Passive PoE output "voltage_too_low" with 802.3af camera — confirmation needed

RouterOS General
1

I'm trying to power an Aqara G5 Pro IP camera from ether5 on my MikroTik PoE switch (connected behind a HEX S router). The camera requires IEEE 802.3af.

Current ether5 PoE settings:
• PoE Out: auto on
• PoE Voltage: high
• PoE Priority: 2
• PoE Out Status: voltage too low

The camera never powers on and the port reports "poe-out status: voltage_too_low".

After reading the MikroTik PoE-Out documentation, my understanding is that my switch provides passive PoE only (up to 57V, no negotiation), and the Aqara G5 Pro requires active 802.3af negotiation — so the camera correctly rejects the voltage and the switch reports "voltage too low" because it never gets the expected resistance handshake back.

Can anyone confirm:

  1. Is this the correct diagnosis?
  2. Is there any configuration that would allow a passive PoE port to power a strict 802.3af device, or is an external 802.3af injector the only solution?

Switch model: CRS112-8P-4S
RouterOS version: 7.16.2

Thanks

2

How (exactly) are you powering that switch?

The switch can provide THREE kinds of power out:

  1. "low voltage" (18-28 V) passive
  2. "high voltage" (48-57 V) passive
  3. "high voltage" (48-57 V) active (802.3af/at)

The switch comes with a 28V power supply.

With that power supply you can only have "low voltage" (passive) PoE out.
(there is no internal voltage conversion, if you input 28V you get 28V out, if you input 48V you get 48V out)

You need to replace it with a suitable 48V-57V power supply if you want to have (active or passive) "high voltage" PoE out from it.

A suitable Mikrotik brand power supply could be the:
https://mikrotik.com/product/48v2a96w
but it depends on how many devices you want to power with PoE out and their power requirements, if you only have that single camera to power, you can go for a lower amperage one.

3

Possibly important to note: I'm currently using the switch to power 4 CAP AC units too, assuming they wouldn’t be affected by this ?

4

Wow really? So simply buying a stronger power adapter should do the trick?

Is this safe?

5

cap AC can accept low POE in voltage, that's why it works. But it also accepts active high input.

Sure it is. The device is made for it.
Just make sure your power adapter can provide enough power to feed switch, 4 cap ACs and that camera.

6

https://mikrotik.com/products?s[0]=CRS112

This product page shows the required powersupply as an optional accessory.

7

The CRS112 by itself is 10W.
CAP AC's are 12 W each, so 48W (assuming they don't have anything powered from them).
The camera is surely within af, so 15W or less.

10+48+15=73W

The 48v2A96w is 96W so it will be fine.

The max output at "high voltage" PoE for the switch is 1.4 A, or 48*1.4=67.2 W, which is just about right for 73-10=63W loads (in reality both the CAP's and the camera will use less power than the max in specifications).

8

so useful! Appreciate it! Now I just have to find somewhere to buy that .. or find a non-MikroTik power supply with this spec. I assume it may be in any electrical supply store

Thanks I'll update how it went

9

Any 48V PSU should do it, as long as there is enough power for all your devices.

1 Like
10

You can use both 28 and 48 volt psu at the same time and you will be able to supply with both voltages depending on your needs.

11

thank you all for your attention and assistance, this has been super helpful. I'll take it from here and report back on results.