Showing posts with label circuit. Show all posts
Showing posts with label circuit. Show all posts

Wednesday, 31 May 2023

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)
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)
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)
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
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 a Double Sided Circuit Board

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

Example of Via Shielding 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.

Sunday, 30 April 2023

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
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
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
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
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
Mains Capacitors

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

AMP Connector D-5200
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
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
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
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
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
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
Component with Solder Thieving Pads

Sunday, 26 March 2023

Maker LED Flasher

Introduction
This blog details a prototype flasher circuit board for a school Maker community. The board design is built to accommodate through-hole and surface mount components. Featuring two component mounting styles allows the board to serve multiple uses in a school environment.

Dual LED Flasher PCB
Dual LED Flasher PCB

Circuit
The circuit in the blog uses a well-worn astable LED flasher design made with discrete components. A transistor pair, wired in a common emitter configuration that drives a total of four LEDs were used. As a DC 9 V battery powers the circuit, more LEDs could be added to the design to interest young Makers.

 

LED Flasher Circuit
LED Flasher Circuit

For the feasibility review of the prototype by the Maker community, both circuits were placed on one side of the circuit board. A single switch (surface mount) was used to control power to the through-hole and surface mount sections.

PCB
An ABS enclosure from a local supplier was initially chosen for the prototype. PCB dimensions and the mounting hole locations for the circuit board were extracted from the ABS enclosure.

Components for the flasher circuits were placed on the top layer of the board. The battery connector was relegated to the bottom layer allowing a battery to be placed inside the ABS enclosure. Routing of the board used two copper layers.

Dual LED Flasher Routed PCB
Dual LED Flasher Routed PCB

3D Printed Case
With many Makers communities having 3D printers a printed enclosure was created based on the commercially available product

3D Model of Plastic Case
3D Model of Plastic Case

The Fusion 360 and STL files are located at the end of this post.

3D Printed Plastic Case
3D Printed Plastic Case

Making
The image below shows the through-hole portion of the circuit board after being populated and partly soldered by a school student. 

Half Populated LED Flasher Board
Half Populated LED Flasher Board

All the through-hole LEDs and capacitors were taken from salvaged components.

To hold the circuit board in position, round head metal self-tapping screws, 3 mm between crests, 7.5 mm in length were utilised.

The surface mount portion of the board was hand populated as a second step for this blog as can be seen in the image below.

Fully Loaded Flasher PCB in 3D Printed Plastic Case
Fully Loaded Flasher PCB in 3D Printed Plastic Case

The video below shows the through hole portion of the flasher board operating.


The second image shows the surface mount section in operation during testing.


Captures from Circuit
For those Maker communities interested in checking the circuit waveforms with a oscilloscope, below are some captures taken from the transistor collector and base connections.

Voltage Measured at Transistor Collector
Voltage Measured at Transistor Collector

Voltage Measured at Transistor Base
Voltage Measured at Transistor Base

Summary
The LED flasher detailed in this blog was published as an example for Maker communities. Available for download below is the artwork for the circuit board and the file for a suitable 3D-printed case.

Flasher Schematic




Flasher PCB

Flasher Gerber

Flasher PCB Bill of Materials

3D Case in Fusion 360

3D Case as STL*

* If the plastic case is used, 4 x round head metal self-tapping screws, 3 mm between crests, 7.5 mm long may be required.



Saturday, 19 November 2022

EPEVER MPPT to Elfin EW11A Adaptor Circuit Board

Introduction
This blog follows on from a previous post relating to WiFi communication with an EPEVER MPPT. In this post, a DIN rail mount adaptor was created to power the Elfin EW11A (WiFi to RS485) device.

EPEVER MPPT to Elfin EW11A Adaptor
EPEVER MPPT to Elfin EW11A Adaptor

Wiring
In a previous post, the connection to an EPEVER MPPT was tested using an Elfin EW11A that was set up for station-mode WiFi operation. The test wiring described in this post was clumsy so a permanent fixture was designed.

DIN Rail Mount Solution
The connections required for the circuit board between the MPPT and EW11A were already established and tested. To power EW11A, a Texas Instruments DC-DC buck converter was selected. 

To mount the circuit board containing the aforementioned parts and rather than spinning up a 3D printed part, Adafruit’s DIN rail mount was used.

Schematic
The RS485 schematic connection between the MPPT and EW11A using RJ45 connectors is shown below.

Circuit Board Connections for EPEVER MPPT to Elfin EW11A
Circuit Board Connections for EPEVER MPPT to Elfin EW11A

In the power supply circuit shown below, a reverse polarity protection diode is at the front end of the design. Following the polarity diode is an optional transient diode (TVS) clamp and PI filter. Bypassing the filter is possible using the two optional bypass resistors which were added in revision 1 of the circuit board. Powering the EW11A is a DC-DC buck converter, notably the Texas Instruments LMR14203; no linear regulators here. At the time of writing the lead time of TI regulators exceeds a year so some equivalents could be the LMR16006X, LMR16006Y or MP2451DJ; these alternatives should be reviewed for compatibility.

Circuit Board Connections for Elfin EW11A Power Supply
Circuit Board Connections for Elfin EW11A Power Supply

For the sundry items on the board, a power LED was included but to conserve power this device could be unpopulated or the series current limiting resistor increased.
To reset the EW11A, a pair of circuit board pins were provided on the circuit board. Shorting the two pins provided on the circuit board will perform the reset.

Circuit Board (PCB)
The board shape was designed using the dimensions shown on the DIN holder datasheet (Adafruit website). The fitment of the circuit board in the DIN holder was accurate, although the placement of components near the edge of the circuit board was tight. A larger keep-out for the components from the edge of the circuit boards was included in the next revision of the board.

EPEVER MPPT to Elfin EW11A Circuit Rev 1 Board Top Layer
EPEVER MPPT to Elfin EW11A Circuit Rev 1 Board Top Layer

EPEVER MPPT to Elfin EW11A Circuit Board Rev 1 Bottom Layer
EPEVER MPPT to Elfin EW11A Circuit Board Rev 1 Bottom Layer

Testing
The populated circuit board was powered with DC 24 V and load-tested. No temperature, climate or similar tests were performed.

With no load, the DC output voltage was 5.02 V with a quiescent current of 5 mA (LED). The output voltage dropped to 4.98 V when the EW11A was powered by the regulator. Greater than DC 6 V should be provided to the DC-DC converter for stable operation.

EPEVER MPPT to Elfin EW11A Circuit Board Rev 0 Bottom Layer
EPEVER MPPT to Elfin EW11A Circuit Board Rev 0 Bottom Layer

A functional soak test of the circuit board over a 24-hours showed no issues. No dropped packets were detected by the virtual COM port application "HW Virtual Serial Port", version 3.1.2.

Downloads
Listed below are the MPPT to EW11A adaptor schematics, circuit board Gerber files and project Bill of Materials. The blank circuit boards can be made available at PCB Way using their Shared Projects option. The supplied schematic and Bill of Materials are for a fully populated circuit board.

Disclaimer: Please note that revision 0 of the the circuit board was tested in this post; no functional changes relating to the MPPT or EW11A connections were made in revision 1 of the circuit board.

Elfin to EPEVER Rev 1 Schematic
Elfin to EPEVER Rev 1 Schematic

Elfin to EPEVER Rev 1 PCB
Elfin to EPEVER Rev 1 PCB

Elfin to EPEVER Rev 1 BOM (Full)
Elfin to EPEVER Rev 1 BOM (Full) Excel

Elfin to EPEVER Rev 1 Gerber and NC Drill
Elfin to EPEVER Rev 1 Gerber and NC Drill

Monday, 26 September 2022

Tornado Cleaning Brush Circuit

Introduction
This
micro-blog presents the electronics circuit and motor part number details for a well-known battery-powered cleaning brush.

Electronics
The product design consists of a DC motor, rechargeable battery and associated battery charge monitor. Provided with the product is an external mains power adaptor as the recharging source.

DC Motor from Cleaning Brush
DC Motor from Cleaning Brush

The motor is rated at DC 3.6 V, part number RS390SH-6213. A similar motor can be sourced at companies such as AliExpress.

Powering the motor during the use of the cleaner is a standard Li-Ion battery (18650) with a rating of 3.7 V 2.2 AH.

Monitoring the charge state of the Li_Ion battery is an unidentified chip. The part number on the 8-pin chip (SOIC-8) was removed by linishing or a similar process.

Top Side of Cleaning Brush Circuit Board
Top Side of Cleaning Brush Circuit Board

Bottom Side of Cleaning Brush Circuit Board
Bottom Side of Cleaning Brush Circuit Board

The circuit containing the unidentified chip is displayed below.

Cleaning Brush Circuit
Cleaning Brush Circuit