The story of the Ü120 started one day when I found myself with a bunch of parts for a micro quad, but no frame (I blame it on Atakorn and Jason from Safety Third Racing who advocate for late night drunk buys). I decided to whip up something that wouldn't be a headache to build but wouldn't break the bank either. You can read about the design story for the Ü120 soon when I get that up.
In the meantime, here's a build log for those of you who have a Ü120.
Start with the frame. Your kit should come with 4 standoffs, 8 screws, the top plate, and the main frame.
The frame is designed to use a 5V buck regulator. Make sure the orientation is correct and check output voltage by hooking it to a power source (more than 5V) and turn the potentiometer (the little dial) until you get 5V on a voltmeter. (As an aside, these type of switching regulators are solid. I use them a lot of my rigs before lightweight PDBs with switching regulators came out.)
To solder up the regulator, I snip off the corners to expose the inside of the via. This makes it much easier to solder onto the frame.
To solder it on, I heat the pad on the frame and apply some rosin-core solder (Kester being my favorite) which allows the solder to flow nice and easily onto the exposed via surface.
Attach the battery leads. The diameter of the vias for power are sized to 18AWG wiring. I used black wires to match the build so if you do the same, make sure your polarity is right. If you're a weight weenie like me, use XT30s. They're almost 6x lighter than XT60s (0.6g vs 3.4g).
Next I attach the Buzzer and VBAT connectors. These connectors come in the kit with the Flip32 Racing Edition.
PLEASE NOTE: If you're using this particular flavor of flight controller, please modify the Buzzer connector by snipping off the red wire and soldering the black wire to BUZZ+. Then flip the frame over, expose the ground plane next to BUZZ- and jump ground to BUZZ- by depositing a solder blob. This is necessary due to a design flaw in the Flip32 Racing Edition. See below:
Next you will need to solder on the SMD components for the LC Filter. Place the tantalum capacitor (the orange component) in the orientation shown onto the pads labeled "C1". Make sure the bold line on the capacitor points toward "L1". DO NOT REVERSE. To solder on the cap, press the capacitor onto the pads, press your solder tip onto the pad to heat it up, and apply solder. It will flow onto the capacitor contacts and the PCB pads.
Do the same with the inductor. Place the inductor (position doesnt matter for this guy) onto the pads labeled "L1". Do the same as above to solder: press against the pads, heat the pads, apply solder.
If you ordered your frame without LC components, jump/bridge the two pads on the top left of the frame with a blob of solder.
Next, insert headers into the vias above the regulator and solder into place. Standard headers that usually come with your FCs should work. If you don't have any, you can purchase some here.
Apply some VHB tape to the top of the regulator to insulate the FC and hold it in place. In case you haven't been enlightened on the wonder of Very High Bond tape, it's a 3M product that, surprise, exhibits very high bond strength to many different materials. There are a bajillion (that's an exact number) variations formulated to work on different substrates. VHB is also nonconductive so it's great for mounting electrical components. I happen to use 4910 when I need clear adhesive and 5952 when I need to bond to lower surface energy substrates (i.e. stuff that sticky stuff normally has a hard time sticking to like teflon or polypropylene [milk jugs]).
Throw the Flip32 Racing Edition onto VHB and header pins. The VHB should hold the FC in place while you solder it into place.
Attach the 5V Buzzer. Make sure you match polarity. Plug in the Buzzer and VBAT connectors.
Insert the VTX connector into the video out vias. The wiring order matches the connector pictured which is for a TS5823S. If you use a different VTX, make sure your wires are connected to the correct vias.
Depending on the RX you use, you will need to follow the channel mapping on the Flip32 Racing edition to find out which wires to attach. I'm using an X4R-SB (with the a-hole mod...basically attach the signal wire to pad "A" directly) to get uninverted SBUS signal into the FC. For SBUS, most FCs receive the signal on input 4 so I keep wire 1 (GND), wire 2 (V+), and wire 6 (input 4) and remove everything else. I also remove the pins and the smart port connector to make it lower profile. You can use an XSR too if you want a smaller rx.
Next is the camera. I'm using the rather ubiquitous 5V Mini CMOS cam with built in mic in this build with an 808D #16 lens. In fact, the camera pads on the frame were laid out to match the order of the camera's wires. I attached a small wedge of foam using VHB to pre-angle the camera. Solder the camera down and affix it to the frame.
ESCs are next. The frame was designed around KISS 18A and are attached using right angle header pins. I first lay down a layer of VHB to hold them in place and then solder on right angle header pins to the positive, ground, and signal vias.
I power on to test everything's working right. Lots of blue lights...yay! At this point, jump the OneShot pads if you have KISS 1.1 ESCs. Jump the motor spin pads for ESCs 1 and 4 if you are using RCX motors.
Throw on some standoffs. I trimmed mine down a little to fit the X4R. A XSR or the new furiousfpv micro rx should fit fine without trimming.
To decrease the weight on the VTX, I snipped the tab holding the SMA connector right off and direct soldered a decased whip antenna onto the VTX. Although the whip is linearly polarized, it does plenty well for medium to short range flying, costs nothing since it's included with your VTX, and is more durable than cloverleaf antennas since there are no lobes to break off.
Plug in your receiver. I add some VHB to keep it in place. Note that I route my antennas to the back of arms 2 and 4 for protection.
Then plug in your VTX. I route the antenna to the front of arm 1.
Screw in your top plate. As I mentioned, I'm a weight weenie so I use aluminum screws.
I heat shrink wrap the upper portion of the ESCs, leaving the motor wire pads exposed. Note that I heat shrink over the Rx and VTX antennas. Clear heatshrink is used in this case so I don't hide those beautiful blue LEDs on the KISSes.
Slip on a shorter length of heat shrink tube to cover the motor pads later.
Solder on your motors.
Slide the heatshrink tubing from before over the motor wire solder joints. Shrink 'em down.
Aaaaand, you're done! Here's an image of the stack from the side:
Woohoo! Congrats on building your Ü120. Hopefully that wasn't too onerous. Now get out there and get flying!
Edit: I've since designed TPU booties, a camera mount, and a front bumper for this frame. You can download them here. The frame wasn't originally designed for booties so there's not much space to "clip" them on. Instead, you can use two of the motor mount screws to hold them in place, or just do what I do and glue them to the frame using CA. I've found the latter to be much more secure.
The camera mount is printed slanted side down. Once complete, snip the camera collar open with a pair of wire cutters and pop the camera in. The front bumper is just attached to the bottom screws of the front standoffs.