I have yet another receipt printer, this one appears to be brand new. It’s possibly the smallest thermal 80mm printer I have at the moment, and has both USB & Serial interfaces.
Controller PCB
There’s not much to these printers at all. Removing a single screw allows the case halves to separate, showing the guts. The controller is based around a Texas Instruments TMS320VC5509AFixed-Point DSP. It’s associated Flash ROM & RAM are to the right.
Power supply is dealt with in the top right of the PCB, with the interface ports further left.
Print Head
Here’s the thermal mechanism itself, with the large print head. The stepper motor to drive the paper through the printer is just peeking out at top right. The paper present sensor is just under the left hand side of the print head.
A lot of the electronics I use & projects I construct use batteries, mainly of the lithium variety. As charging this chemistry can be a little explosive if not done correctly, I decided a proper charger was required. This charger is capable of handling packs up to 6 cells for Lithium, and up to 20v for lead-acids.
External Connections
The usual DC input barrel jack on the left, with an external temp sensor for fast charging NiCd/NiMH chemistry batteries. The µUSB port registers under Linux as USB HID, probably so drivers aren’t required. Unfortunately the software is Windows only, but it doesn’t provide anything handy like charging graphs or stats. Just a way to alter settings & control charging from a PC. On other versions of this charger there’s a setting to change the temp sensor port into a TTL serial output, which would be much handier.
Output & Balance
The other side of the charger has the main DC output jacks & the pack balancing connections.
Cover Removed
Here’s the top cover removed from the charger, showing most of the internals. A standard HD44780 LCD provides the user interface, the CPU & it’s associated logic is hidden under there somewhere.
The PCB has nice heavy tracks to handle the 6A of current this charger is capable of.
Balancing Network
The output side of the board. Here the resistive pack balancing network can be seen behind the vertical daughter board holding the connectors, along with the output current shunt between the DC output banana jacks & the last tactile button.
Main Logic
Unfortunately the LCD is soldered directly to the board, and my desoldering tool couldn’t quite get all the solder out, so time to get a bit violent. I’ve gently bent the header so I could see the brains of the charger. The main CPU is a Megwin MA84G564AD48, which is an Intel 8081 clone with USB support. Unfortunately I was unable to find a datasheet for this part, and the page on Megwin’s site is Chinese only.
I was hoping it was an ATMega328, as I have seen in other versions of this charger, as there are custom firmwares available to increase the feature set of the charger, but no dice on this one. I do think the µUSB port is unique to this version though, so avoiding models with that port probably would get a hackable version.
There’s some glue logic for controlling the resistor taps on the balancing network, and a few op-amps for voltage & current readings.
Power Switching Devices
All the power diodes & switching FETs for the DC-DC converter are mounted on the bottom of the PCB, and clamped against the aluminium casing when the PCB is screwed down. Not the best way to ensure great contact, but Chinese tech, so m’eh.
It’s well known that there are two versions of the 701 type controller available for Eberspacher heaters, the version with the blue logo is the official un-restricted model, while the version with the white logo is a version built for BT that restricts the heater to 1 hour runtime & has no diagnostics built in.
As these devices are microcontroller driven, I assumed that the hardware would be the same, only the code running in the micro being the bit that Eberspacher changed. This option would certainly have been the lowest cost.
Controller PCB Rear
Here’s the PCB removed from the plastic housing. There are definitely some differences that I can tell. As the un-restricted version has an extra wire for the diagnostic serial interface, and this board has no unpopulated parts, the PCB is definitely a different version.
In the centre is a Microchip PIC16C622 microcontroller, the OTP version in this case for cost reductions. (I may try reading the binary from this chip in the future, chances are it’s code protected though).
Below the micro is an NXP PCF8577C 32-segment LCD controller, this has an I²C interface to the PIC.
The temperature control function on these heaters is done via applying a resistance to one of the control lines, between 1750Ω-2180Ω, ±80Ω. (Very odd values these, not to mention no standard components can create this range easily, bloody engineers >_<). This is accomplished in hardware with a BU2092F I²C shift register from Rohm, which is connected to a bank of resistors. The microcontroller will switch combinations of these into the circuit to get the range of resistances required.
The rest of the circuit is local power regulation & filtering.
Controller PCB Front
There’s not much on the other side of the PCB, just the LCD itself & the contacts for the buttons.
I’m no fan of power inverters. In my experience they’re horrifically inefficient, have power appetites that make engine starter motors look like electric toothbrushes & reduce the life expectancy of lead-acid batteries to no more than a few days.
However I have decided to do a little analysis on a cheapo “600W” model that Maplin Electronics sells.
Cover Removed
After a serious amount of metallic abuse, the bottom cover eventually came off. The sheet of steel used to close the bottom of the aluminium extrusion was wedged into place with what was probably a 10 ton hydraulic press.
As can be seen from the PCB, there’s no massive 50Hz power transformer, but a pair of high frequency switching transformers. Obviously this is to lighten the weight & the cost of the magnetics, but it does nothing for the quality of the AC output waveform.
DC Input End
The 12v DC from the battery comes in on very heavy 8-gauge cables, this device is fused at 75A!
DC Fuses
Here’s the fusing arrangement on the DC input stage, just 3 standard blade-type automotive fuses. Interestingly, these are very difficult to get at without a large hammer & some swearing, so I imagine if the user manages to blow these Maplin just expect the device to be thrown out.
Input DC-DC Switching MOSFETs
On the input side, the DC is switched into the pair of transformers to create a bipolar high voltage DC supply.
High Voltage Rectifiers
The large rectifier diodes on the outputs of the transformers feed into the 400v 100µF smoothing capacitors.
As mains AC is obviously a bipolar waveform, I’m guessing this is generating a ±150v DC supply.
Output MOSFETs
After the high voltage is rectified & smoothed, it’s switched through 4 more MOSFETs on the other side of the PCB to create the main AC output.
The label states this is a modified-sine output, so I’d expect something on the scope that looks like this:
Inverter Waveforms
Modified-sine doesn’t look as bad as just a pure square output, but I suspect it’s a little hard on inductive loads & rectifiers.
However, after connecting the scope, here’s the actual waveform:
Actual Waveform
It’s horrific. It’s not even symmetrical. There isn’t even a true “neutral” either. The same waveform (in antiphase) is on the other mains socket terminal. This gives an RMS output voltage of 284v. Needless to say I didn’t try it under load, as I don’t possess anything I don’t mind destroying. (This is when incandescent lamps are *really* useful. Bloody EU ;)).
About the only thing that it’s accurate at reproducing is the 50Hz output, which it does pretty damn well.
System Microcontroller
As is usual these days, the whole system is controlled via a microcontroller.
For a long time I’ve needed a decent vacuum desoldering tool, as I do much stripping of old PCBs for random parts.
Solder wick works well for most things, but it’s expensive & can be fiddly. It also doesn’t keep very long as the copper braid oxidises & after that point it never seems to work particularly well, even when soaked in fresh flux.
Desoldering Station
As usual eBay to the rescue! I managed to pick this one up for £80.
Vacuum Pump
Removing the lid reveals the internals. Front & centre is the vacuum pump, with the mains supply behind it. There’s also a very noisy cooling fan at the back. Not sure why since the unit never gets warm enough to actually warrant a fan.
PSU
On the other side is the PSU. This is an 18v 12A rated SMPS, with a bit of custom electronics for controlling the iron element. Mounted to the back case is a small black box, more to come on this bit.
PSU Board
Cracking the case of the PSU reveals a pretty bog-standard SMPS, with a surprising amount of mains filtering for a Chinese supply. The DC outputs are on the right.
From the rail markings, this is clearly designed to output some more voltage rails – possibly for other models of unit. In this case though, a single 18v rail is present. The iron’s element connects directly to the supply, controlled via an opto-isolated MOSFET.
Chinese Voltage Regulation
As both the fan & the vacuum pump motor are 12v devices, some provision had to be made to reduce the 18v from the power supply to a more reasonable value. Inside the black plastic box are a pair of 1Ω 5W power resistors, connected in series. The output from this connects to the fan & vacuum pump. Because cheap, obviously.
Controller
Finally, here’s the controller PCB, the main MCU is an 8081 derivative, with a Holtek HT1621B LCD controller for the front panel temperature readout. Iron temperature is achieved by a thermocouple embedded in the heater, I imagine the potentiometer on the left side of the PCB is for calibration.
Here’s another retired piece of tech that we used to route media from the NAS to the main TV. It was retired since it’s inability to support XBMC/Kodi & having some crashing issues.
Main PCB
After attacking the case with the screwdriver (Torx in this case), the main board comes out. The CPU in this looks *very* familiar, being a PoP device. There are unpopulated places for an ethernet interface & USB port here.
Flash & CPU
After a little digging is turns out the CPU in this device is a BCM2835, with 256MB of RAM stacked on top. It’s a Raspberry Pi! Even the unpopulated part for Ethernet is the same SMSC LAN9512!
There’s 32MB of Flash for the software below the CPU.
On the far right of the board is a Broadcom BCM59002IML Mobile Power Management IC.
WiFi Chipset
On the bottom of the PCB is the WiFi chipset, a Broadcom BCM4336, this most likely communicates with the CPU via SDIO. There’s also a section below for a Bluetooth chipset.
For a while I’ve wondered how these pancake type (AKA “Shaftless”) vibration motors operate, so I figured I’d mutilate one to find out.
Pancake Vibration Motor
These vibrators are found in all kinds of mobile devices as a haptic feedback device, unlike older versions, which were just micro-sized DC motors with an offset weight attached to the shaft, these don’t have any visible moving parts.
Cover Removed
These devices are crimped together, so some gentle attack with a pair of snips was required to get the top cover off.
It turns out these are still a standard rotary DC motor, in this case specifically designed for the purpose. The rotor itself is the offset weight, just visible under the steel half-moon shaped section are the armature coils.
Weighted Rotor
The armature lifts off the centre shaft, the coils can clearly be seen peeking out from under the counterweight.
Commutator
The underside of the armature reveals the commutator, which in this device is just etched onto the PCB substrate, the connections to the pair of coils can be seen either side of the commutator segments.
Brushes
The base of the motor holds the brushes in the centre, the outer ring is the stationary permanent magnet. These brushes are absolutely tiny, the whole motor is no more than 6mm in diameter.
In the past, I’ve used RC type LiPo packs for my mobile power requirements, but these tend to be a bit bulky, since they’re designed for very high discharge current capability – powering large motors in models is a heavy job.
I recently came across some Samsung Galaxy Tab 10.1 battery packs on eBay very cheaply, at £2.95 a piece. For this price I get 6800mAh of capacity at 4.2v, for my 12v requirements, 3 packs must be connected in series, for a total output of 12.6v fully charged.
For an initial pack, I got 9 of these units, to be connected in 3 sets of 3 to make 20Ah total capacity.There are no control electronics built into these batteries – it’s simply a pair of 3400mAh cells connected in parallel through internal polyfuses, and an ID EEPROM for the Tab to identify the battery.
This means I can just bring the cell connections together with the original PCB, without having to mess with the welded cell tabs.
Battery Pack
Here’s the pack with it’s cell connections finished & a lithium BCM connected. This chemistry requires close control of voltages to remain stable, and with a pack this large, a thermal runaway would be catastrophic.
Cell Links
The OEM battery connector has been removed, and my series-parallel cell connections are soldered on, with extra lead-outs for balancing the pack. This was the most time-consuming part of the build.
If all goes well with the life of this pack for utility use, I’ll be building another 5 of these, for a total capacity of 120Ah. This will be extremely useful for portable use, as the weight is about half that of an equivalent lead-acid.
I needed a decent WiFi adaptor for my latest Pi LCD project, so after trawling eBay for cheapy USB adaptors, I found this one.
USB WiFi Dongle
Unlike most USB WiFi radios these days, it actually has a proper RP-SMA antenna connector, not the low-gain built in jobbies that never seem to work too well.
There are a few versions of this adaptor, all of which seem to use the same casing, there’s a button push cut into the plastic for a WPS button that doesn’t exist on this model. This is fine, as I don’t enable WPS on any of my network equipment anyway. (It’s insecure, and can be cracked in minutes).
MAC Address
Here’s the rest of the essential details, the model is BL-LW08-AR, rated at 300Mbit/s.
PCB Reverse
Here’s the PCB removed from the casing, there are a pair of PCB antennas on here, but they’re not connected to the RF circuitry in this model, the links are missing.
Chipset
The chipset used is a Realtek RTL8191SU, there isn’t much more in this device, as it’s all built into the silicon.
Finally the Raspberry Pi Foundation have released an official LCD for the DSI connector on the Pi. When these were announced, I placed an order straight away, but due to demand it’s taken quite a while for it to arrive in the post.
Interface PCB
The LCD itself is an RGB panel, to interface the Pi via the MIPI DSI port, some signal conversion is required. A small PCB is mounted on the back of the LCD to do this conversion. It also handles the power supply rails required by the LCD itself & interfacing the touch screen.
LCD Power Supply
Taking care of the power supply is a Texas Instruments TPS65101 triple output LCD power supply IC. This also has a built in linear regulator to supply 3.3v for the rest of the circuitry on board. The large transistor to the left of the IC is the pass transistor for this regulator.
Main Controller
The video signal comes in on the FFC connector on the left, into the BGA IC. I’ve not managed to identify this component, but it’s doing the conversion from serial video from the Pi to parallel RGB for the LCD.
There’s also an Atmel ATtiny88 on the board below the main video conversion IC, not sure what this is doing.
The touch controller itself is mounted on the flex of the LCD, in this case it’s a FT5406.
Raspberry Pi LCD
Here’s the LCD in operation. It’s not the highest resolution out there, but it leaves the GPIO & HDMI ports free for other uses.
Pi Mounted
The Pi screws to the back of the LCD & is connected with a flat flex cable & a pair of power jumpers. I’ve added a couple of small speakers to the top edge of the LCD to provide sound. (More to come on this bit).
Here’s another torch from eBay, this time with 5 Cree XML-T6 LEDs.
Label
Having 5 Cree LEDs rated at up to 3A a piece, this light has the capacity to draw about 50W from it’s power supply. In this case though, current draw is about 1.5A at 12v input on the full brightness setting.
Cree LED Torch
Here’s the LEDs mounted into the reflector. Fitting this many high power LEDs into a small space requires some serious heatsinking. The casing is made of machined aluminium.
LED Module
Unscrewing the front bezel allows the internals to come out. The core frame & reflector is all cast alloy as well, for heatsinking the LEDs. The controller PCB is mounted into a recess in the back of the LED mount.
Controller
Here’s the controller itself. The usual small microcontroller is present, for the multiple modes, and handling the momentary power switch.
Switching Inductor
As all the LEDs on this torch are connected in series, their forward voltage is ~12-15v. The battery is an 8.4v Li-Ion pack, so some boost conversion is required. This is handled by the circuitry on the other side of the board, with this large power inductor.
Reflector
The reflector screws onto the front of the LED array, centered in place with some plastic grommets around the LEDs themselves.
LED Array
Finally for the torch, the LED array itself. This is attached to the frame with some thermal adhesive, and the LEDs themselves are mounted on an aluminium-core PCB for better heat transfer.
This module unsurprisingly generates quite some heat, so I have improved the thermal transfer to the outer case with some thermal grease around the outer edge.
Charger
The supplied charger is the usual Chinese cheapy affair, claiming an output current of 1A at 8.4v. I never use these chargers, so they get butchered instead.
Charger PCB
Here’s the main PCB. Overall the construction isn’t that bad, the input mains is full-wave rectified, but there is little in the way of RFI filtering. The supply is fused, but with an absolutely tiny glass affair that I seriously doubt has the ability to clear a large fault current.
Like many cheap supplies, the output wiring is very thin, it’s capacity to carry 1A is questionable.
PCB Reverse
On the reverse side, there’s a nice large gap between the mains side & the low voltage output. There’s even an anti-tracking slot under the optoisolator.
As supplied, the RTL type tuner dongles are a little fragile, especially when they’ve got a rather heavy coax feeder attached for Ham Radio use.
The MCX antenna connectors on the tuner can’t stand up to much abuse, and even the USB plug rips itself from it’s mounts after a while with a heavy weight on the end. Since this dongle sits in my radio go bag, it definitely needed some protection & support.
PCB
The PCB itself is removed from it’s flimsy plastic casing, the USB plug is desoldered from the board.
To the exposed pads, a USB cable is soldered, giving much more flexibility in where the tuner is placed.
Instead of using the MCX antenna connector on the PCB, the coax is stripped & soldered direct to the PCB itself, as this connector has become unreliable.
N-Connector
To get the RF into the device, the case is fitted with an N connector, as is everything else in my shack.
Boxed
The box used is a surplus one which previously housed an electronic lighting transformer. This would be very easy to waterproof as well, for more protection against outdoor use.
Since the boat was still running it’s internal network on 10/100M speeds, an upgrade was decided on, the internal WiFi signal strength was also pretty poor further than a few feet from the NOC.
The new router is a Cisco/Linksys AC1750 model, with gigabit networking, and full 802.11ac 2.4/5GHz Wireless. This router also has a built in media server, print server, USB3 & USB2.
PCB Overview
Teardown time! Here’s the router with the cover removed. Most of the fun stuff is hidden under the shields, but these aren’t fully soldered down & the covers are removable. The 6 antennas can be seen spaced around the edge of the housing, the main CPU is under the large heatsink upper centre. The radio power amplifier stages are underneath the shields, while the main RF transceivers are just outside the shields.
2.4GHz Transceiver
Wireless N is provided by a Broadcom BCM4331, this provides full dual-band 3×3 802.11n support. Being 3×3 it is actually 3 separate transceivers in a single package, to get much higher throughput rates of 600Mbit/s.
5GHz Transceiver
Wireless AC is provided by it’s sister IC, the BCM4360, with throughput speeds of 1.3Gbit/s. Both of these transceiver ICs connect back to the main CPU via PCI Express.
5GHz Power Amplifiers
To get increased range, there are a trio of Skyworks SE5003L +23dBm 5GHz power amplifier ICs under the shield, along with the TX/RX switching & antenna matching networks. Heatsinking for these is provided by a sink screwed to the bottom side of the PCB. The outputs to the antennas can be seen at the top of the image.
2.4GHz Power Amplifiers
The 2.4GHz section is fitted with a trio of Skyworks SE2605L +23dBm 2.4GHz power amplifiers, with a similar heatsink arrangement under the board. Unlike the 5GHz section, the 2.4GHz antenna feeds are soldered to the PCB here instead of using connectors.
Main CPU
The main CPU is a BCM4708 Communications Processor from Broadcom, as for the other Broadcom chips in this router, very little information is available unless under NDA, but I do know it’s a dual core ARM Cortex A9 running at 1GHz, with built in 5-port gigabit ethernet switch.
CPU RAM
Working RAM for the processor is a Hynix H5TQ2G63DFA 256MB part.
More to come on the installation of the new networking, with it’s associated 4G mobile gateway connection system.
I almost forgot about this bit of kit, that came with one of my LED torches as a Lithium Ion charger. As I never plug in anything that comes from China via eBay, here’s the teardown & analysis.
Another Lethal Charger?
Here’s the unit itself. It’s very light, and is clearly intended for American NEMA power points.
Specs
Claimed specifications are 100-240v AC input, making it universal, and 4.2v DC out ±0.5v at 500mA.
Considering the size of the output wire, if this can actually output rated voltage at rated current I’ll be surprised.
Opened
Here’s the adaptor opened up. There’s no mains wiring to speak of, the mains pins simply push into tags on the PCB.
PCB Top
Top of the SMPS PCB. As usual with Chinese gear, it’s very simple, very cheap and likely very dangerous. There’s no real fusing on the mains input, only half-wave rectification & no EMI filtering.
PCB Bottom
Here’s the bottom of the PCB. At least there’s a fairly sized gap between the mains & the output for isolation. The wiggly bit of track next to one of the mains input tags is supposed to be a fuse – I somehow doubt that it has the required breaking characteristics to actually pass any safety standards. Obviously a proper fuse or fusible resistor was far too expensive for these.
The output wiring on the left is thinner than hair, I’d say at least 28AWG, and probably can’t carry 500mA without suffering extreme volt drop.
Here’s another quick teardown, a cheap 5-port HDMI switch box. This is used to allow a single input on a monitor to be used by 5 different external HDMI devices, without having to mess about plugging things in.
Power & Remote
Here’s the DC barrel jack & 3.5mm TRS jack for power & remote control. There’s a little IR decoder & remote that go with this for hands free switching.
PCB Top
Here’s the PCB out of it’s plastic housing. The main logic is a pair of PI3HDMI303 3:1 HDMI switches from Pericom Semiconductor. These are cascaded for the 5-ports, the first 3 input HDMI ports are switched through both ICs to reach the output.
These HDMI switch ICs are operated with TTL input pins, the combination of these pins held either high or low determines the input port that appears on the output.
There’s a button on the left for switching between inputs, with a row of 5 LED indicators.
PCB Bottom
Not much on the bottom side, a lot of passives & bypass capacitors. There’s a 3.3v LDO regulator on the left for supplying the main rail to the active switch ICs. The IC on the right doesn’t have any numbering at all, but I’m presuming it’s a microcontroller, dealing with the IR remote input & pushbutton inputs to switch the inputs.
The multimode dimming/flashing modes on Chinese torches have irritated me for a while. If I buy a torch, it’s to illuminate something I’m doing, not to test if people around me have photosensitive epilepsy.
Looking at the PCB in the LED module of the torch, a couple of components are evident:
LED Driver PCB
There’s not much to this driver, it’s simply resistive for LED protection (the 4 resistors in a row at the bottom of the board).
The components at the top are the multimode circuitry. The SOT-23 IC on the left is a CX2809 LED Driver, with several modes. The SOT-23 on the right is a MOSFET, for switching the actual LED itself. I couldn’t find a datasheet for the IC itself, but I did find a schematic that seems to match up with what’s on the board.
Schematic
Here’s that schematic, the only thing that needs to be done to convert the torch to single mode ON/OFF at full brightness, is to bridge out that FET.
Components Desoldered
To help save the extra few mA the IC & associated circuitry will draw from the battery, I have removed all of the components involved in the multimode control. This leaves just the current limiting resistors for the LED itself.
Jumper Link
The final part above, is to install a small link across the Drain & Source pads of the FET. Now the switch controls the LED directly with no silly electronics in between. A proper torch at last.
Finally, after a couple of weeks wait time, the fan controllers for the power supplies have arrived. They’re small boards, which is good for the small space left inside the case of the supply.
Controller Boards
Here they are. I’m not certain what the pair of potentiometers are for – there’s no mention of them in the documentation. Possibly for calibration.
Beepers are supplied so an alarm can be heard if the fan fails – very useful for this application.
Controller Closeup
Here’s a closeup of the PCB. Options are set with the DIP switch bank on the left, details for that below. The main IC is a STM8S103F3 flash microcontroller.
Temperature Probe
The only issue at the moment is that the temperature probe leads are much too short. I’ll have to make a small modification to get enough length here.
Here’s all the details on the boards, more for future reference when they undoubtedly vanish from eBay 😉
Specifications
Working voltage:DC12V
Circuit load capacity: maximum current per output 5A, the bus currents up 9A
Output Range: The first channel 20% -100%, or 40% -100% (TFL = ON)
The second channel and the third channel 10% -100%
(Note: Above range only for PWM range, the actual control effect will vary depending on the fan.)
Temperature probe parameters: 50K B = 3950
Thermostat temperature zone error: error depending on the temperature probe, generally 3-5%
Stall alarm minimum speed: 700-800 rpm
Function setting switch Description:
TFL (No. 1): The lowest temperature channel PWM setting, when ON state FAN1 PWM minimum is 40%, when OFF the minimum PWM of FAN1 is 20%.
TP1 TP2 (No. 2,3): Temperature channel control temperature zones are interpreted as follows (need to used with the temperature probe):
TP1
TP2
Accelerating temperature
Full speed temperature
OFF
OFF
35℃
45℃
ON
OFF
40℃
55℃
OFF
ON
50℃
70℃
ON
ON
60℃
90℃
When the temperature lower than the accelerated temperature, then output at the minimum rotation speed; when it exceed over the full temperature, then always output at full speed.
BF1 BF2 (No. 4,5): corresponds FAN1 FAN2 stall alarm function switch, when the corresponding open channel fan break down, the controller will alarm with soundand light (works with buzzle), alarm will automatically eliminated when the fan is rotated recovery . If BF1 and BF2 both are open (ON), the FAN1, FAN2 have any one or both stops, the controller will alarm!
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.
Torch
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.
Charger
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?
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.
Charger Bottom
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!
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.
I’m still on my crusade of removing every trace of 240v mains power from my shack, so next up are my computer monitors.
I have 4 Dell monitors, of various models, hooked up to my main PC.
The monitor here is a Dell E207WFPc 20″ widescreen model. There will be more when I manage to get the others apart to do the conversion. However I’m hoping that the PSU boards are mostly the same.
Panel Removed
There are no screws holding these monitors together, the front bezel is simply clicked into place in the back casing, these clips are the only thing that holds the relatively heavy glass LCD panel & it’s supporting frame! The image above shows the panel removed. The large board on the left is the power supply & backlight inverter, the smaller one on the right is the interface board to convert the DVI or VGA to LVDS for the LCD panel itself.
PSU Board
Here’s a closeup of the PSU board, the connector at centre right at the top of the PCB is the main power output, and also has a couple of signals to control the backlight inverter section of the PSU, on the left side. The PSU requirements for this monitor are relatively simple, at 14.5v for the backlight & 5v for the logic board.
PSU
Here’s the top of the PSU board, very simple with the mains supply on the right side, and the backlight inverter transformers on the left.
Hooked In
Here I’ve hooked into the power rails on the supply, to attach my own 12v regulators. The green wire is +14.5v, and the purple is +5v. Black is common ground.
5v Regulator
On doing some testing, the backlight inverter section doesn’t seem to mind voltages between 11.5-14.5v, so a separate regulator isn’t required there. Even running off batteries that’s within the range of both charging & discharging. The only regulator required is a 5v one to reduce the input voltage for the logic PCB.
First Test
On applying some 12v power to the regulator input, we have light! Current draw at 12.5v is 2.65A for a power consumption of 33W.
12v Input
There’s plenty of room in the back casing to mount a 12v input socket, I have left the mains supply intact so it can be used on dual supply.
Final Wiring
Here’s the 5v regulator mounted on the back of the casing, all wired up & ready to go.
I’ve had a couple of viewfinder CRT modules for a while, & haven’t done much with them, so I decided to make a very small B&W monitor.
CRT
I ordered a small transparent ABS box when I made a large order with Farnell, that turned out to be just about the perfect size for the project! The CRT & PCB barely fit into the space. The face of the CRT itself is about 17mm across.
Module Installed
Here’s the main PCB & tube fully installed into the case. Barely enough room for a regulator left over!
Power is provided by a simple LM7809 IC to take a standard 12v input.
Module Rear
Rear of the case, showing the fit of the control board.
Connections
Here’s the back of the monitor, with the DC input jack & a 3.5mm 4-pole jack for audio & video. This allows simple connection to many devices, including the one I’ll use the most – the Raspberry Pi.
Completed
Completed monitor. Audio is handled by a very small 20mm speaker, currently mounted just below the CRT face.
Current draw from a 13.8v supply is 117mA.
Finally, here’s the last part of the Rigol 12v DC Power Supply project, the linear post regulation section to remove some of the ripple.
I have made a couple of layout adjustments since the last post about this part of the project – a little more filtering on the DC outputs. As usual the Eagle project files are at the bottom of the post for those who might find them useful.
Updated PCBUpdated Schematic
Completed PCB
Here’s the completed PCB, partially installed in the back of the scope. The missing regulator is the 5v one, since I already have a source of clean 5v from my original attempt at the supply, it’s not a problem not using a linear after the switcher. The filtering is the same on all channels, input from the switchers is on the right, outputs to the scope on the left.
PCB Bottom
Here’s the bottom of the PCB, with the common mode input chokes. The design of this board has allowed me to remove a couple of the switching modules as well, as I can use a single bipolar supply to run both sets of bipolar regulators on this board. This should help remove some of the noise also.
The ripple level has now dropped to lower than it was originally on the mains supply! Current draw at 13.8v DC is about 1.75A.
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.
While searching around for regulators to convert my new scope to 12v power, I remembered I had some DC-DC modules from Texas Instruments that I’d got a while ago. Luckily a couple of these are inverting controllers, that will go down to -15v DC at 15W/3A capacity.
I’ve had to order a new module from TI to do the -17v rail, but in the meantime I’ve been getting the other regulators set up & ready to go.
The DC-DC module I’ve got for the -7.5v rail is the PTN78060A type, and the +7.5v & +5v rails will be provided by the PTN78020W 6A buck regulators.
These regulators are rated well above what the scope actually draws, so I shouldn’t have any issues with power.
DC-DC Modules
Here’s the regulators for the 5v, 7.5v & -7.5v rails, with multiturn potentiometers attached for setting the voltage output accurately. I’ve also attached a couple of electrolytics on the output for some more filtering. I’ll add on some more LC filters on the output to keep the noise down to an absolute minimum. These are set up ready with the exact same output voltage as the existing mains AC switching supply, when the final regulator arrives from TI I will put everything together & get some proper rail readings.
There won’t be a proper PCB for this, as I don’t have the parts in Eagle CAD, and I simply don’t have the energy to draw them out from the datasheets.
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.
Battery Compartment
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.
Modified Compartment
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.
Modifications
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.
Charger
The charger is located in a slot cut in the bottom of the casing, so the USB port is accessible from outside the compartment.
Wiring
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.
Battery Cover
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.
Charging Port
With the battery cover installed, the USB port is nicely recessed into the edge.
Charging LED
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.
Charging Complete
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