Multirotor, multicopter and quadcopter discussion - The Drone thread

PinkFloyd · 3 Sep 2014 at 13:32

Can you not use a threadless standoff and just run a bolt straight through it? Keeps it nice and simple from a repair perspective.

Tackle_Berry · 3 Sep 2014 at 13:34

Surely running a bolt all the way through would just make it pointless though as the weight would nearly be the same.

gandhi · 3 Sep 2014 at 13:35

Yeah, possibly. They are 35 mm long though, so that's a fairly hefty bolt. I think for the sub 8g weight I saved, the aluminium will have to go back on.

Also, apparently red goes faster........

d_brennen · 3 Sep 2014 at 15:33

I gave up with nylon frame fixings. They do their job and break alright, but it's such a pain when you know proper screws, alu standoff would have been fine

gandhi · 3 Sep 2014 at 16:27

Yep,

I've now given up on them too.

Couple of things I encountered today that I could do with some help on if anybody knows the answer or can offer some guidance?

1) Where can I get the anti-vibe bobbins from for the mobius mount? I know HK have them, but I don't fancy waiting 8 weeks for them! I haven't been able to locate a UK supplier?

2) Batteries/power..... Ok, so I'm running the DYS 1806 motors on HQ5030 props currently. On my 500g quad, this should be giving me (at 50% throttle) approximately 800g lift @ a total of 13.2 amps.

Except it's not. I'm hovering at around 55% throttle, whereas it should be around 40% or less.

Also, my Lipos are suffering from really bad voltage sag. The voltage is dropping to 10.8v or lower within about 1 or 2 minutes of taking off. I'm using the Zippy compact 1500mah 25c batteries, so they should be good for 37.5 amps.

TL;DR - I'm down on projected power and the quad is sucking way too much power. I should have a 3:1 thrust to weight ratio, but it doesn't feel like it.

Naze32 is properly set up to my throttle end points and I have calibrated the (KISS) Esc's.

Could this be a wiring/soldering issue somewhere? Some of my soldering isn't the best, especially on the XT60 connector and the PDB. It's either that or the batteries are grossly overestimating their capacity!

d_brennen · 3 Sep 2014 at 17:42

Hard to say unless you can get a current meter on the machine. Also, thrust testing is somewhat suspect... So pinch of salt needed there. I suspect Zippy batteries are "ambitious" with their stated discharge capabilities. I get about 7 minutes gentle cruse with mine (@~500g) or a little under 5 minutes of giving it some beans. Battery is really toasty after a good flight.

My spec:
5030 Gemfan plastic/nylon 2 blade
DYS BE1806-13 motors
Zippy Compact 1500mah 35c
~500g AIW

I'll see if I have any videos of my climb rate tonight. Mine really does feel like it's falling up into the sky when I give it full stick

e: soldering issue, no. Bad/cracked/dry joints can cause momentary power cuts due to stuff moving about due to vibration, usually happens in one motor and manifests itself as a violent twitch in air (or a cannon ball to the floor for no reason)

spookywillow · 3 Sep 2014 at 18:21

Guys I have tried to find out some proper numbers but everyones giving out conflicting info.

My turnigy nano tech 4s 2200mah 25-50c batteries balance charge to 16.8v, I have read they over charge each cell by 0.5v (rated voltage is 14.8v - 4x3.7v) which seems to be correct as my charger shuts off at that voltage.

Max discharge is 0.5v per cell below the rated voltage of 14.8v - 4x3.7v. So down to 12.8v - 4x 3.2v.

Does any of that sound right?

Tackle_Berry · 3 Sep 2014 at 19:20

Well I nearly lost mine a minute ago, if it wasn't for the KK2 lost alarm it would have taken a while to find. It went into the centre of a big bramble bush.

Also just learnt the hard way how quick the TX video signal drops when going through trees, I could barely see anything right before the crash.

d_brennen · 3 Sep 2014 at 19:32

You need to lose some P gain there Ash

d_brennen · 3 Sep 2014 at 19:37

spookywillow said:
Guys I have tried to find out some proper numbers but everyones giving out conflicting info.

My turnigy nano tech 4s 2200mah 25-50c batteries balance charge to 16.8v, I have read they over charge each cell by 0.5v (rated voltage is 14.8v - 4x3.7v) which seems to be correct as my charger shuts off at that voltage.

Max discharge is 0.5v per cell below the rated voltage of 14.8v - 4x3.7v. So down to 12.8v - 4x 3.2v.

Does any of that sound right?

I always set my LV alarm to 3.2. The fully charged voltage of a lipo cell is 4.2v, it's nominal voltage is 3.7v and it's brown pants voltage is 3.00v. You can go below 3.2v under load for a period, the resting voltage will return to 3.3+. Basically, it's better for the battery not to run it dry.

When you charge your battery, does the charger give you a mah value as to what it's put back in? You want to keep this at 80% or lower of the rated capacity

Tackle_Berry · 3 Sep 2014 at 19:44

d_brennen said:
You need to lose some P gain there Ash

I have never even bothered looking into changing the P gain setting etc I copied a few people's at first and noticed a slight difference but when I flashed it to Steveis firmware I left pretty much everything default.

P gain is what's making the movement twitchy right?

Skeeter · 3 Sep 2014 at 20:13

So... batteries take a long time to charge

.

Looks like charging 1 at a time means taking a day off, especially if I get more than the 3 batteries I currently have. So does anyone:

A) have any recommendations for batteries that can be charged at high C (I'm currently using these which say 5C, but I'm dubious about going over 2C. https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11903)

B) have any suggested ways to charge more than 1 at a time, other than buying another charger (currently using an IMAX B6-AC)

PinkFloyd · 3 Sep 2014 at 20:20

Ash2097 said:
Surely running a bolt all the way through would just make it pointless though as the weight would nearly be the same.

gandhi said:
Yeah, possibly. They are 35 mm long though, so that's a fairly hefty bolt.

Figured there would be bolts at either end and into of the threaded standoff anyway so there wouldn't be a hole lot of difference. Depends which works better in terms of layout I guess

gandhi said:
Batteries/power..... Ok, so I'm running the DYS 1806 motors on HQ5030 props currently. On my 500g quad, this should be giving me (at 50% throttle) approximately 800g lift @ a total of 13.2 amps.
*snip*
Also, my Lipos are suffering from really bad voltage sag. The voltage is dropping to 10.8v or lower within about 1 or 2 minutes of taking off. I'm using the Zippy compact 1500mah 25c batteries, so they should be good for 37.5 amps.

Total of 13.2 amps at half throttle, but what is it at full throttle? Imagine you've got 10-12A escs on a 250 build so you're potentially pulling 40A+ based on that? I'd imagine a 35C battery would make things a little better if you are lacking punch?

Ash - that vid doesn't want to play for me :/

d_brennen · 3 Sep 2014 at 20:23

Ash2097 said:
I have never even bothered looking into changing the P gain setting etc I copied a few people's at first and noticed a slight difference but when I flashed it to Steveis firmware I left pretty much everything default.

P gain is what's making the movement twitchy right?

Unless you're Michael J Fox, I'd say so

High speed oscillations are usually down to having P set to high. IIRC Stevies FW defaults to something like 255? That's WAY to high for such small quads. Dial it down, then dial it down some more and see how she flies. Too low and the quad will wander about, feel sluggish to respond and be hard to manoeuvre.

Low speed oscillation and "toilet bowling", where you have to constant correct for drift until your craft is essentially wobbling in an ever widening circle, is usually down to too low of an I gain. Too high and the quad will be unsettled in hover, with similar but slower wobbles seen with too high a P gain.

PI limits can probably be left alone

Tune her out with self level off, in a nice big area.

spookywillow · 3 Sep 2014 at 20:32

Double post :confused:

spookywillow · 3 Sep 2014 at 20:35

Ash2097 said:
Well I nearly lost mine a minute ago, if it wasn't for the KK2 lost alarm it would have taken a while to find. It went into the centre of a big bramble bush.

Also just learnt the hard way how quick the TX video signal drops when going through trees, I could barely see anything right before the crash.

Yeah trees can be a killer, I lost video feed tonight and feared the worst but my expert skill saved the day

I so need RTL for such events.

d_brennen said:
I always set my LV alarm to 3.2. The fully charged voltage of a lipo cell is 4.2v, it's nominal voltage is 3.7v and it's brown pants voltage is 3.00v. You can go below 3.2v under load for a period, the resting voltage will return to 3.3+. Basically, it's better for the battery not to run it dry.

When you charge your battery, does the charger give you a mah value as to what it's put back in? You want to keep this at 80% or lower of the rated capacity

Well the KK board reads my 16.8v charged battery as 17.4v so 0.6v over, I fly steady for 8-10 minutes and land, The board reads 15.4v so - the 0.6v and that gives me a real voltage of 14.8v so 3.7v per cell, battery charger is saying 3.79v per cell after flight. thats ok isn't it?

I checked my charger just and found that the capacity cut off was turned on but set to 5000mah, I bought the lot off ebay and the guy said it was already set fine as he had been using it for around 4 months so hadn't even looked, it's now set to 1800mah. No wonder the batteries he gave me have puffed up.

Skeeter said:
So... batteries take a long time to charge .

Looks like charging 1 at a time means taking a day off, especially if I get more than the 3 batteries I currently have. So does anyone:

A) have any recommendations for batteries that can be charged at high C (I'm currently using these which say 5C, but I'm dubious about going over 2C. https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11903)

B) have any suggested ways to charge more than 1 at a time, other than buying another charger (currently using an IMAX B6-AC)

I have the same brand battery but the 4s 2200mah, I charged them at 2c (4.4A) on the turnigy accucell 6 and they take about 30mins or so each. You can charge yours up to 6.5A (5c)

d_brennen · 3 Sep 2014 at 20:39

Skeeter said:
So... batteries take a long time to charge .

Looks like charging 1 at a time means taking a day off, especially if I get more than the 3 batteries I currently have. So does anyone:

A) have any recommendations for batteries that can be charged at high C (I'm currently using these which say 5C, but I'm dubious about going over 2C. https://www.hobbyking.com/hobbyking/store/uh_viewItem.asp?idProduct=11903)

B) have any suggested ways to charge more than 1 at a time, other than buying another charger (currently using an IMAX B6-AC)

You can look into parallel charging, it comes with some pretty hefty caveats which you really should understand before attempting it but is safe if you follow the rules. HK has parallel boards for sale, though make sure your charger/PSU is up to scratch on the kind of current this will draw. Charging 4x1300mah batteries at 1c will be draw ~5.2A

Tackle_Berry · 3 Sep 2014 at 20:41

PinkFloyd said:
Ash - that vid doesn't want to play for me :/

Hmm, not sure why think it has been working for other members, I just logged out of youtube and it still worked for me.

Here is the direct link http://youtu.be/wExM1U2X7t4

d_brennen said:
Unless you're Michael J Fox, I'd say so High speed oscillations are usually down to having P set to high. IIRC Stevies FW defaults to something like 255? That's WAY to high for such small quads. Dial it down, then dial it down some more and see how she flies. Too low and the quad will wander about, feel sluggish to respond and be hard to manoeuvre.

Low speed oscillation and "toilet bowling", where you have to constant correct for drift until your craft is essentially wobbling in an ever widening circle, is usually down to too low of an I gain. Too high and the quad will be unsettled in hover, with similar but slower wobbles seen with too high a P gain.

PI limits can probably be left alone

Tune her out with self level off, in a nice big area.

Thanks looks like it's worth having a play then, IIRC the P gain is only around 75, will take a look in a min and post my settings.

spookywillow · 3 Sep 2014 at 20:46

Is there a setting on the KK board that stops the twitching when self level is enabled? It's fine when it's turned off but when on it seems to be skipping on one motor. The gyro sticks a lot too at a weird angle.

Edit, after looking at a vid i'm pretty sure it only does it when it's in a wind. Seems like it's over compensating.

d_brennen · 3 Sep 2014 at 20:51

spookywillow said:
Well the KK board reads my 16.8v charged battery as 17.4v so 0.6v over, I fly steady for 8-10 minutes and land, The board reads 15.4v so - the 0.6v and that gives me a real voltage of 14.8v so 3.7v per cell, battery charger is saying 3.79v per cell after flight. thats ok isn't it?

I have never used the KK voltage monitor, but I hear it can be really inaccurate. Do you have a multimeter to compare what it says vs the KK? Sounds *about* right but remember lipo voltage does not go down in a linear curve, and resting voltage will spring back from on load voltage. I'd be have a fly about as you usually do and as soon as you land, hook up your multimeter and see what she says...

spookywillow said:
I have the same brand battery but the 4s 2200mah, I charged them at 2c (4.4A) on the turnigy accucell 6 and they take about 30mins or so each. You can charge yours up to 6.5A (5c)

Just had a look, his charger is good for 5a charging, or 50w