what are the differences in using the following voltages?

12v -- ?
18v -- ?
24v -- ?

help is highly appreciated...

12v would not recommend it because the voltage drop in long cables could cause you problems.
You can use 18v but stp cable that are not too long.
24V is the voltage works best for me.

do you suggest 12v for system trials or demo? where the unit is very near to the battery... say the distance of is not 1 to 3 meters max??

-sid

do you suggest 12v for system trials or demo? where the unit is very near to the battery... say the distance of is not 1 to 3 meters max??

-sid

In that case, there is no difference which voltage to use.

will 12v 7AH battery do the work? and for how long will that work??

Hi ...

will 12v 7AH battery do the work? and for how long will that work??

Well, the last 2 RB433 I tested was unstable when battery drops to 12V. I mean, I had 411ARs that run ok from 13.6 (battery floating voltage) to almost 11V (drawn) then stops.

I replaced 411ARs by RB433 keeping the same wiring (7m UTP cable). The first time mains power went out the existing battery lasts 2 hours (a 45Ah one) then AP stopped. The 411ARs lasts 24 ... 36h.

Note that the single difference was an extra R52nM card (1.6 watts rated). I only move the existing cards from 411AR to 433 (e.g. a XR9 and changed the built in by a R52nM).

At the bench, the 433 delayed to boot from a 12.0V 2A power supply (using power jack). No problem at all with 15V on POE from a UBNT power supply.

Now my APs are 433, 433AH & 433UAH based.

So I'm changing all existing 12.6V solution (battery + floating charger) which I use to power 411ARs, WRAPs & etc for two 12.6V batteries in series + floating charger (27.4V) + linear 5A voltage regulator (22V).

Regards;

Thz for that, mramos

If you have only 3m of cable, then there is no problem to use 12V. If you run your device from battery, then it is better to use 12V, because then Routerboard takes less power than if you use 24V. Dont know why, just measured this behaviour. If you need longer cable, then use CYKY cable (e.g. 1.5mm) and end it up with a jack.

how much less power?

If you have only 3m of cable, then there is no problem to use 12V. If you run your device from battery, then it is better to use 12V, because then Routerboard takes less power than if you use 24V. Dont know why, just measured this behaviour. If you need longer cable, then use CYKY cable (e.g. 1.5mm) and end it up with a jack.

Are you refering to current draw from the battery @12volts and also current draw from 24v supply and is there a radio card attached.

We used a laboratory power supply with adjustable voltage output. As device we had RB433 with one R52 card. I dont remember the values, but I guess it was something like as few as 3W at 12V and 6W at 24V.

The only problem with battery is that its voltage varies from 13.8V to as low as 9V. Mikrotik says that Routerboard supports 10V supply. Under 10V it wont work I think. Anyway you should not go under 10V at your battery, it's not good for it's health. Usually 10.5V is the low limit. There is not much more capacity under 10.5V anyway. Maybe this is good for you to have 12V instead of 24V because if you use batteries in series and get 24V without any protection, then the routerboard will suck your batteries down to 10V (if that is even possible), but totally drop their voltage, which can be final for them.

Plus if you want more capacity, just plug the batteries in paralel and get more Ah. You can use any amount of batteries like 3, which you cant do when using 24V.

And yes, I remembered one more reason why to use 12V - if you use 2batteries in series, and you recharge them using 24+V (or higher), then the current will be the same in both batteries. But batteries sometimes differ in their capacity. So one battery can be already at 13.8V, but the second one will be at 12.5V. And if you want to get 13.8*2V = 27.4V (theoretical full capacity), then you will keep charging and charging and you will be overcharging the one that first reached 13.8V. Some people made a "battery balancer" or whatever they call it, but its extra money.

will 12v 7AH battery do the work? and for how long will that work??

I used 12V batteries with approx. 5m cables for measurements done in environment where was no electricity. One 12V 7.2Ah battery can power up RB433 with a R52 card approx. 10 hours without any problem (that was the time I spent in terrain, many times I used the battery twice without recharging, so I guess 15hours and more...)

We used a laboratory power supply with adjustable voltage output. As device we had RB433 with one R52 card. I dont remember the values, but I guess it was something like as few as 3W at 12V and 6W at 24V.

The only problem with battery is that its voltage varies from 13.8V to as low as 9V. Mikrotik says that Routerboard supports 10V supply. Under 10V it wont work I think. Anyway you should not go under 10V at your battery, it's not good for it's health. Usually 10.5V is the low limit. There is not much more capacity under 10.5V anyway. Maybe this is good for you to have 12V instead of 24V because if you use batteries in series and get 24V without any protection, then the routerboard will suck your batteries down to 10V (if that is even possible), but totally drop their voltage, which can be final for them.

Plus if you want more capacity, just plug the batteries in paralel and get more Ah. You can use any amount of batteries like 3, which you cant do when using 24V.

And yes, I remembered one more reason why to use 12V - if you use 2batteries in series, and you recharge them using 24+V (or higher), then the current will be the same in both batteries. But batteries sometimes differ in their capacity. So one battery can be already at 13.8V, but the second one will be at 12.5V. And if you want to get 13.8*2V = 27.4V (theoretical full capacity), then you will keep charging and charging and you will be overcharging the one that first reached 13.8V. Some people made a "battery balancer" or whatever they call it, but its extra money.

Ok just to rephase your first comment about

because then Routerboard takes less power than if you use 24V. Dont know why, just measured this behaviour

is correct about using less power but also it should be noted less power for the radio card so instead of giving out say 25dbm is will be much less and lower signal level from your AP than running at 24volts.

this to me needs more testing... if the routerboard is taking twice as many watts just using a different voltage then something is wrong. Watts are watts ...

The tx of the radio will not be affected. Thats just not true.

Can you retest and post exact values of observed draw at certain voltages?

this to me needs more testing... if the routerboard is taking twice as many watts just using a different voltage then something is wrong. Watts are watts ...

The tx of the radio will not be affected. Thats just not true.

Can you retest and post exact values of observed draw at certain voltages?

Using Ohm's law it's simple for power if you drop the voltage current must increase to compensate if not the power levels drop,
http://www.angelfire.com/pa/baconbacon/page2.html remember watts are not watts reduce one the other must increase?
Another example is in a audio PA amplifier with say DC rail voltages of +/- 90volts @230v AC input reduce the 230v to 170v and rail voltage could drop to +/- 70volts and output watts will also be reduced.

is correct about using less power but also it should be noted less power for the radio card so instead of giving out say 25dbm is will be much less and lower signal level from your AP than running at 24volts.

That is a nonsence. The output signal level is driven by programmable setting.

Can you retest and post exact values of observed draw at certain voltages?

Ok, I'm going to test this for you once again

is correct about using less power but also it should be noted less power for the radio card so instead of giving out say 25dbm is will be much less and lower signal level from your AP than running at 24volts.

That is a nonsence. The output signal level is driven by programmable setting.

Just think for a minute why do most WISP's use a 24V power supply @ 1.6Amps (or 800mA) to supply AP's when if as you say "signal level is driven by programmable setting" and just use a 12volt at 800mA, the only way this going to answered is when someone puts a RF dummy load onto the radio card and check with a RF power meter it's output dbm's when the DC supply voltage and current is varied.

Just think for a minute why do most WISP's use a 24V power supply @ 1.6Amps (or 800mA) to supply AP's when if as you say "signal level is driven by programmable setting" and just use a 12volt at 800mA, the only way this going to answered is when someone puts a RF dummy load onto the radio card and check with a RF power meter it's output dbm's when the DC supply voltage and current is varied.

The reason for using 24V instead of 12V is that you can have long cable from the power supply to the device. Using 12V and long thin UTP cable wires will cause significant voltage drop and losses on the cable. When using 12V on distance longer than few meters it is clever to use cable like CYKY or CYSY 1.5mm. But of course these are more expensive and you have to end them with jack... which is much more work than simply use UTP cable.

As you write "24V@1.6A or 12V@0.8A" - this depends on the power supply. You can find 24V@0.5A and also 12V@5A - that is no problem. It just depends on the construction of the power supply.

If you think more voltage = more rf power, or more Amps at power supply = more rf power, just do simple tests to prove you wrong. It does not matter if you use this or that power supply. You can still have your wireless card in Default tx power mode and you will get the very same output signal. Try it.

And now the testing results. Tested 3.11.2011, using laboratory power supply. RB433 was powered via jack, it had one CM9 card using 5GHz band (By the way CM9 card is a really bad card - it does not regulate under 10dBm at all. If you set 2dbm output power, it still transmits 10dBm.... what a piece of trash). Unfortunatelly there is no ethernet connected (it also takes some watts - something tells me it was +0.6W if any ethernet interface was connected), but still the results are nice.

By the way, I think this behaviour is caused by some stabilizator (stabilized voltage) on the board which transferes higher "unstable" voltage to stabilized 5V and 3.3V. The more voltage is on the input, the more loss has to occur on the stabilizer and therefore the device consumes more power.


Voltage Amps Watts
-------------------------------
10.5 ------- 0.25 ------ 2.63
12.5 ------- 0.22 ----- 2.75
15 --------- 0.19 ----- 2.85
18 --------- 0.17 ----- 3.06
20 --------- 0.16 ------ 3.20
24 --------- 0.1516 ---- 3.64
27.5 ------- 0.1420 ---- 3.90


Here are some photos of the measurement. The power supply shows Output voltage on its top LCD and Current on its bottom LCD. Multimeter shows precize value and proves it.

To prove to myself if the output of the radio card varies or not I must setup a variable test bench power supply and vary the voltage and current to a test AP and monitor with a CPE the db signal levels which should not drop when the voltage is reduced and current limiting is used on the power supply.

The radio card itself ALWAYS gets the same voltage regardless of the input voltage to the routerboard. There is a voltage converter on the router that supplies power to the pci card or built-in radio, always the same voltage.

Of course, higher tx will draw more current... and if your power supply can't supply that much current then it will be a problem... but that is current (amperage), not volts.

With reference to UBNT spec sheet http://ubnt.com/downloads/xr5_datasheet.pdf @54Mbps it requires 1.1Amps at 3.3volts, does this mean that the power supply must have a current rating in excess of 1.1amps?

With reference to UBNT spec sheet http://ubnt.com/downloads/xr5_datasheet.pdf @54Mbps it requires 1.1Amps at 3.3volts, does this mean that the power supply must have a current rating in excess of 1.1amps?

No, because the power supply is rated at a certain amps at 12 or 24 volts, not a certain amps at 3.3 volts.

Watts = Volts x Amps

Assume you have a power supply 12volts / 1.0 amps:

So, 12 volts at max 1 amp would be max 12 watts available from the power supply

3.3 volts at 1.1 amp would only be 3.6 watts used by the card. The routerboard itself uses around 6 watts (guessing) for a total of only 9.6 watts, below the 12 watts max from the power supply.

Also remember that the amps or watts on a power supply is the maximum it can output, not a constant. It doesn't always put that much out, it only puts out what the device pulls from it. You can not hurt anything by using a power supply with too big of a amp or watts rating. As long as it is at least enough, then it doesn't matter how big it is. If it is too small of a watts or amp rating, then it won't work properly.

The voltage, however, is constant and it does matter. If the device requires between 12 and 48, then make SURE your supply is within that voltage range.

No, because the power supply is rated at a certain amps at 12 or 24 volts, not a certain amps at 3.3 volts.

Watts = Volts x Amps

Assume you have a power supply 12volts / 1.0 amps:

So, 12 volts at max 1 amp would be max 12 watts available from the power supply

3.3 volts at 1.1 amp would only be 3.6 watts used by the card. The routerboard itself uses around 6 watts (guessing) for a total of only 9.6 watts, below the 12 watts max from the power supply.

Also remember that the amps or watts on a power supply is the maximum it can output, not a constant. It doesn't always put that much out, it only puts out what the device pulls from it. You can not hurt anything by using a power supply with too big of a amp or watts rating. As long as it is at least enough, then it doesn't matter how big it is. If it is too small of a watts or amp rating, then it won't work properly.

The voltage, however, is constant and it does matter. If the device requires between 12 and 48, then make SURE your supply is within that voltage range.

OK but why does the wattage reduce from 3.90watts,0.1420A,27.5volts to 2.63watts, 0.25A,10.5 volts, if the radio card just needs 3.3volts (not sure the current required for the CM9 card) but it must low as listed 13dbm@54Mbps http://www.cfide.com.br/SpecsCM9.pdf, why is there a swing of 1.3watts between the low and high voltage.

No, because the power supply is rated at a certain amps at 12 or 24 volts, not a certain amps at 3.3 volts.

Watts = Volts x Amps

Assume you have a power supply 12volts / 1.0 amps:

So, 12 volts at max 1 amp would be max 12 watts available from the power supply

3.3 volts at 1.1 amp would only be 3.6 watts used by the card. The routerboard itself uses around 6 watts (guessing) for a total of only 9.6 watts, below the 12 watts max from the power supply.

Also remember that the amps or watts on a power supply is the maximum it can output, not a constant. It doesn't always put that much out, it only puts out what the device pulls from it. You can not hurt anything by using a power supply with too big of a amp or watts rating. As long as it is at least enough, then it doesn't matter how big it is. If it is too small of a watts or amp rating, then it won't work properly.

The voltage, however, is constant and it does matter. If the device requires between 12 and 48, then make SURE your supply is within that voltage range.

OK but why does the wattage reduce from 3.90watts,0.1420A,27.5volts to 2.63watts, 0.25A,10.5 volts, if the radio card just needs 3.3volts (not sure the current required for the CM9 card) but it must low as listed 13dbm@54Mbps http://www.cfide.com.br/SpecsCM9.pdf, why is there a swing of 1.3watts between the low and high voltage.

The card always receives the same voltage (and also the same current per tx power). The card can not magically tell the voltage regulator to send it more voltage. In fact, the card has no way to know the actual input voltage to the board.

To prove, you need to measure current or voltage AT THE CARD, not at the power supply.

!!! >>> The operating current of the router's voltage regulator itself can vary based on input voltage. <<< !!! That is probably where the difference is coming from.

The voltage going through the board is always exactly 12 volts (or whatever) because of the regulator regardless of the input voltage.

why is there a swing of 1.3watts between the low and high voltage.

Probably due to onboard switched PSU/regulator efficiency X input voltage. It can (efficiency) vary a lot, depends on design.

If it was a linear voltage regulator, the "math" will be closer to the theory (e.g. if RB needs 6W, with 12V current will be 0.5A and with 24V current will be 0.25A).

Some mini PCI cards may have extra regulators but not at the 3.3V bus (but derived from it), lets say to drop the 3.3V to 1.5V (e.g. for PA biasing purposes) or even sort of built in voltage inverter (to increase 3.3 to 5V at the mini-pci card) to power a huge amp. Just guessin'.

Most cards sink less current at higher rates because the default power is decreased to avoid distortion (IM) at the card power amp. A XR9, for instance, sinks 1.1A (3.63W) at 6Mbps and 0.8A (2,64W) at 54Mbps.

Regards

Need help anyone my RB750Gr3 keeps making a beep noise every 10sec i check the power supply, used shorter PoE cables still getting beep.

A solution anyone please.