Someone’s inspirational iterative approach index card wasn’t 100% accurate.
Someone’s inspirational iterative approach index card wasn’t 100% accurate.
Eating at a picnic spot or wilderness campsite is great, but prep can be tricky.
You still want decent kitchen utensils, but for knives there’s a downside to having something sharp and pointy rattling around in your belongings!
When you have a 3D printer, problems like this have an easy solution…
I want to build a unique mechanical counter and I’ve come across an interesting design challenge.
There are marble “clocks” that count up the time – typically in a rack of single-minute balls, a rack of 5-minute balls, and a rack of hour balls.
When the last ball reaches a rack, it dumps out all the balls and sends a single ball to the next rack.
I’m thinking this concept would be great for a mechanical decade counter – just have one rack per digit of what you’re counting.
With chimes, strange lifting mechanisms, or “complex just because”
Most of these clocks are like type A – they use racks with a “deer scarer” tipping mechanism – when enough balls land in the rack, they all tip out.
Some like type B use a better alternative – the last ball bounces out and releases a gate that allows all the stored balls to roll through the rack.
All the existing designs have a common flaw; balls flow from top to bottom, the least significant rack is at the top. To read the state of the display you have to unintuitively read the racks from bottom to top.
This seems a bit ‘wrong’ to me. Naturally you read numbers from left to right.
An ideal mechanism would:
I want to design a 100% modular “digit” of such a mechanism, so I can stack as many of them horizontally as needed.
Conservation of energy.
If the design is like the above picture, where the rail is flat…
When a rack is emptied, surely those 9 balls that fall out could be harnessed to transfer energy back to the rolling ball?
The devil being in the details, what would you suggest for the design of this “digit”?
Watch this space…
This article covers one method of attaching wires to a bare lithium-polymer battery pouch. This could also be done using a battery spot welder, clamping, or screwing.
Before you solder the terminals, plan your wiring.
Where should the battery wires exit the battery? In what direction will they go, and how far? (A scale printout of the layout may help)
Strip and tin the wire ends.
Each bare end should be slightly shorter than the battery tab’s width.
Peel back one of the battery terminals.
With a small file, roughen the outer half of the battery tab.
Fold the end of the battery tab over, to create a small ‘hook’.
It should be just large enough to fit the wire in.
Put a tiny drop of flux in the hook.
You can spread it around with a piece of wire.
Place the wire into the hook – making sure it matches the polarity – and press it closed.
It may help to clamp a little bit of the insulation in the hook as well.
Carefully, press the soldering iron against the folded hook.
The aim here is to heat up the tab, the wire and the flux, without heating up the battery.
If the battery near the tab is warm, stop and wait 2-3 minutes before attempting again.
Run the solder into the folded hook until it begins to melt and ‘wet’ to the metal.
As soon as it seems that a good contact has been made, stop. The solder should have bonded well to both sides of the hook, and to the wire as well.
Roll the tab up until it is inside the battery sled.
Replace the covering tape.
Repeat for the second battery tab and wire.
Once both tabs are soldered, the wires can be fixed in place with hot glue, and the area covered with a small quantity of masking tape. Complete!
There’s a strange machine in the workshop!
It’s big and interesting, but how do you make it do something useful?
This post will answer that, though it won’t make you a master machinist in one go.
I’ll assumes that you already made a design, and now you want to fabricate it.
The X-Carve comes with some cloud-based software called “Easel”.
There’s been plenty of hate directed at it. Easel is nowhere near perfect, but it can be wrangled into submission, and it can even be useful.
If you have complex requirements you might actually need something more advanced.
It’s possible to side-step Easel entirely, but it is way more complex, and not necessary for 95% of users.
Not typically worth it. So use Easel. Grumble if you want.
Easel works in the browser. Boo. On the plus side;
Easel only supports SVG import, not DXF.
Lots of scaling issues can occur when passing SVG files between programs. Blech.
Here’s a whole section just on getting your design into Easel – I have found a process that works:
Part B: CAM
CAM stands for “computer aided manufacturing”; how to get from a model to instructions that make a physical part.
This step isn’t particularly difficult, but it’s important that you pass the correct instructions to the machine!
I recently bought a heap of these switches – small DPDT toggle buttons – for $0.07 ea.These switches are not that large, the on vs off height difference is only about a millimetre, and I hate to think what the ‘rated cycles’ or debounce graph looks like.
…but how to read them all?
First of all, forget ‘one I/O per switch’, it will not scale well.
The most common method to wire up many switches is in a matrix.
Each row uses an I/O, each column uses an I/O, and pressing the switch connects that row and column together.
16 switches need 8 I/O, 64 switches need 16 I/O, it scales well. (and with a demux on one side, even fewer are needed)
However, switches are only simple electrical devices. When a switch is closed current can freely flow in either direction. If only one or two are closed, the patterns are unique. As soon as three or more switches are closed, a simple matrix can no longer read the switches with certainty. For example, there is no way to distinguish between these five switch states:
The matrix option will not be able to read all the switches.
This is a common problem faced by designers. What is the common solution?
A diode can be placed next to each switch to allow current only in one direction.
“What’s wrong with that?” Well, every switch needs a diode.
So now there are twice as many parts on the board, and you’ve got to find space for them, pay for them, solder them in…not great at all.
What other options are there?
Serves 12 or so?
This lovely cake is very tasty, quick and simple to make, and light but moist.
It was an accidental invention – the first time I made it, I was trying to make biscuits!
Serve with a hot or cold refreshing drink.
So good! Don’t tell your guests that it’s vegan, and they’ll never guess…
Makes a 20cm dia cake – Serves 8
Serve on its own or with ice cream/sorbet.
If vegan: Do your best to keep everyone else away from your precious cake. Precious…
In my previous post, I simulated some mechanical logic gates using a novel 3-bar linkage.
The dimensions of the linkage are critical to achieving correct operation;
Inputs , , must all produce the same output position.
For the simulations, an empirical approach was used. (fiddle with the values until it looks right)
This time, I’m going to attempt to find the exact values to use for a given stroke, separation distance and output position.
Ahead lurks tough mathematics (which may be unsuitable for liberal-arts majors)
If it’s hard to read, then sorry! It was hard to write!
Using this, we can calculate M’:
Now that and are found, and we know …
Ugly, but workable?
Pushed through Wolfram Alpha…
Thusly, one can calculate the input and output linkage lengths for any logic gate.
These dimensions will work for an OR gate too, as the linkages are just reversed.
It’s irksome that I couldn’t work out a symbolic solution for the last equations, especially since in the example came out to such a neat value.
I might revisit this further in the future, and it’ll definitely come in handy when building something with these gates.
Logic gates! The building blocks of computing as we know it. What if we ditch the electrons?
I want some mechanical logic for an upcoming project, so I did some research…
There are several examples of mechanical logic out there on the internet:
|Keshav Saharia’s Lego Logic||Push-pull, needs a spring return.|
|Randomwraith’s Lego Logic||Push-pull with internal rotating elements, reversible.|
|Mechalogic’s Logic Elements||Push-pull, AND & NOT reversible, OR needs a spring return.|
|Xiaoji Chen’s Linkage Computer||Rotating logic, reversible, some mechanical issues with parallelogram weakness.|
|Spillerrec’s Lego Logic Gates||Push-pull, very compact, needs a spring return.|
He identifies the problem with needing springs, but doesn’t have a fix. Mentions how AND/OR gates can be reversed to become OR/AND gates.
|Zeroumus’s AND Gate||Push-pull, needs a spring return.|
|KNEX XOR Gate||Push-pull, needs a spring return.|
|Carolin Liebl and Lisa Hopf’s NAND Gate||Push-pull, reversible, complex.|
For my project, I have the following requirements;
This disqualifies most of the designs I found, particularly the ‘no springs’ requirement.
Mechalogic’s AND gate design uses an elastic band, but doesn’t appear to need it, so it serves as a good starting point:
It’s time consuming to tweak parameters in the physical world, so I wrote a small simulation: (click to see in action)
Success! Meets all the requirements, and only needs three parts.
The geometry is important – the ratio will determine the output’s position when only one of the inputs is asserted, according to;
Now, can an OR gate be designed with the same success?
Most OR gates look like this; the output (on the left of this picture) has a flat plate, and either input will push the flat forward. Unfortunately the design needs that elastic band to return the output to zero.
Inspired by some earlier attempts to couple an AND and a backwards OR gate together, I tried flipping the AND gate around; (click to see in action)
Success! Oddly enough, an OR gate is just an AND gate connected up backwards.
Even the linkage lengths are the same!
Best of all, the OR gate is reversible like the AND gate – no springs and no force required.
As the graphs show, output displacement equals input displacement, so these designs should be chainable. Let’s have a look; (click to see in action)
Now I just have to build something complex with them…