The Engineer – Page 15 – Experimental Engineering

Posted on July 17, 2015July 17, 2015 by The Engineer — 2 Comments

Baofeng UV-5R RF Power Measurements

I’ve noticed that the RF power output from the Chinese radios can be quite variable from model to model, and even from individual radios of the same model & batch.
I’ve bought an RF Power meter (GY561) to do some tests on the HTs I have at present.

All tests were performed with the radio fully charged & still on the charging base, to make sure the supply voltage remained constant at 8.4v throughout the tests.
Frequencies used were 145.500 & 433.500 for VHF & UHF respectively.
The power meter was connected with ~8″ of RG174 Coax.

High Power:

UV-5R 1 (S/N: 13U1136132):
VHF: 6.3W
UHF: 4.9W

UV-5R 2 (S/N: 13U1136114):
VHF: 6.5W
UHF: 5.2W

UV-5R 3 (S/N: 130U541416):
VHF: 7.1W
UHF: 6.3W

Low Power:

UV-5R 1 (S/N: 13U1136132):
VHF: 2W
UHF: 1.2W

UV-5R 2 (S/N: 13U1136114):
VHF: 2.3W
UHF: 1.5W

UV-5R 3 (S/N: 130U541416):
VHF: 2.7W
UHF: 2.1W

Posted on July 16, 2015July 16, 2015 by The Engineer — 1 Comment

SainSmart Frequency Meter

Thanks to Lewis, M3HHY for lending me this one 🙂

Here’s a quick look at a Sainsmart frequency counter module. These are useful little gadgets, showing the locked frequency on a small LCD display.

It’s built around an ATMega328 microcontroller (µC), and an MB501L Prescaler IC. The circuit for this is very simple, and is easily traced out from the board.

Here’s the back of the board, with the µC on the left & the prescaler IC on the right. This uses a rather novel method for calibration, which is the trimmer capacitor next to the crystal. This trimmer varies the frequency of the µC’s oscillator, affecting the calibration.

Input protection is provided by a pair of 1N4148 diodes in inverse parallel. These will clamp the input to +/-1v.
The prescaler IC is set to 1/64 divide ratio. This means that for an input frequency of 433MHz, it will output a frequency of 6.765625MHz to the µC.

The software in the µC will then calculate the input frequency from this intermediate frequency. This is done because the ATMega controllers aren’t very cabable of measuring such high frequencies.

The calculated frequency is then displayed on the LCD. This is a standard HD44780 display module.

Power is provided by a 9v PP3 battery, which is then regulated down by a standard LM7805 linear regulator.

I’ve found it’s not very accurate at all at the lower frequencies, when I fed it 40MHz from a signal generator it displayed a frequency of around 74MHz. This is probably due to the prescaler & the software not being configured for such a low input. In the case for 40MHz input the scaled frequency would have been 625kHz.

Posted on July 16, 2015April 24, 2022 by The Engineer — 15 Comments

Wouxun KG-UV950P Band Unlocking

I have recently come across the software the Wouxun factory uses to set the band limits on the KG-UV950P.

While the software is in Chinese, it’s functional, and allows setting of all band limits on the radio.

Wouxun Band Unlocker

1 file(s) 1.29 MB

Download

Here’s an English version of the interface:

Note when using this software:

This possibly has the potential to damage the radio, if you transmit on a frequency it’s not designed for. Not to mention the legal issues with transmitting on frequencies that aren’t permitted! Use at your own risk!

Posted on July 14, 2015July 19, 2015 by The Engineer — 1 Comment

Cisco PSU Hack & Switched Mode PSU Background

Recently I decommissioned some networking equipment, and discovered the power supplies in some switches were single rail 12v types, with a rather high power rating. I figured these would be very good for powering my Ham radio gear.

They’re high quality Delta Electronics DPSN-150BP units, rated at a maximum power output of 156W.

These supplies have an adjustment pot for the output voltage regulation, but unfortunately it just didn’t have quite enough range to get from 12.0v to 13.8v. The highest they would go was ~13.04v.

After taking a look at the regulator circuit, I discovered I could further adjust the output voltage by changing a single resistor to a slightly lower value.

Firstly though, a little background on how switched mode power supplies operate & regulate their output voltage.

Here’s the supply. It’s mostly heatsink, to cool the large power switching transistors.

The first thing a SMPS does, is to rectify the incoming mains AC with a bridge rectifier. This is then smoothed by a large electrolytic capacitor, to provide a main DC rail of +340v DC (when on a 240v AC supply).

Above is the mains input section of the PSU, with a large common-mode choke on the left, bridge rectifier in the centre, and the large filter capacitor on the right. These can store a lot of energy when disconnected from the mains, and while they should have a discharge resistor fitted to safely drain the stored energy, they aren’t to be relied on for safety!

Once the supply has it’s main high voltage DC rail, this is switched into the main transformer by a pair of very large transistors – these are hidden from view on the large silver heatsinks at the bottom of the image. These transistors are themselves driven with a control IC, in the case of this supply, it’s a UC3844B. This IC is hidden under the large heatsink, but is just visible in the below photo. (IC5).

Here’s the main switching transformer, these can be much smaller than a conventional transformer due to the high frequencies used. This supply operates at 500kHz.
After the main transformer, the output is rectified by a pair of Schottky diodes, which are attached to the smaller heatsink visible below the transformer, before being fed through a large toroidal inductor & the output filter capacitors.
All this filtering on both the input & the output is required to stop these supplies from radiating their operating frequency as RF – a lot of cheap Chinese switching supplies forego this filtering & as a result are extremely noisy.

After all this filtering the DC appears at the output as usable power.

Getting back to regulation, these supplies read the voltage with a resistor divider & feed it back to the mains side control IC, through an opto-isolator. (Below).

The opto isolators are the black devices at the front with 4 pins.

For a more in-depth look at the inner workings of SMPS units, there’s a good article over on Hardware Secrets.

My modification is simple. Replacing R306 (just below the white potentiometer in the photo), with a slightly smaller resistor value, of 2.2KΩ down from 2.37KΩ, allows the voltage to be pulled lower on the regulator. This fools the unit into applying more drive to the main transformer, and the output voltage rises.

It’s important to note that making too drastic a change to these supplies is likely to result in the output filter capacitors turning into grenades due to overvoltage. The very small change in value only allows the voltage to rise to 13.95v max on the adjuster. This is well within the rating of 16v on the output caps.

Now the voltage has been sucessfully modified, a new case is on the way to shield fingers from the mains. With the addition of a couple of panel meters & output terminals, these supplies will make great additions to my shack.

More to come on the final build soon!

Posted on July 11, 2015July 11, 2015 by The Engineer — 1 Comment

Simple Dishwasher Repair

Earlier today, one of my neighbours put their dishwasher out for the scrap man. After asking if I could appropriate it in the interest of recycling the Ham Way™, I was told it wasn’t draining. The engineer called out to fix it had claimed it was beyond economical repair.

A quick test showed that indeed the drain pump wasn’t operating correctly – very poor pumping capacity & a horrid grinding noise.

Here is the drain pump on the bottom of the machine. Strangely for a dishwasher, everything underneath is very clean & free from corrosion.

On removing the securing screw & unlatching the pump from it’s bayonet mount, the impeller instantly tried to make a break for freedom – it has come off the splines of the rotor shaft.

In the past I’ve tried to remove these rotors manually – and totally destroyed the pump in the process. They are usually so well secure that replacement is the only option. This particular one must have vibrated off the shaft somehow.

This repair was easy – removing the rotor from the main pump body & gently drifting the impeller back onto the splines.

Here the pump is reassembled & ready for reinstallation.

On test the pump sounds normal, & works as expected.

Engineer 1 : 0 Throwaway Society

Posted on July 8, 2015February 25, 2017 by The Engineer — 3 Comments

Arduino Based SWR/PWR Meter – The Board

I recently posted about a small analog SWR/Power meter I got from eBay, and figured it needed some improvement.

After some web searching I located a project by ON7EQ, an Arduino sketch to read SWR & RF power from any SWR bridge.
The Arduino code is on the original author’s page above, his copyright restrictions forbid me to reproduce it here.

I have also noticed a small glitch in the code when it is flashed to a blank arduino: The display will show scrambled characters as if it has crashed. However pushing the buttons a few times & rebooting the Arduino seems to fix this. I think it’s related to the EEPROM being blank on a new Arduino board.

I have run a board up in Eagle for testing, shown below is the layout:

The Schematic is the same as is given on ON7EQ’s site.
Update: ON7EQ has kindly let me know I’ve mixed up R6 & R7, so make sure they’re switched round when the board is built ;). Fitting the resistors the wrong way around may damage the µC with overvoltage.

Here’s the PCB layout. I’ve kept it as simple as possible with only a single link on the top side of the board.

Here’s the freshly completed PCB ready to rock. Arduino Pro mini sits in the center doing all the work.
The link over to A5 on the arduino can be seen here, this allows the code to detect the supply voltage, useful for battery operation.
On the right hand edge of the PCB are the pair of SMA connectors to interface with the SWR bridge. Some RF filtering is provided on the inputs.

Trackside view of the PCB. This was etched using my tweaked toner transfer method.

Here the board has it’s 16×2 LCD module.

Board powered & working. Here it’s set to the 70cm band. The pair of buttons on the bottom edge of the board change bands & operating modes.
As usual, the Eagle layout files are available below, along with the libraries I use.

[download id=”5585″]

[download id=”5573″]

More to come on this when some components arrive to interface this board with the SWR bridge in the eBay meter.

Posted on July 7, 2015 by The Engineer — Leave a comment

Mobile Radio Shack Bag

There are times when I am frequently away from home base, usually either on the canal system or at a festival. During these times it’s very handy to be able to just grab a bag, without having to be concerned about sorting everything out.

This post will only detail the portable shack bag. The power supply kit that goes along with it with be detailed in another post.

The bag I use is an VHS Camcorder bag from the early 80’s. It’s very well built, & copes easily with the weight of all the radio gear.

Total weight for this system is 13.4lbs (6kg).

Above is the bag packed. Obligatory International Ameteur Radio Symbol patch front & centre. Being an old camera bag, this easily slings over the shoulder, with it’s padded strap.

Here is all the current equipment laid out. All the equipment to enable me to set up a station anywhere.
In the following photos I will go into the details.

First off, my main radio. This is the same Wouxun KG-UV950P mobile rig I have posted about previously. I have heatshrunk the power cable to keep it together & attached my standard power connector to the end. More on these later on.

In the bag I also carry three Baofeng UV-5R handhelds. Extremely useful for short range site communications, along with their charger bases. The charging base on the right has been slightly modified to support charging of my main LED torch as well, which uses similar Li-Ion based packs as the Baofengs.

As the charger bases for the Baofeng HTs take a supply of 10v DC, I have constructed a 12v adaptor system for them. (Which utter prat of an engineer at Baofeng picked 10v?)

Also included is a small Alinco ELH-2320 35W 2m linear amplifier. This was given to me from the local HackSpace in Manchester. (They don’t have any ham members, besides myself). Also here is my small SWR & Power meter, SDR kit & a pair of syringes. These are filled respectively with Copaslip copper loaded grease, (very good for stopping fasteners exposed to the weather from seizing up), and dielectric silicone grease. (I use this stuff for filling connectors that are exposed to the weather – keeps the water out).

I always keep essential tools in the bag, here is the small selection of screwdrivers which fit pretty much any screw fastener around, my heavy-duty cable shears (these buggers can cut through starter cable in one go!) and my trusty Gerber Diesel multitool.

Main antenna magmount & a spare Raspberry Pi.

Finally, the antennas for the HTs, main dual-band antenna (Nagoya SP-45) for the magmount, a small selection of spare plugs, sockets & adaptors. Also here is a roll of self-amalgamating tape, very handy for waterproofing wiring connections (especially when used in conjunction with the silicone grease), & a roll of solder wick.

Now, the main power connectors of choice for my equipment are Neutrik SpeakOn type connectors:

These connectors have many advantages:

They are positive locking connectors. No more loose connections.
They have a high continuous current rating of 30A RMS.
Relatively weather resistant.

Also, they have two pairs of pins – and as some of my bigger non-radio related equipment is 24v, this allows me to use a single set of plugs for everything. Without having to worry about plugging a 12v device into a 24v socket, and letting out the magic blue genie.

Once everything is packed up, here’s the bag:

Everything has a neat little pocket for easy access. Some closeups below.

I will post more about my portable power system later on, as this bit of my kit is being revamped at the moment.

Stay tuned!

Posted on July 5, 2015 by The Engineer — Leave a comment

Wouxun KG-UV950P RF Connector Replacement

In my original review, I noted that this radio was supplied with a SO-259 socket for the antenna connection.
However I’m less than fond of these, due to their non-constant impedance, which can cause signal loss issues at VHF/UHF. Because of this, I’ve replaced it with a high quality N-type connector. These connectors are much better, as they are a constant 50Ω impedance, they’re weather resistant, and being rated to 11GHz, are more than sufficient for a radio that will only do up to 70cm.

Here can be seen the point where the connection is made to the PCB.
I’ve already replaced the socket in this photo. The pair of solder pads either side of the central RF point were soldered to wings on the back of the original SO-259. As there are a pair of screws, also connected to the ground plane, there have been no signal issues with just using the frame of the radio as the ground point. Shown below is the original socket, with the ground wings.

Finally, here is the back of the radio with it’s shiny new N connector.

Chassis mount connectors are pretty standard, so this new connector fits perfectly into the same recess of the original. Looks like factory fitted!

I am now standardising on N connectors for everything in my radio shack, next on the project list for conversion is the SWR meter I recently acquired.

Stay tuned for more!

Posted on July 5, 2015 by The Engineer — Leave a comment

Wouxun KG-UV950P Teardown & Analysis

Following on from my review, here are some internal views & detail on the components used in this radio. Below is an overview of the main PCB with the top plate removed from the radio.

Most visible are these MOSFETs, which are Mitsubishi RD70HVF1 VHF/UHF power devices. Rated for a maximum of 75W output power at 12.5v (absolute maximum of 150W, these are used well within their power ratings. They are joined to the PCB with heavy soldering, with bypass caps tacked right on to the leads.

Here is the RF pre-driver stage, with intermediate transistors hidden under the small brass heatspreader.

In the top left corner of the radio, near the power input leads, is the power supply & audio amplifier section. Clearly visible are the pair of LA4425A 5W audio power amplifier ICs, these drive the speakers on the top of the radio. Either side of these parts are a 7809 & a 7805 – both linear regulators providing +9v & +5v logic supplies respectively. The large TO220 package device is a KIA378R08PI 3A LDO regulator with ON/OFF control, this one outputs +8v. Just visible in the top right corner are the sockets for the speaker connections.

Here are the two ICs for dealing with DTMF tones, they are HM9170 receivers.

In the corner next to the interface jack, there are some CD4066B Quad Bilateral switches. These make sense since the interface jack has more than a single purpose, these will switch signals depending on what is connected.

Here are visible the RF cans for the oscillators, the crystals visible next to the can at the top. The shields are soldered on, so no opening these unfortunately.
Also visible in this image is a CMX138A Audio Scrambler & Sub-Audio Signalling processor. This IC deals with the Voice Inversion Scrambling feature of the radio, & processes the incoming audio before being sent to the modulator.

Shown here is the RF output filter network, this radio uses relays for switching instead of PIN diodes, I imagine for cost reasons. The relay closest to the RF output socket has had a slight accident 🙂 This is slated to be replaced soon.

Finally, the RF output jack.

Here the speakers are shown, attached to the bottom of the top plate. They are both rated 8Ω 1W.

Posted on July 2, 2015 by The Engineer — Leave a comment

Moonraker SWR270 SWR & Power Meter

As I’m building up my radio shack, I figured an SWR meter would be a handy addition to my arsenal. This is a cheap Moonraker brand meter, which also will measure RF power. Above the front of the meter is shown, with the moving coil meter movement on the left, calibration adjustment on the right & the forward/reverse power switch.

For connections, standard SO-259 jacks are provided. The casing is sturdy 1mm steel. This is good, considering it’ll probably take a beating in my portable radio bag.

Here the cover is removed, showing some of the internals. The large PCB across the back is the directional coupler.

The SO-259 connectors are bridged with a transmission line, (the track covered in solder in the image below), while there are a pair of sense lines running alongside. This main line is electromagnetically coupled to the two smaller sense lines, which are terminated at one end with resistors, with diodes at the other to rectify the coupled signal.
The termination resistors are sized to match the impedance of the sense lines.
The diodes, having rectified the coupled RF, produce DC voltages representing the value of the forward & reverse RF power. These DC voltages are smoothed with the capacitors.

The PCB is dated 19-8-2011, so it’s a fairly old design.

Here is visible the back of the user calibration adjuster, with the factory calibration trimmer.

Back of the meter movement. This is a standard moving coil type. Nothing special.

This meter will soon be modified to accept connection of an external Arduino-based SWR & power meter, which I can calibrate individually for each band.
Stay tuned for that upcoming project.

Posted on June 30, 2015July 1, 2015 by The Engineer — 2 Comments

Wouxun KG-UV950P Radio

After running on handies for all of my Ameteur Radio life, I figured it was time for a new radio, this time a base station/mobile rig, & after some looking around I decided on the Wouxun KG-UV950P.

Shown below is the radio as delivered:

This radio has the capability to transmit quad-band, on 6m, 10m, 2m & 70cm. It also has the capability to receive on no fewer than eight bands. Also included in the feature set is airband receive, & broadcast FM receive.
TX power is up to 50W on 2m, 40W on 70cm, & 10W on 6m/10m.

For once with a Chinese piece of electronic equipment, the manual is very well printed, and in very good English.

Here is the radio in operation, connected to my 65A 12v power supply. I have the radio set here monitoring a couple of the local 70cm repeaters.
The display is nice & large – easy to see at a glance which station you’re tuned to. The backlight is also software settable to different colours.
Status indicators on the top edge of the display can be a bit difficult to see unless the panel is directly facing the user though, not to mention that they are rather small.

This radio is true dual-watch, in that both VFOs can be receiving at the same time, this is effected by a pair of speakers on the top panel:

The left VFO speaker is smaller than the right, so the sound levels differ slightly, but overall sound quality is excellent. There is also provision on the back of the unit to connect external speakers.
The dual volume controls on the right hand bottom corner of the control panel are fairly decent, if a little twitchy at times. There is also a fair amount of distortion on the audio at the higher volume levels.
The controls themselves are potentiometers, but the controller appears to read the setpoint with an ADC – this means that if the control is set to just the right point, the selected level will jump around on the display & never settle down.

The radio itself is built from a solid aluminium casting, mostly for heatsinking of the main RF output stage MOSFETs. This gives the radio a very rugged construction.
A small fan is provided on the rear for cooling when required. This can be set in software to either be constantly running, (it’s pretty much silent, so this is advantageous), or only run when in TX mode. The fan will also automatically come on when a high internal temperature is detected.

Here is the microphone. Like the main unit of the radio this is also very solidly built, fits nicely in the hand & the PTT has a nice easy action, which helps to prevent straining hands while keeping the TX keyed.
Conveniently, all of the controls required to operate the radio are duplicated on this mic, along with a control lock switch, & backlighting for the buttons.

Another output speaker is placed in the back of the mic. This one can be activated through the menu system, to either use the main body speakers, the mic mounted one, or both.
A mounting hook for the mic is provided to attach to any convenient surface.

Here’s the back of the radio, with some of the big heatsink fins, the fan in the centre. To the left is the PL259 RF output, this looks to be a high quality Teflon insulated one. On the right are the power input leads & the external speaker outputs.

The external speaker connections are via 3.5mm jacks. I haven’t yet tested this feature.

The control panel of this radio is detachable from the main body, and a pair of adaptors are provided. This either allows the radio display to be angled upwards toward the user, set parallel, or even mounted remotely. A control extension cable is provided to allow the main body to be mounted a fair distance away.

On the left of the radio is the PC control & programming port, & the mic connector. Wouxun *really* like RJ-45 connectors, they’ve used them for everything on this radio.
Also visible here is the tilted faceplate adaptor.

The supplied software to program the radio, while functional, is absolutely horrific. Hopefully someone will add support for this radio into CHIRP. Anything would be an improvement in this area.

Everything considered, I like this radio. It’s very solidly built, easy to use, and sounds brilliant.
TX audio is great, (or so my other contacts tell me).

Unsurprisingly, the unit gets warm while transmitting, however on high power, it does get uncomfortably warm, and the built in fan does little in the way of helping when a long QSO is in progress. I may remedy this at some stage with a more powerful fan. A little more airflow would do wonders.
If the programming software was built as well as the radio, I’d have zero serious complaints.

At full power, the radio pulls ~10A from the power supply, at 12.9v DC.

As for the antenna I’m currently using, it’s a Diamond X30, mounted on a modified PA speaker stand, at ~30 feet above ground. The feeder is high quality RG-213.

When I manage to get the set disconnected, a partial teardown will be posted, with some intimate details about the internals. Stay tuned!

Posted on May 2, 2015May 2, 2015 by The Engineer — Leave a comment

Precision 10v & 5v Reference

After watching a video over at Scullcom Hobby Electronics on YouTube, I figured I’d build one of these precision references to calibrate my multimeters.

It’s based around a REF102P 10v precision reference & an INA105P precision unity gain differential amplifier.

For full information, check out the video, I won’t go into the details here, just my particular circuit & PCB layout.

In the video, Veroboard is used. I’m not too fond of the stuff personally. I find it far too easy to make mistakes & it never quite looks good enough. To this end I have spun a board in Eagle, as usual.

Here’s the schematic layout, the same as is in the video.

As usual, the Eagle CAD layout files can be found at the bottom of the post.

And the associated PCB layout. I have added the option to be able to tweak the output, to get a more accurate calibration, which can be added by connecting JP1 on the PCB.

As in the original build, this unit uses pre-built DC-DC converter & Li-Ion charger modules. A handy Eagle library can be found online for these parts.
I have however left off the battery monitor section of the circuit, since I plan to use a protected lithium cell for power. This also allowed me to keep the board size down, & use a single sided layout.

Here’s the track layout ready to iron onto the copper clad board. I use the popular toner transfer system with special paper from eBay, this stuff has a coating that allows the toner to easily be transferred to the PCB without having to mess about with soaking in water & scraping paper off.

Here’s the paper having just been ironed onto the copper. After waiting for the board to cool off the paper is peeled off, leaving just the toner on the PCB.

PCB just out of the etch tank, drilled & with the solder pins for the modules installed. Only one issue with the transfer, in the bottom left corner of the board is visible, a very small section of copper was over etched.
This is easily fixed with a small piece of wire.

Main components populated. The DC-DC converter is set at 24v output, which the linear regulator then drops down to the +15v rail for the reference IC. The linear section of the regulator, along with the LC filter on the output of the switching regulator produce a low-ripple supply.

Here’s the scope reading the AC ripple on the output of the DC-DC converter. Scale is 100mV/Div. Roughly 150mV of ripple is riding on top of the DC rail.

And here’s the output from the linear regulator, scale of 50mV/Div. Ripple has been reduced to ~15mV for the reference IC.
In total the circuit as built has a power consumption of ~0.5W, most of which is being dissipated as heat in the linear part of the PSU.

[download id=”5583″]

Posted on April 12, 2015October 16, 2019 by The Engineer — Leave a comment

Another Viewfinder CRT

Here’s another viewfinder CRT, removed from a 1980’s vintage VHS camera I managed to get cheap from eBay.

This unit is very similar to the last one I posted about, although there are a few small differences in the control circuitry.

Viewfinder Schematic – Click to Embiggen

Here’s the schematic, showing all the functional blocks of the viewfinder circuitry. An integrated viewfinder IC is used, which generates all the required scan waveforms for the CRT.
On the left is the input connector, with the power & video signals. Only pins 2 (GND), 3 (Composite video), & 4 (+8v) are needed here. Pin 1 outputs a horizontal sync signal for use elsewhere in the camera, while pin 5 fed the recording indicator LED.

To make connection easier, I have rearranged the wires in the input connector to a more understandable colour scheme:

Red & Blue for power input, & a coax for the video. For the video GND connection, I have repurposed the Rec. LED input pin, putting a shorting link across where the LED would go to create a link to signal ground. Keeping this separate from the power GND connection reduces noise on the CRT.

Here’s the complete assembly liberated from it’s plastic enclosure.

Closeup of the control PCB. The 3 potentiometers control the CRT brightness, focus & vertical size.

The tiny CRT. Only ~60mm in length, with an 18mm screen size. This tube runs on +2294v final anode voltage. Much higher than I expected.

The electron gun assembly, with the cathode, focus & final anode cups.

This screen is just a little bigger than a UK 5p piece! A marvel of precision engineering.

Posted on April 10, 2015January 3, 2021 by The Engineer — 2 Comments

Active Ultracapacitor Balancing

Here’s another active balancing circuit for large ultracapacitor banks, this one is designed for a series string of 6, at 2.5v per capacitor.

Based on the design here, I have transcribed the circuit into Eagle & designed a PCB layout.

Ultracap Balancer Circuit – Click to Embiggen

As can be seen from the circuit diagram above, this is just 6 copies of the circuit from the above link, with screw terminals to attach to the capacitor string.

And here’s the PCB. the MOSFETs & OpAmps are very small SMT parts, so require a steady hand in soldering. This board can easily be etched by hand as there’s only 3 links on the top side. No need for a double sided PCB.

As always, the Eagle project files & my Eagle library collection are available below:

Ultracapacitor Balance Files

1 file(s) 0.00 KB

Download

Eagle Libraries

1 file(s) 0.00 KB

Download

Posted on April 7, 2015October 16, 2019 by The Engineer — 7 Comments

3″ CRT Composite Monitor

I recently managed to score a 3″ B&W portable TV on eBay, a Panasonic TR-3000G. As these old units are now useless, thanks to the switch off of analogue TV signalling, I figured I could find a composite signal internally & drive the CRT with an external source.

Here’s the TV in it’s native state. Running from 9v DC, or 6 D size cells. I’m guessing from somewhere around the 1970’s. Here is the CRT & associated drive circuitry, removed from the casing:

After dissecting the loom wiring between the CRT board & the RF/tuner board, I figured out I had to short out Pins 1,2 & 5 on the H header to get the CRT to operate straight from the power switch. This board also generates the required voltages & signals to drive the RF tuner section. I have removed the loom from this, as the PCB operates fine without. It doesn’t seem to be fussy about power input either: it’s specified at 9v, but seems to operate fine between 7.5v & 14.5v DC without issue.

Tracing the wiring from the tuner PCB revealed a length of coax snaking off to the section marked Video/Sync. I successfully found the composite input!

A quick bit of wiring to a Raspberry Pi, & we have stable video! For such an old unit, the picture quality is brilliant, very sharp focus.

Closeup of the CRT itself. I haven’t been able to find much data on this unit, but I’m guessing it’s similar to many commercial viewfinder CRTs.

Amazingly, there isn’t a single IC in the video circuitry, it’s all discrete components. This probably accounts for the large overall size of the control PCB. Viewfinder CRTs from a few years later on are usually driven with a single IC & a few passives that provide all the same functions.

Posted on January 28, 2015January 29, 2015 by The Engineer — 2 Comments

Roving Networks RN-52 Bluetooth Audio

I’ve been doing some tinkering with the RN-52 Bluetooth Audio module from Roving Networks, in prep for building a portable wireless speaker system, & thought I’d share my designs.

Initially I was having some issues with RF noise on the audio output from the RN-52, as I was only using the outputs single-ended. The module didn’t like this treatment, with all the RF whine coming straight out of the speakers.

To fix this issue I have used a pair of jellybean LM386 audio power amplifiers, running in differential input mode. This solves the high-pitched whine when the audio is enabled, & also allows the module to directly drive a set of 32Ω headphones at a reasonable level.

In Eagle I have designed a simple board, routing only the audio output, serial TTL & command mode pins out, along with the supporting power supply circuitry to operate from 12v DC.

Above is the current incarnation of the circuit on the breadboard. The RN-52 is on the left, audio power stage in the centre & headphone output on the right.

The bluetooth module on a breakout board. I was cheap in this case & etched my own board. I’m not paying Sparkfun, (as much as I like them), an extra ~£10 for a small PCB with the pins broken out. Much cheaper to spend 15 minutes with the laser printer & the iron, & do a toner transfer PCB.
As this board is single sided, I added a ground plane on the underside with copper foil, to help with the RF issues. Breadboards really aren’t all that good at rejecting noise induced when there’s a 2.4GHz transceiver mounted on them.

The LM386 audio power stage. The differential inputs from the module are capacitively coupled with 1µF electrolytics. This setup remarkably reduced the noise on the output. I left these at their default gain of 20, as I’ll be connecting another high power amplifier stage to drive large speakers.

Here’s the circuit laid out in Eagle, ready for PCB.

And here’s the PCB layout. Only one link required for the +5v line from the TTL serial port.

As always, the Eagle PCB & Schematic layout files are available at the bottom of the article.

*Update 29-01-15*
Rerouted a few things:

Moved the audio power stage to the +12v rail to improve sound response. – As the LM386 has a max input voltage of 12v (absolute maximum 15v), a regulated supply is recommended. The LM386-N4 variant has a higher voltage range, up to 18v. This should be suitable for an unregulated supply.
Removed 1µF coupling capacitors to reduce distortion & amplifier hiss. The capacitors appeared to cause some instability on the amplifier, causing random distortion. Removing them has cured this. No signal hiss has also been reduced to a very low level.
Reversed input polarity on input of one of the amplifiers – this appears to produce better audio.
Added PWR.EN header to allow connection of power button. Saves hassle of cycling power to the board when the RN-52 goes into sleep mode.

Improved PCB & Schematic layouts.

[download id=”5579″]

Posted on December 11, 2014December 11, 2014 by The Engineer — Leave a comment

uRadMonitor – Node Online!

It’s official. I’m now part of the uRadMonitor network, & assisting in some of the current issues with networking some people (including myself) have been having.

It seems that the uRadMonitor isn’t sending out technically-valid DHCP requests, here is what Wireshark thinks of the DHCP on my production network hardware setup:

As can be seen, the monitor unit is sending a DHCP request of 319 bytes, where a standard length DHCP Request packet should be ~324 bytes, as can be seen on the below screen capture.

This valid one was generated from the same SPI Ethernet module as the monitor, (Microchip ENC28J60) connected to an Arduino. Standard example code from the EtherCard library was used to set up the DHCP. The MAC address of the monitor was also cloned to this setup to rule out the possibility of that being the root cause.

My deductive reasoning in this case points to the firmware on the monitor being at fault, rather than the SPI ethernet hardware, or my network hardware. Radu over at uRadMonitor is looking into the firmware being at fault.

Strangely, most routers don’t seem to have an issue with the monitor, as connecting another router on a separate subnet works fine, and Wireshark doesn’t even complain about an invalid DHCP packet, although it’s exactly the same.

As the firmware for the devices isn’t currently available for me to pick apart & see if I can find the fault, it’s up to Radu to get this fixed at the moment.

Now, for a µTeardown:

Here is the monitor, a small aluminium box, with power & network.

Removing 4 screws in the end plate reveals the PCB, with the Geiger-Mueller tube along the top edge. My personal serial number is also on the PCB.
The ethernet module is on the right, with the DC barrel jack.

Here is the bottom of the PCB, with the control MCU & the tiny high voltage inverter for the Geiger tube.

A Closeup of the main MCU, an ATMega328p

Logo

PCB Logo. Very artsy 😉

Posted on December 9, 2014December 9, 2014 by The Engineer — Leave a comment

Lying Again Are We? (Mike Webb Of Hydraulicgenerators.co.uk)

Regular readers might remember a previous post about the fiasco we have had with a hydraulic generator, and in particular one person by the name of Mike Webb.

Well here we are a year down the line. The generator still doesn’t function properly, as other things have taken priority, but this is being remedied this week with a replacement hydraulic powerhead. (Correctly sized to 6cc this time, not 11cc).

I even finally got a response from Mike, most likely due to my previous post & the negative publicity that would have brought. In July Mike wrote this:

Good Morning Ben,

I have read your article on the above website, not entirely sure what I can say.

I do however sincerely apologise for the way I handled things, I could give numerous reasons, but I guess they are not your concern, I behaved badly and I am disappointed in myself for treating anyone in this way.

The business has now folded, the domain name www.hydraulicgenerators.co.uk and related products are now owned, manufactured and sold by another company.

My only hope now is that I can in some way repair the damage that has been done and hope that somewhere within yourself you can find a way to accept my apology and forgive me, I am genuinely not a bad person but circumstances outside of my control at the time led me to act in an inacceptable way.

I can understand how you feel, I was defrauded out of a considerable amount of money a while ago and seeking revenge has not been far from my mind for a considerable time, but it won’t get my money back, it won’t undo the damage that has already been done and whilst I might feel better about it for a short while, I have found it difficult from a personal perspective, as, whilst you may cast aspersions about me, my conscience and I do have one just won’t allow me, I can’t help myself from thinking of the other people that would be impacted upon that are otherwise innocent and I know in this particular instance there are several.

I can only hope that you accept my most sincere apology.

Right then. Where should I begin.

No Mike, I will never EVER forgive someone for, what was in my eyes, a deliberate act of fraud & a complete refusal to co-operate.

Now, being the resourceful person I am, and my ability (like anyone else with brains), to find out the registrar of domain names, have discovered the man is yet again lying. Company folded? I think not my son.

Two other domain names have popped up with Mike’s name on the Registrar details:
ukgenerators.co.uk
shop4generators.co.uk

(For completeness, here are the full registrar details, just in case things change after I publish this. This information is correct as of 9/12/14)

Domain name:
ukgenerators.co.uk

Registrant:
Mike Webb

Registrant type:
UK Individual

Registrant’s address:
<REDACTED>

Data validation:
Registrant contact details validated by Nominet on 10-Dec-2012

    Registrar:
        LCN.com Ltd [Tag = LCN]
        URL: http://www.lcn.com

    Relevant dates:
        Registered on: 06-Feb-2004
        Expiry date: 06-Feb-2016
        Last updated: 16-Jan-2014

Registration status:
Registered until expiry date.

    Name servers:
        ns1.hostpapa.com
        ns2.hostpapa.com

WHOIS lookup made at 16:56:14 09-Dec-2014

Domain name:
shop4generators.co.uk

Registrant:
Mike Webb

Registrant type:
UK Individual

    Registrant’s address:
        The registrant is a non-trading individual who has opted to have their
        address omitted from the WHOIS service.

Data validation:
Registrant contact details validated by Nominet on 10-Dec-2012

    Registrar:
        Webfusion Ltd t/a 123-reg [Tag = 123-REG]
        URL: http://www.123-reg.co.uk

    Relevant dates:
        Registered on: 02-Jun-2005
        Expiry date: 02-Jun-2015
        Last updated: 27-Jun-2013

Registration status:
Registered until expiry date.

    Name servers:
        ns1.hostpapa.com
        ns2.hostpapa.com

WHOIS lookup made at 16:55:43 09-Dec-2014

Now for someone who is obviously attempting to tell me that he has no money or resources to reimburse us for the utter hell we have been put through in this situation, seems to be doing pretty well for themselves, in the same business that has apparently ‘folded’.
You have a shiny new logo & business name, and yet apparently have ceased trading?
Now, having been part of a firm during a takeover/company sale, domain names are usually immediately transferred into the name of the buying company. Not in this case it seems. All domains are still registered to you.
Your LinkedIn account still has you as being in the business, along with your Twitter account & YouTube account.
Not to mention, that one one of the aforementioned sites (the original hydraulicgenerators.co.uk), Mike’s E-Mail address is still very much visible on the front page E-Mail Link!

Despite all this evidence of continued trading, according to Companies House, the company is in fact in liquidation: http://data.companieshouse.gov.uk/doc/company/06770818

If this is the case, then Mike Webb is in fact operating illegally.

Mike, if you do read this, I AM NOT AN IDIOT. All I asked was that you put things right, so we would have a WORKING GENERATOR.
So far all this has cost is time & money, and I certainly don’t like being conned.
However I feel it is my duty to make sure that anyone who ever has the misfortune of dealing with you knows exactly what you have previous form for doing.

Legal notice:
All information contained in this post is correct as of 9/12/14. Information will be kept up to date & factually correct to the best of my ability.

Stay tuned for the final chapter in getting this generator fitted & working.

Posted on November 25, 2014November 26, 2014 by The Engineer — Leave a comment

Quantum LTO2 CL1001 Tape Drive Teardown

I have recently begun to create an archive of all my personal data, and since LTO2 tape drives offer significant capacity (200GB/400GB) per tape, longevity is very high (up to 30 years in archive), & relatively low cost, this is the technology I’ve chosen to use for my long term archiving needs.

Unfortunately, this drive was DOA, due to being dropped in shipping. This drop broke the SCSI LVD connector on the back of the unit, & bent the frame, as can be seen below.

As this drive is unusable, it made for a good teardown candidate.

Here the top cover of the drive has been removed, showing the top of the main logic PCB. The large silver IC in the top corner is the main CPU for the drive. It’s a custom part, but it does have an ARM core.

The two Hitachi ICs are the R/W head interface chipset, while the smaller LSI IC is the SCSI controller.
The tape transport & loading mech can be seen in the lower half of the picture.

Close up of the main logic.

Here the main logic PCB has been removed, showing the tape take up spool. The data cartridges have only one spool to make the size smaller. When the tape is loaded, the drive grabs onto the leader pin at the end of the tape & feeds it onto this spool.
The head assembly is just above the spool.

Bottom of the drive with the cover plate removed. Here the spindle drive motors are visible, both brushless 3-Phase units. Both of these motors are driven by a single controller IC on the other side of the lower logic PCB.

The head is moved up & down the face of the tape by this stepper motor for coarse control, while fine control is provided by a voice coil assembly buried inside the head mount.

The face of the tape R/W head. This unit contains 2 sets of 8 heads, one of which writes to the tape, the other then reads the written data back right after to verify integrity.

The tape cartridge loading motor. I originally thought that this was a standard brushed motor, but it has a ribbon cable emerging, this must be some sort of brushless arrangement.

A replacement drive is on the way, I shall be documenting some more of my archiving efforts & system setup once that unit arrives.

Posted on November 22, 2014 by The Engineer — 1 Comment

Superhub Buffer Overflow?

While checking my Virgin Media-provided router recently, I came across this in the status page:

According to this, it seems to think it’s been running for a grand total of 44.8 years, without a reboot. I’m pretty certain that DOCSIS didn’t exist that long ago, let alone the hardware itself…
Tech Fail

Posted on November 20, 2014 by The Engineer — Leave a comment

ZyXel WAP3205 Repair

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.

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:

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 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!

Posted on November 20, 2014November 20, 2014 by The Engineer — Leave a comment

uRadMonitor Network

I’ve joined the uRadMonitor network! I’m told my unit is on the way & it should be going live here in Manchester, UK within about 10 days.

This is a crowd project to monitor background radiation levels all over the world, so far there’s a lot of units already online.

More to come once my unit arrives!

Posted on November 17, 2014 by The Engineer — Leave a comment

LDR Controlled Relay

Here’s a quick project for nightlight use: an LDR controlled relay.

Powered from 12v DC, this circuit uses an LM311 comparator to switch the relay according to the sensitivity set by the potentiometer.

Eagle files can be downloaded below.

[download id=”5577″]

Posted on November 7, 2014November 7, 2014 by The Engineer — Leave a comment

AD9850 VFO Board

Continuing from my previous post where I published an Eagle design layout for AD7C‘s Arduino powered VFO, here is a completed board.

I have made some alterations to the design since posting, which are reflected in the artwork download in that post, mainly due to Eagle having a slight psychotic episode making me ground one of the display control signals!

The amplifier section is unpopulated & bypassed as I was getting some bad distortion effects from that section, some more work is needed there.
The Arduino Pro Mini is situated under the display, and the 5v rail is provided by the LM7805 on the lower left corner.

Current draw at 12v input is 150mA, for a power of 1.8W total. About 1W of this is dissipated in the LM7805 regulator, so I have also done a layout with an LM2574 Switching Regulator.
The SMPS version should draw a lot let power, as less is being dissipated in the power supply, but this version is more complex.

Here the SMPS circuit can be seen on the left hand side of the board, completely replacing the linear regulator.
I have not yet built this design, so I don’t know what kind of effect this will have on the output signal, versus the linear regulator. I have a feeling that the switching frequency of the LM2574 (52kHz) might produce some interference on the output of the DDS module. However I have designed this section to the standards in the datasheet, so this should be minimal.

Nevertheless this version is included in the Downloads section at the bottom of this post.

The output coupled through a 100nF capacitor is very clean, as can be seen below, outputting a 1kHz signal. Oscilloscope scale is 0.5ms/div & 1V/div.

Thanks again to Rich over at AD7C for the very useful tool design!

Linked below is the Eagle design files for this project, along with my libraries used to create it.

[download id=”5571″]

[download id=”5573″]

[download id=”5575″]

Posted on November 1, 2014 by The Engineer — Leave a comment

Eagle Libraries

As most of my projects use libraries not shipped by default with Eagle, here can be downloaded the collection I use, which will be of help to anyone wishing to use one of my projects.

30MB Archive Download:
[download id=”5573″]