Saturday, June 6, 2015

Lawnbot's off road test drive video!

 Here is an updated video of the actual lawnbot running on the lawn.  (water rationing in southern Calif.  So not much actual lawn!)
 Initially it kept stalling out a couple times a minute.  Pause for just a second.  I thought it was pulling to many amps and the code was shutting the circuit down for safety.  This was not the case.  It was actually reading the radio to soon and was dropping packets.  This result in a no connection result that put the code into a loop till it received valid data from the transmitter.
  I did find that the current readings were topping out at 10amps (each motor)  with a quick change of directions.  So I installed the - 30 to +30amp current sensors and have them safety checking at about 15-17amps. I'll check after the added weight of the propane motor and it's electric starter motor,  to adjust it any further.  Right now the pwm is limited to 90 out of a possible 255, so there is still a lot of performance possible in this build!
  In the video,  you will notice that it manages to drive up and over the border bricks.  This was a surprise since I didn't think it had that kind of torque/power.  Still quite a bit of fun left in all these recycled scraps!
  Motor mounts for the propane motor and it's custom starter motor are next on the list (after weight/amp tests).  So be sure to check back.  Any questions,  please let me know!

Wednesday, June 3, 2015

Lawnbot finally moves!

  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!