Lara's Lego H-015 Sentry Droid

[Markus]

Good to see your progress - it's really coming along. The effect from the holonomic wheels is great, it looks as if it is floating around. I am curious what motors you are using, and what battery. For my projects, I have been using the cheap yellow plastic "gear motors" from eBay or AliExpress. But at Shrevecon they had a carpet, and my H015 had big trouble moving forward. I probably need to upgrade the motors and, possibly, the battery. So, it would be nice if you could share what you are using, maybe including details such as torque and RPM.

[kresty]

We have Pololu 37D 30:1 gearmotors - https://www.pololu.com/product/1103

The battery is a "12V" lifepo4 (Shoria, not spec'd for this use, they don't like that at all (they've chided me about it) but have still done returns for me) - In the past the battery killed my R/C motor and ESC because the volts are > 12V, however this is the same motor we use for L3-G0's dome, so I'm not worried about that. The battery's probably overkill, but it's the same as we have in the other droid.

We aren't particularly happy with our batteries, they are motorcycle replacement and not intended for deep cycle, so we kill them faster than we should - however we haven't found a replacement yet.

[kresty]

Uploaded code sample that we're using for the HO15.

Motors "just" add the appropriate inputs together to get values to drive the wheels. Communication with the R/C & Motor Controllers are presuming Pololu simple motor controllers like the 18v7. Our motors are the pololu 37D 30:1 metal gearmotors and they're attached directly to 4" VEX omniwheels.

LEDs are "normal" FastLED code - 5mm WS2811 pololu LEDs fit the technic and are similar to the WS2812b neopixels.

Arduino code for 4-wheel holonomic drive and 5 LED WS2811 lights

For movement, the additions are:

// Everyone gets the rotate speed
// left gets move
// right gets -move
// front gets sideways
// rear gets - sideways

motorSpeeds[SPEED_FRONT_LEFT] = stickRotate + stickMove + stickSideways;
motorSpeeds[SPEED_FRONT_RIGHT] = stickRotate - stickMove + stickSideways;
motorSpeeds[SPEED_REAR_RIGHT] = stickRotate - stickMove - stickSideways;
motorSpeeds[SPEED_REAR_LEFT] = stickRotate + stickMove - stickSideways;

[Markus]

We have Pololu 37D 30:1 gearmotors - https://www.pololu.com/product/1103

The battery is a "12V" lifepo4 (Shoria, not spec'd for this use, they don't like that at all (they've chided me about it) but have still done returns for me) - In the past the battery killed my R/C motor and ESC because the volts are > 12V, however this is the same motor we use for L3-G0's dome, so I'm not worried about that.  The battery's probably overkill, but it's the same as we have in the other droid.

We aren't particularly happy with our batteries, they are motorcycle replacement and not intended for deep cycle, so we kill them faster than we should - however we haven't found a replacement yet.

Thank you very much for the detailed information. Your battery is rather expensive, in particular, as compared to lead-acid batteries like this one: http://a.co/j4ocSk1. But it has probably much less weight, and that may be worth it.

[kresty]

Thank you very much for the detailed information. Your battery is rather expensive, in particular, as compared to lead-acid batteries like this one: http://a.co/j4ocSk1. But it has probably much less weight, and that may be worth it.

Yea, weight was a concern when we chose that battery. (L3-G0 is closer to 30kg than 100kg ) But, like I said, I'm not particularly recommending it. Partially we were lied to about it's Ah rating. (The car/motorcycle battery replacement industry has an "equivalent" rating that they do some math based on the CCA, but somehow end up with crazy numbers. It's about a 6Ah battery IIRC, but they marketed it as an 18Ah battery).

In London, Oliver loaned us a 12V NiMH pack for Lara's mouse and we really liked how that behaved (though we realized part of that was that we didn't run the LEDs on her mouse, so part of the reason we felt it lasted forever is we weren't drawing as much power.) So we have some NiMH batteries that we haven't assembled into a pack yet.

Anyway, from your description it seems more like the motors would be helpful, battery probably doesn't matter so much. The 30:1 gear ratio does make some noise though. And I still need to figure out how to get the omniwheels securely mounted to the motor's D shaft.

[kresty]

My phone died immediately after taking this picture, I think Lara has better ones. All the major groups are together, but we have some loose ends to clean up.

Initial Test Fit of major assemblies.

Since we're missing ECCC, we went ahead and took him to the local Garrison Titan 501st Meet & Greet at Round Table last night.

[Markus]

My phone died immediately after taking this picture, I think Lara has better ones.  All the major groups are together, but we have some loose ends to clean up.  

Initial Test Fit of major assemblies.

Since we're missing ECCC, we went ahead and took him to the local Garrison Titan 501st Meet & Greet at Round Table last night.

It looks impressive!

[kresty]

Thanks, we think it's getting there...

[kresty]

Having trouble getting a round peg to fit in a square hole.  (Well, a D peg)



1/4" square hole, 6mm D shaft (flat spot comes in 0.6mm).  I printed some shims to jam into the gap (really only the flat of the D and the corners), but they broke off pretty quick.  Got some video, but when we tried to play with it again one wheel wasn't moving at all.






   

[kresty]

If it helps, we're using:
* 4 Pololu 37D 30:1 motors,
* 4 VEX 4" omniwheels,
* 4 Pololu 18v7 Simple motor controllers,
* a bad 12V LiFePO4 battery,
* an Arduino (happens to be Leonardo), and
* 5 Pololu addressable LEDs https://www.pololu.com/product/2535 (program as WS2811)

Code is posted http://www.rebeldroids.net/forum/showthr...98#pid3198