daisy chain ws6mini voltage drop

[ColoCenter]

Hi,

I have daisy chained two ws-6-mini's. I have used the PA-50V-65W with POE injector to get power to the first WS6mini. Cable lenght is about 50-60 meters. Then that ws6mini is powering the second ws6mini over again 50-60 meters of UTP.
The problem is that the 50V has already dropped to 43-44V at the first switch, and then dropping even further to 39-40V at the second switch.

The switches are functioning, but the second switch sometimes gives a warning of low voltage. IS this going to be a problem.
Can i also use this PSU for example:
http://uk.rs-online.com/web/p/poe-injectors/7653358/
It's output is 56V, giving a bit more room for the voltage drop.


Thanks

[lligetfa]

AFAIK 56V is the absolute upper limit on the MINI so relying on current affected voltage drop may be risky. Dave may want to weigh in here. ISTR Chris mentioning that they might try to source a 54V PoE brick which would give us an extra 4V of margin. Of course, having an unmanaged PoE source denies us remote toggle capability.

As far as the low voltage alerts, there was talk about possibly suppressing them. I don't know if any work was done on it since the cold weather abated and my cameras no longer go into heating mode so draw less current. If you only use 24V to end devices, the alerts are mostly cosmetic as the MINI can run on lower voltage and the 24V side does not sag.

[sirhc]

50V has already dropped to 43-44V at the first switch, and then dropping even further to 39-40V at the second switch.

IS this going to be a problem.

It's output is 56V, giving a bit more room for the voltage drop.

AFAIK 56V is the absolute upper limit on the MINI so relying on current affected voltage drop may be risky.

Well Les is correct that 56V is the upper limit but as long as you never power the MINI direct without the long cable you should be fine as it will be down to 50V by the time it gets to the first and down to 46V to the top.

[lligetfa]

I wonder how accurate the Vout is on that PoE brick? Some power supplies may float higher under a small load so wonder about adding overvoltage protection.

A while back I asked about powering the MINI with 56V and you talked me out of it. I thought maybe you were concerned the voltage may float higher on a small load.

I also asked if the barrel connector was in parallel with the PoE in and did not get an answer. I suppose I could have put a voltmeter and/or perhaps a small load on it to see. One thought I had was that if the PoE in voltage is also present at the barrel connector I could put a zener diode and load resistor on it to crowbar any possible overvoltage.