This was my entry for a recent contest involving 555 timers (now also an entry for the Open [18+] category for the Robot week Contest) and I wanted to share how to build it! It's a robot that can be set free on any ferrous metal structure. It has rare earth magnets for wheels (covered in hot glue for traction) attached to micro servos modified for continuous rotation. The bot closely resembles the Beetlebot by Jerome Demers (aka Robomaniac), as it uses limit switches to change the direction of the bot. When the switch closes it shorts the connection and cause the servo pulses to manipulate the direction of the servo. I used a 555 timer for each servo to set up the 1.0 – 2.0 mS signal needed. I used servo tester boards from Gadget Gangster that I modified to suite my needs. Here's a video of the bot in action:

Step 1: Materials Needed

Material List:

- Gadget Gangster Simple servo testers
- Neodymium Disc Magnets
- HiTec HS- 55 Micro Servos (Pretty common micro servo at most Hobby shops)
- Limit Switches
- 9v Aluminum Battery Holder
- Antenna wire are salvaged from a Wok Box handle (very solderabe)
- Female Header cables
- Automotive Terminal Connectors
- LM2937 5V Voltage Regulator (a 7805 will do)
- Caps for the regulator and 820 ohm & 15 kohm resistors
- 9V Battery
- Plastic Bead


- Soldering Iron
- Flush Cutters
- Flux Pen
- Hot glue gun
- Needle Nose Pliers
- 1.35mm Drill Bit (or somewhere close to that size)
- No. 0 Philips Scredriver
- No.1 Flathead Scredriver
- Solder Wick
- Tweezers
- Heat gun or Hair Dryer
- Utility or Hobby Knife
- Multimeter

P.S. This instructable will assume you know how to solder, if you don't, please check out info on other instructables, MAKE blog, & Solarbotics as they inlude a tutorial in most of their kit documentation.
I think it be hungry!!!!
And thanks to this instructabe, I now know how to Modify a HS-55 with a minimum of fuss! <br>Thanks! and cool little bot!
This is great! you should put an ultrasonic drop off sensor to detect when it is close to the end of the fridge so it keeps going with no risk of moving of falling off.
I was thinking the same thing while watching the video, but with photointerrupters... Ultrasonic works better though!<br>
great minds think alike!
I was thinking of something like this:<br>https://www.instructables.com/id/Tiny-Wanderer-A-Table-Top-Robot/step4/The-Code-and-How-the-Sensors-Works/<br><br>(phototransistors are cheaper than ultrasonic sensors)
They sure are! plus they are easier to interface.
Hey man,<br>Thanks for the 'ible, I'm adding it to my group! 5/5<br> Win Guy
nice robot :D
Thanks Toby, keep it up with the instructables they look good!
thanks :D

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