### Mechanic NOR gate

Several years ago I tinkered around with making mechanic logic gates, so the LEGO Answers question: Is it possible to build simple logic gates with LEGO mechanics? caught my interest.

Keshav Saharia blog post Mechanical computation from Lego bricks was interesting, but I was not quite satisfied with his NOR gate. First of all the OR gate in it looks rather shabby in my opinion but most importantly it does not reset its state. It starts out in the TRUE position, but when an input becomes TRUE and the output becomes FALSE it will stay FALSE even it the input changes back to FALSE again. So I wanted to try making my own version based on Keshav´s design and the result is shown below:

(CAD file available, I just can’t upload it to WordPress and Brickshelf appears down at the moment.)

My version is a bit smaller as the frame is 6×8 instead of Keshav´s 6×10, but it does use a few more pieces. I’m not quite satisfied with my OR gate either as I’m not sure how much force it can transfer before becoming unreliable.

A rubber band have been added so the gate properly resets itself however it does create a new problem, more force is needed to go through the input in order to operate the gate. This is not a problem with just one gate, but imagine 10 of these stacked together and this force will become rather large.

So I believe that the axle approach will always be limited with that, because while most gates pushes, insert a NOT gate and it will start pulling which could pull the axle out of what might be connecting it.

I tried making an AND gate where the NOT gates are combined with the NOR gate (in order to make it smaller) but I didn’t succeed in making up a good design for the combined double NOT and OR gate. But inspiration have struck me and I have an idea how to make a XOR gate which will end up being about 6×12 and about 5-6 stud high. This will be my next goal.

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##### Comments
2 Responses to “Mechanic NOR gate”
1. RW says:

Credit where it’s due, Keshav Saharia’s gates were an attempt to simplify those found here:
http://www.randomwraith.com/logic.html
Nice to see you’ve identified that Keshav’s gates can’t be reset though.

• Spiller says:

You might be interested in the AND-gate I made afterwards which you can find on my new blog:
http://spillerrec.dk/2012/05/xor-gate/ (I moved to another host, but I’m not interested in paying wordpress.com each year for redirecting.)
There is no reset in it as it is just an example.

I liked yours better (as they actually worked) but I found Keshav solution more promising. However I’m not so sure anymore, so I want to try a completely different approach. I also present a compact XOR-gate in that post, but it is incomplete as I didn’t add the resets and I have no intent to do that, because as said I want to try something else now. Those rubber bands are a pain to work with anyway…