Determining current draw.

stonestatue · 08-29-2009, 09:02 PM

I have all my carputer parts and right now I'm in the planning phase of installing everything. I am currently determining where to mount everything and how to wire it up. My current plan is to run one primary hot wire from the battery through the firewall to power a few devices I intend to install, including the carputer. It will run to a distribution (fuse) block and will branch out in different circuits to power each device.

How do I determine the peak current draw of the carputer? I want to run the right gauge wire accordingly for the carputer. I considered just using the stock radio power wire, but I read some other threads and figured it isn't large enough for the carputer's peak current draw.

For reference purposes, I have this motherboard and this power supply.

V1RUS · 08-29-2009, 09:17 PM

You do no want to use your stock radio wire, I ran 4ga back then fuse split to 8ga. I use the same atom motherboard in my truck also running the screen off the power-supply and it draws 36W on average. That m/b does not draw a lot of power, but the more you hook up (hd's, cd drives ect) all ups your consumption.

stonestatue · 08-29-2009, 10:09 PM

Is it a safe assumption that the most power drawn will be peak at 300 watts per the power supply specification?

csfile · 08-29-2009, 10:12 PM

Quote: Originally Posted by stonestatue

Is it a safe assumption that the most power drawn will be peak at 300 watts per the power supply specification?

Are you running everything off the power supply? Or will some devices be hooked up separately?

Edit: You shouldn't be able to draw more power from the power supply than it can output. So the 300 watts should be about the maximum for your carpc even though it will most likely be much less. So (not considering efficiency), that power line could draw 25A. Based on http://www.mp3car.com/vbulletin/advf...iew&advfaqid=5 , that power line should be at least 10 gauge. Make sure to fuse all power lines.

stonestatue · 08-29-2009, 10:32 PM

I'll run everything I can get away with off the power supply. Here's a list of things I have so far:

- motherboard: 36 watts
- DVD burner: (stated on bottom of drive: 5 volts 1.6 amps (8 watts)
- solid state hard drive: current draw unknown
- Lilliput touchscreen monitor: 9 watts (.75 amps)
- HQCT USB radio: (quoted from website) Stand-by: < 10mA
Playing: 70-80mA on 5V line, 80-110mA on 12V line
- 41hz Amp 9 kit: current draw unknown
- USB audio selector: current draw unknown
- Fusion Brain 4.0: current draw unknown
- USB GPS: 80 milliamps

All of this I will try to put in the carputer case and run off the power supply. However, I might put the Fusion Brain in a separate case for ease of accessibility.

csfile · 08-29-2009, 10:36 PM

Since you have a fusion brain, there is a current sensor you may want to look at: http://www.fusioncontrolcentre.com/F...products_id=45

stonestatue · 08-29-2009, 10:37 PM

I do intend to fuse the power supply even though it's internally fused. It will be one of the fused circuits coming from the distribution block. Let's say something causes the carputer circuit to blow a fuse. Seeing as how it's got two fuses in the circuit, one at the block and one on the power supply itself, both rated at 25 amps, which one would blow first?

csfile · 08-29-2009, 10:41 PM

Quote: Originally Posted by stonestatue

I do intend to fuse the power supply even though it's internally fused. It will be one of the fused circuits coming from the distribution block. Let's say something causes the carputer circuit to blow a fuse. Seeing as how it's got two fuses in the circuit, one at the block and one on the power supply itself, both rated at 25 amps, which one would blow first?

Maybe someone else would have a definite answer. This is just my best guess: I'd imagine the fuse closer to the power source. So in this case, assuming it's the same type of fuse, the one at the block. Maybe if the fuses were made of different materials or different quality, which ever heats up first. But again, that's just my best guess.

stonestatue · 08-29-2009, 10:49 PM

Well thanks for your input. I have at least begun an inventory of what my carputer will consist of and what most devices are rated.

stonestatue · 08-30-2009, 10:06 PM

Just checked the bottom sticker for the DVD burner, and it says "5v 1.6 a". I edited the information I posted accordingly.

Woofnstuff · 08-31-2009, 04:19 PM

and get a breaker if you can, "fuses" are a pain in the ***

Wayne613 · 09-01-2009, 03:52 PM

I haven't noted it spiking much over it's rating on cold start-up. At least for my opus. I used my DMM to check it briefly.

Scotti · 09-07-2009, 03:46 AM

Quote: Originally Posted by csfile

Maybe someone else would have a definite answer. This is just my best guess: I'd imagine the fuse closer to the power source. So in this case, assuming it's the same type of fuse, the one at the block. Maybe if the fuses were made of different materials or different quality, which ever heats up first. But again, that's just my best guess.

To be honest distance won't make that much of a difference when you're talking about meters. So it will be perceivably random, where the individual fuse make-up will determine which goes first and is not really determinable.

You might be best to look at putting in some discrimination here and trying two different fuse sizes to ensure that you control the order at which things are cut out. This can help problem solving and will make sure that nothing else will cut out, well depending on the fault that is.

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