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 .idea/
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+
+*.private.sh
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 # simple-robots
 
-a
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+## Some simple and fun robotics projects 
+
+[pong-catapult.md](lego-ev3/pong-catapult/pong-catapult.md)
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diff --git a/lego-ev3/pong-catapult/pong-catapult.md b/lego-ev3/pong-catapult/pong-catapult.md
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+
+# pong catapult
+
+One of the easiest robotics projects, with a single motor and repeatable interactions.
+
+Distance where ball launched could be controlled with motor speed.
+
+
+
+## Required components
+
+- Lego Ev3
+- wifi dongle
+- microsd card
+- some lego parts
+- several ping pong balls
+
+
+## Steps
+
+1. Install linux on sd card for ev3 brick.
+    https://www.ev3dev.org/docs/getting-started/
+   1. Download, unzip.
+   2. If linux: `sudo dd if=ev3dev-stretch-ev3-generic-2020-04-10.img of=/dev/sdb bs=4M status=progress conv=fsync`
+      1. then `sync`
+   3. If windows: use win32diskimager or similar app.
+   4. Wait 2-10 minutes so OS image is written to the card.
+   5. Turn on, connect to wifi.
+2. Test app for motors.
+   1. Get the project from https://git.makerobots.eu/konstantin/lego-ev3-java .
+   2. Update IP address.
+   3. Connect motor to port A .
+   4. Run gradle deployAndBrickRun task.
+   5. When the brick beeped, press the right button to test motor.
+3. Assemble a sturdy structure with a motor.
+4. Place ball and test.
+5. Iterate (structure and code) and try to launch a pong ball:
+   - as far as possible
+   - as high as possible
+   - exactly 30 cm (use the plastic cup or some bowl)
+   - exactly 1-meter distance.
+
+
+