R
Richard
Guest
I posted about a SBC P4 that randomly failed to boot (Power up) and want
some ideas how to get accurate current measurements. You kind folks helped
out by explaining the Shunt deal.
Since then I have taken numerous measurements and I want to share my setup
in case someone has so ideas.
First, the spec of the SBC is Max. 4.5 amps on Start up, Normal 3.2 amps.
I am using a 5 vdc DC COnverter located 14" away using 18 ga Instrument wire
14" long to carry the power. I "thought" is was large enough, but now I
have second thoughts.
When I first power up the DC Converter, I see a small spike which is right
at 10 amps, and it only last for a few ms. Then the power drops to about
1.5 amps. When the computer beeps, I jump up to 3.5 amps then to 7.5 amps,
then immediately back to 3.5, then it slowly settles down to around 2 amps.
Now I only have 10% Processor Utilization at any given time.
I take it, the 10 amp jump is the initial in rush current? then the 7.5
amps is a very breif spike from the SBC kinking off?
Does this mean my 18 ga is border line and I would really need 16 ga for the
power distribution wires? I did note that with the 18 ga wire there is 90
millivolt drop from the DC Converter terminals to the SBC Power Terminals so
I think that is a good indication I need to step up a size.
Any thoughts,
Richard
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some ideas how to get accurate current measurements. You kind folks helped
out by explaining the Shunt deal.
Since then I have taken numerous measurements and I want to share my setup
in case someone has so ideas.
First, the spec of the SBC is Max. 4.5 amps on Start up, Normal 3.2 amps.
I am using a 5 vdc DC COnverter located 14" away using 18 ga Instrument wire
14" long to carry the power. I "thought" is was large enough, but now I
have second thoughts.
When I first power up the DC Converter, I see a small spike which is right
at 10 amps, and it only last for a few ms. Then the power drops to about
1.5 amps. When the computer beeps, I jump up to 3.5 amps then to 7.5 amps,
then immediately back to 3.5, then it slowly settles down to around 2 amps.
Now I only have 10% Processor Utilization at any given time.
I take it, the 10 amp jump is the initial in rush current? then the 7.5
amps is a very breif spike from the SBC kinking off?
Does this mean my 18 ga is border line and I would really need 16 ga for the
power distribution wires? I did note that with the 18 ga wire there is 90
millivolt drop from the DC Converter terminals to the SBC Power Terminals so
I think that is a good indication I need to step up a size.
Any thoughts,
Richard
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