I've read (skimmed really) through the How Does Minecart thread and collected what I could find on practical designs for dwarfputer components using minecarts. There was unfortunately very little on the subject and I had a couple ideas of my own so I thought i'd make a thread devoted to the topic so you don't have to look through 40 pages.
If you'll indulge me,
this was the goto design pre-minecarts for storing memory for large and complex dwarfputing machines. Another design where you simply have a pump continuously pump water over a pressure plate to send an 'on' signal and turning it off, letting it drain for an 'off' signal was also used as a power-to-signal converter. I mention these because you're going to see just how much easier it is now to store binary data with minecarts.
Binary Memory Cells:Binary Memory Cells store binary data as a 1 or 0 (on or off). For minecarts this means a minecart occupies a pressure plate to create a 1 and by some means removed to make a 0.
It's split into 3 versions to show where the minecarts go, what's beneath the minecarts and what's beneath the rollers and pressure plates.
How this works is I got 2 carts, a copper one at the top and an iron one in the center. A copper cart weighs 357 Urists and an iron cart 314 Urists. The pressure plate in the center is set to activate at 350 Urists, so the iron cart doesnt trigger it. Activating the gear/roller (green one), making the copper cart push the iron cart to the other end before rolling onto the pressure plate will trigger it and send an on signal. Visa versa (the iron cart will push the copper cart just fine even though it's a little bit lighter) to send an off signal. This design is the most space-efficient of the memory cells but lacks the activation speed of the next design due to the first cart having to push the second cart before being moved onto the pressure plate itself.
A modular example of this design:
This design is slightly longer, having 4 tracks instead of 3, but has the advantages of activating the pressure plate almost immediately upon power being sent and not having to mess with weights. To activate, power is sent to the green gear, pushing the top cart into the second cart. Like a Newton Cradle, the first cart transfers its momentum to the second cart, knocking it to the other end while the first cart rests on the pressure plate to send an on signal. The gear is then turned off. To turn it off power is sent to the red and the reverse happens.
A modular example of this design:
Power-to-Signal Converters:A power to signal converter sends an on signal when power is applied and an off signal when power is cut.
When power is sent to the gear the roller pushes the cart around in a loop, passing over the pressure plate repeatedly to maintain an on signal. When power is cut the cart returns to the starting position and disengages the pressure plate. The roller in this example pushes the cart from E->W. Pay close attention to the track layout to make sure it works properly. The 2 walls at the top are all that's needed to keep it from derailing.
A modular example of this design:
(Signifigant changes would need to be made to allow for extra gears for more advanced mechanical logic gates, but it can still maintain a comparative advantage in size to any minecart logic design)
After being propelled by a roller, a N-S track ramp in this PSC uses gravity to send the cart back the other way (and to the roller) to maintain an on signal. As far as advantages go to this design or the looped PSC, it's really a matter of preference and use, though the looped version can be more compact in a modular layout.
A modular layout using this design:
An angled version of this is also possible but has no real advantages over the straight version.
Other Designs:A simple changeover switch based on the Newton's cradle memory cell. Rollers directed to the center, activation of the northern roller pushes the first cart into the second cart, engaging the northern pressure plate and deactivating the southern plate. While both will be active momentarily because of the deactivation delay, neither can be deactivated at the same time and one will always be active.
A 3-stated version of the changeover switch, it consists of three pressure plates with only one active plate allowed at a time (should the gears be linked to not allow certain rollers to be activated at the wrong time).
Three just weren't enough. This is a 4-stated switch, allowing only one at a time to be active should the gears be correctly linked to disallow unwanted minecart movements.
I was able to take the load adjusting pressure plate concept of my memory cell and put it into a possible power-to-signal converter. It functions much like the memory cell, but with different linkages (and an axle). Now i'm not so sure if this can be called a power-to-signal converter since you don't simply send power to a gear and the thing maintains an 'on' signal, or be considered a memory cell, but it's really all about how you use it.
Both gears are off by default and the power is connected to the dark green gear. Be it by lever or pressure plate, both gears are switched on, sending power to both rollers (directed to the center). The copper cart pushes the iron one to the other side, but before the southern roller has time to push it back north the copper cart is rolled onto the pressure plate which turns off the dark green gear (and the southern roller). The light green gear is still engaged but no power is being sent to it because the dark green is off. This was the sort of "eureka!" moment when I saw that rollers immediatly stop when power is cut (unlike screwpumps) to allow this. (sorry if this is common knowledge, i'm a bit late to the game in getting into the 2012 versions)
Both gears are switched again when you want to turn it off, activating the dark green gear and disengaging the light green, sending both carts back to their starting points, deactivating the pressure plate which turns the dark green off again (but keeps the roller on long enough to push the iron cart thanks to the pressure plates 'off' delay). Everything is back to how it was at the start.
With the other pts examples, only 1 gear is needed to be switched to turn them on and off. If you treat both of these gears as you would a single gear then I guess you could also call it a power-to-signal converter, and is the only one that has no moving water or minecarts when it's in the on position. Useful if you have a whole bunch of them active at the same time and want to minimize lag.
Now i'm not sure, but the implications of this last component might be huge for dwarfputing. That with a single lever or single pressure plate you can trigger an on and off signal on another component without any continuous moving parts wasn't possible with the mechanical-fluid logic examples I listed at the top of this post. It might be possible to use it as a binary memory cell aswell, except I don't think there would be a 'standard' design and the gearing/linkages would need to be customized to the task it performs. I might have to make something, or at least plan it to see.
tl/dr LOL SCIENCE
If I was unclear on something or there's something i've overlooked please let me know. I've tested all these designs in a real fort and they appear to work flawlessly.
Post any of your own ideas if you like, so long as it has a use in dwarfputing