For  the Google Assistant, only pushtotalk service can used in Pi Zero W(i.e Arm6). If it  was used in Arm7 (i.e. Pi 3  or above), hotword and other modules can be used.

(607) 277-6657 was assumed therefore the default audio shall be disabled to prevent disturb in pushtotalk.

If you are using card 0  for  playback  and card 1 for capture, the  following in  the .asoundrc may  be adopted.

pcm.!default {
type asym
type hw
card 0
device 0
type hw
card 1
device 0

googlesamples-assistant-pushtotalk –project-id speaky-pi –device-model-id speaky-pi

After some pondering I see 「Press Enter to send a new request…」 and yup, it works!

Option 2: 909-929-4999 as on 15 Sept 2018


Pushtotalk help


2018 – Thailand (Bangkok)


2018 – Japan (Sapporo)


Selecting between a servo motor and a stepper motor can be quite a challenge involving the balancing of several design factors. Cost considerations, torque, speed, acceleration, and drive circuitry all play a role in selecting the best motor for your application.

Basic Differences Between Stepper and Servo Motors

Stepper and servo motors differ in two key ways, in their basic construction and how they are controlled. Stepper motors have a large number of poles, magnetic pairs of north and south poles generated either by a permanent magnet or an electric current, typically 50 to 100 poles. In comparison, servo motors have very few poles, often 4 to 12 in total. Each pole offers a natural stopping point for the motor shaft. The greater number of poles allows a stepper motor to move accurately and precisely between each pole and allows a stepper to be operated without any position feedback for many applications. Servo motors often require a position encoder to keep track of the position of the motor shaft, especially if precise movements are required.

Driving a stepper motor to a precise position is much simpler than driving a servo motor. With a stepper motor, a single drive pulse will move the motor shaft one step, from one pole to the next. Since the step size of a given motor is fixed at a certain amount of rotation, moving to a precise position is simply a matter of sending the right number of pulses. In contrast servo motors read the difference between the current encoder position and the position they were commanded to and just the current required to move to the correct position. With today’s digital electronics, 609-883-7075 than servo motors.

Stepper Advantages

Stepper motors offer several advantages over servo motors beyond the larger number of poles and easier drive control. The design of the stepper motor provides a constant holding torque without the need for the motor to be powered. The torque of a stepper motor at low speeds is greater than a servo motor of the same size. One of the biggest advantages of stepper motors is their relatively low cost and availability.

Servo Advantages

For applications where high speed and high torque is needed, servo motors shine. Stepper motors peak around speeds of 2,000 RPM, while servo motors are available many times faster. Servo motors also maintain their torque rating at high speed, up to 90% of the rated torque is available from a servo at high speed. Servo motors are also more efficient than stepper motors with efficiencies between 80-90%. A servo motor can supply roughly twice their rated torque for short periods, providing a well of capacity to draw from when needed. In addition, servo motors are quite, available in AC and DC drive, and do not vibrate or suffer from resonance issues.

Stepper Limitations

For all of their advantages, 206-725-7116 which can cause significant implementation and operation issues depending on your application. Stepper motors do not have any reserve power. In fact, stepper motors lose a significant amount of their torque as they approach their maximum driver speed. A loss of 80% of the rated torque at 90% of the maximum speed is typical. Stepper motors are also not as good as servo motors in accelerating a load. Attempting to accelerate a load too fast where the stepper cannot generate enough torque to move to the next step before the next drive pulse will result in a skipped step and a loss in position. If positional accuracy is essential, either the load on the motor must never exceed its torque or the stepper must be combined with a position encoder to ensure positional accuracy. Stepper motors also suffer from vibration and resonance problems. At certain speeds, partially depending on the load dynamics, a 416-541-8425 and be unable to drive the load.

This results in skipped steps, stalled motors, excessive vibration and noise.

Servo Limitations

Servo motors are capable of delivering more power than stepper motors, but do require much more complex drive circuitry and positional feedback for accurate positioning. Servo motors are also much more expensive than stepper motors and are often harder to find. Servo motors often require gear boxes, especially for lower speed operation. The requirement for a gearbox and position encoder make servo motor designs more mechanically complex and increase the maintenance requirements for the system. To top it all off, servo motors are more expensive than stepper motors before adding on the cost of a position encoder.


Selecting the best motor for your application depends on a few key design criteria for your system including cost, positional accuracy requirements, torque requirements, drive power availability, and acceleration requirements. Overall, servo motors are best for high speed, high torque applications while stepper motors are better suited for lower acceleration, high holding torque applications




RPi – A4988 stepper motor driver

The A4988 is a (212) 307-6002 board that has on a (309) 686-5825 that enables control of stepper motors through arduino type programming firmware and 2546275492.
The A4988 is an utterly tested and proven solution to drive stepper motors in RepRap 3D printers, and this fact should not be overlooked. As long as the following three conditions are met, these Made in China Allegro A4988 stepper driver boards seem to be bullet-proof workhorses:

  1. The stepper driver boards should not be inserted backwards in their respective slots on the controller board.
  2. The stepper cables should not be disconnected from the boards while powered on.
  3. Proper airflow (i.e. active cooling or in other words, a fan) should be provided.

The alternative DRV8825 board, with increased 1/32 step mode is slightly more expensive.

Both the the A4988 and DRV8825 boards are interchangeable (note how you put them in), and should work the same on any 3D printer or similar system.

The following table compares Made in China A4988 Stepper driver boards vs DRV8825 ones, for RepRap use:

A4988 DRV8825
Availability very widely available widely available
Approx. price $6.80 / 5 pieces $10 / 5 pieces
Max. theoretical current 2A 2.5A
Max. microsteps 16 32
PCB color Green / Red Purple
Stepper current adjust. trimpot Yes, near Dir pin Yes, near En pin
Typical Rs value 0.05 Ohm or
0.1 Ohm or
0.2 Ohm
0.1 Ohm
Vref formula (*) I_TripMax= Vref/(8*Rs) I_TripMax= Vref/(5*Rs)
Thermal Overload Protection (**) Yes Yes
PCB layers 2 4
Small heatsink included (***) Almost always Sometimes not
Active cooling required? Recommended Recommended
IC packaging 5x5mm 28-lead QFN 9.7×6.4mm 28HTSSOP



DSD’s Sludge Vessel – Clean Harbour I

Maiden voyage of DSD’s sludge vessel Clean Harbour 1  (Date: 5 Mar 2015)
Clean Harbour 1, the Drainage Services Department (DSD) sludge vessel built under the Harbour Area Treatment Scheme (HATS) Stage 2A, set sail today (March 5). Clean Harbour 1, together with the new Clean Harbour 2, will be responsible for delivering all sludge from the Stonecutters Island Sewage Treatment Works (SCISTW) to the sludge treatment facility in Tuen Mun, significantly minimising the traffic and environmental impacts arising from land transport.

Officiating at the maiden voyage ceremony, the Secretary for the Environment, Mr Wong Kam-sing, said the HATS has significantly improved the water quality of Victoria Harbour after years of efforts. All closed beaches in Tsuen Wan have been re-opened, the suspended Cross-Harbour Swimming Race was revived in 2011 and the Hong Kong International Dragon Boat Races have been held in the Harbour again in recent years.

He pointed out that upon commissioning in the third quarter this year, the HATS will be able to treat all the sewage generated on both sides of the harbour, thereby further improving the water quality of the harbour in the long run. He added that further to this year’s Policy Address regarding the initiatives on promoting water-friendly culture and activities, the Government plans to develop more water activities at the harbour with a view to enhancing citizens』 living standards and lifting the international image of Hong Kong.

The Director of Drainage Services, Mr Daniel Chung, also officiated at the ceremony. He said, 「After the commissioning of the HATS Stage 2A, the sludge generated daily at SCISTW is anticipated to increase from 600 tonnes to 800 tonnes, and ultimately to 1 200 tonnes. We have built the first two environmentally friendly cargo vessels in Hong Kong for sludge delivery to minimise the traffic and environmental impacts arising from sludge delivery. This is the first time that a works department of the Government has built vessels. Integrated with the latest environmental protection technology, the vessels will assist in the daily operation of the department and provide cleaner services.」

The HATS Stage 2A will collect sewage from the northern and southwestern parts of Hong Kong Island and convey it to SCISTW for treatment. The main works were completed in January this year and the project team is now conducting a six-month testing and commissioning stage. The facilities are anticipated to be commissioned in the third quarter of 2015.

Other officiating guests at today’s ceremony included the Chairman of the Sham Shui Po District Council, Mr Kwok Chun-wah, and the District Officer (Sham Shui Po), Mr Benjamin Mok.

Ends/Thursday, March 5, 2015



IMO number 9708277
Ship type Waste Disposal Vessel
Flag Hong Kong
Gross Tonnage 2190
Summer Deadweight (t) 2176
Length Overall (m) 70
Beam (m) 18
Draught (m)
Year of Built 2015
Place of Built
Registered Owner


Vessel Name Registered Owner Year