By golly, I think this just might work!

Over the weekend I received the Virtuabotix temperature/humidity sensor and plugged it into the Arduino like the included diagram shows, downloaded the library from the Virtuabotix website, and right away I started getting temperature, humidity, and dew point readings. This little gadget will come in handy for monitoring the inside of the rover so I know the electronics are safe. I imagine in sunlight, the inside of the rover will be like the inside of a car so knowing how hot it gets in there, I can decide whether I need to use a bit of Mylar to keep the sun out or if it's not really needed. And also, knowing the temperature inside at night will be good so I can protect against dew build  up on the circuits.

 Since I was now getting information back from my rover, I decided it would be nice to know how many volts I have left on the battery. So I googled the code for such things and actually found the code on Arduino's website. 4 lines of code and a wire running to analog I/O port number 0. Since I'm dealing with a 10 volt battery and the I/O port can only handle 5 volts, I made a simple voltage divider circuit so the port only sees half the voltage and then I tweaked the code a little so it reports back 10 volts instead of 5. Unfortunately I did not take a picture of this set up before I took it apart to work on other things. But I'm sure you'll see it in action soon enough.

 I went out and got the solar panels I needed from Radio Shack and tested those on Sunday. Here I have a picture of a quick set up to take the 11.5 volts generated from the solar panels down to under 5 so I can monitor that voltage as well.

 I also received the ultrasonic range finder in the mail the other day too. I really haven't played with this yet but it should come in handy later for obstacle avoidance when I finally get this project rolling.

 Which brings me to my favorite part. I got the last 4 motors in the mail yesterday. I soldered on some wires, quickly hot glued them in place with some wheels attached, added lines of code for the new motors, and got a few tests done this morning.

 Yes I'm using a sugar dispenser for a test stand. It was the only thing tall and skinny enough around for such a quick test. But anyway, in the video you can see the Amps measured from the battery. I switch between high and low speeds to see the changes in Amp rating. 220 mAhs for all 6 motors on high! This means I can drive around for, ideally, 7 hours on a charge. Once I get the camera and servos in place, that number will likely drop quite a bit though. 

Now of course I had to set it on the floor just to see what would happen. 

 It kind of reminds me of when I was a little kid trying out ice skates for the first time. Obviously I'm not going to simply hot glue motors on and expect them to stay put. So now the next phase in this project is the suspension. I'm thinking hollow tubes for suspension arms, to hide the wires in, and some kind of torsion spring to allow for movement. More on this later. Stay tuned!

A successful drive-motor test!

Nothing too fancy here. Just a couple of my new motors hot glued on with some wheels attached. But I was able to prove that just 2 of these little motors with their gear reduction systems are powerful enough to move the rover.

 So naturally after this test, I ordered 4 more motors from Amazon. And also added a temperature/humidity sensor and a distance sensor for when I finally get this thing moving and outside.
 Also since I had it moving back and forth on the floor, I thought I'd test out my speed settings. In this quick video, you can see me switching from low speed to high speed and back to low. (Sorry I wasn't really watching where I was aiming the camera on this one. Big pet peeve of mine! But you get the idea.)

 I can range the motor inputs from 0 to 210. Low is currently set at 50 and high is set at 200. I'm thinking low needs to be even slower so maybe I'll drop the number down to 20. But that can wait until I get all 6 motors properly attached.

 I'm also leaning towards this Autopilot so the rover can follow GPS way points instead of relying solely on commands from my laptop. It's a bit 'spendy' but this is kind of the ultimate goal with this project so it is a little bit necessary. Otherwise I can go with this GPS tracker to simply send coordinates back and I can plot them on Google Earth for some project "cool factor" points. This option is much cheaper but really has no functionality since the wireless range on the Arduino's XBEE system is about 300ft, which means I'll be able to physically see where it's at.

 Expensive parts are starting to lead me to maybe look into crowd funding for this project. I think total cost of parts, both used and not used, and tools that I needed for this project, is around $500. And I still need the $100 camera system, solar panels, suspension parts, some kind of parachute system, and an entire guided rocket to build. Sooo... next on my to do list is to look into crowd funding websites. Soo.. Stay tuned!  

A maker's dilemma

 For the past couple of weeks I've been working on a prototype for the drive gear system. With the laser at The Hack Factory not cooperating (I'm told a really nice one will be in the shop some time in Sept.), I had to resort to some old school model making. I printed the outline of what I needed on a piece of paper and stuck it to a sheet of acrylic and cut out my pieces with a band saw. Then had to do some sanding but eventually I got this:

 All the pieces I need to put this gearbox together! So I started putting it together and filed the holes big enough for the bearings and motor and lined everything up. I was reluctant to actually glue everything together so I used some double sided tape and hot glue to produce this:

Then I added the motor and slapped on some wheels just to see if the gear system was strong enough for one to pull the whole thing along.

I started out with a simple test to see if it would even work. So I put it on a piece of tupperware and sent it the drive signal.

  And it actually worked! A bit louder than I thought it would be too. After this video it started to skip some teeth and sounded like the battery was going to die. I think the motor got warm enough to soften the hot glue I had holding it in place and caused it to move away from the gear that it was so perfectly meshing with. I also decided that the skipping wasn't horrible so it was time for a floor test. No video of this however since it didn't actually go anywhere. I didn't think it was necessary to glue the main gear onto the axle for the test so of course it slipped and there for did not turn the wheel. Oops..

 So with the battery sounding like it was going to die, I did some electrical testing. The battery was holding strong at 10 volts so I switched to measuring the amps and was a little shocked to see that the motor and gear system, along with the arduino boards, was drawing 750 mAhs. Sooo.. I figure with all six in place, my little 1600 mAh battery would last about 15 minutes at best. Judging by the sound of the motor, it would be far less. 

 I ended up ordering a couple of motors with their own gear reduction system on them. $15 a piece so not too bad. But they were 6 volt motors so I wasn't sure how they'd work.

 So my dilemma is that they do work! Very well actually! They're super quiet and total draw from this and the arduino boards is only about 150mAh! That's about 10mah from the motor! I could drive all day with all 6 of these hooked up. So I guess my dilemma is kind of a no brainer but I still feel like I put so much time and effort into that gear reduction system, it would be a shame not to use it. I guess we'll see how much power these little guys have once I figure out a way to mount them and attach the wheels. Perhaps tomorrow I'll rig up a quick attachment and see if the 2 motors I have will be powerful enough to move everything.

  Also, on the C++ side of things, I figured out pretty easily how to send information back from the Arduino so that I know I'm getting a good signal and also what command I sent it. I also tried some code so that I can control the speed of the motors as well. So by pressing numbers 1 thru 4, I can give it 4 different speed settings (or as many as I want I suppose).

 Hopefully by this weekend I'll get this thing moving and more motors ordered. I'm 4 months behind but finally I might have some real movement!