Tabletops, Vases, Voltmeters and Guitar Pedals

Prepare for another multifaceted update

1) Tabletops

Much searching around Auckland for the required 25mm sheet of plywood took a week of unanswered emails, unhelpful sales staff and staff who claim to have stock until you turn up to find that they’re completely out. When calling one store to ask if they had the product in stock one really “helpful” sales guy even replied “If my staff spent all their time running around the store seeing if we have stuff in stock they wouldn’t have time to do their proper jobs”. Considering that the store solely sold plywood and if they had it in stock I would have brought it I’m not exactly sure what the staff was doing that was more important than making a sale. Thanks non named plywood merchant located in Penrose…

All that aside eventually a sheet of plywood was located and then cut into three sections with a blunt handsaw to fit in the back of the car. This then had the outline of the table top drawn and cut out of it. Next step will be cutting out the hole for the LCD and mounting it to the cabinet. Aside from that the control panel braces and a couple of air / speaker vents are all that will be left on the wood working front. After that a final bog and sand before painting.

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2) Vases

I’ve also started to experiment recently with thin wall 3D printed objects to see how well the printer did printing large single extrusion objects. The main concerns that I had were related to the piece glooping down because it didn’t have time to cool or the layers not lining up, which when printing with a .35mm nozzle is quite important. Aside from a few artifacts on one corner the parts printed quite well however, I’m happy enough with the result at the moment although ill probably fiddle with the density of the walls at some point to make them more solid.

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One interesting discovery I did make however was a strange translucent goopy liquid that started leaking out of the hot end after a while of printing. It’s possible to wipe this off before a print and even after 2.5 hours of solid printing it’s not really an issue but I’d still like to work out what is happening. Seeing as it looks similar to the stuff that ends up inside the V2 nozzle between hot end services I’m inclined to believe that it’s either a result of the temperature settings not being quite right and so the filament is doing something weird when melted and separating somehow or the filament has absorbed too much moisture and that is what is separating out when it is heated. As near as I can figure this is leaking out of the hot end where the nozzle threads on and is then oozing out between the nozzle and the heater block.

3) Voltmeters

Over these next two weeks ill need to spend some time preparing the shopping trolley for Eastercamp. Thus far I’ve replaced a button mount that has snapped off with a beefier version and finished off the Lo-Jack code on the GSM and Comms Nanos. Now sending the correct string to a cellphone number will cause the trolley to TXT you back a Google maps link to its position as determined by GPS. At the moment the number to reply to is hard-coded to one cellphone number but the long-term intention is to have it reply to the number that queries it.

Additionally I’ve added a couple of voltmeters in a printed enclosure to the front of the trolley. These are completely separate from all of the rest of the trolley electronics, connected directly to the batteries via a toggle switch to power them on and off. Testing with a multimeter confirms that their reading are accurate.

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(Mount in the middle without screens)

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(and Screens)

Still remaining on the to do list is an investigation in to the throttle code (sometimes the trolley takes off on its own) which I suspect will require the addition / modification of a greater dead spot for All Stop. Sometime next week one final yet to be unveiled cosmetic change specifically for Easter Camp will also be completed.

4) Guitar Pedals

Recently a friend asked me to look into making a cheap copy of a midi controller / guitar pedal to control a Strymon Timeline “some-sort-of-multi-effect-/-looper-pedal?”. The original controller pedal can be brought online for approx $150 US but that is before shipping from the States and any import taxes etc. I’m afraid I don’t have any photos of this project as it was completed in two days but the concept is as follows.

On the top of the pedal there are three foot switches evenly spaced across its width with an LED above each. The left and right LEDs light up with the switch below is pressed whilst the center LED is an RGB one that changes color to indicate the mode that the pedal is in. Pressing the center foot switch cycles through the modes changing the function of the left and right buttons. In each different mode a press and/or hold and/or release of the button sends a MIDI message out the 5 pin DIN port on the back. Pressing and holding the center switch sends a particular message independent of the mode. An Arduino Nano inside is the brains of the lot

The most “fun” part of the project was fiddling around with the differentiation between a press and hold especially considering the foot switches had a lot of bounce that needed to be programmatically taken care of. The basic functions presented by the controller pedal include scrolling through the Strymon presets, controlling the looper record and playback functions, bypassing (something) and controlling the “Tap” input and “Infinite Repeats”. In the end the project was a success however coming in at around half the price (before shipping) of the pedal available online.


4The gap between my last post and now has been filled with sporadic bursts of activity curbed mostly by the amount of time that can reasonably be spent on projects and whether I’m in the right frame of mind to focus on something that requires a degree of patience and accuracy. All that aside the intervening time has been spent on three particular projects.

1) Arcade machine.

I’ve wanted to build one of these for a while and with the I3 finished and most of the parts already collected it seemed like an ideal opportunity to tackle this one once and for all. A flurry of jigsawing, gluing, screwing, bogging and sanding quickly turned this

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into this

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For anyone interested the plans can be found for free here.

At the moment the base of the table is pretty much finished, all that is needed wood wise is the table top and the braces for the control panels. The top of the cabinet only needs a quarter sheet of 25mm thick plywood but no one seems to sell sheets that small and the people who assure you vehemently that they regularly have offcuts of that size in that thickness never seem to … If anyone knows a good source for less than full sheets or somewhere with a price so good that I could buy a full sheet then I’d be greatly appreciative.

On the control panel front the diagram for the plans was sent off (and then sent off again because everyone bar one source seem to be too lazy to convert 3 measurements from imperial to metric) to 6 places that do sheet metal fabrication so I could get a couple of blanks knocked up. Eventually the quotes started trickling back with prices ranging from $48 for two to a whopping $160 +GST. In the end I settled on the supplier that could be bothered tacking the imperial conversions (even though I later sent them the plans in metric). They responded quickly, had a good price and did a good job. Thanks Classic Sheet Metals in Henderson.

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These blanks were then drilled to a template cobbled together from various other arcade panels and the buttons and joystick were then test fitted

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and given several coats of satin black spray paint before the buttons and joystick were refitted

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2) ARCredit

Turns out that two player machines need two coin slots. Guess that makes sense. This caused a problem as the coin slot thingy that I had only had one slot and the supplier no longer sold identical units. Average.

Anyway coins are on the way out, contactless payments are where it’s at so introducing ARCredit.


Arduino Nano with RC522 RFID reader and the obligatory JY-MCU Bluetooth Module.

This particular reader was chosen due to its low-cost and eBay availability, this came at the cost of having a less than ideal method of communication with the MCU namely SPI. The even more annoying this is that the IC that the reader is based around also has a serial connection, it’s just not broken out. Instead then of issuing simple strings out a software serial port I had to resort to using a specific library created to communicate with this reader, but unfortunately at some point written in Italian? with not much basic documentation. After spending a couple of days trawling through the code and trying different things I managed to get the code working well enough for my specific application and another couple of days of fiddling around had the turd fully coated in glitter.

Basically the reader works with the Mifare chips which you can get in token or card form. Using a custom access key the reader pulls the factory serial number and a 16 byte string from two different places on the chip and makes sure that they both match the strings written into the code. A third location is read with a single byte retrieved which represents the number of “credits” remaining on the token. In practice a player would hold down their “coin insert” button on the arcade machine and swipe their tag. The Arduino would check that the tag is valid and then trigger an output pin to send the coin insert signal to the arcade emulator. Each successive swipe deducts one coins worth of credit from the tag and then triggers another coin insert signal. The software has a customizable pricing structure in which you can define the number of credits that are taken off any particular tag each time the token is swiped.

The Bluetooth module is there for the purpose of adding credit to the tags. Connect a cellphone running the ARCredit software and send the appropriate string to the Arduino. The next tag that is swiped will then have its balance set to the value sent from the cellphone.

Once the rest of the arcade machine is finished the reader module will be mounted to the a perspex window in the side of the cabinet with the Arduino and Bluetooth mounted properly on a PCB elsewhere inside. As usual the code is up on Github, any misuse and token fraud will be met with severe repercussions.

3) Battery Charger

I think I’ve mentioned before that the battery charger in the Shopping Trolley is a little suspect. I’m sure that F&P make some good stuff and that the original charger is perfectly good for the stock batteries but ever since I put the new double capacity batteries in the charging light has always been on and the battery level indicator has been a bit suspect. The last thing that I want to do is over discharge the batteries and shorten their life

To remedy this and protect the investment made in the batteries I decided to fiddle around with the charging system, specifically setting it up to better balance and maintain the batteries when the trolley isn’t being used.

As a result 6 massive-key-switches-of-doom have been added to the foot well. Switching the three on the right connect the batteries in series to the rest of the system for riding around where is switching the three on the left connect them in parallel for charging.

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The string is there to make sure that only one side can be switched on at once and even though the switches each came with one key (making 6 in total) three have been destroyed in the fires of Mt Doom (hidden away where ill never be able to find them). This combined with a healthy dose of “NEVER EVER DO THIS [AGAIN]” to any potential operators should prevent potential 12v deep cycle battery short-circuit fun.

First video upload

So it turns out that filming in HD, editing, exporting and uploading to Youtube without experiencing either massive file sizes, low quality or long upload times isn’t that easy.

In the end however I’ve managed to get the below summary of the trolley on the net.

There’s probably some stuff that isn’t covered in the video or the project blog in sufficient depth so if you have a question then please ask. This post will probably be the last project related one until the end of Jan as I switch to misadventure mode whilst overseas on holiday. Peace out all and have a good Christmas 🙂


Finished Trolley

Wow, two finished project posts in a row. Something must be going right!

Friday evening a couple of weeks ago saw the purchase of two new 71Ah 12v deep cycle batteries for the trolley. Unfortunately this came at the cost of one of the spinners which cracked when it hit a curb (curse you perspex) so these have all been removed pending some serious thought into durability. But back onto batteries… Originally the scooter came with two 32Ah ones but they were pretty old and I only managed to get one decent trip (3 odd km) plus some testing before they didn’t hold charge properly and were pretty much useless. Looking through the service manual the specs list a range of 30kms with the stock 32-35Ah options and whilst this may be a generous estimation either way the new (71Ah) ones should be a distinct advantage.

After charging overnight and a few finishing touches on Saturday morning it was deemed to be time for a proper test. The course chosen was a short round trip from Torbay to Browns Bay which according to Google maps works out to be 8.3 km total. Going each way took about 45 mins so the top speed of the scooter is definitely lower than the quoted 10 kph but the better news is that after the trip the battery indicator still showed 4 bars.

The only annoying part of the whole thing is now the charge light on the scooter is permanently lit… Originally this only came on when the battery level had dropped until only the bottom bar on the battery level indicator was lit and also when the scooter was plugged in to charge. I’m not sure what is going on with this one at the moment, the stock controller has been programmed for the SLA batteries so it’s not like it’s thinking that it has a different type of battery, and as all four battery bars light up then I can’t see how it can be thinking that the battery is both full and also in need of charging at the same time.

Troubleshooting wise I’ve confirmed that the battery level indicated by the display is actually indicative of the voltage remaining in the cells (ruling out the battery management stuff being stuffed completely) and that there isn’t programming error that is reading the output from the original controller wrong. If there was still a LED connected to the original controller board then it definitely would be lit. Either something on the stock controller has been fried at some point (but very selectively as everything else still works), the scooter is confused with the extra capacity provided by the 71Ah cells (although this would be very weird) or the scooter is still getting used to the new cells. A trawl through the service manual has yielded no results so at the moment the only other step that I can think of taking would be running through the original controller board again and confirming that there isn’t something weird happening with the matrix that handles the input and output from the I2C expander on the original control panel.

Apart from that the rest of it is running well, the computer software has been finished to remote control everything apart from the steering and the final few hardware connections have been made connecting all the Arduinos to each other to allow all this remote control stuff to happen.

I’ll post a video (weather permitting) soon going through all the finished features as well as covering how amazing these Plega mobility scooters are for hacking, both in their simplicity and the extreme amount of thought that has gone into the design. It really comes down to the fact that for $150NZD you can pick up the complete chassis, controller, 2 motors and gearboxes, seat, steering stuff, wheels user controls and charger.

In the interim here’s some finished pics

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Drivers View

Drivers View

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Lights and Siren Controls

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GPS and GSM antennas

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Main power switch and Regulators

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Before and After

Before and After

Finally Finished Printer

One of the problems that I’ve found with 3D printers is that once they’re capable of producing reasonably decent objects you can very easily become side-tracked into printing all sorts of stuff whilst not actually tidying up all the loose ends and finishing the printer.

In my case this has meant several things…

Firstly for the last year the electronics has been sitting next to the printer on the table with the leads hanging off the edge of the table threatening to drag the whole lot off with one decent tug.

Secondly my fan mount for the cooling fan on the stepper drivers has been a M6 bolt screwed through a small piece of Aluminium, this has sat next to / under the Arduino MEGA, also with a tendency to slide around the table.

Finally the LCD add-on has never had its mounting case printed and so had ended up sitting under the printer where it’s pretty much pointless.

For the last  little while, whatever time I had to spend on projects has been eaten up working on the trolley but I’m pretty much at the point now where there’s not much more progress that can be made there until a new set of 12V batteries have been purchased and installed. Consequently it’s been harder and harder to ignore these final small but annoying jobs on the printer front and so this last weekend I got them sorted.

Firstly the electronics are now mounted on a printed sled / clamp deal. One of the pain in the ass parts of this was fitting the mounting screws in / around all the components on the Arduino Mega. There’s two things that are amazingly stupid design decisions on these units, the first being the header spacing (which was apparently a mistake…) the second is that it’s almost impossible to fit the heads of the screws in around the headers / SMD components on the top sides of the board. To get around this I had to stick a couple of screws in a poormans lathe (aka power drill) and turn the head down to a smaller diameter to fit. The ends result is below, The angle is a bit average but there’s a lot of cables blocking the view from above.

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Mounting the fan was a bit easier, trawling through the “parts that didn’t print right / werethe wrong size” provided what I believe was a different version of the electronics mount that for whatever reason (maybe I forgot about it, I can’t remember) didn’t get used. Suffice to say it was perfect in that it was designed to clamp to a piece of M8 rod and had a handy hole in the end to which to attach a fan via random section of those “Helping Hands” PCB holders which then clamped onto the fan.

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Finally after a quick look through thingiverse for inspiration I made up and printed the below black clips to hold the LCD to one of the top threaded rods of the frame.

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As a upgrade I also printed several of the black belt tensioners below. Ideally the belt would be tight without the tensioner but in order to adjust this it would be necessary to remove the heated bed (which would then need to be re-leveled again afterwards). I really couldn’t be bothered doing this and the tensioners turn out to be cheap and easy to print as well as pretty effective.

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Since this printer is not marked as finished (apart from upgrades and repairs) I think I can now in good conscience thing about the next one… I3 anyone?

On the shopping trolley front the following has happened;

1) Seatbelt has been attached.

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A short section of chain extends the belt down to the body of the trolley where it is attached be a shackle to a decently thick section of the frame.

2) Cover has been printed for the throttle.

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This is a massive win for 3D printers aye, it’s amazing what they are able to accomplish in regards to bespoke shapes quickly and cheaply. The amount of filament to print this part is way cheaper than what it would have cost to have it made out of metal. Additionally once the part is designed there isn’t that much interaction on the part of the user until the printer has finished its job. The cover is made up of two sections, the first lower section bolts to two handy (yet randomly) drilled holes in the original metal of the handle bars. The top section then slots over the PCB of the controller and then screws to the bottom with a couple of M3 screws and a couple of captive nuts.

3) Driving lights have been fitted.

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Thinking about long missions in low light I realised that I needed some form of front white lighting. I really didn’t want to end up in a position where the flashing LEDs had to be used for this the whole time as it’s a bit of a waste of their potential and functionality really. Scrounging around yielded a couple of LED torches with decent output and small size so these were fitted to the front with a  couple of 35mm pipe clamps and some M10 rod. A couple of aluminium plates secured the lot to the frame.

4) Rims

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White wheels aren’t much fun so whilst waiting for batteries I decided to bling the kart up a bit. From the parts bin came a whole lot of M10 bolts, nuts and washers, some Perspex sheeting and some bearings. Firstly the Perspex was cut into four circles, these were then drilled firstly with a 3mm pilot hole and then with a 10 mm drill bit in reverse so as to not split the Perspex. Printed hubs then had a washer and bearing fitted before being mounted to the Perspex. I then mounted the wheel horizontally to a block of wood and spun it around whist moving a grinder towards it tangentially to correct any wobble from the center holes and hubs not being dead center. The bolts were then fitted and tightened up.

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To mount the rims to the trolley the M6 bolt stopping the wheel from sliding off the end of the axle was removed and a length of M6 rod was put in its place. A nylock nut was then tightened down onto the rod to keep the wheel on. A second nylock nut then gets used as a spacer before the hub is slid onto the rod and held in place with a third nut.

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Result = awesome.

It should be noted that as the rear driven axle actually turns as well as the wheel (front axle is fixed and the wheel spins on bearings) it would be possible to fit blades to the rear wheels for a 21st century scythed chariot effect. Perhaps not as public friendly though

Why 3D printers are awesome

Now that I’ve managed to entice you with the title I’m going to add the caveat that they are also a right pain in the ass. Home made ones are great in that they are comparatively cheap compared to a Makerbot but at the same time because for the most part they are hacked together from components that can be brought from Mirte 10 Mega and Trademe they can also be extremely finicky. When they are in a good mood and are working though they offer the amazing opportunity to design a 3D model on a computer and then have in your hands 20 minutes (depending on the size) later a solid copy of your design at the cost of approx $1.20.

To demonstrate their usefulness and indispensability I thought I’d post some pictures of parts that I’ve printed for the Trolley project, parts that would otherwise have been impossible to produce without a number of other and on their own more expensive pieces of machining equipment.

Firstly the LED headlights on the front,

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These are made up of 5 separate parts, a main case and lid, a backing plate sandwiched between the LED’s and the PCB that they are soldered to and 2 clamps to attach the whole bundle to the front of the trolley. The main case would have to be the part that took the most amount of time to print out of any of the parts on this project, 3 ½ hrs >_<

Next up we have the main LCD case and mount. Three parts, a front surround which the LED bolts to, a backing plate that uses the same mounting bolts and a clamp that attached to the back of all this and then bolts onto the square frame of the original handle bars.

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Thirdly the TPTMs (trusty printed trolley mounts) a total of 14 of these have been used thus far on the Trolley and I imagine that more will be needed before the project is up. 7 minutes to make one of these.

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Forth we have the rear lighting mounts, designed to clamp onto the trolley handle bar and provide a spaced out mounting platform for the rear brake lights and indicators.

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Based upon this basic design we then have the GSM and GPS antenna mounts, These also clamp in a similar manner to the handle bar and only differ in that the mounting platform has been modified to suit whatever is being mounted (GPS mount is the square flat one).

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We then have three more brackets that are all based upon a similar design again. Firstly the controls for the LED headlights mounted to the front. This takes two buttons and angles them down and in toward the rider.

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Based upon this we then have a slightly beefier version to which the siren controls are mounted. This version differs in that it has more bracing between the horizontal and vertical sections and also has 2 TPTMs as opposed to one on the headlight buttons.

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Mirrored off this and with some modifications we then have the mounting bracket for the LCD screen for the LED headlights. The screen mounts to the front casing which is then attached to a combined backing plate and mounting clamp. The connector for the LCD pokes out a port in the back of the backing plate, a TPTM attaches all this to the trolley frame.

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I still have at least one more major part to re-print for this project, namely a cover for the stock throttle electronics. These are quite exposed on the handle bars so a case to protect these really is a must, fortunately should part of the electronics be snapped off the trolley should in theory stop automatically but still… Note I said re-print… the first print of this part demonstrated the finicky nature of 3D printers and how they just love to randomly stop printing 2 hrs through a 2 ½ hr job.