I've a 3DR hexacopter, new. 

It has the PM (Power Module), the PDB (Power Distribution Board) and an APM2.5 with no jumper on jp1.

Online, I've found some instructions telling me that when using the PM, one is to leave jp1 unjumpered, and to plug in the +5v coming from the PDB.


Is this correct?


Yesterday, I USB'd into the APM2.5, and downloaded 2.81 firmware.  So I know it's alive - so far.  Don't want to plug things in incorrectly.

Views: 4709

Reply to This

Replies to This Discussion

I think the wiki should be reworded to "no JP1 when using the power module." why add the ambiguity. I don't think the idea is to power servos with the PM module?

I just setup my Quad using the PM and i did not put the JP1 jumper in i left all the other connections in place as they were and the Quad performs fine.  It real should say if using the PM do not use the JP1 jumper. I also tried it without using the PM and installed the JP! jumper and the Quad ran fine.

Yes I had the +5v from the PDB connected to the APM 2.5 as well as having the PM connected and all works fine.

The electronics refers to the APM and R/C Receiver, it's confusing terminology.

I think that if you power your board using the APM PM you should not ever have JP1 in place to connect INPUT and OUTPUT 5V rails. The reason I say this is that the APM PM is rated 2.25A MAX, so driving additional servos could quickly max this out and cause a brown-out.



I just finished assembling the 3DR kit for Quad Arducopter and has the same questionning. The documentation for using the 3DR power module on one hand and the page on optional additions (voltage and current sensors) are not clear at all.

There is the paragraph that I do not understand clearly :

"..It's also possible to power APM 2.5 from two separate sources, one powering the RC system on the input side, and the other powering the output side (servos or ESCs). This is determined by a jumper on the JP1 pins (see below). If the jumper is on, which is the factory default, the board is powered from the Output rail or the USB. If the jumper is off, the board is powered from the Input rail, but the Output rail will need its own power source. This configuration is used if you want to have two separate power sources in your aircraft, one powering the servos and the other powering the electronics. The ideal input voltage is 5.37v +/-0.0v and may not be provided by a typical ESC."


As I use the Power Module I was forced to remove the JP1 off the APM2.5. Then I understand according to this copied parapgraph that I would need a second battery to power the R/C ? (while the first one only power the motors through the power module connected to the PDB) Is this correct understanding or not ?


Thx for help


thx a lot. Ok so when they say on the wiki "two power sources", they do not mean two batteries but two "wires" or "circuits" from the same battery, right ?

So you use still one battery to power everything ? At the moment I have no extras on my Quad. But later on I would like to add a camera gimbal with servos on it. I wonder if the 5v Cable from the PDB that is connected on the outputs can deliver enough power to these servos ?

If I want a second battery+BEC to power the servos of the gimbal (or other optional stuff besides APM and motors) how do I connect the 5v wires from the BEC of that second battery to the APM ? (on the outputs rail ? If yes, what to do with the 5v red&black wire from the PDB that is already on the outputs ?)



many tx

I agree, this stuff is confusing. I can try to explain, but I think i need to get a good diagram together that will really help. In the meantime, think of it like this. In your system you have one source of power, the battery, and its at a nominal voltage e.g of 11.1Volts (3s 3.7V*3) or 14.4Volts (4s 3.7*4). The APM, RX and servos need only a 5 Volt supply. This means you need something that converts the battery voltage from e.g 11.1V to 5Volts. These devices are known as regulators. Each regulator will deliver 5Volts to a maximum number of amps. You can have many regulators on one system. For example the APM Power Module is spec'd to 2.25A. The ESCs each can deliver a 5V from the battery up to max number of amps of 3A or 5A typically. ESCs have this feature to supply 5V since each one has an internal micro-controller that needs power to operate and they usually a have some capacity left over.

The idea is with JP1 off, is that the APM PM powers the more sensitive "electronics" and the power side of servos and motors are powered by the ESCs internal regulator.

The problem with using the regulator in the ESCs is that when the ESCs is under a lot of load the motor & servos it can cause the regulators voltage to drop, and if it's connected directly to APM  (via JP1) it will reset and this can cause catastrophic outcome (brown out). Having a separate regulator connected to the APM/RX  this event is much less likely to happen. Hence the new APM PM powers the APM and RX but not the servos etc.. The servos would be powered via  ESCs connected to the outputs . The power to the outputs comes via the PDB board which the ESCs are connected to. The ESCs have the regulators converting the battery power to 5V.

Again to repeat, with split power regulation helps avoid a board reset due to brown out, so it will be quicker to recover after the critical event.

With all that to answer you specific question of adding a second battery to power the servos, servos can draw 0.4 to 0.5 A when moving under no load (which is more Amps when they have resistance to movement!), you can supply 5V via a BEC to the OUTPUTS Use a (5A BEC for examples), but disconnect the PDB 5V line as you would need to break that connection as it's not the source of power anymore. This would mean the servos would now not draw any power from the main battery just this second battery.

( as a side maybe it's good to remember that a 'power source' can either mean battery or voltage regulator, but the regulator also needs to be connected to 'real' power source ie. battery!)

Good points about the confusing text -- thanks to everyone who pointed this out. We'll clean that up over the next few days. 

In general, most Copter users should leave APM 2.5+ just the way they got it, with the jumper off. 

>>> Does the jp1 jumper connect the output conn's 5v rail with the APM's 5v rail?

If so, then it's function becomes quite clear.

Yes it does

>>>Yes I had the +5v from the PDB connected to the APM 2.5 as well as having the PM connected and all works fine.

You should only do this when JP1 is removed

>>>Then I understand according to this copied parapgraph that I would need a second battery to power the R/C ? (while the first one only power the motors through the power module connected to the PDB) Is this correct understanding or not ?

No, you only need one battery.  Power module will provide power to the APM and no further connections are required.

Reply to Discussion


© 2018   Created by Chris Anderson.   Powered by

Badges  |  Report an Issue  |  Terms of Service