DJI Naza ESC red wire cutting/removal, urban myth?, I think so

[DarkButterfly]

Just recently put together my heavy lift quad with the DJI Naza - M lite FC.

Before I had even connected a single wire to it, I read the manual front to back and checked out forums and articles on the net and most people seem to have this thing about cutting or removing the red wire from the ESCs, but nowhere in the manual does it say to do this... so I didn';t, all my red wires are still connected.
I';ve been flying it now for about a week or so and so far **knocks on wood*** I haven';t experienced any issues regarding the ESCs, the only time I had an awkward landing is because I was flying with a camera that was too heavy, but it wasn';t a crash or failure.

I think the whole red wire thing is just an urban myth, if DJI needed us to remove this wire, surely they would have mentioned it in the manual, or on their website.

[Biffa]

I never bothered when I had my Naza Lite and never had an issue.

I know some FCs do require only one + feed and do call for the others to be removed, something to do with noise from the different BECs I believe

[atomiclama]

I think it is down to the regulator on the ESC..

If your ESC has a switch mode psu then you sould not put those in parallel.
If it has a linear regulator then it should be ok if there is low value balancing resistor in series with the output. Otherwise they will fight to regulate the 5V one will loose and get hot.

My ESC each have 2 reg on them each has 220 resistor to balance the load.

But that might be a big pile of poo, someone more qulaified might have a different answer 

[flybywire]

Yeah, same as Biffa, I always leave them connected now, but like you, was initially puzzled by the conflicting forum advice.   Best I can tell you, is that somebody said that if they are ';switching'; BEC';s then they';re ok, which most are these days anyhow I believe. 

Interestingly enough, a few years ago, I was advised to disconnect the power wires to my WKM, which I did without question, but I';m not sure if it is actually necessary tho, both my Naza';s V1 & V2 work fine with!

[HowDoIfly]

I don';t know about Naza but this advice is rampant among the APM threads.

AFAICT, the idea is to use a "cleaner" "more reliable" power source for your FC/RX than the cheap ESC regulators. Following this advice makes the red and black wires redundant. There';s other "benefits" mentioned so the conclusion is to remove both wires or at least isolate and tuck them out of the way.

[BJT]

Surely if naza and other flight controllers don';t want the red wire connected then they wouldn';t connect the positive pin internally. Therefore cutting the red wire makes no difference

[DarkButterfly]

Surely if naza and other flight controllers don';t want the red wire connected then they wouldn';t connect the positive pin internally. Therefore cutting the red wire makes no difference

That';s what I thought.

I';ve seen it on many threads with different flight controllers, on the Crius AIO board, there is a jumper, pull that and the board can only be powered from the external power pins, by an external UBEC, the ESC BECs are completely isolated, meaning cutting the red wires is a pointless exercise.

[atomiclama]

I think the jumper isolates the ESC power from the board but it does not isolate each individual ESC so you can still get the regulators fighting each other, not good..

[HowDoIfly]

It';s not pointless if they';re redundant. First off there';s the transmission of vibrations to the FC is eliminated. Secondly, if the grounds are not isolated, there';s something called a "ground loop" to consider.

[Cloudbuster]

Pretty sure that all the inputs are only wired for the control wire on all DJI controllers hence why they supply a PMU which plugs into the specific port !!! Apart from that if it were going to be a problem why would they supply cables with all three wires connected ???

Regards rob 

[BJT]

It';s not pointless if they';re redundant. First off there';s the transmission of vibrations to the FC is eliminated. Secondly, if the grounds are not isolated, there';s something called a "ground loop" to consider.

First point as there are still wires from each esc  connected to the FC I didn';t think cutting the red wire is going to reduce vibration by any measurable amount.
Secondly, for a ground loop the esc end of the neg wire would have to be connected to at least one other esc ground otherwise no loop. Not sure a ground loop would cause a problem anyhow.

[Chami82923]

I know some use the naza with esc';s that have a bec and don';t disconnect the red wire, this was my intention with my latest build, but once built and connected, could I get the bloody thing to work, naza m lite, 3s battery, and 12a Afro esc';s with simonk.

Checked and rechecked everything, then just for sh*ts an giggles! I pulled all the red wires from the esc connectors, simple as that! it all worked perfectly.

I definitely think it depends on your esc';s, my concern would be if you had 3a bec esc';s, they could all be working against the pmu and damage the fc.

Callum

[HowDoIfly]

First point as there are still wires from each esc  connected to the FC I didn';t think cutting the red wire is going to reduce vibration by any measurable amount.
Secondly, for a ground loop the esc end of the neg wire would have to be connected to at least one other esc ground otherwise no loop. Not sure a ground loop would cause a problem anyhow.

The way I see it (as it is on my APM) I have 4 rather than 12 wires acting on my gyro';s. As for ground loops, connecting the ESC';s to the FC is creating the connections. No, I don';t know what the potential risk of a ground loop for the APM is which is why I chose to not connect them if they';re not needed.

[Friskle]

Yeah, same as Biffa, I always leave them connected now, but like you, was initially puzzled by the conflicting forum advice.   Best I can tell you, is that somebody said that if they are ';switching'; BEC';s then they';re ok, which most are these days anyhow I believe. 

Interestingly enough, a few years ago, I was advised to disconnect the power wires to my WKM, which I did without question, but I';m not sure if it is actually necessary tho, both my Naza';s V1 & V2 work fine with!

on my WKM, i used to have the red wire connected, being honest, i missed the bit in the manual at the time, that said remove it if using 3rd party ESCs, and being honest, was never happy with its performance, i later did remove the red wires, and performance was a big improvement, when connected, not all the time, but it would oscillate, small amounts, but annoying, after removing the red wires, it always performed smoothly.

i suppose the way to look at it is, the System has its own BEC system, whats the point in having ESCs with one, a dealer once said to me after questioning it was, effectively you could end up with two BEC devices fighting with each other, how true..who knows, but i do know my WKM performed substantially better with the red wires removed.

my Naza are all connected, as nothing in the manual says remove them, on that i have had no issues  so far.

[SeamusOD]

The new naza lite is powered by the v sens as they call it, a bec with a input to also monitor Lipo voltage.  This is plugged normally into aux 3 port which powers MC and receiver.
The other side of the MC controls the motors and dosnt need power so if the naza designers are clever they would have left the centre pins unconnected

[dirtyharry]

From what I have learn';t the following is about right.

99% of  esc';s have a bog standard 5v  linear voltage regulator, cheap but  in-efficient clean dc supply ,  they  loose voltage by burning it off,   You can link them together with no ill-effect apart from a bit of heat.

The rest have switching regulators.

Switching regulators are way more efficient but can create more noise ( they chop the dc up and glue it back together to create a lower voltage) . After-market "becs " are usually like this , the good ones will have a metal shroud to isolate the noise . (you can';t link them together as they fight with each other).

personally I cut all the + and - wires and use a low noise turnigy 5v bec to run everything. Less wires and it works. -ve is connected to the esc';s anyway so why double it up through the servo wires.

[realpastaman]

The new naza lite is powered by the v sens as they call it, a bec with a input to also monitor Lipo voltage.  This is plugged normally into aux 3 port which powers MC and receiver.
The other side of the MC controls the motors and dosnt need power so if the naza designers are clever they would have left the centre pins unconnected

I just checked a Naza V2 and a Naza lite by connecting an ohm meter between the pins that go to the red esc wires.
From these measurements it seems like the red wires are directly connected together inside the Naza.

In this case it will not be a problem if the esc uses a linear bec but could be a problem if the esc uses a switching bec. I have three Naza flight controllers and dont disconnect the red esc wires. All my esc';s use linear bec.

[John A]

Personally, I would not connect regulator outputs (ESC  or BEC / UBEC) together without knowing details of the circuitry. I would hope that there is some form of protection to prevent back-feeding. If one output is slightly higher than the others you risk back feeding current into the low outputs. This may, or may not be a problem but would be considered bad practice. If one regulator should fail short circuit it would short the others out and possibly cause them to fail. As the ESC needs only a signal input (with a ground reference to work against) I remove the red wires from my ESCs, fold them back and heat shrink them. This way any questions about connecting red wires are negated.

[SeamusOD]

I just checked a Naza V2 and a Naza lite by connecting an ohm meter between the pins that go to the red esc wires.
From these measurements it seems like the red wires are directly connected together inside the Naza.

In this case it will not be a problem if the esc uses a linear bec but could be a problem if the esc uses a switching bec. I have three Naza flight controllers and dont disconnect the red esc wires. All my esc';s use linear bec.

There is no need for the esc positive line to be connected together inside the naza box it serves no purpose, each pin should have had just a single solder pad on the pcb, would have thought the naza designers were clever than that.

No mention in the naza instructions about removing esc wires so if someone does use switching bec and they are damaged when plugged into the naza MC then DJI are at fault,
1 for bad circuit design and 2 for not making users aware of a potential problem.

[Bigtexun]

As a power supply engineer, I am familiar with the issue presented here.

The basic issue is "why shouldn';t I connect the outputs of multiple power supplies, what could possibly go wrong?"

There are several things that can go wrong.  First let';s tackle the large one, you are connecting the regulated outputs of several regulated power supplies.  As is typical for a series of identical power supplies, the exact output voltage of an individual power supply will vary by some small amount.  So if you take three power supplies, you will measure three different voltages (if your measurement equipment has enough resolution).  Let';s say you connect three power supplies, one is at 4.99998v, the next is at 5.00001, and the third is at 5.00000v.  All of these will measure 5.00v on a meter that has two decimal places of resolution.  So let';s connect all three together to feed power to an LED, by way of a current limiting resistor.  The resistor lights, and all seems well.  But when we take a deep look at the power supplies, we see that the 5.00001v power supply is providing all of the current, while the others act like they are off...  This is the best case, one power supply, the one with the highest voltage, powers everything while the others go idle.

But what if the two lower voltage power supplies are designed to bleed-off the extra voltage?  In that case, the 5.00001v power supply will see extra load as the other power supplies source current in an attempt to shed the extra voltage. So two power supplies are generating heat,. as they try to dissipate the excess voltage.  This causes the 5.00001v power supply to work even harder.  You may see nothing but shorder battery life, and excess heat... but you *could* eventually burn something up...  When connecting power supply outputs, you must design the regulation circuits to not fight each other, otherwise you can loose efficiency, or cause circuit failures.

Often a power supply uses it';s own output to power some of it';s own circuitry.  If this load exceeds the carrying capacity of the wires in use, and this is made worse by 2 of the three power supplies being off because the 5.00001v supply is carrying the load for all three.    In this case, the external circuits become overloaded, and a failure results.  The failure can be a burned connector, or something much worse.

Then there is the case of power supplies that cause unexpected current loops.  So for example, say you have an ESC, and it has some sort of issue, perhaps from the power problems above, or perhaps a part fails.  It no longer can produce current for the intended load, and it may attempt to pull power from the output that exceeds the capacity of the circuit.

All sorts of things can go wrong.  The basic error is never, ever connect outputs together, without designing a circuit specifically for this purpose.  You might get away with it.  You might not.  If you do, you are lucky that a broken circuit design hasn';t burned your bird up.  But it is 100% luck and 0% skill.  If you want your stuff to work because you exercise skill, because it is designed to actually work (on purpose),  then don';t connect outputs.  Just because it seems to be ok doesn';t mean that it is.  At best, a bad design will suck power and reduce flight times.  At worse it will cause parts to fail and possibly cause your bird to fall from the sky, and may even start a fire.

Yes, I have connected outputs together.  And yes, it sometimes works. and sometimes fails miserably.  You can do it successfully, but is it dumb luck , or is it skill because you designed it to work?  If you are connecting things coming from different manufacturers, then the odds of success diminish. 

Just because you don';t see a problem doesn';t mean one is not there.

[quadfather]

As a power supply engineer, I am familiar with the issue presented here.

The basic issue is "why shouldn';t I connect the outputs of multiple power supplies, what could possibly go wrong?"

<snipped for brevity>

Just because you don';t see a problem doesn';t mean one is not there.

Brilliant explanation. Thank you!

It';s often said, anecdotally rather than factually, that you shouldn';t hook up several switching supplies, but that linear ones are fine.  Could you shed some light on that?

[rsmith21]

Yes, very informative and confirming other articles I have read regarding benefit of removing the red wires. I had forgot to do it on my latest build but was reminded by another thread and simply slid the pins out and put a little heat shrink on them so that should I want to, I can re instate them.

My thinking was that if there is any doubt about the various power supplies working against each other its safer to not use them, I';ve not had the weather yet to see if flight times are a little better, I suppose in a bad mismatch it could consume a reasonable amount of juice.

Bob