Wednesday, June 3, 2015

Lawnbot finally moves!


06/03/2015
  It's been a while since I have been able to work on this project,  but it is now sitting in the middle of my living room for some major upgrades and testing!  (and my wife is still talking to me?!?)
  I had a 30amp circuit breaker attached.  The first time I tested it, It blew the circuit breaker under load.  So I installed 2 ACS711EX Current Sensor Carrier -15.5A to +15.5A.  The PWM is set to max out at 60 (out of a possible 255) and with the current sensors shutting down the current draw at 13amps per motor,  it seems to run quite well.  Higher Current supply or different motors will be a future upgrade after I get everything running correctly.
  A couple other upgrades you may notice from the video: it has a separate wireless control that will be able to take control during autonomous activities or in an emergency.  The remote is made with an analog thumbstick/joystick,  an arduino nano clone,  4x16 lcd display and an nrf24l01 2.4ghz radio (2nd one on the lawnbot).
  I also added a mosfet and relay switch to allow the lawnbot's mega2560 to turn the high voltage/current to the motor controller.  The mega does a simple voltage check to ensure there is enough of a charge. If so will turn on the motor controller's,  motor current feed.  It does this with a simple voltage divide reading on analog pin 0.
  With the upgrades of the current sensors,  relay,  nrf24 radio,  new main power switch,  circuit breaker and various leds,  it has been rewired a couple dozen times and has some new 3d printed parts.  I think the controller will outgrow the enclosure soon,  so I may have to design another mount.  I'll try to get some newer pictures in the next few days.  (already much different than what is shown in the video above!)
  The next steps are to test the failsafe controller by driving it around the lawn for a bit. The living room is only big enough to do some parallel parking tests.
  If that works out well,  then I will start building a custom mount for the propane motor and it's starter motor as well.  These will always be manually controlled for safety reasons!

Wireless controller before 3d printed housing.  Uses external 5v USB batter

A view of the control assembly from a few weeks ago.  When the wires were still manageable!