Monday, March 17, 2014

Yay! A Successful Steering Test!

As always, this week has bad news, good news, and more good news...

The bad news: My 3D printer bit the dust... well, the PEEK tube that joins & insulates the two halves of the hot end broke, so it's not going to be expensive to fix... just time consuming. I don't expect the parts anytime soon, but I hope they show up in a couple of weeks, since I'm paying $20 in shipping.

So I decided to do a couple of things while I wait:

1. I upgraded my version of SG Project while the upgrade sale was on. I use it to track tasks on the rover build, and it's a decent option for the Mac in terms of project management. I detest MS Project, which I have to use at work, so any alternate is a good. If you didn't know (or guess), MS Project is basically a big bloated joke if you aren't using the advanced features, like MS Project Server. But most clients aren't savvy enough to invest in it, so they basically get a more cumbersome, more expensive version of Excel. Sigh...

SG Project is nice as there is an iPad version as well, and it all syncs up. Considering I can be more effective using the iPad + SG Project than I can with a Windows laptop + MS Project... that's saying something. It's not all roses, however. The Mac version seems to run a bit slow and seems to use advanced graphics... since I can feel my MacBook heat up when it's running.

2. I tested out the voltage regulator PCB that will power the Beaglebone Black and the powered USB hub. It didn't go up in flames, which is good because I just added 4700 uF caps to all the regulator boards (there are four... so far...). When those caps go 'pop' it's loud and smelly... thankfully I haven't popped one in a few years. I was getting a nice 5v (ok, 4.99v) out of it, so that's a win. The four regulator boards are:

  1. Vmcu (for the BBB and USB)
  2. Vservo - distributed on the same I2C bus and used for remote actuators
  3. Vbus1 - half of the i2c slaves
  4. Vbus2 - no surprise, the other half of the i2c slaves.
The last three regulators are actually mosfet switched, so I can power down parts of the rover but leave the brains running. I think that will be handy...


3. I got my Sparkfun order in the mail today! It was actually February 17th that I ordered it, and March 17 that it arrived. So the FAQ says '4 weeks estimated shipping' for the free international economy, and it's 100% accurate. Coolness. In that box were the mounts for the steering motors, so I put the voltage regulators aside.

Now that Sparkfun carries Servocity/Actobotics stuff with free shipping, although with a 4 week delay, I'm happy. I'm not so happy with the $13 in customs fees, which is something I don't usually see/pay for when I order from Adafruit from NYC. I'm not sure why there is a difference...

Anyway... I was really, really interested to prove out that the motors can do the job of pointing the corner wheels, but I couldn't really test it out until those 3/16" clamping hubs arrived from Sparkfun.

These motors have to be fast enough to be responsive, and have enough torque to turn with the load of the rover on the wheels...  The results:

The last win of the day:


I need to get the other three steerable wheels upgraded now, since a reasonable test is to run the rover on the indoor/outdoor carpet in the basement. The nylon of the carpet is very grippy on the rover wheels, more grippy than on grass and gravel in the limited testing I've done outside. So if it can turn the wheels on carpet, it should have no problem in the real world.

The software needs a tiny bit of tuning and dampening, but overall I can see it's going to work. I probably also need to get the bogie bearing supports designed and rush ordered, since I can see that the central screw of the current light duty bearings isn't going to take much abuse. When that screw breaks (not if, but when...), all the ball bearings will fall out, never to be seen again. And the bogie (the two rear wheels on each side) will fall off. That would be a 'Bad Thing'.

Anyway, happy rovering, see y'all soon with another update...








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