So you’ve built a robot. Let’s say that it’s your second one. Typically, we buy a complete one as a kit, for instance, maybe a Smart Video Car from Sunfounder. We had fun building it, rolling it around.
But our developing dreams are growing and we soon realize that most of these type kits are really not much more than toys.
So we want to move up. And we did; we spent some real money and we bought something, maybe from Servo City, or maybe we spent yet even more money and we got a monster from Super Droid Robots.
Regardless, from where, as we move up in the level of robot, they tend to get bigger, heavier, faster, and stronger.
And that can quickly lead to problem. Disaster. Danger. Damage. The Three “D”s. :-)
(Sorry, I got carried away)
Trust me when I say that there will come a moment in your robotics tinkering and developing when you will wish you had built and added in some “robot insurance” to your wheeled menace.
I am making my own robot named Wallace, and it definitely needs this feature.
And that scenario or situation is the motivation for this Instructable.
Most of the higher-end motor-controller boards that can handle the bigger motors that draw upwards of 15A, come with a feature called an emergency-stop. An E-Stop.
It can be as simple as two pins on the board that you short together and that causes all motion to cease.
The concept or main idea in enabling such a feature to your robot implies that you’ll want a “watchdog”. A watchdog - well , it watches. Sort of. Actually, the watchdog is always ready and yearning to do its thing, however it is being constantly held back from doing it.
If we were talking about a real dog, imagine one straining against the leash, and as long as you hold on to the leash, nothing happens. The second you let go of the leash, the “watchdog” takes off to do its thing.
I have seen a few (very good) examples of roboticists creating some emergency-stop circuits, but a lot of times it involves the use of something like an Arduino or some small controller board that acts as the smart watchdog.
I propose to not use anything “smart”. To keep it as simple and as reliable as possible.”

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