My other monitors are a different model, and have a slightly different main PCB inside, but the process is mostly the same for converting these to 12v supply.
Main PCB
In this monitor type, there is only a single board, with all the PSU & logic, instead of separate boards for each function.
PSU Closeup
This monitor is slightly different in it’s power supply layout. The mains supply provides only a single 12v rail, which is then stepped down by a switching converter to 5v, then by smaller linear regulators to 3.3v & 1.8v for the logic. This makes my life easier since I don’t have to worry about any power conversion at all.
PCB Reverse
Here’s the backside of the PCB, the mains PSU section is in the centre.
Attachment Points
Here’s the pair of 12v supply wires soldered onto the main board, onto the common GND connection on the left, and the main +12v rail on the right. I’ve not bothered with colour coding the wiring here, just used whatever I had to hand that was heavy enough to cope with a couple amps.
12v Socket
A small mod later with a cone drill & the 12v input socket is mounted in the LCD frame.
Casing Mod
Some light removal of plastic & the back cover fits back on. Current draw at 13.8v is ~2A.
The OPN-2001 is a very small handheld barcode data collection device, used for stock keeping, inventory, etc.
It’s powered by an internal Li-Poly cell, at 150mAh, and has storage for 1000 barcodes in it’s internal memory.
USB
The unit is charged via it’s USB port, the data can also be downloaded using this interface.
ID Label
Here’s the bottom of the unit with it’s label. Serial number removed to protect the guilty. 😉
Cover Removed
Here the bottom cover has been removed from the scanner, showing the internals. The barcode engine is on the left, this contains all the hardware & logic for scanning & storing the barcode data. The Li-Poly cell is under the FFC cable wrapped in foam tape for protection.
PCB Removed
Here’s the PCB & engine assembly removed from the casing. The lower PCB appears to just handle the user interface buttons, beeper & USB power & charging circuitry. All the processing logic is on the barcode engine itself.
PCB Reverse
Here’s the back of the support PCB, with the pair of buttons for scanning & deleting barcodes. Also on this board is a 32kHz clock crystal & a Ricoh RV5C386A RTC IC. This communicates with the main processor via I²C for storing the date & time with the barcodes. At the bottom right corner are some of the power supply passives.
Support PCB
Here’s the other side of the support PCB, with the beeper, battery connector & the switching regulator to provide the barcode engine with 3.3v power.
Barcode Engine
Here’s the barcode engine itself, which is absolutely tiny, at roughly 20mm square. The main processor & it’s associated Flash ROM are on this PCB. The main processor has an ARM7 32bit core, with 64kB of RAM, and onboard 512kB of ROM for program & barcode storage.
Mirror
Here’s the business end of the barcode engine, the mirror vibrates at 100Hz to produce the scan line. The laser diode is rated at 1mW, 650nm. This is in the deep red range.
I recently dug out my other card printer to fit it with a 12v regulator, (it’s 24v at the moment), and figured I’d do a teardown post while I had the thing in bits.
This is a less industrial unit than my Zebra P330i, but unlike the Zebra, it has automatic duplexing, it doesn’t have Ethernet connectivity though.
Unlike domestic printers, which are built down to a price, these machines are very much built up to a spec, and feature some very high quality components.
Naked Printer
Here’s the mechanism with the cowling removed. This is the main drive side of the printer, with the main drive stepper at left, ribbon take-up spool motor lower right, and the duplex module stepper motors at far right.
Main Motor Drive
The main drive motor runs the various rollers in the card path through a pair of synchronous belts, shown here.
Main Stepper
The stepper itself is a quality ball-bearing Sanyo Denki bipolar motor.
Main Stepper Driver
Electrical drive is provided to the stepper with a L6258EX DMOS universal motor driver. This chip can also drive DC motors as well as steppers.
Ribbon Supply Spool
Here is the encoder geared onto the ribbon supply spool. This is used to monitor the speed the ribbon is moving relative to the card.
Printer Top
Here’s a top view through the printer, the blue roller on the left cleans the card as it’s pulled from the feeder, the gold coloured spool to it’s right is the ribbon supply reel. The cooling fan on the right serves to stop the print head overheating during heavy use.
Spool Take Up Motor
The spool take-up reel is powered by another very high quality motor, a Buhler DC gearmotor. These printers are very heavily over engineered!
This motor drives the spool through an O-Ring belt, before the gear above. This allows the drive to slip in the event the ribbon jams, preventing it from breaking.
Duplex Unit Stepper Drivers
The pair of steppers that operate the duplexing unit are driven by a separate board, with a pair of L6219DS bipolar stepper driver ICs. There are also a couple of opto-sensors on this board for the output hopper.
Main Control PCB
All the mechanisms of the printer are controlled from this main PCB, which handles all logic & power supply functions. Sections on the board are unpopulated, these would be for the Ethernet interface, smart card programming & magstripe programming.
Main CPU
The brains of the operation is this ColdFire MCF5208CVM166 32-bit microprocessor. It features 16KB of RAM, 8KB of cache, DMA controller, 3 UARTs, SPI, 10/100M Ethernet and low power management. This is a fairly powerful processor, running at 166MHz.
It’s paired with an external 128Mbit SDRAM from Samsung, and a Spansion 8Mbit boot sector flash, for firmware storage.
USB Interface & Power Input
Here the USB interface IC is located. It’s a USBN9604 from Texas Instruments, this interfaces with the main CPU via serial.
The latest addition to my radio shack is the GY561 frequency & power meter, which has already come in useful for measuring the output power of all my radios.
GY561
It’s a small device, roughly the same size & weight as a stock UV-5R. Power is provided by 3 AAA cells.
Display
The display is a standard HD44780 8×2 module. The display on this unit isn’t backlit, so no operating in the dark.
Cover Removed
The cover pops off easily to allow access to the internals, without having to remove any screws!
The 4 screws on the back of the unit hold the heatsink plate for the 50W 50Ω dummy load resistor.
Removing the cover reveals a couple of adjustments, for frequency & RF power calibration.
There are also 3 tactile switches that aren’t on the front panel. According to the manual (which in itself is a masterpiece of Chinglish), they are used to software calibrate the unit if an accurate RF power source is available. I will attempt to do a reasonable translation when time allows.
Disassembly further than this involves some desoldering in awkward places, so a search of the internet revealed an image of the rest of the internal components. In the case of my meter, all the part numbers have been scrubbed off the ICs in an attempt to hide their purpose. While it’s possible to cross-reference IC databooks & find the part numbers manually, this process is a time consuming one. Luckily the image I managed to locate doesn’t have the numbers scrubbed.
Total Disassembly
Under the LCD is some 74HC series logic, and a prescaler IC as seen in the previous frequency counter post. However in this unit the prescaler is a MB506 microwave band version to handle the higher frequencies specified.
In this case however the main microcontroller is an ATMEGA8L.
This is complemented by a SN54HC393 4-bit binary counter for the frequency side of things. This seems to make it much more usable down to lower frequencies, although the manual is very generous in this regard, stating that it’s capable of reading down to 1kHz. In practice I’ve found the lowest it reliably reads the frequency input is 10MHz, using my AD9850 DDS VFO Module as a signal source.
It did however read slightly high on all readings with the DDS, but this could have been due to the low power output of the frequency source.
Just like the other frequency counter module, this also uses a trimmer capacitor to adjust the microcontroller’s clock frequency to adjust the calibration.
The power supply circuitry is in the bottom left corner of the board, in this case a small switching supply. The switching regulator is needed to boost the +4.5v of the batteries to +5v for the logic.
Also, as the batteries discharge & their terminal voltage drops, the switching regulator will allow the circuit to carry on functioning. At present I am unsure of the lower battery voltage limit on the meter, but AAA cells are usually considered dead at 0.8v terminal voltage. (2.4v total for the 3 cells).
When turned on this meter draws 52mA from the battery, and assuming 1200mAh capacity for a decent brand-name AAA cell, this should give a battery life of 23 hours continuous use.
On the back of the main PCB is a 5v relay, which seems to be switching an input attenuator for higher power levels, although I only managed to trigger it on the 2m band.
Finally, right at the back attached to an aluminium plate, is the 50Ω dummy load resistor. This component will make up most of the cost of building these, at roughly £15.
On my DVM, this termination reads at about 46Ω, because of the other components on the board are skewing the reading. There are a pair of SMT resistors, at 200Ω & 390Ω in series, and these are connected across the 50Ω RF resistor, giving a total resistance of 46.094Ω.
This isn’t ideal, and the impedance mismatch will probably affect the calibration of the unit somewhat.
The heatsinking provided by the aluminium plate is minimal, and the unit gets noticeably warm within a couple of minutes measuring higher power levels.
High power readings should definitely be limited to very short periods, to prevent overheating.
The RF is sampled from the dummy load with a short piece of Teflon coax.
There’s a rubber duck antenna included, but this is pretty useless unless it’s almost in contact with the transmitting antenna, as there’s no input amplification. It might be handy for detecting RF emissions from power supplies, etc.
For the total cost involved I’m not expecting miracles as far as accuracy is concerned, (the manual states +/-10% on power readings).
The frequency readout does seem to be pretty much spot on though, and the ability to calibrate against a known source is handy if I need some more accuracy in the future.
I’ve also done an SWR test on the dummy load, and the results aren’t good.
At 145.500 MHz, the SWR is 3:1, while at 433.500 it’s closer to 4:1. This is probably due to the lower than 50Ω I measured at the meter’s connector.
These SWR readings also wander around somewhat as the load resistor warms up under power.
I’ll probably also replace the AAA cells with a LiPo cell & associated charge/protection circuitry, to make the unit chargeable via USB. Avoiding disposable batteries is the goal.
Here is a ZyXel WAP3205 WiFi Access Point that has suffered a reverse polarity event, due to an incorrect power supply being used with the unit.
ZyXEL WAP3205
While most electronic gadgets are protected against reverse polarity with a blocking diode, this unit certainly wasn’t. Applying +12v DC the wrong way round resulted in this:
Blown Switchmode IC (Fuzzy Focus)
That is the remains of the 3.3v regulator IC, blown to smithereens & it even attempted an arson attack. Luckily this was the only damaged component, & I was able to repair the unit by replacing the switching IC with a standalone regulator. (Replacing the IC would have been preferable, if there was anything left of it to obtain a part number from).
I scraped away the pins of the IC to clear the short on the input supply, removed the switching inductor, & tacked on an adjustable regulator module set to 3.3v. Luckily the voltage of the supply is handily marked on the PCB next to the circuit.
Replacement PSU
Replacement SMPS in place on top of the PCB. The output of the supply is connected to one of the pads of L4 (on my unit just an 0 ohm link), the +12v input is connected to the + rail side of C8 & C7 & the final ground connection is hooked in to the back of the barrel jack.
After this replacement, the unit booted straight up as if nothing had happened. All the logic is undamaged!
Having two separate water tanks on nb Tanya Louise, with individual pumps, meant that monitoring water levels in tanks & keeping them topped up without emptying & having to reprime pumps every time was a hassle.
To this end I have designed & built this device, to monitor water usage from the individual tanks & automatically switch over when the tank in use nears empty, alerting the user in the process so the empty tanks can be refilled.
Based around an ATMega328, the unit reads a pair of sensors, fitted into the suction line of each pump from the tanks. The calculated flow is displayed on the 20×4 LCD, & logged to EEPROM, in case of power failure.
Water Flow Sensor
When the tank in use reaches a preset number of litres flowed, (currently hardcoded, but user input will be implemented soon), the pump is disabled & the other tank pump is enabled. This is also indicated on the display by the arrow to the left of the flow register. Tank switching is alerted by the built in beeper.
It is also possible to manually select a tank to use, & disable automatic operation.
Resetting the individual tank registers is done by a pair of pushbuttons, the total flow register is non-resettable, unless a hard reset is performed to clear the onboard EEPROM.
Main PCB
View of the main PCB is above, with the central Arduino Pro Mini module hosting the backend code. 12-24v power input, sensor input & 5v sensor power output is on the connectors on the left, while the pair of pump outputs is on the bottom right, switched by a pair of IRFZ44N logic-level MOSFETS. Onboard 5v power for the logic is provided by the LM7805 top right.
Code & PCB design is still under development, but I will most likely post the design files & Arduino sketch once some more polishing has been done.
Here is a home laser hair removal unit, a Rio LAHS4. Shown above is the system overview, with the laser wand & the user controls.
Main PCB Top
Main base unit popped open reveals the main PCB, with the central processor, a PIC16F628A.
Main PCB Bottom
Other side of the PCB is mainly populated with power supply & filtering for the logic sections.
Wand PCB
Cracking open the laser wand reveals a stacked pair of PCBs, a main laser controller & the capacitive sensor PCB. This capacitive sensor connects to a pair of pins on the laser head & prevents operation if the unit is not held firmly against the skin.
Diode Module
Front of the laser diode module with the movable lens, on a pair of voice coil actuators. Very similar to the lens positioner used in any CD/DVD player pickup assembly.
The diode in this unit is an 808nm chip, with power in the 300-600mW range most likely.
Diode Module Rear
Rear of the diode module, with the connections to the diode itself & the voice coil positioner for the lens.
Wand PCB Top
Other side of the wand PCB, showing the capacitive sensor board on top of the main controller board. There is another CPU on the board here, which most likely communicates with the main processor in the base through a serial connection.
Here is a teardown of the Datakom DKG-171 generator transfer controller. Here is the front of the unit, with the pictogram of the system, the indicator LEDs & the generator test button.
Rear
The rear of the unit features the connection points for the mains, generator & generator control I/O.
PCB Rear
Rear of the PCB with the control relays. The two larger relays switch in the remote contactors to switch the mains supply over between the grid & the generator, while the smaller relay switches 12v power out to a terminal to automatically start the generator.
PCB Front
Front of the PCB with the control logic & main PIC microcontroller.
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.
18650 Battery
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.
Amplifier Board
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.
This is the Velleman MK179 Proximity Card Reader, which is supplied in kit form. In the image above you can see the completed kit, the read coil is etched onto the black PCB on the left. Bringing a recognised card close to the coil operates the relay on the main PCB for a programmable amount of time.
Main PCB
Closeup of the main PCB, 12v DC input at top right. Left IC is an LM358 dual Op-Amp, the IC on the right is a PIC12F629 with Velleman’s custom firmware.
Logic power is supplied to the ICs & the oscillator from the LM7805 regulator at the top of the PCB. The relay is a standard 15A SPDT 12v coil relay, with the switch contacts broken out onto the screw terminals on the left.
Schematic Diagram
As it is not provided with the kit, unlike other Velleman kits, here is the schematic for this.
This unit was bought from eBay to experiment with Magnetic Stripe cards, for little money. This unit is capable of reading & writing all 3 tracks, & both Hi-Co & Lo-Co card types.
Interfaced to a PC through USB, this has a built in PL2303 USB-Serial IC & requires 3A at 9v DC to operate.
The 3 Indicator LEDs on the top of the unit can be toggled by the included software for Power/OK/Fault condition signalling.
Unit Bottom
Bottom of the unit with the model labels.
Model Label
Closeup of the model label & serial number.
PCB Bottom
Here the bottom cover has been removed, showing the main PCB. The pair of large ICs bottom center interface with the magnetic heads. The IC above them has had the markings sanded off.
USB-Serial Interface
Closeup of the Prolific PL-2303 USB-Serial converter IC.
PCB Top
Here the connections to the R/W heads are visible, current limiting resistors at the left for the write head, a pair of signal relays, a pair of optoisolators & a LM7805 linear voltage regulator.
LEDs
Here is the trio of indicator LEDs on a small sub-board.
Frame Bottom
The PCB has been removed from the main frame here, the only component visible is the rotary encoder.
Rotary Encoder
The rotary encoder has a rubber wheel fitted, which reads the speed of the card as it is being swiped for writing. This allows the control logic to write the data to the stripe at the correct rate for the speed of the card. This allows the unit to write cards from 5-50 inches per second speed.
The Write head is directly behind the rubber pressure roller.
Read/Write Heads
Here you can see the R/W head assembly. The write head is on the right, read on the left. When a card is written to, it immediately gets read by the second head for verification.
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.
Overview
Front of the PCB, 3 1.5v cells powered the unit, Piezo sounder & sensor cell in the centre of the board.
An early speed radar detector from the early 90’s. Pictures showing the front of the unit with the option buttons.
Bottom
Bottom of the unit showing label. Unlike the newer plastic detectors, the whole casing of this unit is cast aluminium.
Model Uniden Stalker RD-6000W.
PCB Top
PCB removed from the casing. Volume/power control on the left. Option tactile switches on the edge of the PCB, with the indicator LEDs. Power input jack on the right hand side of the PCB. Large aluminium can is the detector assembly, containing the detector diodes. Waveguide horn is at the top.
Waveguide Horn
Shot down the waveguide, showing the detector diodes at the end.
LEDs
Indicators on the front of the unit, X, K & Ka band detection LEDs on the left, Power & detection level (1-4) LEDs in centre. City (C) (Audio (A) & Mute (M) LEDs on the right.
PCB Bottom
Bottom of the PCB, showing detection logic. Piezo buzzer top left.
Another phone from the mid 90s. This is the nokia 7110.
Slider Open
Here the slider is open showing the keypad.
Battery Removed
Here the battery is removed, a Li-Ion unit.
Battery
The battery cell & protection circuit removed from the casing.
Rear Of PCB
This is the rear of the PCB removed from the housing. Data & charging ports on the right hand side f the board.
Front Of PCB
Front of the PCB with the RF sections at the left hand side & the keypad contacts on the right.
RF Sections
Closeup of the RF sections of the board, big silver rectangular cans are VCO units.
SIM Connector
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.
CPU
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.
Mic & Speaker
The Mic & the loudspeaker removed from it’s housing.
LCD
LCD from the front of the unit, SPI interfaced. Flex PCB also contains the power button, loudspeaker contacts & a temperature sensor.
Scroll Wheel
The scroll wheel removed from the front housing.
Vibra-Motor
Tiny vibration motor removed from the rear housing, alerts the user to a text or phone call.
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