that kind of works.

For those that are interested I am learning a lot in regards to marine electronics and board layout from an open hardware project over at Hat Labs - Sailor Hat with ESP32, I am going to buy one of their boards just to say thank you.

Anyway, thank you again for taking the time to reply and read this thread - Any helpful guidance you have, please keep sharing, you will know it is appreciated.
 

kellys_eye

Jun 25, 2010
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For those that are interested I am learning a lot in regards to marine electronics and board layout from an open hardware project over at Hat Labs - Sailor Hat with ESP32,
That's a great little product! I wish I was still involved in the marine electronics side of life (did it for 40 years including a long spell as self employed installer., maintainer and repairer of all forms of marine nav, comms etc).

I'm still considering buying a boat if only to use it as an excuse to design/install stuff that interests me - sonar, underwater exploration etc - but I have another business that takes up all my time (for now!). Perchance to dream......
 
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