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.
I’ve had a couple of larger batteries for my UV-5Rs for some time now, and decided to do a quick teardown to see if they’re actually the capacity claimed.
BL-5L Battery
Here’s the label, claiming 3800mAh (3.8Ah) of battery capacity.
These batteries are held together with glue, but a good way to get these kinds of things open is by whacking the seams with the handle of a screwdriver. This cracks the glue without damaging the casing.
Battery Cracked Open
After a few minutes of cracking the seams, the battery comes right open. The pair of wires link the protection board on the cells to the DC terminals on the top of the pack. The charging terminals are under the cardboard insulator on the right.
Cells
Here’s the other half of the case, with the cells themselves. These are wired in series for a 7.2v pack, and at a capacity of 2600mAh (2.6Ah) printed on them, the label clearly lies about the capacity.
Since I fitted my scope with a SMPS based 12v input supply, there has been a noise problem on very low volts/div settings, this noise isn’t present on the mains supply, so I can only think it’s coming from the switching frequencies of the various DC-DC modules I’ve used.
Scope Ripple
Because of this I’ve designed a linear post-regulation stage for the supply, to remove the RFI from the DC rails.
This board takes the outputs from the DC-DC converters, removes all the noise & outputs clean DC onto the mainboard of the scope.
As the scope internally uses regulation to get the voltages lower, I’ve found that I don’t have to match the outputs of the mains supply exactly, for the +/-17.5v rails, 12v is perfectly fine instead.
Scope Linear PSU
Here’s the PCB layout, with the 6 common mode filters on the input (left), linear regulator ICs in the centre & the output filters on the right.
Scope Linear PSU
Here’s the schematic layout, as usual the Eagle Project files are in the link below, I’ll update when I have built the board & tested!
This is basically an industrial, rugged MP3 player, in an extruded aluminium case.
They are used in commercial settings for generating telephone hold music or continual playback of background music in shops.
USB1100
It’s quite a compact unit, in a nice aluminium case, designed for mounting into a comms setup. This unit will play any MP3 file, up to a maximum size of 11MB.
Connections
Here’s the user connections on the end of the unit. The device takes a standard 12v DC input, and has a single button for setup, user feedback is given through the multi-colour LED next to the power jack.
Both 8Ω & 600Ω audio outputs are provided for maximum compatibility. Volume & tone controls are also here.
On the other end of the unit is a single USB port for loading the audio files from a USB drive, and a reset button.
Main PCB
Here’s the single PCB removed from the casing. Unfortunately the main CPU has had it’s part number sanded off, and I can’t be bothered to try & find out what kind of processor it is at this point. To the right of the CPU are some flash ROM & SDRAM, along with the single USB port at bottom right.
The left side of the board is dedicated to audio output & voltage regulation, there are a fair few linear regulators in this unit.
Audio End
Here’s the audio output side of the board, the transformer on the left is to provide the 600Ω output, the audio amplifier IC (BA5416) is just behind it. To the right are some of the main voltage regulators, a 5v one on the heatsink & a LM317.
Audio Codec
The audio codec is a CS4271 from Cirrus Logic, a really high quality part, 24-bit resolution, 192kHz Stereo codec. Considering this is for telephone & PA systems that aren’t that high fidelity, it’s well built!
All of the parts I required to complete the supply arrived this morning. After several hours of building, here’s what I came up with:
12v Power Supply
I’ve mounted everything on a piece of FR4 PCB, with it’s copper plane grounded to the case. This backing board is the same size as the original PSU PCB to allow it to be screwed into the same location in the scope.
The power comes in via the converter on the right, which outputs a single 24v rail for the rest of the supplies. The other 6 supplies then generate the individual voltage rails that the scope requires. The use of a single input supply allows this system to operate at voltages up to 30v DC, so it’s good for both 12v & 24v systems.
Scope Ripple
At present the only issue is with some ripple on one of the supplies, this is showing up on the scope display with no input connected at the lowest volts/division. Parts are on order from Farnell to build some common mode filters to remove this from the DC output.
On a 13.8v supply, the scope draws about 1.5A total from the supply, giving a total power consumption of 20.7W. This is with all 4 channels enabled.
My wiring assignments & DC-DC converter ratings are in the table below
Connector Pin
PCB Pin
Signal
Mainboard
DC-DC Rating
Wire Colour
1
10
GND
GND
N/A
BLACK
2
2
+9v_GND
FAN --
NA
BLACK
3
8
+7.5V
6.3V
6A
ORANGE
4
14
-7.5V
-7.5V
2A
GREEN
5
1
NOT USED
AC_TRIG
N/A
NOT USED
6
4
+5V
5V5A
6A
RED
7
6
GND
GND
N/A
BLACK
8
7
GND
GND
N/A
BLACK
9
12
-17.5V
-17.5V
3A
PURPLE
10
9
+7.5V
6.3V
6A
ORANGE
11
3
+9V
FAN +
1A
GREY
12
11
17.5V
17.5V
3A
BLUE
13
5
+5V
5V5A
6A
RED
14
13
GND
GND
N/A
BLACK
Stay tuned for the final section of this build with the power supply filtering & main DC input connections!
As the crimp tool for the PSU connector in the Rigol scope is a very expensive piece of hardware, I decided to use pre-crimped terminals, from an ATX power connector. (They’re the same type).
Wiring Loom
Here’s the partially completed loom, with the 13 cores for the power rails. The 14th pin is left out as that is for AC triggering, and this won’t be usable on a low voltage supply.
A couple of the pins have two wires, this is for voltage sensing at the connector to compensate for any voltage drop across the cable. The regulators I am using have provision for this feature.
Sleeving
To keep the wiring tidy, I dug a piece of braided loom sleeving out of the parts bin, this will be finished off with the heatshrink once the pins are inserted into the connector shell.
The remaining parts for the loom have been ordered from Farnell & I expect delivery tomorrow.
Here’s some testing of the first bipolar supply for the Rigol scope. This is the +/-7.5v supply.
Bipolar Supply
Above is the supply built with it’s output filtering. The modules used are a PTN78020W for the positive rail & a PTN78060A for the negative rail.
Under a 1A load across the total 15v output, here’s some scope traces of the ripple on the supply:
+7.5v Rail
Here’s the ripple on the +7.5v rail of the supply, there’s about 75mV of total ripple.
-7.5v Rail
And here’s the -7.5v rail, the ripple on this is slightly lower, at about 50mV. This should be more than satisfactory as the scope has onboard linear regulation after the switching supply.
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.
I really like the UV-82s, over the UV-5Rs I was originally using, so I’ve bought another pair. Here are the power levels on test. Tests were done with a full battery charge on the 2m/70cm calling frequencies.
Now this is amusing, captured tonight on GB3MR, the usual unlicenced plonker is now threatening us all on the air with the Police – not sure where he’s getting a criminal offence out of the fact that everyone on the repeaters is moving around to avoid him, but still. Nor is it an offence to share audio of Amateur Radio transmissions – they’re considered public domain.
Here’s the audio for your listening pleasure.
Since everything in my shack is run from 12v, I thought it would be handy to convert my new scope to 12v as well, as 99% of the places I find myself needing test gear are off grid, with no access to mains supplies.
Mains PSU
Here’s the factory mains SMPS unit from the back of the scope. This is a nice multi-rail unit, with several different outputs, the table below details the wiring of the PSU.
Connector Pin
PCB Pin
Signal
Measured Voltage
Mainboard
Rectifier Rating
Wire Colour
5
1
AC_TRIG
N/A
AC_TRIG
N/A
BROWN
2
2
+9v_GND
N/A
FAN --
NA
ORANGE
11
3
+9V
10.16V
FAN +
2A
WHITE
6
4
+5V
5.1V
5V5A
20A
RED
13
5
+5V
5.1V
5V5A
20A
RED
7
6
GND
N/A
GND
N/A
BLACK
8
7
GND
N/A
GND
N/A
BLACK
3
8
+7.5V
6.9V
6.3V
20A
YELLOW
10
9
+7.5V
6.9V
6.3V
20A
YELLOW
1
10
GND
N/A
GND
N/A
BLACK
12
11
17.5V
17.51V
17.5V
2A
BLUE
9
12
-17.5V
-17.36V
-17.5V
2A
GREY
14
13
GND
N/A
GND
N/A
BLACK
4
14
-7.5V
-6.84V
-7.5V
2A
GREEN
The only feature I will lose if I make this switch is AC line triggering, but I never use that anyway, so it’s not a big issue for me.
Since I have been able to locate the connector, the plan is to design a replacement low voltage supply unit for the scope, with the same footprint as the original AC mains supply. This will allow me to do a direct swap without causing any damage or modifying the original supply.
This method will allow me to swap the 240v supply back into the scope if I ever come to need it.
I’m planning to use the LTC3863 DC-DC Controller from Linear Tech to generate the negative rails, this will go down to -150v on the output, so it’s pretty much perfect to generate them.
PSU Output Side
Here’s the output side of the mains PSU, it has a lot of filtering on the output rails, the two TO220 devices are the output rectifiers for the +5v & +7.5v rails, these are rated at 20A, 60V.
PCB Bottom
Here’s the bottom side of the PCB. It’s a really nicely designed PSU, massive isolation gap, spark gaps on the primary side & good filtering. The output side on the left has the rectifier diodes for the other voltage rails, these are only 2A rated, so designing the inverting supply to generate the negative rails will be pretty easy.
From looking at the PCB markings on both the mainboard & the PSU, the +9v rail seems to be used to drive the fan, both silkscreen markings indicate this.
The voltages marked on the PSU & the mainboard connector don’t quite match up though, there’s a small variation in the stated voltage between the two. This is most likely because all of the regulation of the supplies seems to be done on the mainboard, there are several linear regulators, and a few DC-DC switchers. Providing that the replacement supply isn’t noisy it should work fine.
This is backed up by the fact that the mains PSU only seems to regulate the +5v rail – on measuring the rails that’s the only one that’s close to spec.
Mainboard Power
Here’s the mainboard power connector, with it’s silkscreen labelling on the pins. (Very useful). As can be seen here, there’s at least 5 regulators, of both switching & linear types here, generating both positive & negative rails.
The boat being over 50 years old, there are some parts that are suffering from rather bad corrosion. The bow deck plate is about the worst, so this is being replaced in it’s entirety.
However a hole has developed in the stern deck, this has rusted from the inside out due to condensation in the engine bay.
After Grinding
After taking a grinder to the area, this is how it looks. The steel has gone from 1/4″ to paper thin, not surprising after 50 years or so!
It would be a massive job to cut out the entire plate for replacement, so a patch was made from 5mm steel, and welded over the hole:
Patch
Here’s the patch partially welded. The holes closer to the bottom are another small area of damage, and another patch will have to be cut for this. It’s covering the deck drain channel so it’s frequently under water, so it’s inevitable that this section would corrode.
All that is left to do now is to finish off the welding, grind everything smooth & repaint.
On the boat I have installed custom LED lighting almost everywhere, but we still use CFL bulbs in a standing lamp since they have a wide light angle, and brightness for the size.
I bought a couple of 12v CFLs from China, and the first of these has been running for over a year pretty much constantly without issue. However, recently it stopped working altogether.
12v CFL
Here’s the lamp, exactly the same as the 240v mains versions, except for the design of the electronic ballast in the base. As can be seen here, the heat from the ballast has degraded the plastic of the base & it’s cracked. The tube itself is still perfectly fine, there are no dark spots around the ends caused by the electrodes sputtering over time.
Ballast
Here’s the ballast inside the bottom of the lamp, a simple 2-transistor oscillator & transformer. The board has obviously got a bit warm, it’s very discoloured!
Failed Wiring
The failure mode in this case was cooked wiring to the screw base. The insulation is completely crispy!
Direct Supply
On connection direct to a 12v supply, the lamp pops into life again! Current draw at 13.8v is 1.5A, giving a power consumption of 20.7W. Most of this energy is obviously being dissipated as heat in the ballast & the tube itself.
Ballast PCB
Here’s the ballast PCB removed from the case. It’s been getting very warm indeed, and the series capacitor on the left has actually cracked! It’s supposed to be 2.2nF, but it reads a bit high at 3nF. It’s a good thing there are no electrolytics in this unit, as they would have exploded long ago. There’s a choke on the DC input, probably to stop RFI, but it doesn’t have much effect.
Supply Waveform
Here’s the waveform coming from the supply, a pretty crusty sinewave at 71.4kHz. The voltage at the tube is much higher than I expected while running, at 428v.
RFI
Holding the scope probe a good 12″ away from the running bulb produces this trace, which is being emitted as RFI. There’s virtually no filtering or shielding in this bulb so this is inevitable.
Here’s an odd & sudden failure, the power adaptor for a Samsung device. It’s been working for months & on being plugged into the mains today the magic blue smoke escaped.
Samsung Charger
It’s one of their 2A models, for charging bigger devices like tablets.
Flash Burn
Strangely for one of these chargers, no glue is used to hold it together – just clips. This made disassembly for inspection much easier. Evidence of a rather violent component failure is visible inside the back casing.
PCB
Here’s the charger PCB removed from the casing. As to be expected from Samsung, it’s a high quality unit, with all the features of a well designed SMPS.
PCB Reverse
However, on turning the board over, the blown component is easily visible. It’s the main SMPS controller IC, with a massive hole blown in the top. The on board fuse has also blown open, but it obviously didn’t operate fast enough to save the circuit from further damage!
Alas, my old trusty Hameg HM303 30MHz oscilloscope has finally died. I’ve had this scope for many years, an eBay buy when I noticed they were going cheap.
It’s been replaced with a brand new Rigol DS1054Z, a 4-channel 50MHz DSO.
Scope
This is a big jump from the old analogue CRT scope I was using, it’s certainly going to be a steep learning curve!
System Info
I chose this scope through the help of the EEVBlog & it’s associated forums. Through this I discovered that I could upgrade the scope with a key to enable some extra features! In the above screenshot, the key has been applied, and the model number now shown is the DS1104Z.
This is the next scope up in the model chain, with many more triggering options, serial decoders, higher memory depth, recording & 100MHz bandwidth. While I rarely need to measure anything higher than in the kHz range, these options will definitely come in useful! The list of installed options is below:
Installed Options
And now for some sample waveforms, the scope has the option to save screenshots to USB flash disks, so when I make posts with waveforms in the future, the need to photo the screen of the scope is gone!
Having now tested the supply I wrote about in my previous post, I can now say that it’s nameplate rating far exceeds it’s actual capability.
On running the supply under load, at 6.5A the operating frequency drops into the audible range, a big sign of overload. (It makes an irritating continuous chirping noise). The output voltage also drops to 10.5v.
The temperature of the unit while it’s been running under such a load is also questionable, the external casing gets hot enough to cause burns, I haven’t yet been able to stick a thermocouple into the case to see what the internal temperature is.
I’m currently talking with the eBay seller (wwwstation) regarding this, however they are arguing that the supply is only for LEDs & CCTV cameras.
However those two loads are very different, and the supply has no internal regulation for supplying LEDs. As a simple switchmode supply, any load is suitable, providing it’s within the load rating of the supply.
I would estimate that the supply is only capable of 5A as an upper limit.
They are requesting that I return the supply, but I’m yet to find out if they’re going to cover return postage. The item as listed is not as described, and I will escalate things if required.
I will update this post when I hear more back from the eBay seller.
I recently ordered a PSU to run one of the TVs I converted to 12v operation, and being an older TV, it’s a fairly heavy load at 6.5A. eBay to the rescue again, with a cheap 10A rated supply.
Power Brick
Like all similar supplies these days, it’s a SMPS unit, and feels suspiciously light for it’s power rating.
Cover Removed
Luckily this one is easy to get into, no ultrasonic welding on the case, just clips. Here’s the top cover removed, big alloy plate between the heatsinks.
PCB
The top heatsink plate was glued to the top of the transformer with silicone, some gentle prying released it. From the top, things don’t look too bad. There’s some filtering on the mains input & it’s even fused!
Primary Side
Here’s a closeup of the primary side of the PSU, the main DC bus capacitor is a Nichicon one, but it’s clearly been recovered from another device, look at the different glue on the end!
it’s also flapping about in the breeze, the squirt of silicone they’ve put on does nothing to stop movement.
Also here is the mains input fuse, filter capacitor & common mode choke. At least there is some filtering!
The main control IC is a UC3843B High Performance Current Mode PWM Controller, operating at a switching frequency of 250kHz.
The main switching transistor is visible at the bottom left corner, attached to the heatsink.
Secondary Side
Here’s the secondary side of the supply. The transformer itself is OK, nice heavy windings on the output to suit the high current.
It’s using proper opto-isolated feedback for voltage regulation, with a TL431 reference IC.
The output diodes are attached to the heatsink at the top of the photo, I couldn’t read any numbers on those parts.
The output filter capacitors are low quality, only time will tell if they survive. I’ll put the supply under full load & see what the temperature rise is inside the casing.
PCB Bottom
On the bottom of the PCB things get a little more dire. There isn’t really much of an isolation gap between the primary & secondary sides, and there’s a track joining the output negative with mains earth, which gets to within 2mm of the live mains input!
As with all these cheapo supplies, there’s good points & bad points, I will update when I’ve had a chance to put the supply under full load for a while & see if it explodes!
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.
Here’s the final bit of the radio install now the required parts have arrived!
The radio being inside, we needed a reliable way to route the antenna coax through the hull to the external antenna, I managed to find some N-type bulkhead connectors, that are perfect for this job:
Bulkhead Fitting
This fitting will allow for simple disconnection of the antenna for service, and N-type connectors are water resistant.
Hole
A hole was drilled in a suitable location with a cone drill. The steel here is pretty heavy, at 5mm. A spot between the handrail & the sliding roof was picked since there’s less chance of the fitting being knocked by any flying ropes, windlasses or crew members 😉
Bulkhead Connector
Here’s the connector fitted into it’s hole. The O-ring under the flange seals against the steel hull to prevent water getting through to the radio equipment on the other side.
Completed
Completed connection to the antenna. The short run to the radio underneath (~18″) is RG213, but I’ve used RG-58 on the antenna itself since it’s more flexible. The antenna is only a metre or so away so losses shouldn’t be much of an issue.
Following on from my recent power supply build, I’ve added on a couple of improvements:
Front Panel
I’ve added on my standard SpeakOn type 30A connector, a bank of push terminals for quick connecting test leads, and a 15A FSD ammeter.
Panel Rear
Due to the limited space inside the supply, I’ve had to improvise some insulation on the mains-side heatsink to prevent a nasty accident. The heatsinks are tied to the supply’s HVDC bus negative, so they are energized at -145v DC relative to mains earth. This fact has given me a nasty surprise! The insulation is several layers of Kapton tape, with a couple of layers of Duct Tape. This along with trirated wire to the SpeakOn & the panel meter should ensure safety.
The Ammeter itself was sourced from eBay, for £2. It seems pretty accurate so far!
Ammeter
The shunt is built into the rear of these meters, in an ultrasonically welded part of the case, so I can’t examine it. Hopefully it is indeed rated to 15A!
The only things left to make this supply complete are a mains power switch, and a fan speed control, as the fan I have used is a little noisy at full speed. It will be good to get the speed based from the internal temperature, so the fan only runs at full speed when the supply is under load.
In my shack, 99% of my gear is all 12v powered, which is good for a few reasons:
Single Power Supply – This increases efficiency, as I’m only getting the losses of a single supply.
Safety – Mains voltages are dangerous, I’m not fond of working on such equipment.
Portability – I can power everything pretty much no matter were I am from a convenient car battery.
Convenience – Since everything is single supply, with all the same plugs, I don’t have to think about what goes where. This is more important due to my forgetfulness ;).
The one piece of equipment I regularly use that isn’t 12v is my soldering station. This is a Maplin A55KJ digital unit, which uses a 24v heating element.
While the soldering wand works OK when hooked direct to a 12v power supply (only at half power though), this removes the convenience of having temperature control.
The circuitry inside the unit is PIC microcontroller based, and doesn’t even bother rectifying the AC from the supply transformer before it’s sent to the heater. Because of this there are several reasons why I can’t just hook a DC-DC converter up to it to give it 24v.
It’s sensing the zero-crossing for the triac switch, to reduce heat dissipation, so it refuses to work at all with DC.
On looking at the Great Google, I found a project on Dangerous Prototypes, an Arduino based PID controller for soldering irons.
This requires that the soldering wand itself contains a thermocouple sensor – as the Maplin one I have is a cheap copy of the Atten 938D, it doesn’t actually use a thermocouple for temperature sensing. It appears to read the resistance of the element itself – Nichrome heating elements change resistance significantly depending on temperature.
I’ve managed to find a source of cheap irons on eBay, with built in thermocouples, so I’ve got a couple on order to do some testing with. While I wait for those to arrive, I’ve prototyped up the circuit on breadboard for testing:
Prototype
I’ve remapped some of the Arduino pins, to make PCB layout less of a headache, but the system is working OK so far, with manual input for the sensed temperature.
I’m using an IRL520N logic-level HEXFET for the power switching, rated at 10A. As the irons only draw a max of 4.5A, this is plenty beefy enough.
To come up with the +24v supply for the heater, a small DC-DC converter will be used.
More to come when the components for the thermocouple amplifier arrive, and the soldering irons themselves!
I caught even more abuse on the local repeater this afternoon, this went on for a long time, into the early hours of the morning, having a conversation with himself as per usual. By the sounds of it alcohol was involved, the speech got more slurred as time went on. As usual, here’s the audio for your listening pleasure 🙂
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