Electronics question

[BigFoot]

Hello all

I have an electronics question for you

I've bought a PC that runs on 12v DC and want to run it in my caravan, on 12v

My lowest DC supply circuit is 12v 10 amps but the PC needs 12v 5 amps (60 watts)

How do I limit the supply to this PC - is it just a case of an inline 5 amp fuse off that supply, or do i need a device (like a DC-DC buck convertor) to restrict the supply to 12v 5 amp ?

Many thanks & kind regards, Tony

 

[TonyR]

FWIW, automotive 12VDC is a nominal 13.8VDC and can spike up to 15 when battery is charging; I suggest a stabilizer/regulator to provide a clean 12VDC, like this==>> Cllena DC 8V-40V to 12V 6A Automatic Buck Boost Converter Step Down/Up Regulator Voltage Reducer Converter Waterproof Regulated DC Power Supply

The directions likely state an inline fuse/circuit breaker and its rating and would go between this device's input and the battery's 12VDC. Also, it should state the minimum gauge of stranded copper conductor from battery to circuit protector and on to this device's input.

Up to 18 feet, #14 should do (based on 13.8VDC @ 6A, 2% max voltage drop allowed) ==>> WIRE CALCULATOR

EDIT: do not "restrict" the supply current; a properly functioning device should draw no more than its rating; just use the correct wire gauge and install a fuse rated to protect the supply conductors to the device.

 

[Teken]

Hello all

I have an electronics question for you

I've bought a PC that runs on 12v DC and want to run it in my caravan, on 12v

My lowest DC supply circuit is 12v 10 amps but the PC needs 12v 5 amps (60 watts)

How do I limit the supply to this PC - is it just a case of an inline 5 amp fuse off that supply, or do i need a device (like a DC-DC buck convertor) to restrict the supply to 12v 5 amp ?

Many thanks & kind regards, Tony

I'm not completely sure what you're asking so will infer a few things and perhaps this will give you some insight. if the PC needs 12 VDC @ 5 amps that is all it will consume generally speaking if the 12 VDC supply remains the same. Given, in a automotive vehicle when the vehicle is running the alternator will produce from 14.1 ~ 14.8 VDC and charge the battery at 13.8 VDC.

The PC will also have some form of voltage regulator which will supply a range from 11.XX to 13.X VDC.

If your power supply can provide 12 VDC @ 10 amps that is more than fine and keep in mind the PC will only draw (consume) what it needs. It will not be impacted or damaged by a PSU that can supply 10 amps. Any electrical component should always be protected by inline fuse which should be placed within 6~12" on the Positive (+) side of the wiring. Lastly, the PC will consume (watts) based on the load that is present and drop down to a lower energy consumption when needed.

ie. Watching a movie will cause the PC to consume the most energy (watts) while listening to music less.

 

[BigFoot]

Thank you both - forgot to include, the caravan has its own modular electrical system that delivers a stable 12v DC supply with 6 outputs

2 @ 12v 15 amps & 4 @ 12v 10 amps

 

[Teken]

Thank you both - forgot to include, the caravan has its own modular electrical system that delivers a stable 12v DC supply with 6 outputs

2 @ 12v 15 amps & 4 @ 12v 10 amps

I believe the real question you need to ask and determine is how many electrical items are present now and what do they consume?

If nothing you're good to go . . .

If there are other components that are present on this 10 amp circuit read the label on each unit and add up the current draw. This should be confirmed using a clamp on meter that can measure DC or in line DC current sensing meter to obtain the real world current draw. Keep in mind you'll want to use all the devices in their everyday use case. This will provide you a much better picture of daily consumption vs peak consumption. Which you should be measuring (peak) also because every electronics will over shoot a margin of 2~5%.

You don't want to find out later when you're streaming a video on that PC and its gobbling near the 5 amp max and there are three other things consuming 2 amps each (2 X 3= 6 amps) and it will smoke the PSU and start to heat up the wire which can be a potential fire risk!

NOTE: There must always be a margin of headroom which is below 80% of the rated ampacity of the PSU / Wire. Always feel the wiring to confirm all is good while under maximum consumption.

 

[sebastiantombs]

Fuses and circuit breakers on supply circuits are not meant to protect the devices connected to them. They are meant to protect the wiring from overloads. Think about it, you plug in a 5V wall wart that draws less than .5 amps while the breaker in the panel "protecting it" is rated at 15 amps. The same is true of those fused circuits in your van.

 

[TonyR]

Fuses and circuit breakers on supply circuits are not meant to protect the devices connected to them.

Yep.
Many, many folks think the fuse/breaker protects the equipment.
I lived in my parent's finished/furnished "barn" for 6 months while my house was being built in 2006.
After much flickering when A/C cut on or I vacumed, etc., I pulled the panel looking for loose wiring or whatever.
The panel was filled with 30 Amp breakers, the wiring was #12 (rated 20 A) and #14 (15 A.).
This is why you see so many houses around here burned down....if Bubba can make a light bulb come on, his friends say "...he's a good electrician."

 

[Teken]

I don't think anyone here in North America comes even close to the shit show going on in India. Having seen tons of on line images throughout the years like many here. Our team was sent out to provide technical support on a large infrastructure project. As we drove around I was in complete shock and awe as to the lack of standards and safety best practices!

Standing right there and seeing the same live doesn't even come close to a picture like these . . . Our host who drove us all around the country told me that every day there was a black out / fire somewhere in the country.

You simply can't appreciate how well we have it in North America vs a third world . . .

So Bubba is probably doing pretty good!

 

[TonyR]

So Bubba is probably doing pretty good!

I have seen some of those images and yes, it's mind boggling. It makes what I saw in the Philippines circa 69-72 look great and to code.

Unfortunately, Bubba and his cousin Cooter have been buying NEMA 5-15R (3 prong grounded receptacles) by the gross from Home Depot since the 90's and replacing / or tying them in with new installs to houses built in the 50's and early 60's that are strictly 2-wire.

 

[Teken]

I have seen some of those images and yes, it's mind boggling. It makes what I saw in the Philippines circa 69-72 look great and to code.

Unfortunately, Bubba and his cousin Cooter have been buying NEMA 5-15R (3 prong grounded receptacles) by the gross from Home Depot since the 90's and replacing / or tying them in with new installs to houses built in the 50's and early 60's that are strictly 2-wire.

Whelps, it wasn't knob and tube was it . . .

 

[sebastiantombs]

Don't laugh. I did a replacement, service and all wiring, of a knob and tube system in a house. Original 30 amp service upgrade to150 amp. The inspector couldn't believe it was still operating on knob and tube, complete with braided cotton jacket wiring, in the mid 70's.

 

[mat200]

Don't laugh. I did a replacement, service and all wiring, of a knob and tube system in a house. Original 30 amp service upgrade to150 amp. The inspector couldn't believe it was still operating on knob and tube, complete with braided cotton jacket wiring, in the mid 70's.

I've still seen some Noob and Tube setups today working...

 

[wittaj]

I prefer the copper penny fuse myself



But sometimes you need to use a screwdriver:

 

[Teken]

Don't laugh. I did a replacement, service and all wiring, of a knob and tube system in a house. Original 30 amp service upgrade to150 amp. The inspector couldn't believe it was still operating on knob and tube, complete with braided cotton jacket wiring, in the mid 70's.

Honestly, upon reflection seeing how much power we all use for various appliances and electronics. I simply don't know how living on 30 amps is possible now with all manner of small to large electrical loads in our homes. Can you imagine everything having to be run on gas for water heater, dryer, stove, furnace, etc?

I know depending upon where you live NG / Propane is the way of life with respect to appliances . . .

 

[sebastiantombs]

The house I did was a rehab to make it a rental. It did have piped NG for heat, hot water and cooking but even so I had a problem with how they got by with 30 amp service for that long. No pennies in the fuse holders either, which was surprising but there were half a dozen boxes of 30 amp and a few boxes of 15 amp for spares.

 

[TonyR]

I know depending upon where you live NG / Propane is the way of life with respect to appliances . . .

Lots of propane here in AL for heating and some for cooking & water heating but AFAIK, most here use electric for water heater, dryers, stove top and oven due to the relatively low cost per kWh of electricity from the TVA & many co-op electric co.'s here in the SE. It's now about 12.5 cents, was under 11 when I came here in 2006. Current national average is 13.3, I read.