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What Power Supply??
#11
olewsaa choice has very nice specs a little $$$. I worry a little about encased units as i had one meltdown on me testing. but this look very nice. How would you deal with ground for example a ina219. it is isolated so you don't want to connect the grounds?
I need two types a small type that i can use with esp and nanos. and a larger one that i use with the rpi 3 and 4.
The mean well would work if the power supply is external but this does not work for me as I have the pi mounted in a case that i bolt down. 12 volt is feed by a molex connector. the case has a 12v fan with a simple mosfet circuit to control it. I also don't have anything near it that needs 5V.
I currently use a lm2596 in all of my projects it is barley runs a pi4 and i fine with the 3. and is a little big for esp projects. I am going to try Didier B choice as i like cheapSmile


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#12
I do not know how protected the ND buck converters are, maybe they shut down ? or melt down under overload ? I've never tested this. I cannot recall anything in the data sheet about this.

I have a metal boat (Ovni 395) and are paranoid when it comes to isolation of the computer system and the rest of the boat. Wen you have experienced grounding faults and burned signal cables in a lab, you tend to forget. Same applies onboard a metal boat where negative is also isolated from the hull and superstructure of the boat.

You can read more about it here : https://sites.google.com/site/olewsaa/ya...-isolation

Have fun,
Ole
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#13
I'm using one of these. It is water proof and holds a steady 5.25 V for at least my PI3
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#14
(2020-02-11, 10:39 PM)olewsaa Wrote: I do not know how protected the ND buck converters are, maybe they shut down ? or melt down under overload ? I've never tested this. I cannot recall anything in the data sheet about this.

I have a metal boat (Ovni 395) and are paranoid when it comes to isolation of the computer system and the rest of the boat. Wen you have experienced grounding faults and burned signal cables in a lab, you tend to forget. Same applies onboard a metal boat where negative is also isolated from the hull and superstructure of the boat.

You can read more about it here : https://sites.google.com/site/olewsaa/ya...-isolation

Have fun,
Ole

Hi Olewsaa
I have been reading data sheets for more than 40 years now, and never saw one which predicted a future melt down !!!
The module is fully protected (once a Schottsky diode is used on the In+ line) : overload, over voltage, over current, out shorted, polarity reversion etc.
See  XL4015 datasheet pdf
As you mention in your note about isolation, the presence of a large coil is a must to avoid interference .
Have you checked the claimed galvanic isolation, including the minus line ? This would require a transformer able to deliver 15 W ?
My boat too is made of aluminum (Mopelia 2000) and I just avoid carefully any contact between the ground (hull, deck) and any wires, cables, or electrical equipment ... which includes mechanical protection of the cables ...
I am slightly paranoiac too, but my whisky treatment gives good results Wink.
Cordialement
Didier B
Pi4, SSD, OP 2.4.1-stable, OpenCPN 5.2.0.9




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#15
(2020-02-12, 08:40 AM)Didier B Wrote:
(2020-02-11, 10:39 PM)olewsaa Wrote: I do not know how protected the ND buck converters are, maybe they shut down ? or melt down under overload ? I've never tested this. I cannot recall anything in the data sheet about this.

I have a metal boat (Ovni 395) and are paranoid when it comes to isolation of the computer system and the rest of the boat. Wen you have experienced grounding faults and burned signal cables in a lab, you tend to forget. Same applies onboard a metal boat where negative is also isolated from the hull and superstructure of the boat.

You can read more about it here : https://sites.google.com/site/olewsaa/ya...-isolation

Have fun,
Ole

Hi Olewsaa
I have been reading data sheets for more than 40 years now, and never saw one which predicted a future melt down !!!
The module is fully protected (once a Schottsky diode is used on the In+ line) : overload, over voltage, over current, out shorted, polarity reversion etc.
See  XL4015 datasheet pdf
As you mention in your note about isolation, the presence of a large coil is a must to avoid interference .
Have you checked the claimed galvanic isolation, including the minus line ? This would require a transformer able to deliver 15 W ?
My boat too is made of aluminum (Mopelia 2000) and I just avoid carefully any contact between the ground (hull, deck) and any wires, cables, or electrical equipment ... which includes mechanical protection of the cables ...
I am slightly paranoiac too, but my whisky treatment gives good results Wink.


I have read datasheets, typical for simple stuff like transformeres etc, stating that exceeding max load can cause overheat and damage. 
The MD 1205 converter is isolated, the datasheet (If you trust the supplier) clearly state 1.5 kV isolation, tested at 500V. Using switch mode it require only a very small isolation transformer (high frequency). Modern power electronics are very good, just look at high power computer (servers) power supplies. 

An issue with all power coverting is efficiency, this unit is about 80%. At full load approximately 3W is lost as heat. Most heat is given off by the computer (RPi), ventilation is important.  

The compact size of the unit was the reason for my choice of this power converter. 

I totally agree on mechanical protection of wires, I run all of them in protection tubes. A nice thing with the Ovni is the leakage meter. 


Ole
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#16
LOL I looked on my bench and found a xl4015 sitting there I forgot i bought some a while back. I tested it but had issue with low voltage alarm. I think my meter is off i had to set voltage to 5.37 v or i get low voltage alarm. on rpi4. Or should i put a big cap near the rpi to deal with voltage drops??. I am drawing around then .5 amps @12v. That is a RPI4.. My Usb devices are connected to a self powered hub
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