Rover 2 is Born

posted in: Arduino, Rover 2, Wheelchair | 0
Rover 2 Front Above
Wheelchair Frames Dream of The Day They Are Retrofitted for Robotics Glory

Today we introduce Rover 2! Rover 2 is one small step for our project, one giant leap in terms of utility. This robot frame is made to carry people, and in the USA, that’s often an ambitious proposition.

Enough talk, let’s jump into a photo essay showing the migration from lowly Rover 1 to mighty Rover 2.

We welded a stainless plate to the wheelchair’s seat mount
Rover 2 Stainless Welded Platform
This base will come in handy before long when we want to ramp up the platform size
You’ll find that the ability to weld is irreplaceable when building big robots. Cheap welding machines are readily available. Mr. Money Mustache offers a gentle introduction to welding if you’re anxious about jumping in. Alternatively, you may find that a generous donation to your local trade school’s welding program will pay considerable dividends in your future robotics endeavors.
Rover 2 Electronic Platform
We removed the electronics platform from Rover 1 and added a clear 24v JD2914 relay
Parallel ATC Fuses
Parallel ATC Fuses — Didn’t have a Maxi fuse holder laying around, so we’re using 2 30a fuses in parallel on the battery. This is clearly a hack.

Question: what to do when you don’t have a 60 amp fuse holder laying around the shop and you need to fuse for 60 amps of current? We went for a hack: use two 30 amp fuses in parallel. I fully agree if you’re thinking that this is not an ideal move, but our alternatives were: 1. Wait for Maxi Fuse holder in the mail, or 2. Use unfused power source. Option #1 is out because our project must steam ahead, and option #2 is clearly a sin which could prove deadly. We went for the dual 30a fuse solution and it worked out fine.

Playing with Heat

We’ve previously talked about these curious heat shrink solder connectors. The last experiment with Rover 1 was so short-lived, I decided to give them another go with a little more current on the line.

XT60 Heat Shrink Solder
XT60 Heat Shrink Solder (before heat gun)
XT60 Heat Shrink Pre Solder
XT60 Heat Shrink Solder (before heat gun)
XT60 Heat Shrink Post Solder
XT60 Heat Shrink Solder (after heat gun)

XT60 Connectors Are Great

If you’re planning numerous missions with your big robot, you’ll be charging it every day. You want to be able to easily plug up the charger. Here’s a simple solution: wire an XT60 connector in series to the power supply. I love these little connectors and I’ve never seen them have a failure of any kind. If you don’t have a few male/female sets in your bag, you can snag them reasonably off Amazon or eBay. Keep in mind 2 things when ordering:

  1. Double check that you’re ordering both male and female ends. You don’t want to purchase 5 pigtails, lose sleep eagerly anticipating their arrival in the mail, then receive the package and with horror find that they’re all male adapters.
  2. Keep an eye on the gauge (thickness) of wiring. For instance, in the Amazon link above you’ll see the first/cheapest pigtail results are for 14AWG (2.5mm) wiring. That may work for your application, but you may need 12AWG (4mm) pigtails if you’re pumping a ton of current — we specified 12AWG (4mm) in the eBay link, just to make the point about wire gauge.
XT60 Male Female
Clarifying XT60 Nomenclature (fancy way of saying I won’t remember either)

The picture above is presented in an effort to clear up any confusion about which end is male or female. I’m sympathetic to this confusion because the plastic shroud of either connector is the gender opposite of the inner metal connectors. Wow, this is creating more confusion. Let’s just stick with the picture above.

More Love Letters to the Electric Wheelchair

XT60 Wired to Charger
XT60 Wired to Charger
Charging Rover 2
Charging Rover 2

If you’ve been following this blog you know that I can’t stop raving about these wheelchair platforms. Here is another fun trick: cut the factory 3 pronged end off your wheelchair charger and solder/crimp a male XT60 adapter in it’s place. BAM! Just like that you’ve got a great charging system for your robot.

Mrs. Roby would really appreciate this kind of effusive praise directed her way a little more often. I know a lot of you engineer men out there are with me, right? Why is it so easy to talk at length about wheelchairs but writing 2 paragraphs to your sweetheart in a Valentines Day card seems like an insurmountable mountain?

Wow, things just got way too deep. Let’s sign off with another series of pictures:

Rover 2 Front Right 45
Notice the rubber anti-vibration mounts aren’t really necessary for this application (sans IMU)
Rover 2 Front Angle
If you look closely you’ll see an 80 amp rating on the relay — wouldn’t bet on that if I were you
Rover 2 Back Angle
Notice the green relay ground wire sliding down from the platform connects to the on-off switch
Rover 2 Back
The location of the on-off switch is a little odd due to interference from the frame
Platform Beneath
Here’s a look at how things appear from below
View from above (before wiring up motors)

Wrapping Up

Let’s stop there and save the software and tuning for the next post.

Here’s a hint: sparks are going to fly.



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