Thursday, May 14, 2015

Intel NUC, interesting but troublesome hardware.

I work at an ISP.  ISPs usually have NOCs.  NOCs do really have that room with a bunch of monitors at the front. For the last six or eight years we've had a set of three monitors up front, driven by "normal" pcs.  To get the video there, we have cat 5 based VGA extenders. 

PC's have gotten smaller.  Much smaller.  Small enough to put behind a TV. 

This is a business, so upgrading stuff that works, receives no priority until something breaks.  A week or two ago, one of the PCs that we use to drive the TV's died.  And we have no replacement for it.  Word from above said "get some NUCs."  Tuesday, we did.

Sadly, the i3 ones were out of stock.  So instead we got the i5 based NUCs.  In specific a set of three NUC5i5RYH NUCs.  Monitor PC's don't need a lot of storage, or even a lot of ram.  They just spend their days showing a set of 2-3 webpages all day long.  

NUCs are barebone machines, so they do require some assembly.  To make them not barebone, we picked up some 64 gig SSDs, and 4 gigs of ram for each. 

Here's what you get when you open the box.  you can see the VESA mount hiding in the box. 

 To install the memory, and disk(s), you pop the bottom off the NUC.

 This is the second time you see Intels care over this hardware.  The first bit, was including the VESA mount. Each of the screws that hold the bottom plate on, have bushings and clips, so they're permanantly retained to the bottom plate.  You can't lose them. 

Mmm computer guts.  What we have here are the two memory slots, and the M2 SSD slot.   The SSD slot can take all three standard lengths.  And if you look at the previous picture, there's even some thermal foam to help manage the temprature of a high performance M2 SSD.  Another thoughtfull move on Intels part.  

So lets put the memory in there.  The i3 and i5 based NUCs want DDR3 1600.  

 Speaking of thermal pads, here's a good look at it.  Along with the 2.5" drive bay.  And those fancy retained bottom plate screws.  The 2.5" slot is designed to be tool less.  You're supposed to just slide your drive in from the side.

And it works.  Mostly.  There are two spring tabs are the front of the slot.  SSDs are pretty low profile, and the slot is sized for a spinny disk.  So you need to press on the disk to keep it low enough to mate with the connectors at the far end of the slot.

 I bet intel could have gotten away without the spring tabs.  There's not a lot of extra room in the case for that drive.  And if you're the belt and suspenders type of person, there are two available screw holes for retaining the 2.5" drive in the bay. 

Closing the NUC is just a matter of pressing the cover in place, and tightening the screws. The thermal pad, and ground pad need a little force to get the cover all the way down, but it's not a concerning amount of pressure.  

 After another five minutes of work, we have three PCs to drive three monitors. 
The next step is getting an OS installed.  Which turned out to be it's own little adventure.  

Now we get to start talking about the quirks of the late model NUC. 

The hardware is great.  Low TDP chip, a high quality wall wart power supply with adapters for several countries.  A nice cast aluminum case.  Space for the M2 SSD, and a 2.5" drive.  Gigabit ethernet, wifi, bluetooth.  Mini HDMI, and Displayport output.  Essentially it's a high end laptop, without a monitor and keyboard attached. 

So this latest and greatest laptop, but not, has the latest and greatest integrated Intel video card.  That video card doesn't play nice with older video drivers.  The intended OS for these machines is Linux, and our first choice, Mint 17.2 doesn't have that video driver.  Nor does the LTS Ubuntu.  The only version that worked properly as installed was the latest Ubuntu release.  15.04 IIRC. 

The manuals that come from Intel, in the box, detail the hardware fairly well.  But their details on software is very, very weak. 

After discovering that Mint, and LTS Ubuntu weren't going to work, and the workarounds weren't very appealing. (Installing the OS in another machine, then moving the drive over to the NUC.) Finally we arrived on the latest Ubuntu.  That would boot off a USB drive.  However, after installation it would not boot off the internal SSD. 

So after a day of half hearted fiddling.  I discovered that I couldn't get into the main bios.  And that choosing which boot drive from the boot menu wouldn't do any good.  (Mind, this is not my core duty at work..)  I had a coworker suggest  I contact Intel.  And I did. 

We came up with a few things to try.  First, was installing the latest bios.  Which went swimmingly.  These machines have a bios utility that can read from a FAT32 formatted disk and install from there.  We also decided trying a displayport monitor was worth trying.  And finally a new SSD. 

I couldn't find a displayport adapter yesterday.  I had just bought a SSD off that same coworker, and I decided to give that a swing.  The NUC booted off the new SSD.   Poking through the boot menu screen, I discovered that the SSD had been formatted with a UEFI compatible partition.  And that's the key. 

After getting the drive set up with a UEFI partition, it will boot.  ... I still can't reach the bios. 

That said, now the PC is working.  It's speedy, does what we need, and boots really quickly.  (19 seconds from button press to login screen.) Other than the documentation issues, the machine is great. 

I expect there will be a followup at some point.  Just.. not right now.  :-) 

Thursday, April 23, 2015

More MOSFET nonsense. I need help.

 Help!  One of those two mosfets in the top right hand corner of that board is blown.  They say Y1A1, which appears to be a lot number, not a part number.  

How can  I identify these things?  Alternatively, can you recommend a part to put in place instead? 

Tuesday, April 21, 2015

A blown MOSFET, replacement, and saving a reciever. Losi Micro Crawlers

What a lovely truck.   But there's a story behind it.  And some broken stuff too.  

So this story starts about a month ago.  I have a Losi Micro Trail Trekker.  It's a great little truck.  It seems to be able to climb anything.  I bought it .. back in 2011 I think.  At the time, I put something like five battery packs through it.  Then.. life happened.

Years pass, I pull the thing out of storage.  I spend some time, and I get the battery packs (I have a Micro Rock Crawler too..) fixed, as from sitting one or two cells reversed.  And I go to drive my truck.  I go from reverse, to forward.. there's a puff, and the smell of escaping electrosity.  After that, the truck would only go in reverse.  I had blown one of the mosfets.

So, frustrated, I called Horizon Hobby.  (Horizon owns Losi now.)  After a little begging, they found it in their hearts to replace my ESC, in spite of being so deeply out of warranty.  Thanks a lot guys!  My truck was running again within a week.

That left me with a "dead" $50 reciever/esc package.  $50 is a lot of encouragement to fix something.  The usual rule with electronics, is you look for something that looks wrong.  The truck was happy to deliver clues.

Here's what a seriously blown mosfet looks like.  Yes, that's a hole.
That package is tiny.  But between my camera and some good lighting, I was able to identify the chips.  They're mosfets, two in each chip.  It's also a SOIC-8 package.  Roughly the smallest pin pitch I'd try soldering without a magnifying setup.  But try I shall!

Using the 4205 number I was able to identify on the chip, I tracked down the Datasheets.  The datasheets seemed sane, so I ordered a few.  Sadly, the only decent source was in china, so a month passes....   

Removing a chip like that, is a matter of getting all the pins on one side hot enough to flow.. and lifting it up one side at a time.  So I added some solder, and got to work.  The "near" side was easy.  As it's pins are all normal.  The far side was a bit more tricky.  It's behind a whole bunch of wires.
 To get access, I unsoldered the pink wire.  It was soldered to a giant blob of solder, bridging two contacts.  Which.. is ok.  As those mosfets are designed to have their center channels bridged.
 The bottom of the chip really shows how big of a failure this was.  Big ba-da-boom.  Now once the chip is removed, you need to clear out the excess solder.  Solder wick is big and difficult to deal with.  I end up using some 22ga stranded wire as my solder wick.  I pull the insulation off, and dip it in rosin.

Here is the cleaned off pads, ready for the new chip.
Oh yes, while we're at it, the MOSFET is an APM4502.  They're about $3 each.  I bought five.

Here it is, soldered back into place.  And before you ask, yes it works.  Both forward, and reverse.
 Here's the MOSFET I removed.  I love how they "blow up".
 And here's the receiver, all buttoned up and ready to go.

I'm glad it worked.  Hopefully this might give you confidence to repair your ESC if you ever smoke an IC.  

Monday, April 13, 2015

Smaller and smaller and smaller. Losi Micro Desert Truck

First, lets set the mood.  Smaller and smaller - Faith No More.

The Losi Micro Desert Truck is one the remaining trucks in the 1/36 scale lineup.  So what makes it the Desert Truck (DT) instead of a Micro-T? The DT has bigger tires, with a different tread pattern.  They look scale.  The chassis is stretched in the middle, which makes the battery compartment larger.

Yes, that's the truck sitting on my battery charger.  In spite of being small, it's a very serious truck.  Fully independent suspension, slipper clutch, classic 3 gear transmission, fully proportional everything, with a brake and reverse.


Wheelbase - 3.5"
Length - 5.5"
Front Track - 3.5"
Rear Track - 3.5"
Rear Travel - 0.5"
Front Travel - 0.39"

So, while we are on the subject of travel.  Something I've noticed while reading reviews on the truck note that "the back end sags."  The proper setup for the rear end of a buggy, truck, whatever, is dogbones level, or nearly so.  The truck sags about 3/16" of an inch.. which puts those dogbones level under acceleration.

Now... the proper way of dealing with the back end slapping the ground is damping.  Which is something that this truck is sorely lacking.  Losi appears to sell some oil filled shocks... but at a cost of nearly $30.  Well.. that'll happen soon enough.

The lengthened chassis provides a much bigger battery compartment.  There's a little block of foam in there, to keep the battery forward.  If you pull out the foam, there's room to fit the 220mah battery from the High Roller, or the Trail Trekker.  I just so happen to have a Trail Trekker, and some reasonably accurate scales.

First off, lets compare batteries:
150mah - 15.9g (I have two of these, they were within .1g of each other)
220mah - 23.2g

Empty truck - 98.0g
Truck with 150mah - 115.0g
Truck with 220mah - 121.3g

The battery is between 14 and 19% of the total weight of the vehicle.  That's, a big lump of weight to move around.  I think that might make a significant difference in the handling.

150mah Forward: 39.9f / 60.1r
150mah Rearward: 36.3f / 63.6r
220mah Only:  37.8f / 62.1r

So far, I've driven the truck with the 150mah pack forward, and the 220mah pack.  I can't say I've developed a good feel for both setups yet.

Now, the upgrades have already begun.  I found out how bad dealing the e-clips are.  So I swapped out for the threaded axles.  That's a good excuse to examine how serious of a truck this is.

Ah, the classic R/C car pose.  Topless, and no shoes.  And e-clip axles.  That is about to change, at least in this narrative.

So we'll do the hard ones first.  Now, these i'm describing as "the hard ones."  To pull the front axles, you unscrew the kingpin, and pull it out.  The kingpin retains the axle in the hub.  So once the kingpin is out, you can pull, or push out the front axle.

And the back end is a whole lot easier.  You just unscrew the upper control arm, and when you pivot the hub down, the drive cup and axle can just be pushed out the back of the hub.  Sadly, I didn't take pictures of that.  However, here's what that rear a-arm assembly looks like.

Looks just like a big r/c car.

And here we are, after the conversion.

Now having threaded axles introduces some new things to be concerned with.  Since the front hubs have no steps in them, you can over tighten the nuts and bind against the bushings in the front wheels.  The case is similar in the rear.  You want to tighten the nuts just enough that the slop goes away.  My usual method for dealing with things like this is to over tighten them just a little, then back off 1/4 turn at a time until things spin freely.

Bearings for the truck are in the mail....  And I fully intend on destroying some batteries in this thing.  I'm also trying to find reasonably priced 180mah 2s LiPos to put in the truck.  Not that it needs to be any faster... but it's r/c.  "Need" is such a dirty word...

Now that I think of it... .I don't think I actually reviewed the truck.

The Losi Micro Desert Truck, feels like a 1/10 scale stadium truck.  Everything from the backend squat, to how it likes to be under power in corners, feels just like my old LXT.  The only thing that disappoints is the lack of damping.  

Monday, April 6, 2015

That 3d printed cover. Detail shots.

Loclhst asked me for some detail shots of the RC-305 back cover I had printed for my Quanam goggles. 

Here's what I got from the local 3d printer.

Sunday, March 29, 2015

Playing with FPV stuff.

The other day I was cruising reddit, and I found this guy had designed, and printed a backplate that would let him combine the RC-305 reciever, and the display in the Quanam FPV goggle.

So... I did some digging around, and found a guy who'd do a good job printing it out for me.  

And after some serious surgery, the backplate is installed on the monitor, and it works!  Now there's just one wire to hook up my goggles.  

I ordered a new camera to play with.  I kinda expected it would be the size of the one I showed off on the Maltese.  Turns out.. it's less than 1/8th the volume of that camera.  That's a dime sitting next to it.  


Oh, I glued the whole shebang together.  That's now an install-able unit.  I should really hunt down some dip switches so I can vary channels.  

Oh yeah, I was also quite suprised by how small the 808 cameras are.  That will eventually live hanging under the QFO, with a couple servos to keep it steady.

Monday, March 23, 2015

The Maltese - A testflight.

Generally speaking, flying a 250 quad in a 10x10 room is not considered a smart move. Yet.. that's what I did tonight.

I wanted to know how the Maltese would fly with a 2200mah pack strapped to it.  As it turns out, it flys ~very~ well.  I suppose when your airframe is not much more than some 3mm fiberglass, things move quickly.

That platform on top is just asking for something isn't it.  Wait.. I know!

9 grams of FPV gear!