Hi all,

I've got a TP link AP model WA901ND

Issue is, the client im installing this for cannot get another power point for a transformer to the cupboard it's required in and does not want to add another power board as it's cluttered.

:. I have a power AC/DC to DC Buck Step Down Adjustable Volt Converter 9V. With this I am able to use the power from the access control module which is 12vDC maximum 0.5amps to run through the (buck) and step it down to 9vDC. I cannot draw more than 0.5amps, otherwise I will cause issues on the access control module.

My questions is if this TP link device uses 5.8watts @ 9vDC how many amps will it require when stepping down from 12vDC.
The original transformer supplied is 9vDC 0.6amp supply.(not being used)

Can someone tell me this and how this is calculated.

Thanks in advance.

 

Hi PistolTech,

At 100% efficiency the power used will remain the same.. so 5.8W / 12V = 0.483A. However your regulator will not be 100% efficient, more likely around 80% (if you check the data sheet for the IC used, you can get a better idea.)
So actual power will be something like 5.8W x 120% = 6.96W = 0.58A @12V

 

Hi pmd34, thanks for your reply.

So that said, since the access module only allowed a maxmium 0.5amp load, it would be fair to say this concept will not work.

Question answered
Thanks again!

 

Do you have a POE switch? I use a 24 port POA switch here at home so my Voip phones are directly powered via the 48V supplied on the Ethernet cable. Also, a number of other devices are powered over POE with these TP-Link POE10R devices...
https://www.amazon.com.au/TP-Link-TL-PoE10R-Splitter-Adapter-compliant/dp/B0141JRPSU
They can supply 5, 9 or 12V to your target device.
This saves running extra power so my IP cameras and other devices just plug into the network. Very handy.

 

Hi all,

I've got a TP link AP model WA901ND

Issue is, the client im installing this for cannot get another power point for a transformer to the cupboard it's required in and does not want to add another power board as it's cluttered.

:. I have a power AC/DC to DC Buck Step Down Adjustable Volt Converter 9V. With this I am able to use the power from the access control module which is 12vDC maximum 0.5amps to run through the (buck) and step it down to 9vDC. I cannot draw more than 0.5amps, otherwise I will cause issues on the access control module.

My questions is if this TP link device uses 5.8watts @ 9vDC how many amps will it require when stepping down from 12vDC.
The original transformer supplied is 9vDC 0.6amp supply.(not being used)

Can someone tell me this and how this is calculated.

Thanks in advance.

The description of that AP says it can do PoE, why not use that?

 

The description of that AP says it can do PoE, why not use that?

Thanks for reply

There are no PoE switches there. Only thing available is 12VDC 0.5amps from access control system

 

Thanks for reply

There are no PoE switches there. Only thing available is 12VDC 0.5amps from access control system

So the ethernet port of the AP plugs into a switch in the same room?

 

You could put a PoE injector on an ethernet run that goes near a receptacle, and use an extractor in the closet for your power.

Here's an example: https://www.lifesafetypower.com/docs/ds_npe130.pdf

 

#1. 9 V @ 0.6A; What does that mean. You could supply 9v at 1.5 A and it would work fine, The actual power requirements and the adapter specs can be different. The adapter provides a bit of current limiting etc, 9v at 12 A would work too, but if the 0.6 A device has no other method of current limiting, you can be in trouble.

#2. The relationships are V1*I1 = V2*I2 , so 9*0.6 = 12*I, so I supplied would have to be 0.45 A which is close to your 0.5V rating.

#3 The relationship of power in to a power supply and power out of a power supply depends on the efficiency of the power supply. Numbers might range from about 60% to 95% with 80% being a good number if you want to guess.

example: A 120 VAC input 12 V 1A power supply.
It can supply 12 W to the load.
it would draw 0.1A at 120 VAC if 100% efficient.
Since it's 80% efficient, it would draw 0.125 Amps.
Power in is greater than power out.

POE is a good way to get power some place when you need it. I think you can get up to 90W, I think with some of the standards.
When you have say devices with a 12V 1A DC barrel connector that doesn't support POE out of the box, you can use a midspan POE injector and a POE splitter.

Somewhere midspan convienient, Ethernet goes in an POE Ethernet comes out. That device needs 120 VAC power typically. the real POE standard has some signature tests that it preforms that sets power limit. It will not apply the full 48-50 VDC UNLESS there happens to be connected to a POE device connected.

There is also passive POE. that generally uses the spare cables and just puts power there. You risk damage, but it's significantly cheaper.

At the PD (Powered Device) end you again have a POE cable going in and a non-POE Ethernet cable coming out. That goes to your device.
This PD splitter takes the 48-50 Vdc and creates nominal voltages for devices.

The whole POE mess is tough to sort out. it's relaively easy if all 4 pairs of the Ethernet cable are used. For reference, a gigabit cross cable would only have PR1 (Pair 1) and PR2 crossed. PR3 and PR4 are straight. My definition Gigabit Ethernet auto MIDX, so it does not matter,

So, at home, I can run my DSL modem close to the NID where it belongs from a POE Ethernet cable originating where my NAS server, router switches are that are UPS backed up. I happened to run 2 pair cables from the modem to the router because I got them free. They were installed at work when 10 baseT was the standard. That got ripped out and replaced.

For home I bought two boxes of 250' CAT6 in two jacket colors. Only CAT6 RJ45's will be installed in rooms for Ethernet or telco. If I need an RJ11 for telco, I'll use inserts and have a IP phone upgrade path.

 

Thanks Yaakov for detailed reply

I could put a meter on it and test it I guess.
To answer the PoE portion. I will Ben using this in client mode, which basically allows the AP to connect to the wifi signal coming from somewhere else that it will talk to.
This will allow the access control unit a feed to the outside world.