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HobbyKing Blue Series
During the last months the Chinese manufacturers have started to replace the Atmel based controllers with the cheaper 8051 based controllers. So the HK BlueSeries is actually the only known BLDC which is completely based on Atmel micro controllers and low resistance N-FETs only. The following chapters will give you an overview of the architecture of the BlueSeries controllers, the needed modifications at the hardware level and the reused Quax controller software.
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There are no guarantees for the correctness of the following stuff. Please be careful and work carefully when doing the modifications on your controllers. Make sure to test your modifications with the current limit set to maximum 1 ampere.
Architecture
In wide parts the architecture is the same as described by Quax in his earlier BLDC modifications. Only the pin out of the controller, the high power stage and the layout have changed.
The reconstructed circuit can be found in the following files:
The battery voltage is stabilized by the 2 capacitors C1 and C3. From this voltage rail the power-stage with the engine, the BEC and the internal voltage regulator are supplied. The BEC of this controller was built with three parallel connected voltage regulators of the type 7805 with the series resistors R43..R45 for load balancing at the outputs. This voltage is stabilized through the low ESR capacitors C4 and C16 in conjunction with C6 which is suppressing oscillations. This voltage (+5V) will be supplied to the external hardware eg. the receiver and the servos of an RC-model. IC1 is responsible for powering the on-board controller. It's a small linear regulator with 5V output voltage and the stabilization capacitors C2 and C5.
An Atmel ATmega8 with a 16MHz ceramic oscillator has been used. For higher EMI immunity the RESET pin of the MCU will be pulled high through R27 with a lower resistance compared to the internal pull up of the MCU self.
For battery voltage detection there is the voltage divider with R30 and R31 and the stabilization capacitor C14 connected to Port PC2 of the MCU. The temperature is measured in the same way on port PC1 of the MCU, using the the voltage divider built with R28 and R29, while R29 is a NTC Resistor with 8.2kOhm at 25deg Celcius.
The PPM signal from the receiver, which controls the BLDC are coming over the RC low pass filter from JP6 and is connected to the INT0 pin of the MCU. Additionally it's connected to the RXD pin, for programming functionality with special BLDC programmers.
The power stage of the controller is built only with N-Channel FETs. The circuit of phase 'U' will be described representatively for all three phases (U, V, W).
On the low side of the FET's T2, T8 and T10 are driven over 100R resistore directly from one GPIO PD5 of the MCU. The pull-down resistor R23 pulls the GPIO PD5 from the MCU low, while it is in RESET state. For driving the high side FETs, the circuit is built with R5, Q2, D2, R2 and C7. When the output of phase U is low, the capacitor C7 is directly charged over D2 from the battery rail. When the low side opens (UL goes low) and !UH goes low, the voltage of the collector from Q2 rises and the gates of T1, T7 and T9 are driven over the 100R resistors from the stored energy of capacitor C7, while phase 'U' rises too.
For correct commutation the brushless engine's back-EMF will be used over the voltage dividers build with resistors R14..R16 and R20..R22 in comparison to the virtual central point 'M' of the engine built with the resistors R17..R19 from the divided phase-voltages 'U'..'W'. The capacitors C11, C12 and C15 are only for suppression of spikes on these measurement rails.
For factory programming the AVR ISP interface of the MCU is connected to test pads at the PCB as seen in "Load new Firmware".
Needed hardware modifications of the BLDC
For using the HK-Blue series BLDCs for NG-UAVPs, there is one realy important change to do: We need I2C for speed control, similar to Quax's BLDCs.
For this we have to get a external connection to the I2C-Interface of the BLDC, but these pins are currently used for control of the power-stage of phase "V" (signals VL and !VH on Port PC4 and PC5).
The software will use use GPIO operations instead of the old hardware PWM interface for the PWM operations. For this its possible to use every other, free port pin of the MCU.
So the signals we are using now for "VL" and "!VH" will be Port PB2 and PB1. After this modification we can use the free I2C interface to communicate with the controller. Additionally we are removing the BECs from the Board (IC2, IC4, IC5, and R43...R45).
If you want to power your BLDC's CPU from your NG, you should also remove the voltage regulator IC1. This will allow you to switch on the BLDCs with the power switches of your NG.
Needed software modifications of the Quax-Firmware
To use the Quax firmware it's only necessary to modify the include file of the firmware. For these BLDCs we use the Firmware of the TP-17A Version.
In the include file we have to modify the port definitions and their macros for the FET-switching dependend to the circuit of the BLDC. The hardware modifications for the BLDC are shown below.
********************* ; PORT D ;********************* .equ c_comp = 6 ;(in) midpoint M .equ AnFET = 5 ;(out) phase low switch control UL .equ ApFET = 4 ;(out) phase high switch control /UH .equ rcp_in = 2 ;(in) r/c pulse input .equ INIT_PD = (1<<ApFET) .equ DIR_PD = (1<<ApFET)+(1<<AnFET) .equ BRAKE_PD = (1<<AnFET)+(1<<ApFET) #define ApFET_on cbi PORTD,4 #define ApFET_off sbi PORTD,4 #define AnFET_on sbi PORTD,5 #define AnFET_off cbi PORTD,5 ;********************* ; PORT C definitions * ;********************* .equ mux_b = 7 ;(in) phase input V' .equ mux_a = 6 ;(in) phase input U' .equ CpFET = 3 ;(out) phase high switch control /WH .equ accu_adc = 2 ;(in) ADC0 voltage control input .equ temp_adc = 1 ;(in) ADC1 temperature control input .equ mux_c = 0 ;(in) phase input W' .equ INIT_PC = 0x30+(1<<CpFET) ; set pullup for i2c .equ DIR_PC = (1<<CpFET) .equ BRAKE_PC = (1<<CpFET) #define CpFET_on cbi PORTC,3 #define CpFET_off sbi PORTC,3 ;********************* ; PORT B definitions * ;********************* .equ BnFET = 2 ;(out) phase low switch control VL .equ BpFET = 1 ;(out) phase high switch control /VH .equ CnFET = 0 ;(out) phase low switch control WL #define BnFET_on sbi PORTB,2 #define BnFET_off cbi PORTB,2 #define BpFET_on cbi PORTB,1 #define BpFET_off sbi PORTB,1 #define CnFET_on sbi PORTB,0 #define CnFET_off cbi PORTB,0260px .equ INIT_PB = (1<<BpFET) .equ DIR_PB = (1<<BnFET)+(1<<BpFET)+(1<<CnFET) .equ BRAKE_PB = (1<<BnFET)+(1<<CnFET)+(1<<BpFET)
To consider: You need Atmel AVR-Studio to compile these firmware. AVR-GCC-ASM didn't work.
You can find the modified firmware for these BLDCs in the modification instructions section below.
Detailed modification instructions specific to BLDCs
These pages describe how to modify a HobbyKing BlueSeries N-FET only ESC for I2C usage: