Laser-cut dogbone wire storage

29 Oct


Some convenient storage for small amounts of wire.



The problem. I’m a bit of a hoarder, I admit. This is a tangle of twisted pairs of wire, each about 2.5m long. It’s messy, which means it’s in the shed, rather than the craftroom where I’m likely to use it.


I tried cutting a spool out on the laser cutter. This is a 120mm diameter spool, with 3x tabbed plates in the centre. It fitted together very well. Once I squeezed it in the vice, it held together with no problem, even when not glued. However, it’s far bigger than I need.


I made some smaller spools. These are just 80mm across. Again, they fitted together well, and they are a more convenient size, but still too much work.

About then, I realised I really didn’t need anything so complicated (though I’ll use the spools for some things, I’m sure). Instead, I went with a very simple, and therefore quick to cut, ‘dogbone’ shape. These are 80mm long, 40mm wide, necking down to 20mm. All cut from 3mm mdf. I can cut 6 of these in the time it takes to cut one of the small spools.


I designed a 3d printed holder that the end will just fit into, located by the shape and the 4mm hole/pin. There’s a hex shaped handle to fit in a cordless drill. A clip fits over the side to keep it in place, though the fit was actually so firm that I wound some without bothering with the clip. One of the nice things about this was that I could use the .dxf file from cutting the dogbones to define the shape. The actual size of the mdf part was smaller all around by 0.1mm (half the 0.2mm kerf of the laser) than the design specified. That proved just enough margin to get a good fit.


Here’s the 3d printed holder with the laser-cut dogbone in place.


Mounted in a drill chuck, with wire being wound on. I wound with very little tension which makes for a messy coil, but I hadn’t bothered rounding the edges of the mdf so I didn’t want too much force kinking the wire. I did design the centre of the dogbone to be just big enough for a wrapping of 50mm/2″ masking tape, but didn’t bother. If I want to use this for valuable wire, I’ll just 3d print some barrel pieces to make it round.


This is the “after” shot. I’m *much* more likely to use up this wire on projects than when it was a tangled mess. I cut 42 dogbones out of a $1 piece of mdf, though I could have got 60 out with a more careful packing.


Compact ATX power supply to lab supply conversion

7 Oct


I wanted a simple 12V + 5V supply of power available on my (already very crowded) desk. There were already two other supplies in the room (one of them a fancy fully ajustable lab supply), but they were … metres away. I wanted something right beside the keyboard for powering Arduino experiments, etc.

I took a standard PC power supply, cut off the plugs that go to the motherboard, and wired a small (100mm x 75mm x 30mm) box onto the end. The actual supply is tucked a few feet away.

This is my original 12V/5V conversion. It’s ugly but it’s been in use for nearly 20 years. At the time I didn’t know what types of (cheap) connector would be most useful. I fitted a push to open, release to clamp fitting off a stereo, a ‘chocolate block’ screw terminal block, some RCA phono connectors, and a solder tab that alligator clips attach to easily. In actual fact, I’ve found the RCA connectors the most useful. They’re quick, easily salvaged from old electronics, and I haven’t melted any yet, even running 5+ amps through them for hot wire cutters.

Here’s another compact conversion – just a simple terminal block with GND, +3.3V, +5V, +12V, and GND again.


And another one where I unsoldered everything except three of the 12V lines and three of the ground lines, plaited for convenience.


Here’s the victim – a bog standard supply. I’ve cut off the mother board plugs and removed the zip ties. Note the messy tangle of wires.


I used the laser cutter to make up a couple of “cable combs” to tidy up the tangle of wires. I split the wires into two sets, as they were different lengths.


Here you can see a comb in use, taking a tangle of 12 wires and keeping them nicely parallel as I zip tied them. A side effect was that the resulting cable was much straighter, without the curves that were in the original wires.


This is the unit that will sit on my desk. A simple laser cut tabbed box (yay for Inkscape and the Tabbed Box Extension). There’s a chunk of angle iron (20x20x3) glued in for weight, and beefy resistor to put a load on the 5V rail. (I believe most modern supplies no longer require this). Two rows of RCA connectors – 3.3V, 5V, 12V. Since I long ago standardised on red for 5V and yellow for 12V (same as the power supply wires), I don’t need to label them. There’s a socket (black) for the 5V standby which stays on when the supply is turned off, a switch which turns on the supply, a power led, and another press connector stolen from a stereo. (They come red and black, I painted one tab yellow).


As I mentioned, some of the wires were shorter, so I decided to add in another box with just 5V and 12V and some salvaged connectors. This box was made with thicker 6mm mdf to give it some weight. The black objects were 3d printed covers to disguise the salvaged state of the connectors.


The printed covers did make things look tidier. However, they were a BAD IDEA. It took way more effort than they were worth, and the one fault I found when I tested the system was in one of those covered connectors – now potted with hot glue and no longer accessible.


I rebuilt the “secondary” box with a new design. I made another 100x75x30 tabbed box in 6mm mdf, but this time with a cutout area and four 3mm holes. I tapped the holes, M4, with a tap in a cordless drill. A 3mm mounting plate goes over the top, this time with proper panel connectors, and screws down. This was much better than the first attempt, and I’ll use the technique again.


Here’s the result. It all took more time than I’d expected, particularly the actual soldering of the wires. With so many wires fitting in a small space, I had to do some messy joins. Lots of incentive for me to get on top of laser cut/etched printed circuit boards.

However, I’ve got a useful tool that may get me doing more Arduino/robotics projects. I also learned a lot about using Inkscape, and found some techniques for making enclosures that I will definitely use again.

Cheap laser engraved plant markers

5 Oct


We recently planted a whole heap of berry plants (Cranberries, Chilean Guava, Orangeberry, Loganberry, Boysenberry, Blueberry, Blackberry, Black Currant, Red Currant, Gooseberry, Pomegranate, and Strawberry).  They came with stickers, but we wanted something more permanent.



This is the berry patch (and the neighbour’s house)  it’s hard to tell but there’s about 50 plants in there, excluding the 100 stems of raspberry.


I bought a cheap ($7) box of kindling from the supermarket. These boxes came with various sizes of wood, but the one I picked had a lot of 300 x 50 x 10 (about 12″ x 2″ x 3/8″) pieces, at least at the top. I probably got at least 20 good pieces out of the box, and the rest was good kindling anyway. I imagine this is all cheap pine (roughsawn).


The result was not bad, certainly good enough for a quick and dirty marker. My first experiment was the one at the the top (Orangeberry). This was RASTER engraved and ended up about etched about 1mm deep. It was clear and readable, apart from the smoke damage at the top. The downside was that it took ages to burn – nearly 20 minutes just for one marker.

Inkscape, once again, came to the rescue. There’s a very handy extension under Extensions – Render – Hershey Text, which takes text and writes it in VECTOR format, using the sort of fonts that were used by pen plotters in days gone by. It’s very readable, and far, far, faster. The slowest label above took under 30 seconds to draw.

Note: Tucked in the documentation was a suggestion to run Path – Simplify on the text produced. This only takes a moment, and it does smooth out the text and make it look nicer.



These were the engraving parameters I used on my 80W CO2 laser. Basically 85%, but reduced slightly on the corners. However, to make the text more readable, I mis-focussed the laser. I set the focus distance with a 12mm thick block sitting above the target. This made the lines quite a bit wider. Interestingly, it also changed the cross section to a much more V shape, rather than the usual |___| shape.









Laser cut boxes to tidy kitchen bench

2 Oct


A quick project, most of it done the night before a party.


My wife complained about the mess on the kitchen bench. Lots of little bits of “stuff”, of many sizes. I thought about making a partitioned tray, but decided we might do better with an array of small boxes, allowing flexibility to use the space efficiently, and to swap boxes around if one section outgrew its container. Also, as anyone who’s had to get pointy things (e.g. drawing pins) out of a fixed compartment will attest, it’s much easier to lift up a box and empty it out.



We weren’t too sure what would be a good base size for the boxes, so I ran off a few samples of different sizes. We tried a 40mm x 40mm, and 50mm x 50mm, but quickly found that 60mm x 60mm worked well. We settled on 30mm high. Since these were just test boxes, I didn’t bother flattening the top edge, as that was the slowest step. These are all made from (cheap) 3mm mdf.


All of these boxes were designed with the wonderful (free) “Tabbed Box Maker” extension for the (free) Inkscape program.


The interface is very simple – just put in your dimensions and instantly get all the tabs worked out. It’s *much* slower doing it by hand, as all the tabs have to be a bit wider than the slots, to account for the laser’s kerf (cutting width).


The laser cuts quickly, but do enough cuts and it adds up. For 5 of the 60×60 boxes and 5 of the 120×60 boxes, the cutting took 17 minutes. I really need to realign the laser as I’m sure I should be getting better speeds. Here are the 50 pieces required.


And here is the remainder after I cut them out. This is a 600×400 piece of mdf, worth about $1. Alert viewers may notice a problem with the shapes. I carefully flattened one edge of each side, so the the top of the box would be flat, not crenelated. However, in a moment of dumb, I flattened one edge of the base (far left) as well. Had to recut those.


Here are a few of the boxes. Default settings in tabbed box maker gave me parts that fitted together easily but tightly, and could be squeezed into firm position. They held together quite well, but I added a bit of PVA wood glue just for certainty.


The result looked very promising. I burned a second set of 5 x 60×60 and 5 x 120×60, and one long 300×60 for scissors and a letter opener. Much tidier.


I wanted to store pens and markers as well so I made a double height box (60x60x60) and some dividers.


When you get the measurements and calculations right, laser cut parts just slide together in a very nice way.



Here’s the final (so far) result. It does spread things out more than the original piles, but at least you can find things. When we decide it’s finished growing, I’ll make a laser cut tray that just fits around the whole set.

Tidying up cables for the laser

26 Apr


I’ve had the new laser cutter hooked up via various extension cables and plug boxes. Every time I turned the shed lights on, I had to listen to the sound of the laser’s exhaust fan and air pump, as it was too much trouble to hunt down the appropriate cables and unplug them when I wasn’t using the laser.

I decided to make it easier on myself by using a switched plug box – but then I needed to remember which switch turned on which device.

With a cad diagram sorted out, I grabbed a random chunk of white painted hardboard (I have no idea what it came off – probably some bit of demolished furniture). I covered the surface with masking tape.


Next step – burn all the mounting holes. There was some metal shelving near the laser, with holes at 50mm spacing, so I made holes for attaching the board using those. Also holes for zip ties, and for the plug board (which I’d hot glued small feet to).


Now, lightly engrave the text, along with some indicating lines. The sockets on the plug board weren’t evenly spaced, hence the odd angles.


The result, fresh our of the laser.


I peeled off the masking tape over the letters. It came off easily, but I should have been more careful to press the remaining tape back down. I’d wiped the board down with a damp rag before I applied the masking tape (it was very dusty) and the heat of the laser may have bubbled the remaining moisture.


Now an application of black spray paint.


After an hour, I peeled the remaining masking tape off. There’s a few blotches, especially near the bottom, but it’s certainly readable. The letters are about 50mm (2″) high.


The final result. A bit rough, but quite satisfactory for a first try, and it should do the job.


Straw and cardboard vegetable bed

21 Nov

S vegetable bed - 06 complete

As a bit of an experiment, we knocked up a couple of beds for vegetables.


The outer frame is just four length of Oregon 100×25, joined at the corners with screws. I added 8x 45° braces in the corner as well. The result was fairly rigid. I did try nailing them together with my framing nailer but it didn’t work well. Here you can see Barbara watering the ground inside the frame, which is simply plonked on the ground.

S vegetable bed - 01 watering

We covered the ground with a couple of layers of cardboard from packing boxes.

S vegetable bed - 02 cardboard

We marked out a grid of points (about 200mm spacing). Then I got out an electric drill and a 75mm (3″) holesaw and drilled 48 holes through the cardboard. The slowest part was digging the cardboard disks out of the holesaw.

S vegetable bed - 03 holes

I didn’t have any proper soaker hose, but this “sprinkler” hose was on special so we wound that between the rows. Once the straw goes on, it should still let us water under the mulch.

S vegetable bed - 04 hose

Then the planting! Here Barbara and Rachel are placing seedlings (cabbage, beans, etc) and putting pea straw around them. I dibbled a bit of dirt out of each hole with a grubber, and Alexandra recorded which seedlings went where. Ignore the messy wood pile in the background.

S vegetable bed - 05 planting

Final result doesn’t look to bad. This represents about $5 of wood, $2 of screws, a $7 sprinkler hose, and about $20 of seedlings.

S vegetable bed - 06 complete

If it works, we can easily replicate a bunch of these.



Seedling propagating bed – two week update

19 Apr

First – there are seedlings growing!

S seedling bed improvements 002

And quite a lot of them. The first seedlings came up after about 7 days, and now there is at least one seedling growing in 215 of the 350 pots.

An automatic cutoff when the bed is flooded.

S seedling bed improvements 004

This is a simple float switch. When the float (a section of pool noodle) is lifted by the water, the wire rotates around a bearing and presses the microswitch which cuts off power to the pump. There’s a “control panel” visible to the left. Pressing the square button powers up a relay which turns on the pump, but it also supplies power to the relay so it keeps running after you take your finger off the button. When float rises, it cuts power to the relay which switches off, and stays off until pressing the button starts the cycle again. There’s also an override switch, a fuse, and an LED to light up.


S seedling bed improvements 008

As the water flowed across the bed, then sat in the reservoir, it started forming algae. We started considering options to stop the buildup, then hit on the idea of advancing towards our eventual goal of aquaponics by adding a couple of fish to the system. We’ve always intended to have goldfish as part of the larger system we’re planning, but we had to do some furious research to see if it was workable.

The reservoir is renamed “the fish tank”

S seedling bed improvements 010

A visit to a pet shop netted us two quite small fish, some fish-food, a thermometer, and an air pump. I modified an old sieve by cutting holes for outlet pipes and wires, then placed two water pumps (the original pump and a smaller one) inside the sieve. A collection of stones from the beach at Birdlings Flat and a couple of chunks of brick all serve to hold the sieve firmly against the bottom of the tank. I’m fairly confident that the fish won’t be able to get near the pump intakes. The air pump is outside the tank, with a hose leading to the bottom of the tank. We used it before the fish moved in to make sure the water was well oxygenated but haven’t kept it up as (a) it was really too loud and vigorous, and (b) it ran off 240V whereas everything else is running off 12V (solar) power. As an alternative, the second (small) water pump inside the sieve feeds out to a hose which splashes water back into the tank, adding oxygen in the process.

The algae has gone, the fish seem happy, and they have definitely grown.

Anti-cat barrier and air circulation fans.

S seedling bed improvements 001

We strung some loose strands of bright 4mm rope on three sides to dissuade the cats from jumping up onto the seedlings. Seems to have worked so far.

We’re quite worried about “damping off”, the fungal disease(s) that like to destroy young seedlings. The seedling pots are quite moist and, while we haven’t had any problems so far, conditions are quite good for fungus to develop. Many sources recommend fans moving the air about to dry the top layer of soil, prevent stagnant moist air from sitting around, and also toughen up the young seedlings. I didn’t want to use a mains powered fan so I grabbed eight PC fans salvaged from various computers and hooked them up. They’re hooked up in pairs, with each pair joined in series so the fans, designed for 12V, only get half the voltage (6V) and turn over slowly and quietly. It took a surprising amount of time to hook them up but they seem to work very well. The biggest problem, and one that almost caught me out, is that each pair of fans should be of similar power. I was amazed how many different ratings there were in the my fan collection – each of the four pairs in use here is a quite different rating.

More controls

S seedling bed improvements 005

Each step we take seems to require more controls, especially adding the fish. I really need to add some timers to the system, and perhaps a water level detector for the fish tank. Perhaps a moisture detector to tell how damp the soil is. Lots of options. I’ve started working up a system based on an Arduino microcontroller.