Chip prices have gone up significantly in the past couple of years, making FPV electronics more expensive than ever. The Speedybee F405 V3 FC and 50A BLHeli_S 4in1 ESC might be the best value stack you can get right now. It offers most if not all the modern features one would want in a standard FPV drone, and it’s also suitable in a huge range of different builds and styles.
New to FPV? Check out my flight controller buyer’s guide.
Where to Buy?
Stack: Speedybee F405 V3 FC + 50A BLHeli_S 4in1 ESC
- GetFPV: https://oscarliang.com/product-szri
- AliExpress: https://s.click.aliexpress.com/e/_DDolH5v
- RDQ: https://oscarliang.com/product-oibq
- Amazon: https://amzn.to/3FdpdlQ
- Newbeedrone: https://oscarliang.com/product-3dpx
Just the FC: Speedybee F405 V3 FC
- GetFPV: https://oscarliang.com/product-hbaf
- RDQ: https://oscarliang.com/product-vrin
- NBD: https://oscarliang.com/product-3dpx
For the FC:
- 5x M3 30mm steel hex screws
- 1x SH 1.0mm 30mm-length 8pin cable (for FC-ESC connection)
- 5x M3x8mm Silicone Grommets
- 1x 6pin cable(80mm) for DJI Air Unit / Vista
For the ESC:
- 5x M3x8mm Silicone Grommets
- 1x 35V 1500uF Low ESR Capacitor
- 1x XT60 Power Cable(70mm)
- 5x M3 Silicone O Ring
The Best Value Stack?
At US$69.99 for the whole stack, or US$40.99 for just the FC, I believe this is currently one of the best value stack/flight controllers on the market. It’s truly amazing how they managed to pull it off with this low price.
Maybe cheap, but it has all the features one would need in an FPV drone, and fits in almost any build you can think of: 4S/6S, quadcopter/hexacopter/octocopter, analog/digital, freestyle/racing/long range, Betaflight/iNav…
F405 V3 FC
- Betaflight Firmware Target: SPEEDYBEEF405V3
- MCU: STM32F405
- IMU(Gyro): BMI270
- USB Port: Type-C
- Supports 3S – 6S Input
- OSD Chip: AT7456E (Supports Analog)
- Built-in Barometer
- BEC: 9V 2A + 5V 2A + 3.3V 500mA
- Micro SD Card Slot for Blackbox
- Onboard LED battery indicator
- 8 Motor outputs (ESC signals)
- 4 x full UARTs + 1 x half UART (RX4)
- Dedicated DJI Air Unit JST connector (solder pads are also broken out)
- Built-in Bluetooth for wireless configuration via Speedybee App
- I2C: Supported. SDA & SCL pads on the front side. Used for magnetometer, sonar, etc.
- Supported Firmware: BetaFlight, EMUFlight, INAV
- Mounting holes: 30.5 x 30.5mm (4mm hole diameter)
- Dimension: 41.6(L) x 39.4(W) x 7.8(H)mm
- Weight: 9.6g
50A 3-6s BLHeli_S 4-in-1 ESC
- BB21 MCU
- Firmware target name: JH-50
- Power Input: 3-6S LiPo
- Current Rating: 50A x 4 (continuous), 55A (burst 5 seconds)
- Onboard Current Sensor: Scale=386 Offset=0
- Supports DSHOT300/600
- TVS diode
- Mounting holes: 30.5 x 30.5mm( 4mm hole diameter)
- Dimension: 45.6(L) * 44(W) * 6.1mm(H)
- Weight: 13.8g
Closer Look at the Speedybee F405 V3 Stack
F405 is slower than F7 in terms of clock speed, but it does not matter so much for the current version of Betaflight since 4K PID loop frequency can perform arguably just as well as 8K. But if you insist on running 8K looptime you may consider a F7 FC instead. It uses the BMI270 gyro, which means you will be running 3.2KHz PID looptime at most. In fact the F405 has more memory than the F722 which is used in the F7 V3 stack, so in a way the cheaper F405 is better when it comes to longevity.
The F405 V3 FC has a great layout, the solder pads are large and easy to solder, and they are well labelled without the need to look it up in the manual.
There is a 22mm wide cutout in the front of the FC, which is to leave room for the FPV camera in certain tight frames which is thoughtful.
There are 8 motor outputs (M1-M8), allow you to use this FC on an hexacopter or octocopter.
Unfortunately there’s no flash memory for Blackbox which is a shame, but there’s an SD card slot for that instead. Personally I prefer flash memory as you can just plug in the USB cable and download the logs, but I guess the SD card slot might have helped to keep the cost down. Looking at the bright side, you can have up to 4GB of storage when using an SD card so you will almost never run out of storage.
There are 5V and 9V BEC (both are rated for 2A), you can power your VTX off the 9V to reduce the chance of voltage spikes damaging the VTX. There is a JST connector on the FC, makes it plug and play with DJI Vista/Air Unit, Walksnail Avatar, and HDZero VTX.
There’s an OSD chip onboard, so it also supports analog FPV system.
Something I have not seen before on an FC is the battery indicator (4 LED’s), which shows the voltage level of the LiPo plugged in.
It has Bluetooth built-in, which allows you to configure Betaflight from your phone wirelessly (using the Speedybee App that you can download from the App Store)! Unlike the F7 V3 version, the F405 V3 doesn’t have WiFi, so you cannot flash firmware from the app, to do this you have to use the USB cable or Speedybee Adapter.
There are 5V, GND and LED_Strip solder pads at each corner (D1-D4), making LED wiring easy and clean. Note that all LED pads are connected in parallel, they will just mirror each other, so you cannot have different LED config for each corner. Actually the F405 V3 has a built-in LED system, to let Betaflight control the LEDs, you need to long press the boot button when the quad is powered on. However, the FC doesn’t seem to remember the setting and you have to press the button every time to switch to Betaflight’s LED system, which is slightly annoying.
There are 4 full UART available (plus a half UART – RX4 dedicated for ESC telemetry), these UART can be used for connecting your receiver, VTX (smartaudio), camera (UART control), GPS etc.
There is a barometer onboard, not really useful for Betaflight but need it or not, it’s good that it’s there.
And it uses USB-C connector which is more robust and easier to plug in than Micro USB.
When it comes to the ESC board, BLHeli_S has almost the same capability as BLHeli_32 when you flash Bluejay firmware, it supports bi-directional DShot and RPM filter, also custom startup tones as well. The main downside is that you can’t use higher or variable PWM frequency. So you are not compromising too much performance using the cheaper BLHeli_S ESC over BLHeli_32.
How To Use
Here’s the wiring diagram.
To power receiver and GPS, I’d recommend using the 4V5 pad instead of the 5V pad. These pads can supply power with the LiPo unplugged. This allows you to configure/test your receiver by connecting the USB cable without LiPo, and get a GPS satellite lock before powering up the quad. The 5V pads only have power when you connect the LiPo battery.
If you are pairing the F405 V3 FC with the SpeedyBee BLHeli_S 50A ESC, make sure to set the current sensor scale to 386 and Offset 0.
You will need a decent SD card for Blackbox logging, see my SD card recommendations. Betaflight firmware requires the type of the microSD card to be either Standard (SDSC) or High Capacity (SDHC), so extended capacity cards (SDXC) are not supported (Many high-speed U3 cards are SDXC). Also, the card MUST be formatted in FAT32 filesystems. So basically, you could use any SD card smaller than 32GB, but Betaflight can only recognize 4GB maximum, any additional storage would be wasted.
The Boot button has two functions. When the FC is off, by holding down the Boot button and power up the FC will put it in DFU mode, this is used when the FC has trouble flashing firmware. When the FC is powered on, the BOOT button can be used to control the LED strips connected to D1/D2/D3/D4 solder pads. By default, short-press the BOOT button cycles through the LED displaying modes. Long-press the BOOT button switches between SpeedyBee-LED mode and BF-LED mode. In BF-LED mode, all the D1-4 LED will be controlled by Betaflight firmware.
Official Manual (link provided by Speedybee): https://store-fhxxhuiq8q.mybigcommerce.com/product_images/img_SpeedyBee_F405_V3_Stack/SpeedyBee_F405_V3_Stack_Manual_EN.pdf
This stack is going into my next build, I will be sharing the build log along with some PID/filter tuning guide: https://oscarliang.com/how-to-build-fpv-drone/