Read: 3G Servo Bus Concern

[HiroboFreak]

I'm having great results too.

T-rex 700, AR7100R, DS8915's/8717's @8v, single piece of 3m #4010 tape with NO MODIFICATION TO THE POWER SYSTEM.

It just works.

[DesertClimber]

Originally Posted by chosen69

Desert climber - I don't see how this is gonna avoid getting all the power to your system either way via just one thin wire connection - namely the one from your battery to the receiver

It doesn't avoid one wire powering everything, as most receivers only have one wire powering everything anyway. That wasn't the issue.

The issue was one wire powering the 3G system, and the 3G system bus providing power to everything past that point. The diagrams posted earlier (and what I did as well) completely bypasses the 3G unit for cyclic servo power so if there are any issues with the bus power provided by the 3G unit, it becomes a non-issue anyway.

Just taking a possible weak link out if the chain...

[Footey]

LOL I skipped the last 300 posts on this one....

Now your whole heli is full of single wires that can send the machine into the ground, I reckon I could cut any single wire on a heli and render it usless.

I know a lot of guys love to think that the servos on thier little helicopter can drain the national grid and could be the sole reason for global warming but the reality is that you can do four hard 3D flights on a 1900mAh battery and still have some left in the tank so exactly how much power do you really think your servos are pulling?

Looks like a storm in a tea cup to me.................

[Globs]

Originally Posted by Footey

LOL I skipped the last 300 posts on this one....

Ok..

Originally Posted by Footey

Looks like a storm in a tea cup to me.................

Then you were correct with your first statement.

[DesertClimber]

Originally Posted by Footey

Now your whole heli is full of single wires that can send the machine into the ground, I reckon I could cut any single wire on a heli and render it usless.

Yup, that's just the way it is... That's just a lack of redundancy. Cut the ELE servo signal wire and see how it flies, or the AIL power wire, or the Gyro... or...


Shoot, I seem to fly erratically after a haircut!


.

[egiraldo911]

It doesn't make sense what you are saying about full of single wires. There are just single wires sending the signals to the servos anyway. So, what are you talking about? The heli is not more supceptible to a crash just because there is only two wires that are left by themselves in the 3G unit. I think you guys don't get the whole picture. It was proven in tests that a sudden overdemand of power from the servos can shut down the 3G unit. Maybe because of a bind link or whatever. What is wrong with having a robust system? Besides, all the wires still stay where they are, all you are doing is splitting the power cables coming from the two servos and pluging them in the receiver instead. That is all! Nothing to it. The signal wires stay where they are suppose to be and there is no more additional wires added. Just get a sharp point to unlock the connectors from the power plugs of each servo and reconnect them in the plugs of the PIT and ELE signal cables comming from the 3G unit and going to the RX. If you look carefully and think about, there was already single signal wires coming from the 3G unit to the RX for the PIT and ELE connection. You just change where the single wires are now, but, most of the power demand is now coming from the RX which can handle it better, and in case of a brown out, it can restart. I understand the 3G unit just shuts down and that is it.

I say, don't be afraid of adding a little security to the system. You will fly with confidence.

[JesusFreak]

Originally Posted by egiraldo911

It doesn't make sense what you are saying about full of single wires. There are just single wires sending the signals to the servos anyway. So, what are you talking about? The heli is not more supceptible to a crash just because there is only two wires that are left by themselves in the 3G unit. I think you guys don't get the whole picture. It was proven in tests that a sudden overdemand of power from the servos can shut down the 3G unit. Maybe because of a bind link or whatever. What is wrong with having a robust system? Besides, all the wires still stay where they are, all you are doing is splitting the power cables coming from the two servos and pluging them in the receiver instead. That is all! Nothing to it. The signal wires stay where they are suppose to be and there is no more additional wires added. Just get a sharp point to unlock the connectors from the power plugs of each servo and reconnect them in the plugs of the PIT and ELE signal cables comming from the 3G unit and going to the RX. If you look carefully and think about, there was already single signal wires coming from the 3G unit to the RX for the PIT and ELE connection. You just change where the single wires are now, but, most of the power demand is now coming from the RX which can handle it better, and in case of a brown out, it can restart. I understand the 3G unit just shuts down and that is it.

I say, don't be afraid of adding a little security to the system. You will fly with confidence.

Yep, 100% Agree. Simple and it works like a charm.

[jondabear]

Just curious........any one recall what voltage the 3g would shut down at?

I already know this answer but just am curious if people realize how low of a shut off it really was.

Good strong batt. will take a beating and......maintain proper v ,even under load or loads.

I m not gonna really get into this whole 3g "BUS " thing as I believe differently from the research and applicational knowledge ive gathered. BUT.......if it makes you feel better to do a power mod. Fly with confidence as my friend has stated.

From my angle, and for me and me ONLY, The BUS concern is like a UNICORN. MIght exist, ......might not.........Ill choose the latter from the tech that Ive explored inside the boxes. But thats just me.

100 + flights on 2 -3g STOCK systems, and not an once of worry or probs. Ill keep updating my other thread so everyone gets a chance to see JUST how long my two systems LAST without ANY mods. I might even take a pic of the control board to show if theres been any overheating or degredation of the traces for the power side of this system.

Most of all, have fun with whatever you do and Ill c ya in the air! PEACE!

[TopGunRC]

Originally Posted by jondabear

Just curious........any one recall what voltage the 3g would shut down at?

I already know this answer but just am curious if people realize how low of a shut off it really was.

Good strong batt. will take a beating and......maintain proper v ,even under load or loads.

I m not gonna really get into this whole 3g "BUS " thing as I believe differently from the research and applicational knowledge ive gathered. BUT.......if it makes you feel better to do a power mod. Fly with confidence as my friend has stated.

From my angle, and for me and me ONLY, The BUS concern is like a UNICORN. MIght exist, ......might not.........Ill choose the latter from the tech that Ive explored inside the boxes. But thats just me.

100 + flights on 2 -3g STOCK systems, and not an once of worry or probs. Ill keep updating my other thread so everyone gets a chance to see JUST how long my two systems LAST without ANY mods. I might even take a pic of the control board to show if theres been any overheating or degredation of the traces for the power side of this system.

Most of all, have fun with whatever you do and Ill c ya in the air! PEACE!

Totally agree

[MrMel]

I think it's as simple as it depends on the soldering job, in the pictures in the beginning of this thread, there is some very dubious soldering work.

I finally got a unit to test, and this one the soldering looks good and it has NO problem with power supply with only one cable.

Using a Oscilloscope I used 2s A123 pack with about 6.63v input, and measured at the servos during fast movement it never dipped below 5.04v.

That said, I have personally seen those that has failed too, meaning either Align changed something (this was a V2 unit I tested now) or simply put its down to the soldering work.

- Fredrik

[rceccleston]

Originally Posted by MrMel

Using a Oscilloscope I used 2s A123 pack with about 6.63v input, and measured at the servos during fast movement it never dipped below 5.04v.

WOW.. that's a 33% drop in voltage, that can't be good for servo performance.

Originally Posted by MrMel

That said, I have personally seen those that has failed too, meaning either Align changed something (this was a V2 unit I tested now) or simply put its down to the soldering work.

Not that Align would tell us....

[MrMel]

WOW.. that's a 33% drop in voltage, that can't be good for servo performance.

I can check at the battery, but I would NOT worry, its within normal I would suspect, i.e. NO PROBLEM. (all depends on the quality of the pack and charge level)

[rceccleston]

Originally Posted by MrMel

I can check at the battery, but I would NOT worry, its within normal I would suspect, i.e. NO PROBLEM. (all depends on the quality of the pack and charge level)

Such a drop in voltage would either suggest the pack can't provide the amps under load or the 3G wiring is causing resistance in the circuit.

In relation to the Align DS610 cyclic servos, the performance would drop from 12kg.cm/0.08sec/60° at 6.0 volts to 9.6kg.cm/0.10sec/60° at 4.8 volts.

●Stall torque:9.6kg.cm(4.8V) 12.0kg.cm(6.0V)
●Motion speed:0.10sec/60°(4.8V) 0.08sec/60°(6.0V)
●Rating voltageC 4.8-6V

[lindahl]

Can you test the unit with a fully charged 2s lipo also, please?
Also, a storage charged lipo could be interesting. (After about 3 flights on my machine)

[MrMel]

Such a drop in voltage would either suggest the pack can't provide the amps under load or the 3G wiring is causing resistance in the circuit.

In relation to the Align DS610 cyclic servos, the performance would drop from 12kg.cm/0.08sec/60° at 6.0 volts to 9.6kg.cm/0.10sec/60° at 4.8 volts.

We are talking about 1 million samples per second, a "high end WR BEC" drops to 3 volts under the same load, still without brownout since the drop is so short, so I rate this quite well, but I will do additional tests with more detail.

[MrMel]

Originally Posted by lindahl

Can you test the unit with a fully charged 2s lipo also, please?
Also, a storage charged lipo could be interesting. (After about 3 flights on my machine)

Yep, and I will measure both infront of and behind of the 3G unit, then I know exactly how much the 3G is responsible for

[MrMel]

Here is two logs, using 2s Lipo direct (8.0x voltage level, i.e. 80-90% charge level)

One measured at the power-bus of the 3G (ingoing)
One measured at the Servo cable, center between servo & unit.

In the test I used 3 x JR8717 to produce load (moving the sticks)

as you can see, there is 0.96v difference between the two low's, but there is no where near any low voltage.

[MrMel]

One more test, this time using two probes, so you get an exact match between voltage at Input vs Output with the 3G.

Here you can EXACTLY how much disappear in the 3G unit at X load.
(scaling is the same on both)

[MrMel]

Just to clarify how to read graphs like this;

Ch1 & Ch2 "top" are the same voltage, it's just presented at different places in the graph., so both tops are at around 8v.

[jondabear]

BEAUTIFUL. Wish I still had cool test equipment like that.

Now we can SEE what is really going on.

Thank you.