Risinglink PD201W Power Failure Detector

Introduction
This blog provides a teardown of the Risinglink PD201W Power Failure Detector and wall plug adaptor.

Risinglink Module

Power Failure Detector Supplier
The power failure detector is branded with the logo of the company Risinglink. There are no product specifications for the detector on the Risinglink website but documentation is provided with the detector when purchased.

Package Contents
A mains wall plug (USA), USB cable and documentation are shipped with the power failure detector shipment.
Opening the Detector
A thin flat bladed screwdriver was used to release the lid from the case. The joint near the R and K in the Risinglink logo was the optimum lid leverage position. The plastic lid has two clips to retain the lid in the housing.

Risinglink Module Internal

The ESP-12F WiFi module, CR2 battery, buzzer, switches and LEDs are immediately visible on the circuit board upon opening the unit. Removing the circuit board was possible by pressing the green LED away from the edge of the case. There are no components on the bottom side of the circuit board.

Risinglink Circuit Board

The battery manufacturer’s website (Tenergy) shows that the battery cell has a capacity of 800 mAh (Lithium). 

According to the ESP datasheet, operating the WiFi at continuous transmission draws an average of 71 mA. This would theoretically mean that a fully charged battery could monitor the status of the mains for hours.

As detailed in the documentation shipped with the detector, the white switch powers the detector with visual feedback provided by the red LED.

The black pushbutton is used to change operating modes as required when configuring the detector.

For the USB connector, only the power connections are utilised for monitoring the mains. No USB communication is possible to the detector. USB power is indicated through the illumination of the green LED.

Email Details
Notification emails are sent with “via amazonses.com” in the address. Emails events are received on the initial start-up, when a power outage occurs or when power restoration is detected.

The device PowerDetector started. Below is the device status at 01/01/2023 12:00PM.

• Power Status: ON
• Battery: 100%
• WiFi Signal: -51

As mentioned in the documentation, an email is sent after 24 hours if there is no communication with the module.

The device, ............, may be OFFLINE. No ping from the device within 24 hours. Please check WiFi connection, Internet service, etc. Please contact support@...... if any question.

Wall Plug
The wall plug (model HNT-H510) features an internal On-Bright controller responsible for the control aspect of generating DC 5V in either Constant Voltage (CV) or Constant Current (CC) mode. As the image from the wall below shows, the design is the usual compact solution.

Wall Plug Internals

ESP-12F
On the detector circuit board is an unpopulated 6-pin straight header (H1). Using the datasheet of the ESP-12F and a multimeter, the pinouts of the header were determined as displayed in the image below.

Pinouts for Risinglink Connector

A TTL to USB converter was connected to the header pins Tx, Rx and 0 V. An oscilloscope was used to measure the transmitted UART data bit time which was approximately 13.3 ms or 75 bps during bootup. Data was shown however this was not reviewed in further detail. Programming information for the ESP can be found on dozens of sites, on example here.

Example data on boot.
ets Jan  8 2013,rst cause:4, boot mode:(3,7)
wdt reset
load 0x40100000, len 30596, room 16
tail 4
chksum 0x3e
load 0x3ffe8000, len 2004, room 4
tail 0
chksum 0xa1
load 0x3ffe87e0, len 4752, room 8
tail 8
chksum 0x6a
csum 0x6a

Modifying the Power LED
Situated on the side of the detector housing is a green LED. When a 5 VDC USB power adaptor is connected, the green LED bursts into operation. The brightness of the LED may be beneficial for a large factory but for a confined space, the LED brightness may benefit from a reduction.

Bright LED on Risinglink Unit

The green LED uses a 1 k 0603 current limit resistor, R1. 

Resistor R1 on Risinglink Unit

To reduce the brightness of the LED, resistor R1 was increased to 10 k with the effects shown below. Resistor R1 was located between the green LED and the USB connector as shown in the capture above.

Dimmer LED on Risinglink Unit

 
Final Thoughts
The Risinglink PD201W is reasonably designed and simple to use. An option to use a custom email client over Amazon services would be preferable, especially for clients needing to security harden their network. 

Additionally, a helpful upgrade to the detector could be a battery-only access panel or a rechargeable battery.

Model Rocket Launcher WiFi ESP8266

Introduction
This blog follows the redesign and development of a model rocket launcher controller that features WiFi communications to control the launch process. This design uses an ESP-based microcontroller module. The Arduino platform was chosen for code development.

Rocket Launcher 3D Model

Redesign
To control the launch in the previous model rocket launcher design, Bluetooth communications were used between a PSoC microcontroller and an Android phone. The interface was changed to WiFi to remove the need for developing a phone application. Controlling a rocket launch through WiFi would be independent of a phone or computer operating system.

WiFi Module
For the launcher redesign, an off-the-shelf ESP module capable of WiFi was chosen from Adafruit. The ESP module was chosen for a few reasons. Firstly, the module’s price was relatively low (USD 10). The module was readily available compared to other dedicated microcontrollers. Lastly, using an ESP module meant that the rocket launcher design could be migrated more easily to other ESP devices.

Adafruit Huzzah ID 2471 (Courtesy Adafruit)

Reused Design
The same section of circuit responsible for driving the rocket engine igniter was taken from the previous design. This section consisted of high (VN7040) and low-side (VNL5030) switching drivers (ST Microelectronics).

Rocket Launcher Igniter Drive Circuit

Circuit Updates
To begin the schematic update process, the ESP module was created in the schematic libraries. The new part replaced the previous PSoC microcontroller and associated circuitry.

The Altium PCB model was downloaded from the website SnapEDA.

Capture of Adafruit Huzzah PCB Footprint from SnapEDA

Schematic Updates
On the ESP module schematic page, the power supply connections and ST driver control signals were mapped to the ESP.

Rocket Launcher - Huzzah Circuit Connections

Audible notification of an impending launch was retained using the buzzer. Connections were mapped to the ESP.

Rocket Launcher - Buzzer

The display (LCD) was infrequently used in the previous design so it was removed and replaced with an LED.

The launch button input to the ESP module was retained for testing purposes.

Rocket Launcher - Optional Launch Button

Connections were made to ESP module pins that had no special functions.
 
Output Drivers
Schematic changes were made to the ST output driver’s power supply. This was required to match the ESP module’s DC 3.3 V supply voltage. The feedback monitoring from the ST drivers was removed from the design because of the reliable performance of the ST drivers.

Power Supply
A DC-DC step-down converter was retained for the power supply. Texas Instruments part LMR50410 featuring an integrated diode was selected to replace the previous DC-DC converter.

Another benefit of the DC-DC converter is its operating voltage which is wider than the ESP modules linear regulator (LDO). The LDO has a maximum rated input voltage of DC 6 V. This voltage does not suit all battery chemistry types.

Rocket Launcher - Power Supply

Battery voltage monitoring using the ADC on the ESP through a resistor divider was kept for experimentation and possible future use.

Circuit Board
There were no caveats defined for the shape of the circuit board (PCB). The placement of components drove the PCB shape. Minimal design constraints for the PCB meant that the PCB was set up for components on both sides.

The capture below shows the PCB top layer with the ESP module, power supply underneath the ESP module, buzzer and optional screw terminals. To fit the power supply beneath the ESP module, pluggable headers were utilised to space the ESP module off the board.

Rocket Launcher PCB - Top Layer

The next capture below shows the PCB bottom layer containing the output switching drivers and related components.

Rocket Launcher PCB - Bottom Layer

Four PCB layers were used for the launcher board stack-up. Captures of the two internal power planes have not been shown.

After component placement and routing, the board size reached a comfortable size of 62 x 44 mm. On the longest PCB axis, a set of 3 mm strips were added to suit mounting in an enclosure. Pictured below is a 3D side and rear view of the board.

Rocket Launcher - 3D Side View

Rocket Launcher - 3D Rear View

In part 2 of the launcher blog, the PCB construction and initial testing will be performed.

Circuit Board Return Path Via Placement Options

Introduction
This blog discusses a few options that new circuit board designers may use for return path vias as a result of signal traces changing circuit board layers through using vias.
 
Further Literature
It is highly recommended that existing content from industry figures such as Eric Bogatin or Rick Hartley are reviewed. Related circuit board information is available from YouTuber channels such as Robert Feranec or Phils Lab to mention a few.

PCB Routing Example
For circuit board designs that feature microcontrollers, microprocessors, FPGA or similar devices with high pin count or spacing density the existing connections to power rails through vias can serve as return paths. In the image below, taken from the Altium Mini-PC board, the green highlighted vias indicate the several 0V (GND) power connections that may function as return paths for the DDR memory address, data, clock and control signals.

Altium Mini-PC Board Highlighted GND (0V) Vias (Courtesy Altium)

 
Reducing Return Path Distance
The capture below is a further extract from the Mini-PC demonstration board showing a distance measurement between a return via and a differential DDR clock pair.

A Texas Instruments Application Note, High-Speed Interface Layout Guidelines, 2023 states that the signal to return via distance should be a maximum distance of 5 mm (200 mil) although that value could be considered design dependent. For the Mini-PC demonstration board, the distance between the return via and differential pair is small, some 2.1 mm.

Altium Mini-PC Board Differential Via Pair (Courtesy Altium)

Consider a situation where the return path distances needed to be reduced. On the Mini-PC board, a smaller distance could be achieved following a circuit board review. Traces on the layers could be moved to make room for a via closer to the differential via pair. The capture below shows one possible change with a reduction to 1.4 mm.

Altium Mini-PC Board with Closer Return Path Via (Courtesy Altium)

Board Space Limitations
A more common limitation when adding or altering return path vias could be related to circuit board space. In the example below, the traces in the red colour identify a differential pair. There is no return path via in close proximity. The while highlighted rectangles represent pads on the other side of the circuit board.

Differential Pair with No Return Path Via on a Double Sided Circuit Board

The reason for no return path via in the area is two-fold. On the opposite side of the circuit board is a surface mount component with large pads making return via placement difficult. The second limitation is due to the PCB rules. The smallest via hole size is configured for 0.3 mm.

The limitation created by the component on the opposite side can be overcome using a number of solutions. Using the existing circuit board via the size of 0.3/0.5 mm (via hole size/via diameter) three vias could be placed onto the circuit board as shown below. This solution yields a differential pair to return path via distance of 2.3 mm.

Differential Pair with Three Return Path Vias on a Double Sided Circuit Board

Differential Pair with Three Return Path Vias on Other Side of Circuit Board

Another solution to consider is changing the board design rules. The circuit board clearance rule could be reduced from 0.2 mm to 0.15 mm since the smaller clearance is supported by many fabrication houses. 

Paired with the board clearance change, the via hole size could be reduced. For instance, a via of hole size and diameter 0.254/0.444 mm could be selected. In regards to capabilities, circuit board fabrication houses can manufacture smaller via hole/diameter measurement of 0.15/0.28 mm (drilled). Applying the two changes mentioned in this section, a via can then be placed less than 1 mm from the differential pair.

Differential Pair with Single Smaller Return Path Via on a Double Sided Circuit Board

No Space or Other Limitations
For some board designs, it may be impractical to place a via close to a signal that requires a return path. Should board space and routing permit, via stitching throughout the board or a via shielding around the board or relevant section of the circuit may be alternative solutions.

Example of Via Stitching on a Circuit Board

Example of Via Shielding on a Circuit Board

Summary
Even though the placement of return path vias may be a semi-automated process with some software design tools, the lack of circuit board space to position vias in optimum locations still vexes novice and experienced board designers alike. This blog puts that other solutions may be found by reviewing the nominated fabrication house’s manufacturing capabilities and the minimum manufacturing circuit board requirements.

Salvaging from LG Controller Board EBR369328

Introduction
This microblog reviews the electronic components (parts) that could be salvaged from an LG air conditioner compressor inverter controller board.

LG Control Board EBR369328 Top Side

Summary
After being provided with the inverter controller board for spare parts, it seems relevant to detail salvageable electronic components in this blog.

Being unfamiliar with air conditioning (AC) equipment, AliExpress was used to identify the function which is listed as an LG three-phase inverter compressor (motor) control board.

It should be noted that the LG control board was supplied not working. In these instances when salvaging electronic parts, additional testing and diligence should be taken.

Salvageable Top Side Components
For the current measurement on the three-phase supply, an Allegro device capable of + 50 A, part number ACS756 was utilised. The Allegro part is listed as obsolete however this does not prevent is being used again for testing a design concept. This is one of the devices that should be tested once removed because of its use in the circuit.

Allegro ACS756

The bulk of the electrolytic capacitors are manufactured by the Korean company, Samyoung. Some of the electrolytic through-hole capacitors associated with the mains (line) supply may be handy for spares if mains voltage projects are an area of interest.

Mains Rated Electrolytic Capacitor

The large 10 to 20 W wire-wound ceramic resistors had no signs of overheating or physical damage. These resistors may be worth salvaging even for simple dummy loads.

Wirewound Resistors

Located near the wire-wound resistors are mains capacitors manufactured by the Korean company, Pilkor. On this LG board, those capacitors were in excellent condition and worth salvaging.

Mains Capacitors

The large vertical connector, AMP series D-5200, should be considered for anyone involved with high-current designs.

AMP Connector D-5200

The circuit board is fitted are a few different types of optocouplers. One of the interesting parts is the HCNR201 which is a high-linearity optocoupler from Broadcom.

Broadcom HCNR201

Other optocouplers include Toshiba TLP781, TLP559 and TLP521. All these Toshiba optocouplers are obsolete however they may serve well as spares or for repair purposes.

Various Toshiba Optocouplers

A TE relay with the part number T92S7D12-12 is fitted to the board. This relay is rated at a 12 V at 20 A and is still actively manufactured by TE.

High Current TE Relay

Contained on the board are a plethora of remaining components to consider for salvage. These include an oscillator, heatsinks, LEDs, chokes, axial resistors and unidentified components.

Salvageable Bottom Side Components
Fitted on the bottom side of the PCB is the motor switching module (IGBT). This device is most likely not worth salvaging.

Motor Driver Module

The semiconductors on the bottom side appear to have no identification markings or those markings have become obscured by what appears to be a protective (conformal or lacquer) coating.

LG Control Board EBR369328 Bottom Side

All electronic parts on the bottom side of the board are epoxy glued to the as part of the circuit board assembly process. There is little to salvage from this side of the board because of the glue although removing components is possible with the correct tools. For low-cost and high-throughput printed circuit board assemblies, soldering using wave solder in a single pass has been a common manufacturing method. This LG board employs some solder-thieving designs in the circuit board layout as pictured below.

Component with Solder Thieving Pads