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.
Time for another teardown! Here’s a pocket-sized headphone amplifier for use with mobile devices. This unit is powered by a built-in lithium cell, and can give some pretty impressive volume levels given it’s small size.
The 3.5mm audio input & output jacks are on the front of the unit, along with the relatively enormous volume knob & power switch. There’s a little blue LED under the switch that lets the user know when the power is on, but this is a very sedate LED, using very little power.
On the back is the High-Low gain switch, and the µUSB charging port. There’s another indicator LED to show that the internal cell is charging, in this case a red one.
Removing a couple of cap screws allows the internals to slide out of the extruded aluminium casing. Most of the internal space is taken up by the 1Ah lithium cell, here on the top of the PCB secured by some double-sided tape. The volume potentiometer is mounted on a small daughterboard at right angles to get it to fit into the small vertical space in the case.
The bottom of the PCB is equally as sparse – the only ICs being the main audio amp in the centre & the battery charger IC at the top.
The main audio amplifier is a TP9260, I couldn’t find a datasheet on this, so I’m unsure of what the specs are. The row of resistors above the IC are for the gain divider circuit. There’s also a pogo pin on the right that makes contact with the back panel of the case for grounding.
Battery charging is taken care of by a UN8HX 500mA linear charging IC, not much special here.
This little amplifier seems to be pretty well made, considering the price point. The only issue I’ve had so far is the audio cables act like antennas, and when in close proximity to a phone some signal gets picked up & blasted into the headphones as interference.
Recently my phone decided it was going to die a battery-related death, and having not found much useful information on the Great Google, (all the information I could find, was hinting at many issues from firmware to a faulty motherboard, nobody seems to have actually done any investigation into similar issues), I decided to dig into the phone to try & repair the problem.
The phone would work correctly for a while, then with the slightest movement or knock, would spontaneously switch off, and not turn back on without being whacked on a hard surface.
This symptom pointed me at a power connection problem. After removing the back of the phone (glass & heavily glued in place, so an awkward process), This was what I was presented with on the cell flex PCB.
In the above photo, the positive connection to the flex is fractured just after the solder joint with the BMS board.
I managed to scrape some of the insulation off the flex PCB & solder a jumper on to restore power. Unfortunately, this repair generated another fault, where the battery level was always shown at 50%, and plugging into a USB supply wouldn’t charge the phone. The other two pins on the cell are for communication & temperature sensing, clearly one of these traces was also broken in the flex.
The above photo has a pair of very small wire tails as well, for connecting an external charger.
Here’s a screenshot of the phone with the original cell, even though it’s at about 4.15v (virtually fully charged). The battery management is having trouble talking to the phone, so for safety reasons, the charging logic refuses point-blank to charge the thing up.
The connector on the cell & phone motherboard is absolutely tiny, so I didn’t fancy attempting to solder on any bridge wires to try & bypass the broken flex.
The cell BMS has some intelligence on board, besides the usual over-current, over-charge & under-charge protection. The very small IC on the right has a Microchip logo, and the marking FT442, but I was unable to dig up any datasheets. The current sense resistor is directly connected to this IC, along with the main power FET to the left.
On the other side of the BMS board is another IC, again unidentifiable, and what looks like a bare-die, or CSP IC.
At this stage I figured the only way forward was to buy a new battery, eBay turned one up for less than £5. Above is the new battery fitted to the phone, datestamped 2014, so definitely old stock.
Booting the phone with the new battery quickly lets me know the fix worked, with a 100% reading & the ability to again charge properly!
Since this phone has been in my drawer for some time, I figured it was time for a teardown. (It’s never going to see any more use).
The back cover on these phones is easily removed, as it’s just clipped on.
Once the back cover is removed, the Li-Polymer cell is exposed, along with the logic board. Pretty much all of the PCB is under RF shields.
Under the small RF can on the back of the board is the battery management circuitry & the charger. There’s an extra connection to the cell for temperature monitoring. Just under that circuitry is the eMMC flash storage.
Just to the left of the battery circuit is the NFC transceiver IC, from NXP.
The cell is connected to the main board with a FFC, with a very small SMT connector, although not as small as the more modern Xperia series phones.
The other side of the mainboard holds the large RF transceiver section, with a Qualcomm RTR8600 multiband transceiver IC. In the bottom corner is a Skyworks SKY77351-32 Quad-band power amplifier IC, along with 3 other power amplifier ICs, also from Skyworks.
The top corner of the board holds the various sensors, including an Invensense MPU-3050 3-axis gyro. To the right of that is the Audio Codec, a WCD9310 from Qualcomm.
Everything is controlled from the last section on the board, with the main CPU & RAM in a PoP (Package-On-Package) configuration. Under the main CPU is the main power management IC, also from Qualcomm. No datasheet for this one unfortunately, but it gives it’s purpose away by being surrounded by large inductors & capacitors.
This is a System On Chip from Motorola, designed for network routing applications. This chip contains a hell of a feature set, so I’ll just include an excerpt from the datasheet:
Embedded single-issue, 32-bit MPC8xx core (implementing the PowerPC
architecture) with thirty-two 32-bit general-purpose registers (GPRs)
— The core performs branch prediction with conditional prefetch, without
conditional execution
— 4- or 8-Kbyte data cache and 4- or 16-Kbyte instruction cache (see Table 1)
– 16-Kbyte instruction caches are four-way, set-associative with 256 sets;
4-Kbyte instruction caches are two-way, set-associative with 128 sets.
– 8-Kbyte data caches are two-way, set-associative with 256 sets; 4-Kbyte data
caches are two-way, set-associative with 128 sets.
– Cache coherency for both instruction and data caches is maintained on 128-bit
(4-word) cache blocks.
– Caches are physically addressed, implement a least recently used (LRU)
replacement algorithm, and are lockable on a cache block basis.
— Instruction and data caches are two-way, set-associative, physically addressed,
LRU replacement, and lockable on-line granularity.
— MMUs with 32-entry TLB, fully associative instruction, and data TLBs
— MMUs support multiple page sizes of 4, 16, and 512 Kbytes, and 8 Mbytes; 16
virtual address spaces and 16 protection groups
— Advanced on-chip-emulation debug mode
Up to 32-bit data bus (dynamic bus sizing for 8, 16, and 32 bits)
32 address lines
Operates at up to 80 MHz
Memory controller (eight banks)
— Contains complete dynamic RAM (DRAM) controller
— Each bank can be a chip select or RAS to support a DRAM bank
— Up to 15 wait states programmable per memory bank
— Glueless interface to DRAM, SIMMS, SRAM, EPROM, Flash EPROM, and
other memory devices.
— DRAM controller programmable to support most size and speed memory
interfaces
— Four CAS lines, four WE lines, one OE line
— Boot chip-select available at reset (options for 8-, 16-, or 32-bit memory)
— Variable block sizes (32 Kbyte to 256 Mbyte)
— Selectable write protection
— On-chip bus arbitration logic
General-purpose timers
— Four 16-bit timers or two 32-bit timers
— Gate mode can enable/disable counting
— Interrupt can be masked on reference match and event capture
System integration unit (SIU)
— Bus monitor
— Software watchdog
— Periodic interrupt timer (PIT)
— Low-power stop mode
— Clock synthesizer
— Decrementer, time base, and real-time clock (RTC) from the PowerPC
architecture
— Reset controller
— IEEE 1149.1 test access port (JTAG)
Interrupts
— Seven external interrupt request (IRQ) lines
— 12 port pins with interrupt capability
— 23 internal interrupt sources
— Programmable priority between SCCs
— Programmable highest priority request
10/100 Mbps Ethernet support, fully compliant with the IEEE 802.3u Standard (not
available when using ATM over UTOPIA interface)
ATM support compliant with ATM forum UNI 4.0 specification
— Cell processing up to 50–70 Mbps at 50-MHz system clock
— Cell multiplexing/demultiplexing
— Support of AAL5 and AAL0 protocols on a per-VC basis. AAL0 support enables
OAM and software implementation of other protocols).
— ATM pace control (APC) scheduler, providing direct support for constant bit rate
(CBR) and unspecified bit rate (UBR) and providing control mechanisms
enabling software support of available bit rate (ABR)
— Physical interface support for UTOPIA (10/100-Mbps is not supported with this
interface) and byte-aligned serial (for example, T1/E1/ADSL)
— UTOPIA-mode ATM supports level-1 master with cell-level handshake,
multi-PHY (up to 4 physical layer devices), connection to 25-, 51-, or 155-Mbps
framers, and UTOPIA/system clock ratios of 1/2 or 1/3.
— Serial-mode ATM connection supports transmission convergence (TC) function
for T1/E1/ADSL lines; cell delineation; cell payload scrambling/descrambling;
automatic idle/unassigned cell insertion/stripping; header error control (HEC)
generation, checking, and statistics.
Communications processor module (CPM)
— RISC communications processor (CP)
— Communication-specific commands (for example, GRACEFUL STOP TRANSMIT ,
ENTER HUNT MODE , and RESTART TRANSMIT )
— Supports continuous mode transmission and reception on all serial channels
— Up to 8Kbytes of dual-port RAM
— 16 serial DMA (SDMA) channels
— Three parallel I/O registers with open-drain capability
Four baud-rate generators (BRGs)
— Independent (can be connected to any SCC or SMC)
— Allow changes during operation
— Autobaud support option
Four serial communications controllers (SCCs)
— Ethernet/IEEE 802.3 optional on SCC1–4, supporting full 10-Mbps operation
(available only on specially programmed devices).
— HDLC/SDLC (all channels supported at 2 Mbps)
— HDLC bus (implements an HDLC-based local area network (LAN))
— Asynchronous HDLC to support PPP (point-to-point protocol)
— AppleTalk
— Universal asynchronous receiver transmitter (UART)
— Synchronous UART
— Serial infrared (IrDA)
— Binary synchronous communication (BISYNC)
— Totally transparent (bit streams)
— Totally transparent (frame based with optional cyclic redundancy check (CRC))
Two SMCs (serial management channels)
— UART
— Transparent
— General circuit interface (GCI) controller
— Can be connected to the time-division multiplexed (TDM) channels
One SPI (serial peripheral interface)
— Supports master and slave modes
— Supports multimaster operation on the same bus
One I 2 C (inter-integrated circuit) port
— Supports master and slave modes
— Multiple-master environment support
Time-slot assigner (TSA)
— Allows SCCs and SMCs to run in multiplexed and/or non-multiplexed operation
— Supports T1, CEPT, PCM highway, ISDN basic rate, ISDN primary rate, user
defined
— 1- or 8-bit resolution
— Allows independent transmit and receive routing, frame synchronization,
clocking
— Allows dynamic changes
— Can be internally connected to six serial channels (four SCCs and two SMCs)
Parallel interface port (PIP)
— Centronics interface support
— Supports fast connection between compatible ports on the MPC860 or the
MC68360
PCMCIA interface
— Master (socket) interface, release 2.1 compliant
— Supports two independent PCMCIA sockets
— Eight memory or I/O windows supported
Low power support
— Full on—all units fully powered
— Doze—core functional units disabled, except time base decrementer, PLL,
memory controller, RTC, and CPM in low-power standby
— Sleep—all units disabled, except RTC and PIT, PLL active for fast wake up
— Deep sleep—all units disabled including PLL, except RTC and PIT
— Power down mode— all units powered down, except PLL, RTC, PIT, time base,
and decrementer
Debug interface
— Eight comparators: four operate on instruction address, two operate on data
address, and two operate on data
— Supports conditions: = ≠ < >
— Each watchpoint can generate a break-point internally
3.3 V operation with 5-V TTL compatibility except EXTAL and EXTCLK
357-pin ball grid array (BGA) package
I was looking around eBay for decent deals on a branded CO alarm, and came across these for next to no money, so I thought I’d grab one just to see how bad they could be.
Popping the casing open shows the very small circuit board inside, with the CO sensor cell on the right. I can’t find any manufacturer information on this cell, nor can I find a photo of anything similar on the intertubes, so no specifications there. The other parts are pretty standard, a Piezo sounder & it’s associated step-up transformer to increase the loudness.
The sensor cell has the usual opening in the end to allow entry of gas.
The other side of the board doesn’t reveal much, just an LCD, a couple of LEDs, a pair of transistors, Op-Amp for the sensor & a main microcontroller.
The microcontroller isn’t marked unfortunately. It’s not had the number scrubbed off, it’s just never been laser marked with a part number. Above the micro is a SOT-23 LM321 low-power Op-Amp which does the signal conditioning for the CO sensor.
I tried to make this alarm trigger with the exhaust from the Eberspacher heater, which on a well-made branded alarm registered a reading of 154ppm after a few minutes. In the case of this alarm though, I couldn’t make it trigger at all, no matter how long I exposed it to hydrocarbon exhaust gases. I won’t be trusting this one then!
Nothing quite like a piece of safety equipment that doesn’t work correctly from new!
This detector has now been retired from service since it’s a fair bit out of date. So here’s the teardown!
Unlike older detectors, this unit has a built in battery that never needs replacing during the life of the sensor, so once the unit reaches it’s expiry date it’s just trashed as a whole.
4 screws hold the cover on, here’s the internals of the detector. There’s a 3v CR123A LiMnO² cell at the right for power, rated at 1500mAh. A 7 year life is quite remarkable on a single cell!
The sensor is just to the left of the lithium cell, and is of quite unusual construction. Previous CO sensor cells I’ve seen have been small cylinders with a pair of brass pins. This one appears to use a conductive plastic as the connections. These sensors contain H²SO⁴ so they’re a bit hazardous to open.
There are no manufacturer markings on the sensor & I’ve not been able to find any similarly shaped devices, so I’m unsure of it’s specifications.
The alarm sounder is on the left, the usual Piezo disc with a resonator to increase the loudness.
The brains of the device are provided by a Microchip PIC16F914 microcontroller. This is a fairly advanced device, with many onboard features, and NanoWatt™ technology, standby power consumption is <100nA according to Microchip’s Datasheet. This would explain the incredible battery life.
The choke just at the right edge of the photo is actually a transformer to drive the Piezo sounder at high voltage.
Here’s the PCB with the LCD frame removed. Not much to see on the this side, the silence/test button top right & the front end for the sensor.
Here’s a closer look at the front end for the CO sensor cell itself. I haven’t been able to decode the SMT markings on the SOT packages, but I’m guessing that there’s a pair of OpAmps & a voltage reference.
In my previous post, I mentioned I’d be replacing the factory supplied charging gear with something that actually charges lithium chemistry cells correctly.
Here’s the base as supplied, with an indicator LED on the right hand side. This LED indicates nothing other than power being applied to the charging base. It’s just connected across the power input with a resistor. This also means that any battery left in the charger while it’s unplugged will discharge itself through this LED over time. Great design there China!
Here I’ve removed the PCB – there’s no need for it to be taking up any space, as it’s just a complete waste of copper clad board in the first place. The battery tabs have been desoldered & hot snot used to secure them into the plastic casing.
The charger modules I use are USB powered, so a small hole has been routed out in the casing to allow access to the port.
Here the charging module has been installed & wired to the battery tabs. Output is now a nice 4.18v, and will automatically stop charging when the cell is full.
Safety has been restored!
A member of the family recently bought one of these torches from Maplin electronics, and the included chargers for the 18650 lithium-ion cells leave a lot to be desired.
Here’s what’s supplied. The torch itself is OK – very bright, and a good size. Me being cynical of overpriced Chinese equipment with lithium batteries, I decided to look in the charging base & the cigar-lighter adaptor to see if there was any actual charging logic.
Answer – nope. Not a single active component in here. It’s just a jack connected to the battery terminals. There’s all the space there to fit a proper charging circuit, but it’s been left out to save money.
OK then, is it inside the cigarette lighter adaptor?
Nope. Not a single sign of anything resembling a Lithium-Ion charger IC. There’s a standard MC34063A 1.5A Buck converter IC on the bottom of the PCB, this is what’s giving the low voltage output for the torch.
Here’s the IC – just a buck converter. The output voltage here is 4.3v. This is higher than the safe charging voltage of a lithium ion cell, of 4.2v.
The cells supplied are “protected” versions, having charge/discharge protection circuitry built onto the end of the cell on a small PCB, this makes the cell slightly longer than a bare 18650, so it’s easy to tell them apart.
The manufacturers in this case are relying on that protection circuit on the cell to prevent an overcharge condition – this isn’t the purpose they’re designed for, and charging this way is very stressful for the cells. I wouldn’t like to leave one of these units charging unattended, as a battery explosion might result.
More to come shortly when I build a proper charger for this torch, so it can be recharged without fearing an alkali metal fire!
From the factory, the GY561 meter uses alkaline AAA cells for power. As these are not rechargable, and I don’t carry any other devices that take such batteries, I figured I’d replace them with a single Lithium Polymer cell that I can charge via USB.
Here’s the battery compartment, with the original spring terminals removed.
I searched eBay for a suitable sized cell, and settled on a 1000mAh type, with dimensions of 47mm x 28mm x 7mm.
This size cell required a small amount of modification to the battery compartment to make it fit properly with the associated charge & protection circuitry.
Here’s the modifications made to the compartment, I’ve ground away the plastic to make the bottom flat, and the plastic tabs that retained the original spring terminals.
After grinding away the original battery spring holders with a dremel, the cell fits perfectly in the available space. The small PCB on the top of the cell is the USB charger & protection.
The charger is located in a slot cut in the bottom of the casing, so the USB port is accessible from outside the compartment.
Here’s the rest of the wiring completed, with the power wires going through holes in the bottom of the battery compartment to join onto the PCB where the original terminals were located. I have insulated the solder joints on the control PCB with some Kapton tape to prevent any shorts against the lithium cell.
A small cutout was also required in the battery cover to allow the USB connector to poke out. This was easy to do on the soft plastic with a Dremel tool.
With the battery cover installed, the USB port is nicely recessed into the edge.
The indicator LEDs on the charging & control board show nicely through the plastic, here’s the unit on charge. When the charge is complete, another LED lights as shown below.
After watching a video over at Scullcom Hobby Electronics on YouTube, I figured I’d build one of these precision references to calibrate my multimeters.
It’s based around a REF102P 10v precision reference & an INA105P precision unity gain differential amplifier.
For full information, check out the video, I won’t go into the details here, just my particular circuit & PCB layout.
In the video, Veroboard is used. I’m not too fond of the stuff personally. I find it far too easy to make mistakes & it never quite looks good enough. To this end I have spun a board in Eagle, as usual.
Here’s the schematic layout, the same as is in the video.
As usual, the Eagle CAD layout files can be found at the bottom of the post.
And the associated PCB layout. I have added the option to be able to tweak the output, to get a more accurate calibration, which can be added by connecting JP1 on the PCB.
As in the original build, this unit uses pre-built DC-DC converter & Li-Ion charger modules. A handy Eagle library can be found online for these parts.
I have however left off the battery monitor section of the circuit, since I plan to use a protected lithium cell for power. This also allowed me to keep the board size down, & use a single sided layout.
Here’s the track layout ready to iron onto the copper clad board. I use the popular toner transfer system with special paper from eBay, this stuff has a coating that allows the toner to easily be transferred to the PCB without having to mess about with soaking in water & scraping paper off.
Here’s the paper having just been ironed onto the copper. After waiting for the board to cool off the paper is peeled off, leaving just the toner on the PCB.
PCB just out of the etch tank, drilled & with the solder pins for the modules installed. Only one issue with the transfer, in the bottom left corner of the board is visible, a very small section of copper was over etched.
This is easily fixed with a small piece of wire.
Main components populated. The DC-DC converter is set at 24v output, which the linear regulator then drops down to the +15v rail for the reference IC. The linear section of the regulator, along with the LC filter on the output of the switching regulator produce a low-ripple supply.
Here’s the scope reading the AC ripple on the output of the DC-DC converter. Scale is 100mV/Div. Roughly 150mV of ripple is riding on top of the DC rail.
And here’s the output from the linear regulator, scale of 50mV/Div. Ripple has been reduced to ~15mV for the reference IC.
In total the circuit as built has a power consumption of ~0.5W, most of which is being dissipated as heat in the linear part of the PSU.
These speakers are available free from Pringles, with two packs bought. Normally running on 3x AAA cells, I have made modifications to include a high capacity Li-Ion battery & USB charging.
New battery is 3x 18650 Li-Ion cells in parallel, providing ~6600mAh of capacity. These are hot glued inside the top of the tube under the speaker, with the charging & cell protection logic.
The battery charging logic is salvaged from an old USB eCig charger, these are single cell lithium chargers in a small form factor ideal for other uses. Charging current is ~450mA.
The cells are connected to the same points as the original AAA cells, with the other pair of wires going into the top of the device to connect to the MicroUSB charging port.
The amplifier in this is a LM4871 3W Mono amplifier IC, connected to a 6Ω 1W speaker.
The other IC on the board is unidentifiable, but provides the flashing LED function to the beat of the music.
The final part for the battery pack has finally arrived, the PCM boards. These modules protect the cells by cutting off the power at overcharge, undercharge & overcurrent. Each cell is connected individually on the right, 12v power appears on the left connections. These modules also ensure that all the cells in the pack are balanced.
This is just a few notes on the repair of an eCig battery (1Ah Tornado).
These batteries seem to have a flaw in which they will randomly stop working, while still displaying all the normal activity of the battery.
Here is what I have found.
Here the battery has been partially disassembled, with the control circuitry exposed here at the end of the unit. All the wiring here is fine & the electronics themselves are also OK, due to the LEDs still operating as normal when the button is pushed. The 1000mAh Li-Poly cell is to the right.
Here the end cap has been removed from the opposite end of the battery & the problem is found: the short wire here is the GND return for the atomiser, normally connected to the negative terminal of the battery in the tube, however here it has broken off.
This is most likely due to either the cell moving inside the tube during normal operation, weakening the solder joint, or simply a bad solder job from the factory. (This lead-free ROHS bullshit is to blame).
Here the wire has been successfully soldered back on to the battery tab. I have also added a small dab of hot glue to hold the battery in place on the inside of the tube, & replaced the solder on the joints with real 60/40 leaded solder. £15 saved.
This is a cheap Sigma branded keychain photoframe. User buttons for power & selecting photos are on the left.
There are two white LEDs on the bottom edge that function as a torch as well.
Front of the unit removed, showing the LCD module. The USB jack is bottom left, next to the pair of white LEDs & above that is the 32kHz watch crystal that the CPU uses for timekeeping.
Here the back has been removed showing the 3.7v Li-Ion cell used to provide power.
Here the display has been removed from the PCB exposing the chipset.
Here the CPU blob-top chip & a flash memory IC are visible. The CPU is a Sitronix ST2205U.
Here is an old electrochemical type carbon monoxide detector cell, from Monox. Hole in the centre is the inlet for the gas under test. DO NOT TRY THIS AT HOME! Electrochemical cells contain a substantial amount of sulphuric acid, strong enough to cause burns.
This is a type of fuel cell that instead of being designed to produce power, is designed to produce a current that is precisely related to the amount of the target gas (in this case carbon monoxide) in the atmosphere. Measurement of the current gives a measure of the concentration of carbon monoxide in the atmosphere. Essentially the electrochemical cell consists of a container, 2 electrodes, connection wires and an electrolyte – typically sulfuric acid. Carbon monoxide is oxidized at one electrode to carbon dioxide while oxygen is consumed at the other electrode. For carbon monoxide detection, the electrochemical cell has advantages over other technologies in that it has a highly accurate and linear output to carbon monoxide concentration, requires minimal power as it is operated at room temperature, and has a long lifetime (typically commercial available cells now have lifetimes of 5 years or greater). Until recently, the cost of these cells and concerns about their long term reliability had limited uptake of this technology in the marketplace, although these concerns are now largely overcome. This technology is now the dominant technology in USA and Europe.
Rear of unit with connection pins. Hole here is to let oxygen into the cell which permits the redox reaction to take place in the cell when CO is detected, producing a voltage on the output pins.
Cell disassembled. The semi-permeable membrane on the back cover can be seen here, to allow gas into the cell, but not the liquid electrolyte out. Cell with the electrodes is on the right, immersed in sulphuric acid.
Closeup of the electrode structure. Polymer base with a precious metal coating.
This is an old CO alarm, which was totally dead, having been connected to the wrong PSU.
Here is the front of the unit, with the Test button & indicator LEDs.
Front of the PCB, 3 1.5v cells powered the unit, Piezo sounder & sensor cell in the centre of the board.
This is an old legacy wireless mouse from Logitech. This uses a ball rather than optical technology.
Bottom of the mouse, showing the battery cover & the mouse ball.
Top removed from the mouse, showing the PCB inside. The smaller PCB on the left supports the microswitches for the buttons & mouse wheel.
Closeup of small PCB showing the microswitches & the IR LED & phototransistor pair for the mouse wheel encoder.
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.
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.
This is a little security measure you get with Internet Banking with the Co-Op, generates codes to confirm your identity using your bank card. About the size of a pocket calculator, this is the keypad & screen.
The rear of the unit, the card slots into the top, manufactured by Gemalto Digital Security.
Outer back cover removed, showing the 8 contacts for the chip on the bank card, the 2 contacts below that switch on power when a card is inserted. Power comes from 2 lithium coin cells in the compartment on the lower left.
PCB removed from the casing, showing the internal components. Two large pads at top left are battery connections, while the only IC on the board is the main CPU, under the card connector. 6MHz oscillator & 32Khz crystal on board for processing & timekeeping. LCD screen connection at far right.
Reverse side of the PCB, with the keypad contacts. LCD on right, with programming interface pads at side of keypad.
Here is a Bosch 14.4v Professional cordless drill/driver, recovered from a skip!
It was thrown away due to a gearbox fault, which was easy to rectify.
Here is the drill with the side cover removed, showing it’s internal parts. The speed controller is below the motor & gearbox here. The unit at the top consists of a 12v DC motor, coupled to a 4-stage epicyclic gearbox unit, from which can be selected 2 different ratios, by way of the lever in the centre of the box. This disables one of the gear stages. There is a torque control clutch at the chuck end of the gearbox, this was faulty when found.
Here is the drive motor disconnected from the gearbox, having a bayonet fitting on the drive end.
This is the primary drive gear of the motor, which connects with the gearbox.
The motor is cooled by this fan inside next to the commutator, drawing air over the windings.
This is the gearbox partially disassembled, showing the 1st & second stages of the geartrain. The second stage provides the 2 different drive ratios by having the annulus slide over the entire gearset, disabling it entirely, in high gear. The annulus gears are a potential weak point in this gearbox, as they are made from plastic, with all other gears being made of steel.
Here is the charging unit for the Ni-Cd battery packs supplied with the drill. The only indicator is the LED shown here on the front of the unit, which flashes while charging, & comes on solid when charging is complete. Charge termination is by way of temperature monitoring.
Here the bottom of the charger has been removed, showing the internal parts. An 18v transformer supplies power to the charger PCB on the left.
This is the charger PCB, with a ST Microelectronics controller IC marked 6HKB07501758. I cannot find any information about this chip.
Here is a battery pack with the top removed, showing the cells.
This is the temperature sensor embedded inside the battery pack that is used by the charger to determine when charging is complete.
This is a device designed to reset Epson brand ink cartridges that are reportedly out of ink, so they again report full to the printer Here is the front of the unit, with the guide for attaching to a cartridge.
Back of the device removed. 3 button cells provide power to the PCB. Indicator LED sticks out of the top of the device for reset confirmation.
Row of pads on far left edge of the PCB are presumably a programming header for the uC on the other side of the board.
Here is the front of the PCB, main feature being the grid of pogo pins to connect to the cartridge chip. IC on lower right of that is a MSP430F2131 uController, a Texas Instruments part.
The IC directly to the left of the pogo pin bed is a voltage regulator, to step down the ~4.5v of the batteries down to the ~3.3v that the uC requires.
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.
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