FT Gremlin as My First Quadcopter Build

[Huffheinz]

I was very happy to receive my gremlin kit in the mail on Saturday. I started working on it tonight (Sunday) after dinner. I was able to flash the correct firmware on the FC after messing around with it a little. Once I figured out that I needed to use zadig to install the correct driver to the FC according to the FC manual on page 2, everything followed along with the video.



So I pre-tinned the pads on the FC and cut my ESC wires to length and tinned them up. I soldered them onto the board but when I checked them with the multimeter (22:00 minute mark in the build video), I found that I had a dead short somewhere. Everything looked good visually under the magnifying glass but there was no resistance between any positive and any negative anywhere on the board. So I got out the wire braid and de-soldered all the ESCs from the board and removed most of the solder, checking for continuity as I went to see if I had uncovered the culprit. Unfortunately, I took all the ESCs off and still had the dead short.

Here's what the board looks like after de-soldering it:




Since I can't see anything bridging any contacts, and I'm still getting full continuity between positive and negative, I can only assume that I have cooked this FC. Something must have melted internally to the board that is causing the dead short. I'm open to any troubleshooting suggestions, but it looks like I'll be ordering a new F3 Femto FC tomorrow (GetFPV.com has them for $23).

 

[JimCR120]

I got nothing but sympathy. There are a couple of us frustrated just at the flashing step. I guess it'll be a few more days before we see these things in the air.

 

[Huffheinz]

I got nothing but sympathy. There are a couple of us frustrated just at the flashing step. I guess it'll be a few more days before we see these things in the air.

Yeah...the flashing step threw me for a loop too. I don't know if this helps but, using my Windows laptop, I figured it out from page 2 of the FC manual under "flashing steps". My FC wouldn't go into DFU mode until after I updated the driver using zadig. I had to follow the 2nd bullet point to select 'Options'-->'View all devices' and then chose 'STM32 BOOTLOADER' from the drop down. After I reinstalled the WinUSB driver to the STM32 BOOTLOADER I was able to boot up into DFU mode on both cleanflight and betaflight just by pinching the end of a wire across the boot pads (just like in the video). I don't think the lights on the FC flashed any differently when starting up in DFU mode.

On another note. I ordered a replacement F3 Femto from getfpv over lunch today. I'm wondering if my soldering skills are up to the task. The worst part is that I don't know where I messed up. And if I don't know where I messed up, then I don't know what I need to improve on. I guess I'll give it another shot being very careful with heat management and checking continuity every step of the way.

 

[PsyBorg]

I just managed to get mine flashed today as well but I had to do something different to get mine to work. I worte it up in my Bill's Law Thread for anyone who can not get theirs to flash by normal methods.

I was hoping to maiden mine this evening but other issues are now in the fore front. I WILL get this thing in the air tomorrow if I have to toss it in the air and hit it with a baseball bat. Hopefully it will be under its own power though.

 

[JimCR120]

Aww, don't hurt the little fella.

 

[Huffheinz]

Aww, don't hurt the little fella.

And don't get him wet. And whatever you do...don't EVER feed him after midnight.

 

[PsyBorg]

Well he did get fed after midnight and that's when he actually flew hehe. No baseball bat needed.

 

[HughHemington]

Hope you have better luck that I did!

I used a Weller solder station with a needle tip, and the same "helping hands - magnifier" you did. I finally resorted to a jeweller's loupe! And after all that, the board lights up, but won't connect to BetaFlight after the soldering. I have a USB microscope on order now in case I try this again (with a new controller board).

Try this: After each ESC you attach, re-connect the controller to the computer. That way you may find out there is an issue AND what led to it.

I have a buzzer on order too. It would be a good idea to put one on yours so you can find it easier. i probably won't have any trouble finding my parts in the junk bin.

 

[PsyBorg]

Got mine out and about again today. Was a brutal day for video though. Wasted two whole batteries trying to find a happy channel. At the end of the day I think the antenna set up on these along with the poor video settings for contrast, brightness, and day night change times is going to give a lot of people problems.

It was so bad today that when I came back in I removed the CP antenna and hacked up a freebie dipole like LB showed. Signal in the living room was exponentially more clear and hardly any interference when hovering from the motors.

I think at this point I would suggest that FT either speak with the manufacturer or promote another product as there are far to many quality issues with these right out of the box. It starts with the REALLY bad focus and the fact there is enough gluing on the lens you will more then likely break the lens mount trying to loosen the glue to refocus. Then when you get that taken care of unless you are in brightly lit areas with little changes from sun to shade you can actually loose video from subtle changes in light. At least that has been my experience so far I even cranked my googles up to where everything was washed out it the settings were so high and still had transitional issues. Then the antenna tuning is so far off I am surprised these tx's are not blowing up from how lossy they are.

I did manage to get a little closer on the tune and will post my settings in a new thread just for the Gremlin over view I want to do. I was flying today in what the weather channel called 6 - 8 mph winds that were more like 12 - 16 steady and +20 gusts. My fiberglass flag poles were flexed over 45 degrees at times. I still had control for the most part. The I term will come up another few points now that I know how much wind these things can take effectively so that's another piece of the tune I got out of the days flights.

 

[Huffheinz]

Help Needed - Motor Issues

I got my replacement FC in and went back to work last night. I got everything soldered up nice and neat and completed the build. I was able to connect to betaflight, bind the receiver, and verify that the camera was working with my goggles. Unfortunately, when I spun the motors up, only 2 and 4 were spinning.

Motors 1 & 3 are not moving at all. When I connect to BL Heli configurator, it only recognizes 2 and 4. So now I need to figure out how to determine if it's bad ESCs or bad FC but I'm not sure how to make that distinction. The solder joints look good so the only thing I can think of is to swap one of the "bad" ESCs with one of the "good" spots on the FC and see if it works. Does anyone have any suggestions on other ways to troubleshoot this?

I'm really starting to regret choosing the Gremlin as my first build.

 

[cranialrectosis]

I got my replacement FC in and went back to work last night. I got everything soldered up nice and neat and completed the build. I was able to connect to betaflight, bind the receiver, and verify that the camera was working with my goggles. Unfortunately, when I spun the motors up, only 2 and 4 were spinning.

Motors 1 & 3 are not moving at all. When I connect to BL Heli configurator, it only recognizes 2 and 4. So now I need to figure out how to determine if it's bad ESCs or bad FC but I'm not sure how to make that distinction. The solder joints look good so the only thing I can think of is to swap one of the "bad" ESCs with one of the "good" spots on the FC and see if it works. Does anyone have any suggestions on other ways to troubleshoot this?

I'm really starting to regret choosing the Gremlin as my first build.

Been there... All multi-rotor builds are a challenge. If it were easy it wouldn't be nearly as cool. I find a Snickers really helps.

Have you synched your ESCs?

 

[Huffheinz]

Been there... All multi-rotor builds are a challenge. If it were easy it wouldn't be nearly as cool. I find a Snickers really helps.

Have you synched your ESCs?

Hah! Yes...I walked away from it last night, had a bowl of ice cream, and watched a movie with my teenager. Now I'm considering next steps over coffee after a good night's sleep.

I calibrated the ESCs according to the method TJ uses in the build video around the 1:02:45 mark. Everything on the betaflight screen shows up correctly and I get the same beeps but motors 1&3 don't spin. When I open BL heli, it "sees" 2&4, but not 1&3. So either I have (A) bad connections from FC to ESC on 1&3, (B) bad ESCs on 1&3, or (C) fried the FC in some way that effects 1&3.

 

[PsyBorg]

It could very well be the motors. I have seen posts where these motors have come bad from the factory. OR if you did shorter wiring they tend to separate where the feed wire meet the coil wires.

I would leave the Esc's connected and try a different motor temporarily to test that.

 

[Huffheinz]

Success! I am happy to report that I have sorted out all the ESC issues I was having and have logged my first two batteries on my little Gremlin!!

It turns out that the motor/ESC issue I was having all boiled down to my soldering skills (or lack thereof). A little continuity testing with the multimeter showed me that I had a bridge between positive and signal on FC at #1 (too much solder) and a loose ground wire on #3 at the FC. A little careful resoldering and I was off to the races.

The only other little snag I hit was programming the arming function in betaflight. A quick check on this forum showed me that someone else was having this problem and that it was most likely that the throttle travel on my DX6i didn't fall below the min_check threshold. I had never even heard of min_check before, but a quick throttle travel adjust on the DX6i and I was armed and dangerous (but in a totally safe way).

So, despite 20mph winds gusting to 30mph, I HAD to take her out for the maiden. I flew for a minute LOS at the open garage door in angle mode, and it did great. I landed and put the goggles on my 10yo daughter for a ride along and flew around the front yard for a bit. It was her first FPV experience and she loved it! On the 2nd battery I strapped on the goggles for my first FPV piloting experience and it was a blast! I kept it in angle mode because I was in pretty tight quarters and I was blown around by the wind gusts pretty good, but she fought the wind well and I didn't even crash.



Thanks to everyone who helped me along with my first quad build. I couldn't have done it without the support and encouragement from this fine community. You guys rock.

 

[French]

Congrats!!!! It's always a great feeling after a good maiden flight

 

[PsyBorg]

I had mine out in those same winds. Its amazing how well these actually do. They don't hover so well and drift with the gusts but hey its a quad its not meant to be still.. EVER...

Glad to see another success story. Keep an eye on motor temps if you are running stock pids they are high for the Gremlins.

 

[Michael9865]

Congratulations!

 

[cranialrectosis]

Video or it didn't happen.

 

[Huffheinz]

Hah! I remember when it was "Pics or it didn't happen!" I must be getting old.

Here you go...

 

[cranialrectosis]

Hah! I remember when it was "Pics or it didn't happen!" I must be getting old.

But its the toyz and kids that keep us young!

Very nice maiden. She flies pretty well!