Drone Build Questions - First build

[ched]

Soldering looks OK maybe a little more solder would make a stronger joint?
In theory swaping 2 wires on half your motors sill work but on odd occasions during manufacture they get things wrong. I don't know what rx you have (can't remember) but you can test them before you heat shrink them by connecting to power and to the pwm out put of your powered rx(correct voltage), (ideally on throttle channel). That way you can test if motor is spinning in correct direction.
Worst cast just do as you say and swap wires on half motors and just check after you have built. I find a sort of loop of electrical tape so the end stick out like a flag easiest way to see which way a motor is spinning.

You should be OK mounting the esc there but sometimes its worth getting some air flow over them to keep them cool. Just check after first flight but you should be fine. Might be worth using a cable tie to hold them in position.

[Crimond84]

Been looking at PDB's today.
Given I want to run a gimble at some point, I assume I'll need a BEC - Should I keep them separate, or does it make sense to get one built into the PDB?

Below is a selection from the very simple, to something more fancy. Any comments or recommendations on what I should consider?


https://www.flyingtech.co.uk/cablesconnectors/multi-rotor-power-distribution-board-diy-8-x-output-pcb


https://www.flyingtech.co.uk/cables-connectors/300-amp-octocopter-power-distribution-board


https://www.flyingtech.co.uk/cables-connectors/tarot-8-1-power-distribution-board-hub-tl2909


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[ched]

It should have a built in pdb. Are you sure the that lower centre plate doesn't have solder pads on?

PDB for a hex are a bit thin on the ground. I would go with the cheap one with a case. I think it was Tarot £8.49 one as then you have the soldered joints covered up nicely.

As for bec this is the sort of one I have used https://www.ebay.co.uk/itm/uBEC-2A-3A-Mini-Adjustable-Step-Down-Voltage-Regulator-BEC-Multirotor-FPV-Pololu/231750382434?epid=1088884515&hash=item35f5663362:g:4H4AAOSwcdBWSmJS
or have a look at this selection https://www.hobbyrc.co.uk/power-distribution

Basically you need to provide all components are provided with the correct voltage. So you might need a couple of different voltages ones. So sometimes buying a few variable ones might be handy.

[Crimond84]

Ordered the 8 way PDB tonight.
I double checked the main plates on the frame, and definitely no mounting / soldering points.

I too thought it had a built in PDB. Will need to go back and check the advert where I bought it from.






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[Crimond84]

Am cracking on getting some of the power cables soldered tonight.
Its been a steep learning curve, having never soldered before, but quickly got the hang of it.

Am now moving on to the small bullet connectors, and that seems a little more challenging, especially without a jig.

Anyway enough of the rambling - I'll post some pictures of progress later.
The main reason of my post was to ask whether I should be concerned about the length of the power cables to the ESC's etc.

I've seen people saying that you should not extend the cables between the battery and ESC, but extend the cables between ESC and motor instead.
Also seen things like a max of 20CM.
All of the above feels like a bit of mumbo jumbo, but that's exactly what some ignorant newbie like me would say!

So thought it best to check before I get too far...

Battery to PDB = 10cm
PDB to ESC = 30cm
ESC to Motor = 5cm

[hoverfly]

Small bullet connectors can be held in a clothes peg ,has the advantage over ally jigs as it doesn't act as a heatsink..

[ched]

I've seen people saying that you should not extend the cables between the battery and ESC, but extend the cables between ESC and motor instead.
Also seen things like a max of 20CM.
All of the above feels like a bit of mumbo jumbo, but that's exactly what some ignorant newbie like me would say!

So thought it best to check before I get too far...

Battery to PDB = 10cm
PDB to ESC = 30cm
ESC to Motor = 5cm

OK so first think battery to pdb needs to handle all current to all 6 motors. So use the thickest you have.
As for the others I wouldn't worry about length. I was trained as electronics engineer and while there are technical reasons for limiting cable lengths for the sort of current on the lengths we are talking about it's not worth worrying about.
Basically the thicker the cable the less resistance it has. So therefore the easier it is for current to flow. So think of it like most current from battery so thickest wires, then 1/6th of current to each esc so thinner wires, then wires to motors (3 not 2, so less average current than wires to esc) are generally fitted by manufacturer so should be fine.

The above is generalisations and should be fine. It's not worth going in to minute calcs because the currents we are talking of are quite variable and not really constant so wont really cause any heat issues.

I think Josh Bardwell has a video on youtube about battery wires if you are interested.

[atomiclama]

There are plenty of discussions and some people get very worked up about the pros and cons of where to put the ESC in relation to the PDB and Motor.

I'd suggest just put them where is convenient for the build, if this happens to be far from the battery and close to the motor then I would suggest putting some good quality low ESR caps direct onto the ESC input. This will reduce the volt spikes on the input to the ESC and prolong it's life.

[Crimond84]

So bit of an update.
Mostly good, but a few issues as always!

Firstly let me show where I'm at;









So good progress, but I did have to redo all the power cables as my first attempt were too short 🤦🏻‍â™,️

I've ordered the servo extension cables, so these will just need feeding through when I have them.
I'm also yet to solder on the male end of the bullet connectors to the ESCs, and heat shrink them.

I've also not planned the layout of all the components on the frame yet, so hoping the PDB can stay there as it will keep things neat.

I also went to fit the legs tonight, but ran into some issues here.
It's not overly clear from the picture, but with the landing gear on, I can't tighten up the screws for the two fixed arms, as they impede on the landing gear.
I've tried flipping the screws and brackets round, but then you can't get to the screw head to tighten up the arm....

I'm sure I am missing something obvious like before;






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[ched]

Good to be progressing.
Difficult to see from photos but can't you put the fixed arms on then bolt landing gear on? Surely the landing gear is something that comes off to transport?

Picys maybe easier if you use the 'add image to post' link below the post when you are typing as it puts small images in the post but they can be clicked to enlarge.

[Crimond84]

There's a cross bar you can't see, that is screwed on by passing a hex driver through the upper plate, screwing down through the lower plate info the cross bar of the landing gear.
With the arm in place, that's not accessible [emoji848]

Going to have a look at some more videos tomorrow. Will also try and put up a better pic from camera rather than phone


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[atomiclama]

Picys maybe easier if you use the 'add image to post' link below the post when you are typing as it puts small images in the post but they can be clicked to enlarge.

Maybe this is the problem with the pics

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[Crimond84]

I've just logged on via my Mac and wow - I see what you mean....

Apologies as via Tapatalk, it looks fine.
I'll re-upload and use a proper browser from now on.

[Crimond84]

Re-uploading pictures to make them more visible;

[Crimond84]

Here are the pictures associated with the issue I mentioned of attaching the legs;

[Crimond84]

[ched]

OK so could you bolt in the silver crossbar without the rest of the landing gear. Then put the arm in, then attach the landing gear to the frame and silver crossbar?
Sometimes you cant bolt an assembly on when it's built, sometimes you have to construct the assembly directly on the frame.

Looking good, picys much better 

[Crimond84]

I came to a similar conclusion as the cross bar does indeed unscrew from the sides.

Tonight I've pulled through the servo extension for a couple of motors, finished the bullet connections, and mounted the motors to the arms.

In order to get the servo extension cable through the motor mount where it clamps on to the carbon fibre arm, I'm having to remove the mount, and reverse feed the extension through.
This is because the female end is to big to fit through the gap, but the male end on the servo goes through fine.
This is all good, except that the two mounts that came pre-installed on the two'fixed' arms will not move for love nor money.
I've obviously removed the screw that goes through the mount and arm, and with the others I can just twist the mount off.
I've tried a hair dryer, and soaking it in very hot water, on the assumption the plastic mount would expand more / quicker than the carbon fibre tube.
I'm no weakling, but I cannot budge it, and am at risk of breaking the tube if I just try harder.

Any tips and tricks for removing these?


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[ched]

One thing you can do is remove the plastic plug from the servo extension wires. This is done with a sharp knife or very small screwdriver.There is a little clip that you have to lift a little then pull the wire. it should just slide out. Then slide the wires down the tube and slide the connector back on the wires making sure to get the correct wires in the correct plug holes.
Hope that helps.