How to make simple "motion" sensors

Step 2 First type - construction

You need to solder the ball and the spring together like you can see it on the picture. Then solder a piece of the hard copper wire (from the mentioned one) to the other side of the spring. Next you need to make a circle at the end of the remaining wire - the bigger the circle the less sensitive will the sensor be (but maintain the proportions - or position the spring correctly). You can also set the sensitivity of the sensor by shortening the spring (or by stabilizing the root of the spring - e.g. by soldering). I know it is a little bit hard to tune it properly for your needs, but it is possible.