3D printing opens up a lot of interesting applications and the printing technology should not be controlled. However I think releasing the pattern for a gun is irresponsible. Very few people would have the skill required to develop their own pattern and there is no advantage in making such a thing widely known.

Now that somebody has 3D printed and fired a plastic gun (no metal parts apart from the firing pin, bullet and perhaps a spring) and the design is out in the wild - is this good or bad?

You got through several electric blankets in five years in Australia!
"Quite cold" seems to be a very subjective statement in Oz.

Have you tried a hot water bottle? They will take the chill of a bed but also have the advantage of very localised heat.

Built in obsolescence is a nightmare, there should be a law against it. There was a film in 1951 "The man in the white suit" with Alex Guinness, I think in part it's story line was based on nylon stockings. Apparently when these were first introduced they were almost indestructible. A great boon for women but sales plummeted. As a result design changes were made to reduce lifespan.

Didn't the transistor come before the valve?
The transistor was bypassed because the manufacturing technology of the time made valves easier to produce.
Then manufacturing processes advanced and the transistor was rediscovered.

I am sure I saw recently some new audio equipment boasting of having valve based amplifiers, where would be the advantage in that?

one beam at ~1.5' and another at ~4.5' to try to cut down on false positives

Sorry I forgot to add you are thinking about this the wrong way round. False positives are fine in this instance, false negatives are what you want to avoid.

If you are going to do this then go for belt and braces. In other words laser curtains plus something like PIR.
Also make everything is fail safe in other words alarm on loss of signal. The system also needs to be self checking.
Best thing to do is look up how to design safety critical systems.

I don't know how well PIR works during the day. My experience of it is that deer enjoy floodlight banquets eating my garden at night, but detection in daylight may be a problem.

If you are coming from a software background, or even an electronics background, to a mechanical project then a key thing to think about is momentum. In software and electronics you are used to everything happening instantly. With mechanical systems you have to think of accelerating and decelerating masses and the time and energy involved. You also need to think about containment - if you have a mechanical failure how will you contain the sudden release of stored energy.

I agree with the comments about replacing the control board. That in itself sounds like quite a fair project and a good incremental step towards replacing parts of the mechanism.

If you are a new dad then this is a very young child. Unfortunately the only answer (and it comes a shock) is constant vigilance. You are on guard 24x7x356.

Physical barriers would be the next line of defense, but they won't work.
For electronic detection look at commercial systems to see how they tackle the problems, but they won't work either.

I have been in a pool on a couple of occasions when healthy teenagers have slipped silently into to trouble, no fuss, no noise, no splashing. Fortunately both times somebody spotted things were wrong i.e. floating face down unconscious on one occasion and just sinking to the bottom on the other.

Sorry.

Plugging in would not be easy, the inductive charging idea is much better.
Colliding with patients would be a problem.

The UV sterilization I don't see working with keyboards etc. or do you use membrane boards.
Perhaps some plastic cover that the computer could be operated through - but users might not like that.

[big]

ban all Fritzing circuit images? I think that they belong on the kindergarten wall.

As a beginner in electronics I find the circuit images help me to wire things correctly.
To convey the circuit design to others it does also provide schematics.

It is free, easy to use, and as CrossRoads said will probably move people towards more powerful tools.
When I look at some of the posts on this site it is actually a big step in the right direction so don't knock it.

PeterH asked

What is the nature of the 'thermal switch'?

That is a good question. You are having to constantly check something that has to run every 8-9mins for several months!
The switch sounds like some kind of protection device to stop overheating. Rather than sending messages can you not get to the bottom of the problem? If the system is regularly overheating them mechanical failure may be the end result.

You need to be exact about what you mean by controlling it.
You could certainly use an arduino to replace the manual controls.

uniquely identify someone walking (or jogging) by

Take a step back and try to be very clear and precise about what you want to do.
When I read the sentence above I think you want to tell if Jane ran past as opposed to John.
Is that really true or do you just want to know that somebody ran past?

RFID is only going to work if people carry tags.
You them seem to branch out into image recognition and an arduino is not going to do that.

An arduino will tell you if something has come close to your sensor but you are right it might be a deer not a person.

You might get more responses if you wrote your question in english.

If I understood your question the answer is that you are correct - it is not possible.

What might be possible is to use an arduino to build a WiFi signal strength detector.
You would then move the detector around to detect the strength in various locations.

Of course most laptops etc. already display signal strength so you could just use that.

A much larger asteroid trundled past between the Earth and the geostationary satellites on the same day. Was that complete coincidence or did they come from the same direction?

Apparently there is a fairly large one that currently has a 1% chance of a hit in 2048.

The odds of a hit in a populated area are low, but I doubt NASA can give strike positions accurate enough to be really meaningful.
Apart from the difficulty of accurately calculating trajectory once the thing enters the atmosphere surely there must be a large random factor ?

Maybe they could say an asteroid will hit the East coast of USA and the blast might be 2M tonnes, but is that helpful?

It seems there may be loads of entire planets cannon balling through space but again the chances of getting hit are slim.