|Sep 22, 2012, 11:04 AM|
While waiting for the epoxy to dry, started to work on the ESC mod.
I removed all the cables that came with it. This is the Turnigy TRUST 55A SBEC.
The bullet I replaced with is Zero Loss 5mm from Astro Flight. They are expensive stuff because Mil grade UAV uses them too.
You can find the link here:
After finishing the soldering, place it on the template to check the height balance.
Here's why this connectors are so expensive.
Double wall female socket to make sure the slide in and out is so precise and smooth that no sanding, no powdering is required.
|Sep 22, 2012, 11:23 AM|
man, youre really going hardcore on this. cant wait to see it done. i am confused about how this center plate thing works, why are the three ABC motor conenctor alone in the plate and not connected? maybe i should just wait.
edit: oh haha i see the other ESC plate
|Sep 25, 2012, 11:37 AM|
2nd layer done.
Left in in my DIY enclosure which can double as oven.
I actually set the temperature at 90degC.. I'm not sure if that is the right or best but no harm actually. The epoxy hardens in an hour to 2..
After I epoxy down the ESC track layer, I relaid another thicker layer on the power track layer. I realized later that due to the sheet not flat enough, the copper actually lifted high enough (the eye can't tell exactly) to cause unevenness.
After 1 thick layers, and spot drop epoxy the 3rd time on some dip spots, i finally sand it down with Perma Grit Tungsten Carbide file.
Then turn to fine paper to smooth it out. This should do for now and will do polish after soldering the connectors.
That's what happen when I flatten the whole surface.. Not to worry, will spray conformal coating over once more after all is done.
Get down to open up a hole on each phase's track.
Did this using a rotary Dremel on small grinding wheel.
Then apply flux on these opening. I use this white one. Got it from a component shop. Not sure if this is good stuff or maybe just normal.. I have seen and used one which is brownish and came in bigger tub. I do not know what are their differences.
Done with laying and filling up the exposed copper..
And then the first connector. This is a 4mm.
With a little tilt to give easy access and insertion from the motor end.
All 3 done.
|Sep 27, 2012, 12:18 AM|
After seeing countless people try and fail with their RTF or ARF multirotor projects, it's nice to know people like you still exist, prodriverex.
|Sep 27, 2012, 12:57 AM|
Now we proceed to solder all 4mm bullets around the concentric location.
That done, progress to create bore hole to expose just enough copper to solder the zero loss bullet.
Another view of the bullet inserted. The hole above need to be increase to 4.3+mm so lucky I have imperial sized drill bit set..
[IMG] http://i41.photobucket.com/albums/e2...t/IMAG1809.jpg [/img]
Here's when all of one ESC connection is done up.
The 3phases bullets have their soldering done on the underside. Remember where there was suppose to be the punched out copper sheet dots? The plan was to bore a hole on top of it too, and let enough copper exposed so the top part of the bullets can also have solder flow over them..
Alas, its only a 4mm dot, there wasn't much left when we drilled a 11/64 hole through it although not on the centre of it, just a tiny wee bits of left over copper dot. The moment if we bore a 6mm square shoulder hole over it, I'm afraid the copper dot will be spun off and come out. So we ditched that idea and left it alone. The solder on the underside should be good enough and strong enough. We ate anyway, going to flow another layer of epoxy over the power track to insulate the exposed thinned out portion.
Here's another look on the underside where the solders are.
As for the +ve and -ve bullets, we did the boring too, just deep enough to expose the copper.
There is no need to be precise, just eye balling will do since there was no need to drill a through hole for this. So anywhere close to the bullet's diameter will do. The bore drill size is 6mm, so there's a little room for off centre.
You can see the 2legs dropping down from the ESC are the power connectors. The one closer to the edge of the plate is the -ve one.
See the off centre causing the solder to bob out on one side rather than a nice shape which ideally should look like Mount Fuji! Lol.. anyway, that was too much solder in a haste.. will correct it if have time.
|Sep 27, 2012, 01:10 AM|
During non work time, I thought how best to locate the battery, receiver and FC. FC most likely will be located at the top tier due to sensors' sensitivity requirement, nothing to block it. Will the receiver perform better under the belly with its antenna pointing downwards in V shape?
|Sep 28, 2012, 10:58 AM|
After seeing some portion of the epoxy thinning out from the surface sanding and heat from the soldering causing it to soften further, I decide to lay another layer of epoxy on the Power track side.
But I have already drilled some holes and if i did the layering, the epoxy will flow down and clog the hole again. Well I could just redrill them again but it won't be nice again.
Came out with an ingenious way to use the slippery backing from thin double sided tape, roll into a tube small enough to slip in the hole then block it.
Also, this time I wanted to pour a thicker layer to make sure eveything gets covered up. But the side will flow over and drip down. Using the same method, except that I stick that double sided tape onto masking tape so that the slippery side faces inner side within the perimeter of the square.
Here is shown how smooth it tears away after drying.
Alas, after drying, the surface just refuse to be 100% flat! I gave up.
Another day of drilling and boring, soldering, finally done.
The 2 taller connectors are for battery source connection. They were from 4mm plug and the longest I can find:
And here's the final version:
|Sep 28, 2012, 11:21 AM|
While waiting for the epoxy to dry, I started to assemble the 4S battery packs.
I have a lot of surplus stock as distri so i am free to play with them.
The backing is stuck together using thin double sided tape.
Flux on both tabs to be joint. Solder some on the tabs individually first. Close them up this way:
Then push new flux in between them, melt more solder onto the iron, place it on the closing part. With the flux being heated up, the solder will flow in on its own and remove the iron.
For cells that are back to back, it is so close as if no gap at all. For this, I use the tweezer to twist them but before that, flux again so that the solder will flow in on its own.
Here's the pack so far without the balancing wires yet. I ma waiting for the connectors to arrive.
Here's what you probably interested in.
The cell is 3450mAh, 2P make it 6900mAh. 4S make it 14.8V.
14.8V * 6.9Ah = 102Wh
102Wh / 0.483kg = 211Wh/kg
Well these are not the best yet. Once this project is done, I'm gonna try the H format and that will be able to make use of 260Wh/kg cell. Will be interesting..
|Oct 01, 2012, 11:17 AM|
Hi there, I'm back from the weekend!
Did a little here and a little there during weekends.. And the connector's pins arrived this afternoon.
Ok let's rock with pictures!
So the PCB is done, lets hook up the motors with the 4mm bullets soldered.
Here's the view of how the connection is done:
Then its time to bolt it down with damper. This version is stiffer..
Plug in all the ESC and weigh it to get a feel..
And with a little bit of time today, I worked on the battery tray layer and FC tray layer. They can actually share the same template.
After doing some aligning of the battery, just felt the tray is too small as those nuts are popping out at places causing the useful space to become limited..
Am planning to relocate the battery to the side now.. so the connectors gone to waste..
|Oct 01, 2012, 09:15 PM|
He's a pic of how the two plate should look like:
And when they are stacked up:
The battery is suppose to be inserted in between the FC and the ESC POwer Board. It should be designed as plug-in and power, that's what the tall connectors are for.
Now it certainly look very tall. I think shifting the batts to the side will spread out the CG a little to the centre and even better if the underslung camera comes into action.
|Oct 01, 2012, 09:30 PM|
So I should clarify this in my blog too..
I have foot print of 100x100mm to play with. Much larger than any in the market. After some drawing, it was extended to 114x114mm.
And this copper sheet is already thicker than 1oz or even 2oz copper found in most PCB.
Definition of 1oz of copper: Means it is rolled out to 1 square foot, which yields 1.4mils or 0.03556mm thickness.
I just measured the copper sheet in my hand, 0.15mm. That's about 5.9mils.
Coming from a Mil-Spec definition, as a guide to Mil Std 275E - Trace Current Carrying Capacity of Copper, http://www.armisteadtechnologies.com/trace.shtml
every 1/2oz thick of copper PCB, under 0.2" wide track width, can carry 7.5A.
My average track width is 5mm minimum, ie. 0.19685", close to 0.2" definition.
I have 5.9mils, so that makes it 63A if it travels for one long foot! Since it is shorter, it can take in much more.
Hope this help in theoretical planning at least. No, I dun intend to put it through any bench test to see how high it can take.. I dun have a 2nd piece yet..
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