Sunday, October 20, 2013

Brains behind Arduino Lawn Mower!

Finally got a delivery from China.  It is the new Arduino Mega 2560 R3 compatible MCU along with a the v2 Sensor Shield.  (this combination had the same pin to usb short I discussed in an earlier post.  Be sure to check that post for the fix or it will fry your mega 2560! (Arduino Mega 2560 shorts against v2 Sensor Shield)
 It took a couple weeks to be delivered,  but the price is less than a quarter of what the cheapest price vendors are offering it here in the U. S..  Not only do a lot of local vendors order them from china,  but a lot of auction sellers will take your money and have it drop shipped from china.  Well worth it to do some research and cut out the middle-man! 

Now that I started to put the components into the battery box,  it is getting very tight with the new SLA 12Ah 12v battery.  The solution is to build a multi-level control board that will slip right in beside the battery. Seems like it works very well,  but it might get a little tight after I start adding sensors and more wiring. 

Thursday, October 3, 2013

Hobby RC remote for testing the Lawnbot!

I've been stuck indoors, unable to work on the mechanical parts of our robotic lawn mower.  I took advantage of this time and wired a Futaba FP-R127DF 7 channel Receiver to an Arduino Uno r3 and wrote a few lines of code to see if I could get it to read the signal from a Futaba T6XH-Super PCM1024 6 channel transmitter.  Was a lot easier to get the Arduino to display the signals than it is going to be for me to figure out what they all are.  This is a programmable aircraft/helicopter remote with settings for just about everything.  Ailerons, flap, Swash Plates and mixing of all the signals.  Wish it was a standard RC car remote!  It's going to take some research to program the transmitter.  With what I do know now, I believe I can get it driving the bot. 
 I started out the day knowing nothing about how to read or interpret rc hobby remotes.  I searched and found a real nice tutorial over at sparkfun.  Wasn't as complete as I thought,  but there is additional info in the comments that will help get it working with dual motor controllers.  The actual page is:
 BTW, not sure if the Raspberry Pi running Raspbian allows for enough time slicing in the multi-tasking to be able to poll the serial ports (usb)  for an rc transmitter combo.  I originally started using the Pi to program the Arduino as I always do.  When I opened the serial port monitor to view the signals, the cpu bogged down and brought the entire system to an absolute crawl at 9600bps.  Made it unusable.  Was forced to bring out another machine with an OS that I loathe! If it weren't my kids, I would install linux on it.  If you were to really delay the polling, you may be able to read it, but I would really check into other OSs or distributions if you want to use it with the Pi.  This is one of the reasons I  will be using the arduino with the Pi on this robot. 
 Tomorrow I hope to post some new updates on the chassis.  At the latest I hope to have something actually moving my the end of next week!  
 I also updated the current hardware page.  This is really starting to run together.  I think it's time to separate the parts by project.  That way if you are trying to duplicate something,  you will know exactly what I  did it with. 

Tuesday, October 1, 2013

Large mower-robot chassis progressing quickly !

Here's a quick update since I haven't posted in a bit.  Work is going on daily.  At least a couple hours a day is what I have been trying for.  Lately I  have been working on getting a physical chassis up and running.  What is pictured is a first mock-up of my 3 wheeled mower bot.  
The 2 rear wheels are salvaged, geared drive, dual 12v, 25 amp motors.  Taken from a kid's power wheels ride on jeep.  Along with the dual 45amp mosfets driven H-bridge should be more than enough to drive this bot through any urban environment . 
 The cutter motor is a 25cc, 4 stroke propane string trimmer (weed whacker) motor.  I had built the system around the string trimmer's 18" inch cutter head, but the body size of 18x24 inches is extremely large for my yard and would not only cut the lawn in a couple passes, but prevent me from maneuvering in the tight areas.  So I believe I  will not only shorten the cutter head, but also the overall size by about 2/3rds.
  The next step is to mount the battery box and some of the computer equipment so I  can start testing the base with a 6 channel remote control.  I will be sure to post some videos of this step as well. 
 The next hurdle is going to be cutting up the motor's clutch housing and fabricating a cutter head drive.  Obviously I won't be able to use the 8 foot drive shaft that came with the weed whacker. 
  So anytime I am not posting,  it's not that I have given up on any of this project!  It's more like I am so involved and barely have time to do anything but work on this bot.  I really want it to move forward quickly and have a working, remote controlled chassis in the next couple of days!  (did I mention a contractor has the front of my house torn off at the moment?  Ah,  Busy days!)