WS-12-250-DC Input voltage too low

[petecarlson]

What's up with this?

Dec 31 19:07:01 UI: Port 1 PoE: changed from 'Off' to '48VH'
Dec 31 19:07:05 switch[795]: Input voltage too low (47.2) for 48V operation, not enabling port 1

[petecarlson]

Cranked up the input voltage. Getting:

Dec 31 19:24:25 UI: Port 2 PoE: changed from 'Off' to '48VH'
Dec 31 19:24:29 switch[795]: Input voltage too low (52.6) for 48V operation, not enabling port 2

[lligetfa]

What firmware version? The bit of code was meant only for the DC model without power supply and has since been removed from all others.

[sirhc]

Cranked up the input voltage. Getting:

Dec 31 19:24:25 UI: Port 2 PoE: changed from 'Off' to '48VH'
Dec 31 19:24:29 switch[795]: Input voltage too low (52.6) for 48V operation, not enabling port 2

FIXES
Changed input voltage safety check to only work on WS-12-DC model
This routine could cause switches with AC or DC power supplies to turn off 48V POE if the input voltage sensors were damaged.

ENHANCEMENTS
- Added ability to emails log to arbitrary email address
- Added version selection for SNMP

Please read the release notes and upgrade your firmware viewtopic.php?f=17&t=240

[petecarlson]

Yeah, I've read it. It's running 1.3.2

[sirhc]

Yeah, I've read it. It's running 1.3.2

OK so I am stumped then.

This is a WS-12-250-DC unit and it is running v1.3.2?

Cranked up the input voltage. Getting:

Dec 31 19:24:25 UI: Port 2 PoE: changed from 'Off' to '48VH'
Dec 31 19:24:29 switch[795]: Input voltage too low (52.6) for 48V operation, not enabling port 2

If you goto the Device/Status Tab what power supply firmware is it reporting?

What did you mean by you cranked up the input voltage?

[petecarlson]

It is powered by a DC PS with adjustable output power (48-53V). Turned the adjustment screw.

[petecarlson]

Current Time 12/31/1969, 7:46:02 PM
Uptime 00:46:02
CPU Usage 30%
Memory Usage 44.02 MB
MAC Address ec:13:b2:81:02:5a
IP Address xx.xx.xx.xx
Firmware Version 1.3.2
Board Rev D
Power Supply Firmware Version 28

[sirhc]

It is powered by a DC PS with adjustable output power (48-53V). Turned the adjustment screw.

AC to DC Power supplies with a Trim Pot sometimes drop output voltage way down when adjusting the Pot as they are not meant to be a LAB power supply. This is why normally the factory uses nail polish to seal the pot once adjusted because if it moves it does weird things as the adjustable trim resistance can either OPEN the circuit or become just a short with no resistance.

We just purchased one for Dave to do this project and it costs thousands of dollars.

I ran into this on my bench using the trim pot on our 250 watt AC power supply to feed a DC switch I was adjusted the pot and voltage the voltage just dropped way down and I was like WTF?

But that does not explain why the WS-12-250-DC would report what it did other than possibly when you were adjusting the POT the output voltage went very low real fast and the DC power supply adjusted it's POE budget and refused to allow the port to be turned on?

I am not sure? Dave and Eric will have to weigh in on this as they worked together on this part and Eric would know what messages would be reported for what conditions more than me.

[petecarlson]

Didn't adjust it at all till after we were getting the low voltage warning. In fact, it was initially on a different power system and we powered it down and then moved it over to its own isolated power supply for testing.

I have techs on-site right now. Anything I can test or data I can pull?