Power Tracking

One of the things I’m quite interested in keeping an eye on (and wish I’d started making notes a lot earlier) is how much battery power I consume at an event.

R2 is quite a heavy droid, with lots of gadgets, and is generally very active at events. I like to drive round and entertain rather than staying in one place. I also may have gone overkill on the battery, tho that being said by never fully depleting the cells I’ll probably get a lot more life out of the packs.

So, I have started a spreadsheet to keep track of how much actual power I use in a given event, to hopefully get some meaningful stats for my droid(s).

Besides standard stuff like the event name and date, I’ll be logging the amount of power put back into the droid after the event, as measured by the charger I’m using. I’ll also log approximate hours the droid was powered up, along with how much of that time he was actually active and moving around.

The spreadsheet will be public, as it may help other builders:

https://docs.google.com/spreadsheets/d/1nrjr1D3ImDR60H5FOuAsUtE8fBIQ3wupA-TJVFXjUx0/edit?usp=sharing

I just have to remember to keep it updated now! 😀

One droid is never enough

The time has come….

R2 needs a friend.

I’ve actually started collecting bits to make my next droid. I’ll be picking up the bulk of the droid in a couple of weeks at R2UK. I’ve already got the motors, speed controller, Pi, and a few other little bits. Most of the other electronics are on order too.

Not 100% certain on what type of dome the droid will have, nor the colour scheme that I’ll use. That can all come later.

What I do know:

  • Brushless Q85 motors (e-bike hub motors).
  • ODrive controller for the motors (a lot cheaper than the Roboteq most people use).
  • Will use r2_control (of course), but be able to swap out to standard RC quickly.
  • Same battery as R2, so I’ll have two identical ones.
  • All electronics will be on a removable board so that I can pull them out to work on outside of the droid.
  • Dome will be wireless with its own (small) battery.
  • Cheaper than R2 (much cheaper!)

I’ll probably also use steel feet to keep the center of gravity nice and low for stability.

So, it will mean a fair bit to do. I’ve never really worked with styrene before and with using both wireless comms for the dome and an ODrive there will be a fair amount of coding work to do on r2_control.

I’m going to try and keep a better build log for this one, with more work in progress pictures.

r2_control Shopping List

A few people have expressed an interest in my r2_control system, so I thought I’d do a post about how it works, and what it needs.

At the core is a Raspberry Pi 3B+. This runs the main code, and also any programs to interface controls (PS3, Web, Instant Messenger). It also acts as a wifi hotspot.

From this Pi you can add a Sabertooth 2×32 and Syren 10 via USBSerial to allow control of those using packet serial communications. A python library for which I have written to make things easier.

Recently, a GPIO option has been added to the core code so that you can trigger relays and other switched items directly from pins on the Pi. I use this to trigger the relays that break the connections to the foot motors and dome motor.

Lastly, an i2c connection is available for communicating with various other boards such as the Adafruit 16 Channel PWM controllers, RSeries lights, ReelTwo system, etc.

A basic system to have simple control over a droid with no opening panels and no triggering of dome light sequences can be had with just:

  • 1 x Raspberry Pi 3B+
  • 1 x Sabertooth 2×32
  • 1 x Syren 10
  • 1 x USB FTDI (For USB interface to Syren 10)
  • 1 x PS3 controller (Or PSMove)
  • Whatever dome lights you wish, eg TeeCees.
  • Battery
  • Power distribution (Fuses, power switch, etc.)
  • 2 x Drive motors (eg. 100W Scooter)
  • 1 x Dome motor (eg. pittman)

You can run the Pi from the BEC built into the Sabertooth if you wish, but I do recommend at least a 2A buck converter on its own fuse.

If you want to run any servos, you can add the Adafruit PWM controllers onto the i2c bus, up to 6 can be added by configuring the address jumpers. One in the body and one in the dome is usually enough.

This system can of course be added to. Relay control over the motors, light sequence triggers, and other gadgets such as smoke machines.