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Arduino Based SWR/PWR Meter – The Board

I recently posted about a small analog SWR/Power meter I got from eBay, and figured it needed some improvement.

After some web searching I located a project by ON7EQ, an Arduino sketch to read SWR & RF power from any SWR bridge.
The Arduino code is on the original author’s page above, his copyright restrictions forbid me to reproduce it here.

I have also noticed a small glitch in the code when it is flashed to a blank arduino: The display will show scrambled characters as if it has crashed. However pushing the buttons a few times & rebooting the Arduino seems to fix this. I think it’s related to the EEPROM being blank on a new Arduino board.

I have run a board up in Eagle for testing, shown below is the layout:

SWR Meter SCH
SWR Meter SCH

The Schematic is the same as is given on ON7EQ’s site.
Update: ON7EQ has kindly let me know I’ve mixed up R6 & R7, so make sure they’re switched round when the board is built ;). Fitting the resistors the wrong way around may damage the µC with overvoltage.

SWR Meter PCB
SWR Meter PCB

Here’s the PCB layout. I’ve kept it as simple as possible with only a single link on the top side of the board.

PCB Top
PCB Top

Here’s the freshly completed PCB ready to rock. Arduino Pro mini sits in the center doing all the work.
The link over to A5 on the arduino can be seen here, this allows the code to detect the supply voltage, useful for battery operation.
On the right hand edge of the PCB are the pair of SMA connectors to interface with the SWR bridge. Some RF filtering is provided on the inputs.

PCB Bottom
PCB Bottom

Trackside view of the PCB. This was etched using my tweaked toner transfer method.

LCD Fitted
LCD Fitted

Here the board has it’s 16×2 LCD module.

Online
Online

Board powered & working. Here it’s set to the 70cm band. The pair of buttons on the bottom edge of the board change bands & operating modes.
As usual, the Eagle layout files are available below, along with the libraries I use.

[download id=”5585″]

[download id=”5573″]

More to come on this when some components arrive to interface this board with the SWR bridge in the eBay meter.

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Logitech Cordless Ball Mouse

Top
Top

This is an old legacy wireless mouse from Logitech. This uses a ball rather than optical technology.

Bottom
Bottom

Bottom of the mouse, showing the battery cover & the mouse ball.

PCB Bottom
PCB Bottom

Top removed from the mouse, showing the PCB inside. The smaller PCB on the left supports the microswitches for the buttons & mouse wheel.

Switches
Switches

Closeup of small PCB showing the microswitches & the IR LED & phototransistor pair for the mouse wheel encoder.

Main PCB
Main PCB

View of main PCB, with interface IC lower right. Pair of quartz crystals provide clocking for the transmitter & internal µC.
Battery contacts are on lower left of the PCB. At the top are the IR pairs for the X & Y axis of the mouse ball.

Encoder Pairs
Encoder Pairs

Closeup of the pairs of IR LEDs & phototransistors that make up the encoders for X/Y movement of the mouse, together with the slotted wheels in the mouse base that rotate with the ball. Steel wire around the smaller PCB is the antenna.

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Southwestern Bell Freedom Phone

Phone
Phone

This is an old cordless landline phone, with dead handset batteries.

Handset Radio Board
Handset Radio Board

Here’s the handset with the back removed. Shown is the radio TX/RX board, underneath is the keyboard PCB with the speaker & mic. All the FM radio tuning coils are visible & a LT450GW electromechanical filter.

Handset Radio Board Bottom
Handset Radio Board Bottom

Radio PCB removed from the housing showing the main CPU controlling the unit, a Motorola MC13109FB.

Keypad Board
Keypad Board

The keypad PCB, with also holds the microphone & speaker.

Handset Keypad Board Bottom
Handset Keypad Board Bottom

Bottom of the keypad board, which holds a LSC526534DW 8-Bit µC & a AT93C46R serial EEPROM for phone number storage.

Base Main Board
Base Main Board

Here’s the base unit with it’s top cover removed. Black square object on far right of image is the microphone for intercom use, power supply section is top left, phone interface bottom left, FM radio is centre. Battery snap for power backup is bottom right.

Power Supply Section
Power Supply Section

PSU section of the board on the left here, 9v AC input socket at the bottom, with bridge rectifier diodes & main filter capacitor above. Two green transformers on the right are for audio impedance matching. Another LT450GW filter is visible at the top, part of the base unit FM transceiver.

ICs
ICs

Another 8-bit µC, this time a LSC526535P, paired with another AT93C46 EEPROM. Blue blob is 3.58MHz crystal resonator for the MCU clock. The SEC IC is a KS58015 4-bit binary to DTMF dialer IC. This is controlled by the µC.

Base Main Board Bottom
Base Main Board Bottom

Underside of the base unit Main PCB, showing the matching MC13109FB IC for the radio functions.