Apologies for not being able to updates as our fiscal year end process really tied me down.
Anyway, our eBuggy has been our main mean of transportation for the morning walk every saturday and sunday. But being a sensorless means that there are huge of possible improvement from the performance side.
Hence, started up my Enhancement project for a Sensored Alternator conversion with Integrated motor controller.
The Idea is to go for a sensored commutation mode with budget motor controller which has a build in rotor controller. To make thing more interested, put an initial goals of:
1. Low Cost sensor and should use the rotor magnetic field rather than go for optical sensor wheel /separate sensor. The consequences would be that this will be a fix non adjustable sensor.
2. The Controller should be easily constructed, cheap and with High Amps (at least 100A) and Hi Voltage (at least 30V) Half Bridge Driver. The Driver should be easily upgraded into IGBT
To push the research cost down, I'm using small Nippon Denso 35A converted alternator (USD20) and use plain old TIP2955/3055 transistor in the development phase. The Savvy driver will only be implemented if the Transistor model already working flawlessly.
1. Sensor & Installation: The First attempt is to utilized AN276 hall sensor IC from salvaged Computer fans. I do have the experience with this IC for my RPM meter and it works ok. The only challenge is as this IC gots 4 pins so its wider than normal hall sensor. Trying to install this near the end or rotor as in the picture below
It has been found though the sensor work flawlessly, but the magnetic field was not. Due to the arrangement of the Claw Pole, if the sensor was put too near to the end of one pole, there isn't enough opposite flux to toggle it as it should be. Hence the only solution is to have the hall sensor installed exactly in the middle of the stator where both claw size is exactly the same. But it will means that I could not use the wide sensor for this and need to make a grove in the stator tooth.
Hence, ordered HONEYWELL S&C SS40A (SGD 1.98 each) from farnell singapore, had a machine shop make the grove and voila... the sensor work as expected (six commutation phase).
2. Controller logic
Implements the sensor input into 2 external interrupt channel and 1 Analog Comparator channel, as I need to detect toggle event in every sensor. So far the Sensor & Interrupt works ok (with output only to LCD screen), I'm currently working on the Transistor driver when the work held me down. Should have the POC model in a week or two. Atmel's application notes helps a lot especially on the commutation logic. Still looking out for additional PWM output for the rotor controller without huge processing expense as if approached through normal port.
3. Controller Driver
Rather than going into a standard push-pull on each Phase driver which requires N & P Channel MOSFET, I'm planning to used IR2101 ICs (SGD 4.66 each, one in every phase output) to drives 4xIRF3007 (75V/80Amps N-Channel Mosfet giving a total of 160Amps for each phase, its a clearance sale item hence it only cost SGD 2.24 each). With this approach, I don't have to use the P-Channel mosfet which was more expensive do to its more complex manufacturing process. Nevertheless, the boostraping technique enabled by the IR2101 is quite complex hence to isolate the problem, this will only be implemented once the transistor Model works ok. So far, the IR2101 documentations shows that MOSFET-IGBT conversion is just plug and play with a special attention only on Gate Voltage threshold.
Will share the progress later on if anybody interested