microphone – Experimental Engineering

Posted on September 12, 2017 by The Engineer — 3 Comments

103RS GPS Tracker Teardown

I thought it was time to add a bit of security to the gear I take camping, so this GPS tracker unit was sourced from eBay. This is a Rewire Security 103RS, a slightly customised version of the common Chinese TK103 GPS tracker.

The small module has all it’s power connections on one end of the unit, on a Molex multi-way block. The white connector is for a piezo-shock sensor – this interfaces with the alarm functionality of the unit. There’s an indicator LED for both the GPS & GSM status, and a switch for the backup battery.

The other end has the antenna connections, microphone connection for the monitor function, along with the SIM & SD card slots.

Once the end panel is removed, the PCB just slides out of the aluminium extruded casing. It’s pretty heavily packed with components in here. A switching regulator deals with the 12v input from the vehicle battery, and is protected by a polyfuse on the right. The GSM module is hiding under the Li-Po backup cell, unfortunately the sticky pad used to secure this wouldn’t come off without damaging something. The pigtails for both the GPS & GSM antennas are permanently soldered to the board here.

The bottom of the PCB has the GPS module, and mainly input protection & bypassing components. There is a FNK4421 Dual P-Channel MOSFET here as well, probably used for switching the external relay or alarm siren. The SIM socket for the GSM modem is located here in the corner.

Posted on February 2, 2016 by The Engineer — Leave a comment

Portable Hearing Induction Loop

These units are used to broadcast local audio, such as from a public address system or local microphone. They accomplish this by producing a modulated magnetic field that a hearing aid is capable of picking up.

Not many controls on this bit of equipment. A bi-colour LED for status indications, a microphone, external audio input, charging input & a power switch.

Popping the cover off reveals a small lead-acid battery, 2.1Ah at 12v. This is used when the loop is unplugged.

Here’s the main PCB, which takes care of the audio & battery charging. The inductive loop itself is just visible as the tape-covered wire bundle around the edge of the casing.

Here’s the input section of the main PCB. The microphone input is handled by a SSM2166 front-end preamplifier from Analog Devices.

This audio is then fed into a TDA2003 10W Mono Power Amplifier IC, which directly drives the induction coil as if it were a speaker. Any suitable receiving coil & amplifier can then receive the signal & change it back into audio.

Posted on June 16, 2011 by The Engineer — Leave a comment

XM2000 Marine VHF Radio

Here is an old XM2000 marine VHF tranciever.

Here is the casing split, with the main CPU board & display on the right, & the RF tranciever board on the left.

View of the main CPU board, with the mic & loudspeaker on the right hand side.
The channel display is on the reverse side of the PCB.

View of the RF board, with it’s brass shielding attached. This radio will transmit at 5W max.

Shielding removed, power regulation bottom right corner of the board, tranciever on the left.

CPU board removed from the casing, showing the LCD & the user buttons to the left.

Posted on February 28, 2011February 10, 2011 by The Engineer — Leave a comment

Sanyo Talkbook VAS

Here is a Sanyo tape recorder, with built in voice activation. Takes standard audio cassettes.
Here visible is the speaker on the left, microphone is on the right of the tape window. The tape counter is at the top.

Back cover removed from the unit, showing the PCB & the connections. The IC is the controller/amplifier.

Top of the PCB, control switches, volume potentiometer & microphone/headphone sockets on the right. DC power jack top left. Switch bottom centre senses what mode the tape drive is in.

Rear of the tape deck, main drive motor is bottom right, driving the capstan through a drive belt. This drives the tape spools through a series of gears & clutches. Belt going to top left drives the tape counter.

Front of the tape drive. Read/write head is top centre. Blue head is bulk erase head used during recording.

Main speaker. 8Ω 0.25W.

Simple mechanical tape counter.

Posted on December 6, 2010 by The Engineer — Leave a comment

Southwestern Bell Freedom Phone

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

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.

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

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

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

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.

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.

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.

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

Posted on August 26, 2010 by The Engineer — Leave a comment

Motorola V360v

Here is a more modern phone, the Motorola V360v. Features include Dual screens, 640×480 VGA camera, full col

our TFT Main LCD, SD-Micro slot.
Here on the back the grey scale LCD can be seen, with the camera lens to the right of the Motorola logo

Here the phone is opened showing the keypad & the full colour TFT LCD display.

Here the battery is removed from the unit, showing the SIM connector. The antenna cover is still on at the bottom.

The antenna cover has been removed in this shot, the antenna is the white section at the bottom, With the loudspeaker & the external antenna connector hidden at the right.

Here is the main PCB. Parts from left are the Bluetooth module at the top, supplied by Broadcom, the SD Card socket at the bottom. Main CPU next to that is the Freescale SC29343VKP. Above right of the CPU is the Freescale SC13890P23A Charger, Power & Audio IC. Below is the SIM card socket. Under the main CPU is the Intel Flash memory IC. ICs inside the shields are the RF sections for transmit & receive.

Rear of the display unit showing the monochrome LCD. The camera module on the bottom left. Ear speaker on the far right of the unit.

Main colour TFT LCD.

Camera module removed from the LCD unit.

The vibration motor attached to one of the LCD looms.

Posted on August 26, 2010 by The Engineer — Leave a comment

Nokia 7110

Another phone from the mid 90s. This is the nokia 7110.

Here the slider is open showing the keypad.

Here the battery is removed, a Li-Ion unit.

The battery cell & protection circuit removed from the casing.

This is the rear of the PCB removed from the housing. Data & charging ports on the right hand side f the board.

Front of the PCB with the RF sections at the left hand side & the keypad contacts on the right.

Closeup of the RF sections of the board, big silver rectangular cans are VCO units.

Closeup of the top rear section of the PCB, with SIM cnnector, battery contacts, IR tranciever at the far left. Bottom centre is the external antenna connector.

The logic section of the board, Large chip is CPU, to right of that is the ROM storing the machine code. Other chips are unknown custom parts.

The Mic & the loudspeaker removed from it’s housing.

LCD from the front of the unit, SPI interfaced. Flex PCB also contains the power button, loudspeaker contacts & a temperature sensor.

The scroll wheel removed from the front housing.

Tiny vibration motor removed from the rear housing, alerts the user to a text or phone call.

Posted on August 25, 2010 by The Engineer — Leave a comment

Ericsson GA628

Here is a phone from the mid 90s, the Ericsson GA628. Here visible is the front of the unit with keypad, & single line monochrome LCD for number display.

Here the battery is removed from the phone, showing the SIM card socket. At the top under the antenna stub is the socket for an external antenna.

Here the front is removed from the phone, PCB on left, rear of keypad on right. Microphone is at bottom of keypad, with speaker at the top. Top right of the PCB is the ringer buzzer, left is shield for RF amplifier.

Here is the back of the main PCB, RF sections on left & centre. Processing & memory on right.

This phone had a Ni-Mh battery, before Li-Ion batteries were introduced.

The LCD from the front of the phone is shown here. A simple dot matrix single line unit.