DIY-Duino – The minimalist Arduino DIY

I’ve been looking for a simple project to play with since moving states. My goals for a simple project would be:

• Extend my current knowledge and experience;
• Useful in terms of my other projects;
• Something that I haven’t tried before;
• Uses components that I have on-hand

While hunting around for projects to play with, I found the “DIY-Duino” on Instructables by robonerd (http://www.instructables.com/id/DIY-Arduino-or-The-DIY-Duino/). The DIY Duino is a simplified Arduino clone that works on a single sided PCB and has a minimum of elements ( a couple of resistors, a couple of ceramic and electrolytic capacitors, a 16MHz crystal, a bunch of female pin headers an LED and a pushbutton switch).

This project was a leap of faith for me because I was using someone else's design where the circuit template was a bitmap image (all of that nasty antialiasing means that the edges aren’t terribly crisp, compared with a raster image).

The first step was to transfer and etch the board. This was done with a reasonable amount of success. My only problems were with the antialiased image tending to make bridges between some of the close solder pads. That’s OK … I was expecting that.

I also had some gaps in some of my traces, that was down to the toner transfer and entirely my fault. I ended up bridging the only significant gap with a piece of cut-off wire (a leg from a previously used resistor … I keep most of my cut-offs for this purpose).

My longer term goal for this board will be to drive an automatic watering system for my veggie patch (I may need to make a few more) and will connect in an SPI (or I2C) network.

After the etch/inspection and correction process, it was simply a matter of populating the board.

Robonerd used jumper wires as bridges on the board (there are three of them) whereas I used 0Ω Resistors. The main reason for this is that I’m not all that keen on the appearance of cut-off jumper wire on the component side of the circuit … plus, the resistors are better insulated. Apart from that, it is an entirely personal choice (AFAIC).

When the board was all populated and soldered up, I got down and did some testing.

The voltage between the input power and the LM780 was 7.89V (battery not at full charge). The voltage between the LM780 and the 2nd capacitor was 4.98V, well within the 5% tolerance for the LM780 and safe for the ATMEGA329P chip.

Next, I did a continuity test throughout the board and found that all of the traces were good and the pin headers were correctly connecting to the DIP28.

Also, I made sure that the LED indicator did was it was supposed to do.

I will still need to test the circuit with the ATMEGA328P in place, but I kinda have to wait until my AVRSIP arrives (I just bought one from adafruit).

Well … that’s it for now. I’ll report later on how the circuit performs as a Duino clone.

New Toy!

Today, my wife’s surprise for me arrived. I had NO idea what it was … she kept telling me that I’d love it and that it was something that we had spoken about previously.

Turns out, she was dead right … I love it!

My surprise was a USB Digital Microscope (50x optical 200x digital magnification).

My eyesight has been getting poorer over the last couple of years and I’ve been getting more and more into wanting to solder SMD … in fact general soldering was only happening because of my 20x desk lamp/mag. It seems that, as my interest/need for closer and finer work has increased, my eyesight has degraded correspondingly, ah the joys of getting older.

The stand that comes with the device is nice, but not that practical. The first thing that I did was take the magnifying glass off one of my “Third Hand” tools and mount the microscope on that.

That lifts the scope end of the device up by about 10 cm, giving me enough room under the scope to actually work.

Next, I played with the software that comes with the scope. It’s pretty simple to use, but it has enough functionality to make it very useful.

Now I can …

look at components on an Arduino clone and identify them.

look at my SMD components in their packaging (and identify them)

some NE555 SMD

0805 2N2222 transistors

0805 Super bright White LED

Identify Diodes

IN4148

See the colours of resistors … although, I’m still colour-blind. I’m still taking it on faith that these are 10Ω resistors

One day, I’ll write some software to identify the resistor by colour … ‘till then, I’ll use my multimeter for that.

Look at some of my soldering work and identify the IC type

 

As well as inspect my soldering and printed circuit boards

Overall, I am very happy with my present … now I need to set it up on the laptop on my electronics workbench. I probably also need to make a better stand for it. I’ve got a mini camera tripod, maybe I can make an adaptor for the attachment … hmmm … gears are whirring in my head.

New Workspace

Now that I have thoroughly moved in to our new house, I have been busy setting up my hobby workspace.

My office/workspace is a 3m x 3m room with a good sized window for natural light. I have set up a table in my office for my hobbies (mostly electronics)

The first thing that I did was to make a pegboard that I could hang my tools on - so that they were within easy reach and easily seen.

Then, I mounted my small components drawers onto the wall facing my workbench. Jaycar have discontinued these cabinets, so it was a bit of a pain to get the last two. There are six of them, each with 32 small component drawers and one large drawer. That gives me 192 small drawers and six large drawers. These drawers contain my through hole components, blank PCB, breadboards and some other bits and bobs.

You’ll notice that there is a binocular microscope on the bench, my darling wife (an entomologist) gave me her old ento-scope for soldering small components.

I have a couple of pencil cups on my workbench with pens and pencils as well as a collection of Staedtler Lumo Colour and Sharpie markers (for fixing PCB laser transfers).

My solid core wire, stranded wire and solder are all in easy reach too.

 

The workbench is a fold-up table that we bought some time ago. The LED magnifying lamp is mounted on the end of the workbench so that I can swing it into place whenever I need it. I’m using an old office chair for comfortable seating … it’s pretty sweet.

I mounted the drawers on the wall with a gap underneath for other miscellaneous tools and project parts. The hobby/cutting mat on the peg-board is usually on the workbench when I’m working so that I don’t make a mess of the workbench and to make cleaning up easier.

Right beside my workbench I have a couple of bookshelves for books and other larger components. On the white bookshelves (on the third shelf down) I have my collection of SMD components. I bought a mixed collection of 0805 capacitors and resistors some time back, so that I could practice and learn soldering of these tiny components. I have the components in a bunch of fishing tackle boxes that I bought from K-Mart ($2.50 each). I made the timber bookshelf last weekend. I was hunting for a bookshelf that fitted in the space between the white bookshelf and the door, I couldn’t find one the right size, so I bought some pine and made it myself … I’m pretty happy with how that turned out.

Anyway, that’s my new electronics workspace. I’ve tried to organise the tools and consumables as efficiently as possible, making sure the things that I use most often are most available.

I am, however, moving the PCB manufacturing tasks out to my workshop in the back yard. Mostly so that I can keep things like Hydrochloric acid and hydrogen peroxide out of harms way, it also means that the fumes from acid etching don’t stink up our house.

Now all I need to do is to work out what my next project is going to be … I’ve been thinking about making an SMD version of my 9V to 5V Voltage Regulator circuit.

ATX Lab Power Supply – Planning Progress 1

I think that this project is going to take me some time … there are some bits of information that I need to gather before I can really do very much, some case modifications and some decisions about how I go about providing connections to the power outputs.

I have been given an Antec SmartPower 2.0 500W power supply with dual “pull through” cooling fans. The power supply seems to have all that I need (and some redundant bits that I need to plan how to handle).

I downloaded the manual from the Antec website and it seems to have most of the information that I need … so far.

My requirements are:

• Break out connections for 3.3v, 5v and 12v;
• Switch between 12V and variable power output;
• voltmeter display to show voltage output on 12V/variable;
• 5V USB output;
• LED power indicator;
• LED standby indicator.

To achieve the 12V/Variable I plan to put in a SPDT toggle switch to select either 12V or Variable. When the 12V/Variable is in either state, for the voltage to be displayed on a voltmeter. This means that I’m going to have to dedicate one of the 5V outputs to power the voltmeter.

The 5V USB should be fairly straight forward, I just need to connect the outer two pins on the USB connection block  to 5V and GND (the right way around).

I could embed the power supply inside a purpose built case that simply connects the power supply 20+4 connector into a compatible PCB connector and then break the connections out from that. That would also mean that, should I need to change the power supply later, that it is independent of the case and breakouts.

Anyway, I’m going to do some research and mull over the options before I do anything else with this project.

ATX Lab Power Supply – Plan

Well, my next project is a more reliable power supply for my bench. So far, I’ve managed my power needs by using a 9V battery, a 5V USB cable that I modified, or a AC power adaptor.

That’s been fine, to a point, but it doesn’t really give me the power that I need to supply multiple projects, plus, I’m forever having to set the power up to connect to my projects. I’ve made a couple of USB power cables and modified a couple of AC power adaptors that have the right DC power output, but I guess I want to go further.

I will be acquiring an old ATX PC power supply unit that I plan to modify to provide me with 3.3V, 5V, 12V and a variable power supply. The 3.3V, 5V and 12V will really just be a matter of minor modification to the ATX power supply. I intend to use an LM317 to build a variable supply from one of the 12V outputs on the ATX.

I’ll also build a new case for the power supply so that it both looks decent and is a bit safer. I don’t want to have an ugly and dangerous power supply on my desk, my darling wife would, most likely, object (truth is … so would I).

When I have the ATX, I’ll go ahead and void the warranty so that I can see how many of which value supplies I have to play with. I’ll also go through some testing to make sure that the on board supplies do what it says on the box.

According to Pinouts R U and Help With PCS the 20 pin Molex connection provides the following:

3 x 3.3V, 5 x 5V and 1 x 12V. There are some other connections (like ground, power OK, and power on). I can use the 3.3V and 5V as they are, but I’ll need to do something with the 12V so that I can get 12V as well as 1.25V – 11V (I think … there is some power drop across the LM317, so I’ll need to test that).

I think that what I can do is provide a SPDT switch on the 12V rail to either give me 12V or power through the LM317. Ideally, I’ll need a voltmeter on the adjustable power rail so that I can see what power I’m dialling in.

The 12V rail will go out to the LM317 with a potentiometer and voltmeter. I will keep the cooling fan in the build so that power that is dissipated as heat can be managed.

I’ll drill a few holes in the front to put in some banana plug connectors through the case.

I’ve found some pretty nice designs online so far, so I’ll be able to simplify my design process somewhat.

Anyway, that’s the plan so far. I’ll follow up when I have the ATX and I’ll make sure that I record the discovery and design phases.

AC Adaptor Power Supply – Acrylic Enclosure

This weekend I made an enclosure for my AC Adaptor. The requirements were pretty simple … make an enclosure that has holes for the power switch, potentiometer, input wires, output wires and for the nuts to anchor it to the base.

I also wanted the enclosure to be clear so that the LED power indictor would make the device light up when it was powered … I didn’t want to have to look for a single 5mm LED on a black enclosure, so I decided that it would be a good idea to make it from clear acrylic. It would also add to a 70’s kind of vibe, a.la. “Orac” from Blake’s 7.

Another reason that I thought that a clear enclosure would be good was that I had spent some time and effort in making the simple breadboard design uncluttered and “pure”, and I didn’t want to hide the electronics away from the world. It is what it is, and there is a certain aesthetic appeal.

So, with that in mind, I went and (carefully) hacked up some 5mm clear acrylic sheet. I did the rip sawing of the sheet using a jigsaw with a hacksaw blade (24 TPI – teeth per inch). I made a guide from a straight piece of pine that I had lying around and this gave me a piece that was about 10cm x 80cm. I then cut the work piece using a chop saw. I got some chip-out on the cuts with the chop saw because the blade was just a standard timber blade with 3 TPI. I’ll be getting a higher TPI blade for the chop saw when I can afford it.

After cutting the sides, base and lid, I then measured out where the holes should be, and the diameter of the holes. The Potentiometer needed a 6mm hole, the switch needed a 5mm hole and the holes for the wires and nuts were all 3mm.

Then i had to cut another top and another face piece because I had not accounted for the height of the breadboard inside the case (d’oh!). The breadboard sits on 4x12mm threaded nylon standoff spacers … I forgot the 4mm of nut that came through the bottom of the standoff.

I used an general purpose Tarzan’s Grip glue (the kind you use for gluing plastic models together). This kind of glue melts the plastic pieces together and forms a weld. You don’t want to use a cyanoacrylate (superglue) because:

1. It doesn’t glue the pieces together well enough and
2. It causes “ghosting” on the plastic … kind of a white smut on the surface that is very difficult to get off.

I then used some acetone to clean up the joints. You need to use some care with acetone in this case because it can also cause some ghosting and because breathing in the fumes is toxic. I dipped a cotton bud into the acetone and then rubbed the joints vigorously.

Then I sanded the edges until I was happy with the surface … I could have sanded more and I could have gone to a higher grit (I only went as high as a 600 grit). I didn’t want the joints to be invisible as I wanted them to catch some of the glow from the LED. This was going to highlight the edges and make them more of a feature.

Here is the end result.

With the power turned off … and

With the power turned on.

At the moment, the top is just sitting on the enclosure. I want to make some acrylic hinges from some cut-off pieces so that the enclosure is all one piece.

The only real downside to using clear acrylic for the enclosure is that it shows up fingerprints very well … and I don’t want to keep cleaning it.

The next thing that I want to make for this is the bending jig for the heating element so that I can actually use it to bend acrylic. Well … that’s a project for later.

NOTE: After using this circuit with a 12V Adaptor, the potentiometer started smoking, so I would NOT recommend that you use it for anything beyond 9V. For 12V, you would need a higher resistance potentiometer at least.

Further Note: After more investigation, this is entirely the wrong approach for building a variable voltage supply. I’m now going to start looking at building one based on an LM317 transistor.

AC Adaptor Power Supply – Recycle – Part 2

CAUTION: Modification of AC Power Adaptors is potentially dangerous. Read the specifications on the adaptor and observe output and polarity. Mistakes with AC Power can kill you. If you are unsure of the specifications of the adaptor that you are tinkering with … throw it away and get one that you know. Do not do ANY soldering on the adaptor or it’s cable when the adaptor is plugged in. I take NO responsibility for your safety, that’s your job.

Okay, so I’ve repeated the safety warning … I’ve completed the breadboard edition of the circuit and, honestly, this is enough. I don’t need to make a PCB for this at all.

This is the top view of the supply. The power comes in from the left (at the moment it is connected to a 9V NiMH battery, but I intend to connect it to a 9V AC Adaptor). You can see the layout, it’s pretty straight forward.

This view shows the arrangement more clearly. I have spaced everything to fit on a 50 mm x 70 mm prototype board. It could be smaller, but it really doesn’t need to be.

I’ve pad soldered the components and used the component legs to bridge. It’s a pretty tidy solder job and I’m pleased with that aspect of the build.

When the SPDT switch is thrown, the LED lights up to indicate that there is power running through the circuit.

When I built this on the solderless breadboard, I had the unattached SPDT pin connected to GND and another indicator LED connected to the wiper (Leg 2) of the potentiometer. There was also a connection from Leg 1 to GND in t he solderless breadboard version. When it was running, the 9V battery was getting very hot, so I decided to cut these elements from the circuit rather than try to work it out (I know, sometimes I’m lazy) … I figured that there was re-routed power going back to the terminal block (and on to the 9V battery). I was going to look at putting in an IN4001 diode to protect the power source … not sure if that would have any benefit, but I’ll re-breadboard it at some later date and report back and improve the circuit.

I probably should connect Leg 1 on the potentiometer to ground via a resistor, but what the hay … this configuration works out just fine. There isn’t much variation in the power output when you spin the dial though. With a charged 9V battery I get 8.9V through to 8.1V when turning the pot.

I plan to make an enclosure out of acrylic sheet and using the circuit to supply power to a resistive wire for a heating element.

AC Adaptor Power Supply – Recycle

NOTE: This project was a bit of a failure … I’m redoing this project using an LM317 instead of just using a POT to try to adjust the power. If you follow this project, you will only end up with a pretty circuit that doesn’t do anything very useful.

CAUTION: Modification of AC Power Adaptors is potentially dangerous. Read the specifications on the adaptor and observe output and polarity. Mistakes with AC Power can kill you. If you are unsure of the specifications of the adaptor that you are tinkering with … throw it away and get one that you know. Do not do ANY soldering on the adaptor or it’s cable when the adaptor is plugged in. I take NO responsibility for your safety, that’s your job.

In my previous article on power supplies for electrolytic etching I made use of an old AC Adaptor (wall wart) to provide power via a switch and potentiometer to an anode and cathode used in a simple circuit to an electrolytic etching bath. The adaptor recycle can be used for other purposes, and in fact I made a polystyrene hot-wire cutter using this same circuit. Now that I’ve used the project in a couple of different “tools” I suppose that it’s time to revisit the design and see what can be improved or changed.

My new application for this project is in a tool that will be used to bend acrylic sheet. There are a couple of interesting articles that can be found on various sites scattered across the interweb. I’m not going to list any here, they change too often. You can look at sites like lifehack and instructables for some pretty good examples of polystyrene cutters. The power supply is really what I’m interested in, so I’m going to focus on that for now.

Essentially, the AC Adaptor power is passed through a circuit adding a switch to make it easier to turn the power on and off, and through a suitably resistant potentiometer to allow the user to adjust the output power, effectively controlling the heating element (or in the case of the electrolytic etcher, the copper electrolysis anode). It’s also a good idea to install a power indicator in the circuit to improve safety (a visual indicator that there is current passing through the circuits output terminals.

So, in my case, I’m using this supply for three tools and two different types.

• Heat:
  • Polystyrene Hot Cutter;
  • Acrylic Heat Bender; and
• Current:
  • Electrolytic Etcher

So there is some versatility in the simple circuit.

The circuit above has two two pin screw terminal posts. The left-hand side is where the AC Adaptor will be connected to the circuit and the right-hand side is where the power will be output.

There are 6 parts (well 7 if you include the circuit board):

• 2 x 2 pin screw terminals;
• 1 x Red LED;
• 1 x 220Ω resistor;
• 1 x SPDT switch;
• 1 x B 10kΩ potentiometer (the resistance value of the pot should be increased to 100kΩ if you are using adaptors between >9 and 16V, I’m using a 9V adaptor, so 10kΩ … larger than that and you should probably not be using the adaptor at all).

I have connected the input power to a SPDT switch. This is where we turn the power to the output off. Of course, the power to the circuit is still live, you need to turn the wall socket off to completely power the circuit off.

The 3rd leg of the SPDT connects to the power indicator LED, which is connected to ground via a 220 ohm resistor. Additionally, the 3rd leg of the SPDT connects to the Power (leg 3) of the B10K potentiometer. The Wiper (leg 2) of the B10K potentiometer connects to the positive output terminal.

The negative input terminal connects to the resistor of the power indicator LED (as mentioned previously) and to the negative output terminal.

Connecting the load anode/cathode is done via the output terminal. I have a couple of banana plug to alligator clip connectors that I use, but bare wire end to spade connectors or any other appropriate connectors should be OK.

This is a good project candidate for mounting in a project box. I’m planning on bending some acrylic sheet to make the project box for this circuit … or you could make a pretty one by adding an instrument panel like my Steam Punk themed Electrolytic Etcher panel.

Create your own Order Tracking Excel

Here is a simplified version of my order tracking application. I’

Start out with columns…

• Order Number – you increment this … it’s there for sorting
• Date of Order – The date you placed the order (and paid)
• Category – An arbitrary category used for column filtering
• Item – A short description of the item
• Description – A more detailed description of the item
• Cost – The total cost for the order
• # Items – the number of pieces
• Cost Each – a calculated value of the cost per item
• Vendor – the name of the vendor (sorting and filtering)
• Sent Date – the date that the vendor tells you the order was sent
• TTS Days – Time To Send days (calculated)
• ETA – The date that the vendor estimates for delivery
• ETA Days – the estimated number of days to deliver (calculated)
• Arrived Date – the date that the item actually arrived
• ETA/ATA Difference – the difference between estimated and actual (calculated)
• Travel Time – the time that the order was in transit (calculated)

Now to put in some calculations … This is where the value is added. I’m using Excel 2010, so these formulae are using functions that I know are there in this version … don’t blame me if your spread-sheet doesn’t have the DATEDIF function!

Cell Reference	Formula	Purpose
H2	=F2/G2	calculates the cost per item
K2	=IF(J2<>"",DATEDIF(B2,J2,"D"),"")	Calculates the number of days to send the order
M2	=IF(L2<>"",DATEDIF(B2,L2,"D"),"")	Calculates the estimated number of days to arrive
O2	=IF(N2<>"",IF(N2>L2,DATEDIF(L2,N2,"D"),DATEDIF(N2,L2,"D")),"")	Calculates the difference between the Estimated and Actual time to arrive days
P2	=IF(N2 <> "", IF(N2>J2,DATEDIF(J2,N2,"D"),DATEDIF(N2,J2,"D")),"")	Calculates the number of days for the order to arrive

Copy the formulae down the columns in the spread-sheet and you should be good to go.
You can turn on Filtering in the spread-sheet so that you can track individual vendors and item categories.
When you don’t enter an ordered date, the item is, effectively, a wish-list item.
Well … that’s my piece for today. Hopefully, I’ll have some free time on the weekend to carry on with my LED bedside light.

Here is a copy of the spread-sheet for personal use.

Speaker Cable Rats Nest Tester

Our new house has speaker cables wired into the walls. There are quite a few pairs coming out in a couple of locations and a manual switch carrying 4 speaker positions. Some of the speakers are dead, none of the cables are labelled = hassle.

I figured that the easiest way to start would be to connect the speaker switch to an amp and see which speakers activated.

When I tried this I got some confusing results. Switch position 1, one of the speakers in the lounge room come on (there are 2). Switch 2 … nothing, Switch 3 … nothing, Switch 4 … nothing. Now for the confusing bit. Switch 1 and 2, I get Lounge and Kitchen. No other combinations give any results.

The next approach is to pass a current down the speaker cable attached to an LED. If there is any illumination in the LED, then the cable is OK. I’d then label the speaker cable and I can then move on. The cables that don’t illuminate are dud.

I built a very simple testing tool that has a power supply at one end (a 9V battery) and an LED at the other end. I connect the speaker cable at one end of the wall to the power supply and probe the remaining speaker cables (including in the roof) until I get a glow.

I must stress that this is a VERY simple tool.

The idea here is that the speaker cable should carry the power from the source to the indicator. It really is that simple.

So far I’ve tested and identified one set of cables, but I still have to crawl around in the roof to locate the others. I don’t know what I’m going to find, but I know that one set of speakers that I pulled apart to investigate (internal speakers mounted out-doors under an awning) had disconnected spade connectors inside. I fixed these and now they work just fine … I just haven’t found the other end of those cables yet.

I expect that I’m going to find speakers in parallel as well as in series. I’ll probably also find cables that have been gnawed by critters.

By the way, the test tool cost be about $10 and the most expensive part of the tool was the pair of project boxes that I bought from Jay Car.

If you run cables through the wall, please label them so that, later when you sell your house, the new occupants don’t curse your name.

Hot Wire Polystyrene Cutter–Part 4

Finally! I got the time to install the 12V AC Adaptor into the polystyrene cutter.

I also put in a 5mm red LED and a 470 Ω resistor between the switch and the NiChrome wire. I did this because my switch doesn’t really tell me when the device is on. I simply soldered the Anode leg of the LED to the switch, the resistor to the cathode leg and a short length of wire between the resistor and the cutter “head”.

I cut the adaptor coupler off the end of the adaptor wire, stripped and tinned the wire and connected it to the terminal block.

Using a ready made power adaptor makes this a very simple circuit.

A possible enhancement would be to add a 10K pot between the resistor and the NiChrome wire.

I powered the cutter up and, presto, the NiChrome wire got good and hot. Hot enough to cut through the polystyrene with very little resistance. The polystyrene leaves some residue on the wire, but this can be picked off without any trouble.

I will make a smaller, hand-held version of the polystyrene cutter using a 9V battery as the power supply. The main reasons for making a smaller version are:

1. I can use the smaller pieces of NiChrome wire when it breaks (and it does break, so be prepared for it);
2. A hand held cutter can be useful for smaller more complex cuts.

The way that this works is fairly simple. The NiChrome wire acts as a resistor, the energy has nowhere else to go in the circuit so it is converted into heat … the end. I am bleeding off a tiny amount of electrical energy with the LED, but it is a trivial amount overall.

My youngest thinks that the cutter is cool and wanted to cut some shapes using it, she had no trouble after I gave her instruction. Then I got to explain the physics of the project … she thought that bit was boring (hahaha)

Hot Wire Polystyrene Cutter–Part 3

I’ve been doing some tinkering and going through old AC Adaptors to see what I had hanging around (mostly from old mobile phone chargers).

I connected a 9V adaptor to the styrene cutter and I still didn’t get enough current through to heat the Nichrome wire. It seems that my wire is too long to be able to generate enough resistance in a short enough space to produce the heat that I need to cut the polystyrene.

I have a couple of options:

1. Reduce the length of the Nichrome wire. This isn’t a particularly attractive option as it means that I have to do some structural remodelling of the table and arm;
2. Reduce the gauge of the Nichrome wire. This option doesn’t seem practical as I have pretty much exhausted my supply here in Hobart. I could harvest some Nichrome wire from an old soldering iron (that’s what’s used to heat the iron) … this is possible, but I’ll use this as a fall-back option; and
3. Increase the voltage of the adaptor that I’m using. This is probably the best next step in the design evolution of the polystyrene cutter.

I tried connecting my 12V car battery charger to the cutter to see if increasing the voltage to 12V would have the desired effect. The cutter certainly made some clean cuts, but the internal fuse in the recharger kept on tripping, so I can’t really use that in the long term.

Cleaning out some old electronic equipment, I found a 12V adaptor that used to power a TV antenna (with boost/gain). The antenna is now obsolete since analogue TV has now been phased out. The adaptor is 12V 600ma, so that should deliver the power that I need.

I will probably also need to remove the 5V fuse from the circuit … I’d also like to put in a light (such as a LED) so that I can see when the power is on. At the moment, the toggle switch doesn’t give any indication that the power is on … so I am also guessing when the circuit is actually live.

I’ve made power connection a little bit easier for myself by including a screw terminal block.

Changing the power should be a fairly quick operation, I just need to cut the connector from the end of the adaptor cable, tin the wire and then connect the cable ends to the screw terminal block. Fixing in the LED is going to be a little bit harder … but not too hard.

Hot Wire Polystyrene Cutter–Part 2

I gave the base of the cutter a coat of wood filler and then sanded it down. The next step was to go to the electrical supply store. Off we went.

I bought a single throw switch (push button), an inline fuse holder, a couple of 5V slow fuses (in case one blows, I now have some spares) , a couple of speaker wire holders and a 4m length of NiChrome wire.

I wanted to mount the switch in the arm so that it would be easy to turn the cutter on and off. The plywood for the arm was a little thick, so I drilled a hole through it for the switch (1/4”) and then cut a rebate into the front so that the switch would be slightly recessed.

The washer and nut were then put on the other end of the switch and tightened.

The power supply hot wire attaches to the switch and then goes into the fuse.

I am using some speaker wire clamps to hold the NiChrome wire. The clamp in the top arm is attached to a small plate inside the arm so that the wire is held over the hole. This gave me a little bit of a problem, because turning the knurled head is difficult in the space that I’ve left myself. Bad design, but OK for what I need. I can tighten the head with a pair of pliers.

The other end of the fuse attaches to the clamp.

Underneath, the job isn’t very hard. There is just so much space underneath that it is a dream.

I made a small barrier under the body that will hold the lower speaker wire clamp in place. Then I wired it up.

The AC Adapter is then threaded through the back of the arm and we are done.

The last thing to do was to take the cutter out to the shed and see what I could do with it.

Turns out … not very much.

The cutter does indeed cut, but it does it very slowly. I think that the adapter that I am using just doesn’t have the chutzpah that I need. However … it is more likely that I just have to wait for the NiChrome wire to heat up sufficiently. I certainly didn’t give it that much time. Oh well, I’ll give the cutter some warm-up time and see if that makes much difference, although I am leaning toward the point of view that if 5V ain’t enough, then maybe 12V will … I’ll start hunting for a 12V AC Adapter.

The bottom line here is that, I made a Hot (Warm) Wire Polystyrene Cutter for a total cost of about $20. If I had to buy the plywood for this project and the AC Adapter, then it would probably have cost me closer to $60. But that is still a hell of a long way shy of the $600 that I’ve seen these puppies advertised for.

I will repost when I have jiggered around more with the power for the cutter.

Hot Wire Polystyrene Cutter

There are definitely two schools of thought when it comes to carving polystyrene. On the one hand, there is the sharp knife, saw, rasp and sandpaper camp. The benefits of using hand tools is that you have the pleasure of being able to handle your material and the designs can be more organic. The down side to this method is … polystyrene dust. I have seen some truly awesome models using this method of carving. On the other hand, there is the hot wire camp. Hot wire gives you a clean, crisp. The down side there are fumes from burning polystyrene.

I’ve tried using the saw and knife method and, clean-up is a pain in the ass. I used to have a little hand-held hot knife that I used to use for making terrain for wargaming. It was a little 9V battery in a plastic grip connected to a U bar with a wire running between the ends of the U. This was a pretty easy way to cut polystyrene.

Finish is the other determining factor with the choice of methods. Knife, rasp and sandpaper leaves you with a rough surface. Hot wire leaves you with a sealed surface … but one that has been melted.

I’ve decided to make a bench hot wire cutter. The machine will have a opening that is about 12” high and the bench itself will be about 12” x 24”. The first job is to make the body of the cutter. This is basically a 12” x 24” box with a L shaped box added to the short end. The L has a hole in it for the wire to pass through and the bed has a hole that takes the other end of the wire.

Add a wall adapter, a fuse and a switch and we should be away.

I had an old mobile phone charger (5V) which is, basically an AC to DC transformer that steps the power down from 240 to 5V. I’ve cut the plug from the end of the adapter and exposed the two wires (black and green). I have soldered a red wire to the green and a black wire to the black wire of the adapter.

I’ll put an in-line fuse into the wire and mount a switch onto the arm so that I can easily turn the cutter off.

The cutting wire attaches between the red and black wires to complete the circuit. I am planning on using fine steel guitar string as the cutting wire, so I’ll either take one off the Fender, or go and buy another one.

I plan to put a spring loaded connector at both the top and bottom attachment points to that the cutting wire is held taught.

Today I did the timber work. I had some old plywood sitting around with nothing to do, so I did some cutting, gluing and screwing in the workshop. Tomorrow it’s back to the electrical store to get a switch and fuse. If the music store is open tomorrow (Sunday in Hobart) then I’ll get a guitar string as well.

To get the position of the wire hole in the base, I had the arm detached and positioned in the right place in relation to the body, but with the arm resting on the base and then drilled a pilot hole through the arm and base at the same time.

The arm is attached to the base with four bolts that pass through the inner wall of the arm and then into the wall of the base. I want the arm to be able to be removed for when I want to store the tool on the shelf.

Well … now I’m going to go to the electronic store and get some more electronic stuff to make the hot wire circuitry. If they have NiChrome wire at the store, I’ll get that instead of using a guitar string.

Sickle repair

A while back, I bought a broken sickle from the tip shop. The blade was in good condition and not twisted. The reason that the sickle was at the tip shop was that the tang was broken and the handle was long gone.

When I got it home, I beat out a new tang for the blade and welded it on, then ground it down (roughly) … and then it stayed in my shed for a while.

On the weekend, I did some mowing with my ride-on Husqvarna. I just went around the paddock fence line so that I would have an easier time of putting up the new fence. I also cut around the chicken coop so that the chooks could scratch up some insects.

As the goats hadn’t been out, I decided that I’d cut the grass closer to the coop than the mower could get … and that I’d use the sickle.

I honed the blade to a nice sharp edge and then went to town on the long grass, cutting it and dropping the cuttings into the wheelbarrow. Of course, not having a handle on the sickle gave my hand a pretty hard time … and before long, my hand was bleeding from the rough parts of the tang gouging my finger.

Enough was enough! Last night I took the sickle back to the shed and cut a new 2 piece handle from some spare cedar and then I cut some 5/32 brass rod to make some rivets. I cut the cedar on the band saw and then I drilled three holes in the tang and matched the tang holes with holes in the handle blanks. I gave the handle a rough shaping with my bastard rasp and then set the rivets (that just means I hammered the rivets until they were flush and then used the centre punch to finish them off, rivets in handles don’t need to be mushroomed, just thickened a little). Then I rasped at the handle some more until I got the shape that I wanted, then it was onto the sandpaper.

The place that my finger was taking the most damage from was the 90^o angle between the blade and the tang, so the new handle is cut to ease this into a soft radius. I also shaped the handle so that it fit the curve of my hand better. Later on, I’ll rub some linseed oil into the wood … but that isn’t all that necessary.

Sickle repair

A while back, I bought a broken sickle from the tip shop. The blade was in good condition and not twisted. The reason that the sickle was at the tip shop was that the tang was broken and the handle was long gone.

When I got it home, I beat out a new tang for the blade and welded it on, then ground it down (roughly) … and then it stayed in my shed for a while.

On the weekend, I did some mowing with my ride-on Husqvarna. I just went around the paddock fence line so that I would have an easier time of putting up the new fence. I also cut around the chicken coop so that the chooks could scratch up some insects.

As the goats hadn’t been out, I decided that I’d cut the grass closer to the coop than the mower could get … and that I’d use the sickle.

I honed the blade to a nice sharp edge and then went to town on the long grass, cutting it and dropping the cuttings into the wheelbarrow. Of course, not having a handle on the sickle gave my hand a pretty hard time … and before long, my hand was bleeding from the rough parts of the tang gouging my finger.

Enough was enough! Last night I took the sickle back to the shed and cut a new 2 piece handle from some spare cedar and then I cut some 5/32 brass rod to make some rivets. I cut the cedar on the band saw and then I drilled three holes in the tang and matched the tang holes with holes in the handle blanks. I gave the handle a rough shaping with my bastard rasp and then set the rivets (that just means I hammered the rivets until they were flush and then used the centre punch to finish them off, rivets in handles don’t need to be mushroomed, just thickened a little). Then I rasped at the handle some more until I got the shape that I wanted, then it was onto the sandpaper.

The place that my finger was taking the most damage from was the 90^o angle between the blade and the tang, so the new handle is cut to ease this into a soft radius. I also shaped the handle so that it fit the curve of my hand better. Later on, I’ll rub some linseed oil into the wood … but that isn’t all that necessary.

I’ll post some pictures of the finished sickle later on.