3D Printing – using the Cocoon Create (Wanhao i3)

*** Note: some of the info presented here may void your warranty, opening  the control box exposes you to potentially lethal 110/240V connections – please take care and disconnect power before opening the unit. The following are not instructions, just descriptions of my work, I accept no responsibility on how you use his information ***

I don’t know why I bother keeping this site alive. 😛 If you do not understand any of the terms here try Googling them (maybe adding ‘3D’ to the search term).

Well, back in February, I bought a Cocoon Create (http://www.cocooncreate.com.au/) from Aldi here in Australia. Yes Aldi does sell some strange stuff here on occasion.
It is, in fact, a re-branded Wanhao I3, and was a good price at A$499.
This is my first foray into 3D printing, although I have been tempted to have a go for a while. From the start I have been impressed with the quality of the prints from this gadget, I guess my expectations were rather low.

As we are now at about mid-June, I’ll share my thoughts about owning one, pitfalls, urban myths, fun, frustration but thankfully no disillusionment – not yet.

This printer is really suitable for the tinkerer types who are not afraid to pickup a screwdriver and learn a bit. It is not plug and play (mostly) and requires some mechanical skill to deal with running the thing, even in its standard form before you might even consider improving it with mods.

The 3D community… well to paraphrase a Star Wars quote… “3D Printing. You will never find a more wretched hive of scum and villainy”. No that’s not quite true. What is true is the usual clash of amateur learners with (not so) knowledgeable experienced users sprinkled with a few experts (with real engineering understanding).

3D printing covers a few areas of engineering – Mechanical/Electronic (Mechatronic), materials engineering (Plastics and their properties) and a sprinkling of thermodynamics. I’m quite adept at the electronics side of things, had some experience with the mechanics (bearings, stepper motors, etc) but I’m new to thermo-plastics, at least in the formation of objects.

Really simple 3D description: The 3D printer essentially moves a nozzle in 3D space, depositing a stream of plastic to create an object. To do this lot’s of stuff moves and is heated up.

This 3D printer mostly works at a safe voltage (12V DC) for its electronics.

240/110 V comes in through a rear fused receptacle and is fed to a fan cooled switch mode power supply that produces 12 VDC at up to 20 Amps. This DC voltage primarily feeds the controller board (called a Melzi – an Arduino clone) and directly feeds two of the fans, the rear panel fan on the electronics box and the cooling heatsink fan on the hot end. These two fans are always on when the power switch is turned on ate the rear.

The Melzi board is the brains and controls the movement of all things that move – stepper motors for movement – X, Y, Z (2 motors) and the extruder. The Melzi comes pre-programmed with it’s own firmware (although you can re-flash it). It can talk to the outside world in two ways – via files on a micro SD memory card or through a USB serial port.

To print a 3D object, it needs to be ‘sliced’ into layers. Cura is the suggested package for doing this and a great tutorial to get you started on adjusting the settings for Cura in here.

Mods – modifications – here’s were you get your screwdriver fix!

I’ll list the ‘stuff’ I’ve done to my printer (with or without explanation!). Most of this has come from various sources on the internet.

The first thing everyone pretty much agrees on (rare in this hobby) is to print off some dials to replace the wing nuts on the platform levelling screws. I replaced the adjusting nuts with 3mm nyl-loc nuts and the bed adjustment stays pretty stable. Also lock those screws onto the bed with the same type of screws – 3mm ny-loc nuts, this stops them wobbling about.

I added gantry stabilisation (or “Z arm stabilisation”). Use this link from Thingiverse – http://www.thingiverse.com/thing:921948. I profess, I didn’t do any before and after quality measurements but it does make the printer much more stable, especially if you feed your filament from a roll mounted up there. I did not use the full Y Brace bracket either, no particular reason not to.

Fan Noise – Fan Noise – Fan Noise.

Fans are the most intrusive noise from the printer (next to the noise from the Y stepper motor that’s amplified through the platform!). I rate the noise frome the fans as (loudest to quietest): Fan on rear of control box (40mm), internal power supply fan (80mm), hot end (40mm) and extruder fan (30mm). All the fans are 12V.

I have installed a Noctua 40mm fan on the hot end. It runs slower and is designed for quiet operation. I have checked the thermal dissipation with this fan using a Flir thermal camera and it is quite acceptable. I could not see a great difference between this and the stock fan for cooling but the reduced noise was a real benefit.

I have replaced the rear panel of the control box to fit an 80mm fan – see here and added a 100 Ohm, 1 Watt resistor to the fan in the internal switch mode power supply. This again has reduced the fan noise considerably. There was no measurable difference on the Melzi board temperatures after the rear fan change and thermal measurements for the power supply have it running at 29 degrees C with a room temp of 25 after two hours doing a PLA print.

I have not changed the cooling fan for the extruder… yet. Although the fan and duct have been angled more to point at the nozzle now.

If the power supply ever fails, it will be replaced with a quiet PC power supply on standby for the job.


As noted above, I added a resistor to the power supply fan.I have also done the temperature stability mod for the hot end – see here. This does improve the endpoint stability by improving the grounding to the switching MOSFET for the hot-end.

The Vref for the current limits of the stepper motors have been set to 0.684V for X,Y & Z steppers and 0.864V for the E (Extruder) stepper. The extruder stepper motor has a higher current rating. There are a few online guides for setting these, search for “Vref wanhao i3”.

I have also cabled 12V out of the electronics box to the platform area to run overhead 12V LED lighting.

Running the printer.

Initially I was sending files to the printer by loading them onto the micro SD card (supplied with the printer, by the way) on my PC and ‘sneaker net’ them to the printer – this quickly becomes a real pain. Using Octopi,  I have set up a Raspberry PI 2 with a  Microsoft 3000 webcam and WiFi to wirelessly upload objects and to monitor the print process. Here is a good tutorial on how to set it up and if you do use it (it is great!) – then please consider supporting the author.

Filament – so far I have only printed in PLA. I have used the Cocoon filament (blue, green, grey and black), 3D Fuel (Orange and Red), miscellaneous EBay PLA – white, transparent, Bilby glow in the dark, Jaycar wood filament. I have copper and ABS clear to try but I’m wanting to convert the hot end to a Micro-Swiss one first as the ABS runs hotter and the copper/glow/wood might be abrasive.

Repairs and bits…

I have already replaced one of the platform linear bearings. This might be because I used fine machine oil and it *may* to have gelled the grease in the bearings.

Grease – bearings seem to run dry but I think it is the quality of the bearing here. I find a few drops of Singer Machine oil helps if you start getting odd noises when things are moving.


Google Wanhao GroupGoogle OctoPrint Group

… more to follow…

2013 Mitsubishi ZJ Outlander stereo upgrade.

Would you rather have this?  ….   Then read on!




Also – do not expect any response to questions you may ask about this information, although I will try. If you feel that you are in any way incompetent – don’t wait for me to point it out, go to a professional to get the install done.

Levering panels and plastics: modern vehicles are mostly plastic inside, removing panels and fittings requires a gentle but firm hand to lever the parts apart. Do not use quick snappy movements or you risk doing just that – snapping a plastic fitting or scratching the finish on a visible surface.

Explanatory note: When I talk about OEM gear in the following article, I’m referring to any parts, cables, accessories that originally came with the Outlander. I also mix the words ‘head unit’ and ‘stereo’ referring to the same thing. This article was written in Australia where we are right hand drive, we also solder wires as opposed to ‘soddering’ them (which sort of mildly sounds like some sort of life choice).

Crappy stereo?

Why on earth do car manufacturers insist on putting half assed, partly dysfunctional head units in new cars? I have a 2013 Outlander Aspire,  top of the range here in Australia – well almost – at the time I could pay another $5000 for the Rockford-Fosgate stereo, electric tailgate, adaptive cruise control… but that was another $5000 I wasn’t willing to part with.

The head unit functionality was marginal to say the least.

–          The Bluetooth audio and iPod connection had frequent drop outs, I suspect due to the fact that the Bluetooth/USB module was separate to the head unit.

–          Navigating the menus was a half way attempt – you never quite got to where you wanted to go in a timely fashion, which kept your eyes from the road for way too long.

–          The damn thing never remembered where you were up to in a song or a podcast, always restarting it from the beginning after turning the power off.

–          The rear vision camera was blurry.

–          No DVD/Video support

–          And on and on.

About the same time I replaced the stereo in our other car, a 2003 Pajero, as the OEM (Original Equipment Manufacturer) one had died. I put a double-din Pioneer (AVH-X3500DAB – now replaced by the AVH-X3600DAB) in its place. I was mildly impressed (we engineers are a conservative bunch) with the performance, even with the old 15W dual cone standard speakers! It had DAB+, played DVDs, a quick and responsive interface, logical menu system and no wacko quirks (well, no serious ones that I’ve found yet).

After having it for a few weeks, I just had to make it fit into the Outlander. During a car sound sale I purchased another one. This will be great I thought, both cars with the same head unit, no gnashing of teeth by the better half when trying to figure out each one. My research showed that it looked possible.. I wanted to retain the steering wheel controls, I wanted it to be seamless and look like part of the car, I wanted it to use the existing reversing camera and hands free microphone.

Above all, I wanted to make it a neat install with the ability to revert back to the old OEM stereo if needed; no chopping of wiring looms, etc

One of the installation problems associated with new cars is that most of the electronics is tied together with the CAN communication bus – a data bus for sending information around harsh electrical environments like cars and machinery. As I found out, for example, the fact that you have selected reverse gear is communicated to the stereo via the CAN bus. Most current stereos sense reverse by directly tapping into a wire that changes from 0 to +12V (or vice-versa) when reverse is selected.

I will describe how *most* of these problems can be circumvented in the Outlander. This is all accumulated knowledge from measuring, probing cables and scouring over the Outlander wiring diagrams

What you will need

2 x AP0113 Mitsubish wiring harness by AerPro (APP0113)  –  why two? See the steering wheel control section.

1 x Metra 95-7015CHG double din dash kit for a 2014-up Mitsubishi Outlander (eBay)

1 x AXXESS ASWC-1 Universal car OEM steering wheel control interface module (eBay)

Wire, other bits and pieces as mentioned in the following description and oh.. and a new head unit.

Basic connections

For just replacing the stereo and getting sound out, it is all pretty simple. Connect the AP0113 between the wiring loom C109 connector and the ISO connectors at the end of the Pioneer loom. This supplies Battery and Accessory power, speakers, ground, illumination (to sense when headlights are on) and the Antenna relay control – which can switch an auxiliary amplifier on or in this case it supplies power to the antenna amplifier at the antenna.  Just connecting this and the radio antenna and you will have a working stereo.

Getting the dash apart – just involves getting a thin flat lever around the edge of the silver rim and gently levering. I used a 12 inch steel ruler but a butter knife might do. Be carefull not to mark the plastics. I notice that there are a lot of places selling kits containing an assortment of ‘spludger’ type tools for cars for this task. After the surround has been removed, disconnect the ventilation control cables and put it somewhere safe. The stereo itself comes out with four screws.

This is the rear of the Mitsubishi OEM unit:

OEM Stereo Rear_WM


The OEM stereo has a double din body size but a larger face area than the Pioneer unit. This required the use of the Metra facia kit. It comes with a left and right mounting bracket, made of plastic, which mount onto the facia trim using four PK type screws. Even though the brackets are plastic, once it is all together and mounted on the new stereo it seems solid enough. The facia has the same sparkly finish as the dash in the Outlander and looks quite the part.

But you want more… you want the steering wheel controls to work, and the rear camera to connect, and the microphone to work for hands free, and … so let’s go through it bit by bit.

OEM Camera

To use the OEM reversing camera is the hardest part of this upgrade. For a start the camera uses a Mitsubishi custom connector, designated C107, on the rear of the stereo unit. The hardest bit is the fact that the supply voltage for the camera seems to be 6-7VDC (6.8V actually), present between the CACC line (C107, Pin 41, White/Black Stripe) and CGND is earth (C107, Pin 45, Violet). The video feed from the rear is fed down a coaxial cable until it gets to the radio at just prior to C107, where it is spliced to two wires on the connector CMP+ (Active signal – Pin 46, White) and CMP- (Coax Shield – Pin 47, Black).


To utilise the rear camera you need to supply it with the correct supply voltage + to CACC and GND to CGND. I accomplished this using an LM7806 Regulator with a 1N4007 diode in the ground lead to boost the output by 0.8V…


This gives a composite video signal from the camera, and I have it working well in my setup.

Not everyone will be able to build such a circuit, you might try using a dedicated 6V DC converter designed for servos used in the radio control hobby, sometimes called a battery eliminator circuit. I have not tried this and can’t vouch for it as a solution.

I then cut the end off of an RCA video cable and spliced it directly to the coaxial cable coming from the rear (centre conductor to CMP+ and Shield to CMP-. The picture below shows the little 6.8V power supply I built to run the camera.

Rear Cam_WM

Rear Cam 6V8 supply_WM

There are no marker lines on the image from the Outlander  camera, these were generated by the OEM system I was replacing, so my rear camera doesn’t have the warning marker lines superimposed on the video..  The OEM camera works a treat into the Pioneers Rear Camera input which leads us to…

 Reverse Sense.

This is how the head unit knows to switch the rear camera vision on and it’s a real pain in the Outlander, it is available digitally on the CAN bus but if you just want to have a single wire sense to the reverse on your head unit, then you need to go hunting. It is not available on C107, the camera connector or anywhere else on the stock AV head unit wiring.

I traced the circuit diagrams and found that the reverse light signal appears at the ETACS ECU panel (to the left and behind the glove box on RHD vehicles). It enters the ETACS on connector C421 (Pin 9) and exits on C418 (Pin 12) via a blue wire. This wire then goes down to the rear of the car to connect to the reverse bulbs. The bundle of wires containing this wire bypasses another connector panel (below the ETACS) – see photo. The problem is that there were at least three blue wires running in this bundle.Reverse wire_WM

Finding Reverse wire_WM

To find the right one I used my multimeter connected to a pin and inserted the pin into each wire, turning the car on, selecting reverse until I found the wire that changed when going to reverse, third wire I tried in my case. The voltage present was around 10.6V when reverse is selected and 0V normally. The Pioneer setting was to switch the camera video through when the sense wire was at Battery.

I labelled the wire and ran it behind the glove box to the stereo area.

But wait there’s more…

Handbrake Sense

After you’ve hunted down the Reverse sense, now you have access to the Handbrake wire as well if you need it. It is on the connector panel below the ETACS on C24 (Pin 2) and is purple. Quite easy to find, it is the purple wire in the photo,  this wire is switched to earth via a diode when the handbrake is applied. Use your meter on the diode setting when you confirm this (it will be 100-200k ohms on the Ohms setting if you don’t have a diode setting).

I labelled this wire and ran it with the reverse wire to the head unit.

Handbrake Wire_WM

HBrake Reverse Wires_WM

OEM Hands Free Microphone.

Well this was a lost cause. The original hands free mic is in that perforated area between  the reading lamps. There is an amplifier attached to the mic up there and is powered via the connection to the blue tooth module. I experimented but couldn’t get a clear audio connection by piggy-backing off the returning audio. In the end it was easier to run the supplied Pioneer mic from the head unit via the dash area and up the windscreen pillar behind the plastic cover on the inside, away from the curtain air bags, then pushed up into the head liner adjacent to the windscreen.. There is a bit of space up in the reading light assembly  – enough room to hide the new microphone, attaching it with the Pioneer supplied double-sided tape. The dome/reading light assembly just levers out of the roof head liner with a large flat steel ruler as a lever.

USB Connection

Another crappy Mitsubishi innovation with the OEM gear is to use non-standard USB sockets on their Hands-free adaptor and the original stereo. They look like USB but the housing is smaller. Apparently if you strip off the metal shield on the USB connectors they can be “made” to fit.

It would have been really nice to use the built in USB cabling to the centre console, but the weird USB connector has put me off. I may, in the future, hack off the end of the OEM cable and solder in a standard USB connector but for now I have the Pioneer supplied USB cable running to the glove box and that’s where the iPod resides.

 Wired Remote / Steering Wheel Controls

Steering wheel controls… I purchased an Axxess ASWC-1 to translate the steering wheel controls to those suitable for the Pioneer. I had considered ‘rolling my own’ but I went for the easier pre-built option.

The steering wheel controls basically consist of switching resistors across two lines that connect to connector C109. The APP0113 harness does not have these pins installed and as I wanted to avoid soldering two wires to the harness, I bought two APP0113 harnesses (they’re about $16 each).  I carefully removed two pins and the connected wires from the donor harness to fill the empty SWC connections (Pins 2 and 12) in the installed harness. In the photo showing the two circled added pins, the top pin (pin 2) goes to the Black/green wire on the ASWC-1, the bottom pin (pin 12) goes to earth.

Aerpro Connector_WM

Aerpro Cable and Donor_WM

If you’re really interested these are the values for the steering wheel resistances (in Ohms):

No button press               5.3k

Mode button                     260

Volume Up                         1.57k

Volume Down                   2.02k

Previous                              1.07k

Next                                      660

Speak                                    2.6k

Off Hook                              3.06k

On Hook                              3.54k


Following the instructions for the Axxess unit worked well but the Phone buttons do not work for the phone, they are re-mapped, Speak does nothing, Off Hook is Mute and On Hook is Next Track. I have tried manually remapping them but it looks like either the ASWC-1 does not output the right phone control codes to suit the Pioneer or the Pioneer unit doesn’t support phone control via the wired remote input.

The only extra thing I did was use the supplied window mounted DAB+ antenna, just watch the pillar trim here as it sits rather snug close to the windscreen glass and may rub on the coaxial cable coming from the antenna. The cable ran down the pillar on the inside, avoiding the curtain airbags, and with the Reverse and Handbrake sense cables ran across behind the glove box to the stereo.

Things to (possibly) do:

Make use of the Mitsubishi USB connection.

Make a delay circuit for the Accessories power to the stereo. My car is key-less (push button) start – when you turn the car off it all goes dead. Not like a regular key ignition where you turn back to accessories then off, you need to push the button again to get accessories back on. I’m thinking of putting a 10-15 second relay in so you can choose to hit the button again within that time to keep accessory power going to the stereo and not drop its power.

Turnigy TX9 Transmitter backlight mod.

While my Towel was convalescing, I decided to add a white back light to the Turnigy TX9 transmitter. Hobbyking supply this as a little kit,” all you need is a screwdriver”… I would add.. ‘and a little manual dexterity’.

I pulled my TX9 apart, there’s a pictorial guide under the part listing on the Hobbyking website here. It was all straight forward, the cabling of the adapter is a little stiff and because the back light panel doesn’t fit neatly into the space, it will drag it about as you reassemble. The suggested double sided tape will help, once the back light has adhered to the foam it will allign every time. Use thin double sided tape – the thick stuff I used showed up under the back-lighting. I also found the Menu micro switch died in the process, I think this happened when the switch didn’t allign correctly with the button hole, I replaced it with a similar one from my parts.

I think the back light is worth the effort and helps the display readability even in daylight.

Building a Towel..

Building a Towel? What?

Well a Towel is a delta shaped Remote Controlled Aircraft with an airframe  that’s pretty much made of scrap materials.

Firstly a little background:

The “Towel” was developed by Brooklyn Aerodrome and I read about it in Make magazine.

Being a bit of a plane nut, I decided to have a go at building one.

RC Materials were sourced from Hobbyking online, Hobbyrama in Stafford, Brisbane. I’m using; Turnigy 9X RC Tx/Rx Combo, Hobbyking SS Series 18-20A ESC (Motor controller), a T2830-1000 Turnigy motor and a couple of HKSCM16-5 mini servos.

The foam sheet was purchased from Fix-A-Frame at Mt Gravatt (about $25 for white 4mm thick, 1500 x 1000) and the ‘Coroplast’ material for the deck was from a recycled real estate sign. I had scrap aluminium for motor mounting, cable ties, tape etc, etc.

Building it took pretty much 7-8 hours. That included learning how the RC transmitter worked, and setting up the Elevon feature on it. If you do use the 9x transmitter, you can actually power up the servos and set up the Elevon mixing in real time, which was a lot easier for me to visualise. I use it in Mode 2 (throttle on left joystick up/down, elevator – right joystick up/down which is mixed with aileron – right joystick left/right controls).

Things I found – my servo wires were short, a tight reach on my plane. Foam board folds easily in the wrong place if you stress it. Channels 1 – Aileron#1, 2 – Aileron#2, 3 – Throttle (ESC).

TGY9X Elevon setting –

State – ACT, AIL 1  -100  -100, AIL2  -100  -100, ELE1  -100, ELE2   100

It’s sitting here built, but it’s blowing a gale outside so not flown yet.

Update: Well, that went well! 20m flight and the prop nut came off, crashed. Nose bent. New 5mm nut sourced ready for try out number two!

The iSub Hack


This hack/mod may be a bit scant on some details and is meant for dedicated hack/makers with a bit of skill under their belt. No details are given for the physical dismantling of the iSub but, screws are under the feet (carefully remove feet) and just follow your nose after that. Use lots of padding – you don’t want to put scratches all over it as you work. All the following is used at your peril or elation 😉

I picked this up from Ebay as a purposeful hack project. Apple no longer supports the iSub, although on my Windows laptop it does appear as an audio device and I can play sound through it.

The iSub by Harmen Kardon was designed for Apple as a USB only subwoofer. It is a fairly iconic looking subwoofer, which has since been replaced with the HK Soundsticks range, using the same looking subwoofer but with two small stereo speaker stacks, all running via standard audio (USB has gone). The electronics in the iSub consists of two parts, one is the USB to audio section and the other is a plain and simple subwoofer amplifier.

The iSub is well constructed, with audio seals everywhere, even on the power socket. The USB had to go and to maintain the air seal integrity,  the USB cable would be re-purposed as the audio cable, re-wired for audio in via a 3.5mm stereo plug.

As far as reverse engineering went, I did not go as far as to re-create the full circuit diagram. It appears that the circuit board is multi-layered, so recreating the circuit would be a nightmare! I have found that the electronics in the iSub consists of two parts, one is the USB to audio section (UDA1321, USB to Audio IC + 8582C 2kbit – 256x8bit i2c EEPROM to store the audio settings for the 1321 chip) and the other is a plain and simple  amplifier (TDA7256, 30W Amp IC).

Here’s the PCB.

So what I have done…

Soldered a short across the C-E of Q01 – this stops the iSub from being constantly muted,  Q01 is actively driven by the USB audio chip, which I disabled by removing the little 3.3V regulator (top right in the picture above).

Then the audio trace from the USB audio circuitry was cut. The direct audio feed will be soldered to the cut track on the left.

Now, using the USB cable to feed the audio. As mentioned, this keeps the air-tight integrity of the iSub and saves drilling holes, etc to feed another cable. The cable diameter is a little large, but I was able to force fit a metal (for strength) 3.5mm stereo jack to the end, in place of the USB connector. The earth/ground is connected to the shield an I chose two random conductors for the L&R audio signals. For a Sub, though, you can just get away with using the Tip conductor of the plug, generally the very low frequency signals in stereo are pretty much the same.

On the PCB, I removed the small inductor array (L01) then fitted two 10k-ohm resistors to combine the L&R signals into one and then wired it to the left of the cut track.

It was then a case of a quick bench test, then re-assembling the iSub.

Final observations: The whole mod works well as an audio amplifier. BUT,  I thought that the power amp circuitry may have had some Subwoofer filtering (given the number of electrolytic capacitors around the audio path), it appears not. The subwoofer profiling may have been done on the USB audio chip, or in the Mac OS when it was able to drive the iSub, so after the mod the iSub needs to be driven by a dedicated Subwoofer output from a audio processor or a sound card.

Have fun!

Safety tip : A good supply of ice helps with soldering iron burns.


Be Careful – Lethal Voltages inside

–   This information should only be used be qualified and technically competent  souls –

2/Jan/11 Power Tech MI5160 180W Sine wave Inverter picked up from the trash and treasure market, supposedly working (why I didn’t plug it into the car before leaving? Grrr). Attempts to power up greeted by merrily chirping of the buzzer and flashing of the Red Protection LED. So I stripped down the inverter, here’s the basic circuit layout…

and here are the internals…

What goes on in here?

The DC comes in, it is chopped up by a couple of low voltage/high current FETs (IRFZ44V) controlled by the TL494 SMPS IC, then into the step up transformer The secondary is then rectified by four high speed 3A diodes (HER308 ) and smoothed by a 68uF/450VDC capacitor. This HV DC is then supplied to, what is essentially a high voltage amplifier. A small daughter board in the unit generates the 50Hz sine wave, which is then fed to the four High voltage/low(ish) current FETs (IRF830), which in turn feeds the 240V output socket. I do not know what the two trimpots do, probably voltage settings, etc There is a heap of detail left out of this description, but as I don’t have a circuit diagram….


First thing to do was check the 12V lead, 25A fuse and DC input circuitry – all appeared OK. Then knocked the container with screws onto the floor. Next was the PCB, I did a basic power semiconductor test, and somehow missed one of the HV Rectifier diodes as conducting both ways. Promptly went on a joyride of examining each of the MOSFETs, a leading up the garden path with ESR checks of capacitors and re-soldering any suspect looking joints.

Eventually went around in a circle and got back to double checking (I thought) the diodes. Well, diode #1  appeared to be the problem, but I had no suitably fast 3A/1000V rectifier diode.

The fix:

I then stuck a 1N5408 in as a replacement (same electrical specs but not very fast at all), which proved the inverter would idle happily, but it promptly went to diode heaven after a few minutes of driving a 60W incandescent light bulb.

Farnell (Element14 or whatever) have an order for replacement diodes and FETs (just in case). Be aware that the circuit board copper is not the best, and lifts after a few solder applications.

5/Jan/11 OK, parts arrived and I replaced the HER308, and that’s all the problem appears to be. Ran the 60W/240V lightbulb for half and hour without any issues so far.


Fixing the Logitech S125i MiniDock

I picked up this little dock a while back and it has been a good little performer for charging and casual listening of Apple iDevices. Last night it had a sort of pink fit, turning on and off multiple times, then dead.

After checking the obvious; power supply and several different devices, it was time to disassemble and see what was going on. First trick was how to dismantle the little sucker… I unscrewed the battery holder underneath, moved it aside, and saw that the case was held together with screws from under the speaker grill area.

As you can see the white plastic surround is gently prized off, it is held on by plastic weld posts, and some of these were lost to the cause! The grill is next, again gently prying off with a sharp tool. Now remove four screws holding the speakers and the other four case screws, then pull apart.

It turns out the problem was cracked solder joints on the DC connector (circled below), re-soldering them with a little scrap wire on the PCB to give some mechanical strength, should make it last quite a bit longer.

Here’s another shot, this is the PCB…

and here we are all working once more, listening to some classic music!

Maximite and the ESMC receiver

I’ve been playing with the Maximite to control the Rohde and Schwartz ESMC receiver I recovered from flood damage (see Silicon Chip Magazine – June 2011). These receivers are pretty much just grey boxes, some versions have a nice digital front panel, mine don’t – it’s all controlled be software via the RS232 port. Here are some of the shots of my efforts…

This is the interface, just a MAX232 on that little board does the level translations to RS232. The cable goes off to the serial port on the ESMC receiver (19200,8,N,1). The ribbon cable at the top comes from the Maximite to a ‘breakout’ board, which is just a strip of veroboard with a single in line pin header installed. Each of the 20 I/O pins are mapped to the connector. Connections (right to left) are GND, PINs 1-20, 3.3V, 5V, GND. I installed the bargraph LEDs and resistor arrays (those black stripes below the LEDs) as an easy way of showing what was happening on the port.


So far I’ve implemented fixed frequency monitoring (20-650MHz), bandwidth control (500Hz up to 100kHz!), demodulation control (FM, AM, LSB, USB, etc), scanning and a command line control.

This is the shot of the screen with the scanning mode functioning, if the signal breaks through a set level, it’s frequency is recorded on screen. Each printout is cascaded up to ten levels down the screen to reduced clutter. The scale on the left of the screen is not accurate by the way!! The current frequency and signal level are at the bottom of the page. The graphing, spectrum analysis scrolls from the left to the right in a continuous loop.



Scratch Built Maximite


After two weeks on holidays in Tasmania, I was itching to get back to the soldering iron. Here’s my latest Maximite, built on a PCB made from the original Gerber PCB files (thanks Trippyben!) with a 32MX795 chip on board and various support parts. If you build this way, you will need the PicKit3 to initially program the PIC. The Altronics and Dontronics kits are pre-programmed.

Notes on my construction…

Soldering the PIC. If you’re accustomed to soldering it is quite easy, believe it or not. Just allign the PIC with Pin 1 to Pin 1 on the mask, tack a few corners and solder away. Firstly i ran some liquid flux down the row of pins I was a bout to solder, then I ran the iron gently down each line of pins, using a reasonable amount of solder. This produced a few bridges, especially at the end of the row, which i cleaned up with some thin solder wick. Overall, I was happy with the result. Silicon Chip Magazine in March this year gave some instruction on soldering this type of chip.

Programming – be aware that the PicKit3 will not fit over the ICSP pins once the keyboard socket is mounted on the PCB (see photos above). I remedied this with a short jerry-rigged extension lead, which now resides with the PicKit for future use. See the pictures above.

Initially the PIC programmed all right but would not start up. I immediately though my soldering wasn’t up to scratch but it appears that there is a problem with the Core voltage filtering. My build, like a few others, would not kick over with the Vcap 10uF capacitor, C5 – even though it’s measured ESR was at around 0.3 ohm. This has a work around with a 22uF Electrolytic capacitor between the positive lead and the 3.3V supply, this sort of kick starts the Maximite on power up. I will be replacing the 10uF/22uF combination with a ceramic type mounted right next to the chip when I get time and hopefully this will be a better fix.
As far as the ability to program but not to run… this is not unexpected as the clocking regime is different internally for programming as it is for running.

Once it was running, I upgraded from 2.1 to 2.4 using the USB upgrade method.

I used an LM3940-3.3 in place of the LM1117T-3.3 regulator specified, this works but you need to contort the legs into the different holes. The LM1117 goes (L-R) Gnd, Out, In whereas the 3940 is the standard In, Gnd, Out. My regulator looks like it’s part way through a game of Twister. I also screwed a bit of aluminium to the 5V regulator to help it with the thermal load when the supply voltage is 12V.

The SD card socket has to be the original specified (from Altronics) so it fits the footprint on the board. I quite like it with its spring loaded eject. The case is also the original specified from Altronics.

The VGA connector sticks out a fair way from the back, which means that if you want to cut out the rear panel to accommodate it, there is very little plastic left. My case has the rear panel permanently missing!

Oh, and that grey dongle looking thing sitting on the VGA connector is a DB9-15 plug to RCA socket for getting composite video out to my monitor.

Any questions? email me.