Olinuxino-Lime2 power question

Started by mbosschaert, August 31, 2021, 11:48:06 pm

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mbosschaert

I have several olinuxino-lime2 boards which I use for backup systems running backuppc. In general that works quite fine however on one of the boards I notice that on one specific server there are substantial numbers of SATA disk errors, even on a brand new 2T disk. As the power level is one of the critical factors I've started monitoring the input voltage and the voltage_now value. The power source is a balanced 5V 3A power supply (Meanwell). I feed the board 5.25V and when I read /sys/class/power_supply/axp20x-ac/voltage_now it reports values below 4.95V sometimes dropping as low as 4.6V. On the other boards with exactly the same hardware and software (latest debian kernel) the values are always above 5.06V with the same input level.

My question is what is the value of /sys/class/power_supply/axp20x-ac/voltage_now and why would there be such a voltage drop. And finally could voltage drops be the cause of SATA disk failures?

Thanks for your thoughts
Mike

LubOlimex

Swap around boards and components to figure which piece is at fault. Maybe start with the hard disks.

Then take the board in question to the exact same setup as board without that issue and measure again.

Check if the hardware revision of Olimex boards are the same.

Where do you apply the power supply? Do you attach it to the power jack?

What about the cabling - are you using SATA-CABLE-SET or something similar?
Technical support and documentation manager at Olimex

mbosschaert

The boards are powerd through the power jack and the official Olimex SATA cable set is used in all boards. The only connected hardware is the harddisk which is replaced by a new one. I'll have to check the hardware revision versions, will do that and report back to the forum.

mbosschaert

After swapping components the critical factor seemed to be the power cable. Besided the harddisk there was no other hardware connected anyway. The original power cable apparently was not sufficient (it was made of an old USB cable) and gave me a drop of 5.25V (source) to as low as 4.7V during disk activity. The new cable did not go below 5.12V during disk activity.

What is the AWG value or diameter of the official Olimex cables (https://www.olimex.com/Products/Components/Cables/PWR-CABLE/)?

BTW the hardware revision is G2.

LubOlimex

Good find. AWG values mean little. Cable state, quality and brand are more important. We've had cables here that when you cut - don't have one solid wire inside but tightly packed metallic dust...
Technical support and documentation manager at Olimex