Eachine, a company known for its budget RTF miniquads, recently came out with a microquad called the QX90 that really pushes the frontiers of toy quadcopter technology. The QX90 is clearly an attempt to try to capture some of the enthusiasm behind the “tiny whoop” movement where many pilots are strapping a tiny camera/VTX combo on the top of a Blade Inductrix microquad. The beauty of this aircraft is that you can fly FPV indoors near other people without much risk. The problem thus far is that it is expensive: an Inductrix with the FX798 camera/VTX and the necessary upgraded motors and batteries can cost up to $200 and requires some fine soldering skills to assemble. This is the market the QX90 is looking to capture.

The QX90 is a ready-to-fly microquad that comes packaged with a pre-soldered camera/VTX combo and an (optional)FrSky SBus receiver. It brings all of this to the table for under $60. What’s more, the flight controller it uses is an extremely small brushed variant of the popular SPRacingF3 board. I’ll state that a different way – this thing is rocking a full-fledged F3 board capable of running all of the popular racing miniquad firmwares!

The QX90 can be purchased here for $70.99 at the time of this writing.

In The Box

img_20160922_135628I purchased my QX90 from Banggood for $60 plus their phenominal $1 “priority” shipping. It arrived in a little over a week. I remember only 2 years ago shipping from HobbyKing’s international (Hong Kong) warehouse used to cost a quarter of the entire order amount and would take up to a month to be delivered. Now we’re down to $1 and a week – I don’t know how that’s possible, but I like it.

The quadcopter was packaged in little more than a foam case wrapped with bubble wrap. It comes fully assembled with the following accessories:

  • 4x Spare props
  • 2x Spare motors
  • 2x Batteries with Velcro
  • Charging cable (requires a LiPo balance charger)
  • Manual

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Unlike most manuals for Chinese products – this one was actually pretty helpful. It walks you through all of the steps required to bind the quadcopter to your Taranis and set it up so it can be flown. Included in the manual are great pictures of each step.

Assembly

The QX90 requires some minimal assembly before it can be flown. In particular, the camera needs to be strapped to the top of the quadcopter. I used one of the packaged rubber bands to do this.

frontal_camera_mount

Credit: ftaysse on Thingiverse

Some folks have made some neat 3d-printable camera mounts if you want to make this a little more robust:

http://www.thingiverse.com/thing:1717374

http://www.thingiverse.com/thing:1721528
Early buyers of the QX90 have also passed down a few recommended modifications which I performed:

  • Remove the “landing gear” standoffs. These apparently break very quickly and do nothing (other than add weight)
    img_20160922_135809
  • Add dabs of glue to the flight controller where wires are soldered.
  • I put some black hot glue over the blue light on the FC board in the front of the quad. This light washes out your video feed when flying at night. With the black hot glue over it you can still see it but it is very dim.

Binding to your Taranis

This process is actually very simple. I highly recommend reading the manual as it makes the process very clear. If you don’t have a manual, here is a summary:

  1. Create a new Taranis model.
  2. Power the QX90 up while holding the pushbutton on the receiver (sits on top of the flight controller)
  3. The RX light should turn green and stay lit, indicating it is waiting for the TX bind command.
  4. Go to the Taranis bind menu. Select “D8” mode and click Bind.
  5. The RX light should turn off indicating the binding process is complete.
  6. Power-cycle the QX90.
  7. Bind channel 6 to a 2-position switch on your Taranis. This switch is the arming switch.

After this, you should be able to take the QX90 off and fly without any further work. The quadcopter will be locked in Angle mode but I found it flew pretty well with the stock settings after the prop problem was fixed…

The Props

Let me be blunt: the props shipped with the QX90 are absolute garbage. Straight out of the box, 2 of the props were so poorly balanced that the quadcopter was unflyable. In a hover it vibrated audibly and drifted all over the place. I swapped the props out for the spares and that fixed the problem on one of them – but on the other, the spare had the same problem! I then swapped it out for the second spare, and had the same problem again!

I ended up ordering some spare props from a Amazon. Fortunately the props used are the same as those used for the Hubsan X4, so spares are abundantly available on Amazon with two day shipping. I purchased this set for $7.

img_20160922_164207

Since I really wanted to get airborne without waiting for the spares to ship, I was able to fix the props that came with the kit by balancing them. I took one of the bad props, inserted a bent staple into the hole, and watched which blade fell downwards. I then added tiny bits of scotch tape to the tip of the blade that was pointed upwards until the prop was able to balance on the staple with the blades pointing out horizontally. Low and behold, after this was done, the quad flew great.

Customizing the QX90 with Cleanflight

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This is why the QX90 was a must-buy for me: it runs an F3 flight controller compatible with Cleanflight! I couldn’t wait to get tinkering with this thing.

Man, that’s a beautiful sight. The first thing I did was disable Angle mode:

noratemode

Being able to fly a true rate mode on a micro quad is one of the most enticing reasons to buy this thing for me. With it enabled, a whole new world of diving buildings, doing flips, and generally having greater camera control is opened up, I even prefer it when flying indoors – albeit with the rates significantly turned down. I did add a switch so that angle mode could be re-enabled from the transmitter though – in case friends or family want to try flying

disable_motor_stop

I also disabled motor stop. I like knowing when my quad is armed and with this disabled, the motors spin up when the quad is armed – just like a normal miniquad. Considering the props are hardly going to hurt you on this little thing, you can probably get by without doing this – your choice.

The QX90 was really hard to fly in acro mode with the stock rates. They are just too twitchy for a small quad. I reduced the rates substantially – about 25% of the stock rates and it flew great. The high rates are great for outdoors though, where the thing flies around at tremendous speed.

Betaflight

Next up, I had to try out flashing Betaflight 3.0 on the QX90. Sure – I said it flies fine on Cleanflight, but I adore Betaflight and wanted to see what improvements it had in store for this tiny little drone.

For the QX90, I downloaded the SPRacingF3 EVO image for Betaflight. As always, releases can be found here:

https://github.com/betaflight/betaflight/releases

betaflight_img_ss

The QX90 uses a virtual COM port, which means it uses a DFU bootloader that can give you some trouble if you are using Windows on your computer. If you have problems, check out the instructions found on the Cleanflight wiki:

https://github.com/cleanflight/cleanflight/blob/master/docs/USB%20Flashing.md

Once I used Zadig to overwrite the DFU drivers as instructed in the manual, the flashing went off without a hitch.

dfu_betaflight_flash

Check out our software setup guide for detailed instructions on how to configure a quad with Betaflight 3.0. Here are some cliffs notes on some specific setup options for the QX90:

  1. Ports tab, set Serial RX to UART 2.
  2. Configuration tab, enabled “BRUSHED” motors as is pictured in the screenshot under “Customizing the QX90 with Cleanflight”.
  3. Configuration tab, set the Receiver Mode to RX_SERIAL and the Provider to SBUS.
  4. PID tuning – drastically reduce your RC Rate and Super Rate unless you are flying outside.

Sure enough, on Betaflight the QX90 flew great right out of the box with the stock PIDs. I’m not sure it’s worth the effort if you aren’t as invested in the Betaflight experience as I am, but it’s nice to know the option is there.

Flight Performance

Alright, enough toying around with configurations and settings – how does this thing fly.

First, let me say once again that being able to fly rate mode is a real breath of fresh air in the microquad universe. It’s really cool to be able to tilt the quad forward when flying down a hall and let go of the stick – and it will continue flying forwards. It’s also neat to be able to do funnels and extremely fast forward flight outside.

That being said, the thrust to weight ratio on the QX90 is pretty comparable to most other microquads out there – not great. That means recovering from a free fall is pretty hairy so Skitzo-esque flow maneuvers are off the table without some sort of power upgrade. The quad also has some strange reactions when it is tilted at high angles – it will occasionally “lose grip” and spin out uncontrollably. I haven’t figured out why yet but I think it is because Betaflight is maxing out the motor thrust and is unable to correct attitude deviations with that available thrust. So when it comes to flying hardcore acro routines, the QX90 is not going to be replacing your miniquad.

That being said, racing around courses and shooting gaps is an absolute blast. Control response is quick and the thing can fly much faster than you would believe. I was going to add a wedge under the camera to tilt it up slightly, but after flying for a while I decided it’s really not necessary – half the fun of the QX90 is being able to hover in place while you slowly approach an obstacle or person and that just isn’t possible with camera tilt.

Speaking of the camera – the FPV picture quality is actually pretty good! Like other CMOS cameras, there is a substantial delay for the camera to adjust its exposure whenever the lighting conditions change (like turning to face the sun), but other than that I was seriously impressed. Range is also great, too – I can fly throughout my house with decent video reception – even to places where my home WiFi is quite weak.

Durability-wise, I was worried about the QX90 but it has survived quite a few crashes. What finally knocked it out of the air was my dog biting the camera/VTX combo – necessitating a $25 replacement. I don’t think I can fault the airframe for that though. I have crashed many times into fan blades, chair legs, trees and even concrete once or twice (from trying to do flips….) – it just keeps popping back up – often times without even having to replace or bend the props.

If you are looking to strengthen your QX90, you can always check out our post on increasing quadcopter durability here!

The batteries the quad comes with are 600mAh 1S LiPo batteries. They have the same connector the Syma toy quadcopter uses, which are not compatible with the Inductrix or the Tiny Whoop. I am getting about 4 minutes of flight time indoors and 2 minutes of flight time outdoors (where I fly much faster). I intend to experiment with other batteries in the near future as I have been told that this is one way to get more performance out of the quadcopter.

Conclusion

I’ve been having a total blast with my QX90 over the past month. It really does a great job of capturing the Tiny Whoop experience for a much more digestible price. Not only that, it comes from the factory with a “big boy” flight controller you can plug into your computer to fully customize – and it works with your Taranis out of the box.

While it definitely flies more like other microquads like the Hubsan or Inductrix than a racing miniquad, I will be now be recommending the QX90 as any new pilots first FPV quadcopter rather than a cheap miniquad kit. It’s a fantastic way to experience FPV without spending too much money, and is a great learning aid at that.

Props:

  • Configurable F3 flight controller in a microquad.
  • Built-in FrSky receiver.
  • Lots of spare parts included.
  • Fantastic price.

Slops:

  • Unbalanced props can make the quadcopter nearly unflyable from the factory.
  • No prop guards like those found on the Inductrix makes the QX90 less safe indoors than the Tiny Whoop.

The QX90 can be purchased here for $70.99 at the time of this writing.

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