Full Version: B-robot EVO. OFF ROAD version
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(05-08-2018 07:15 AM)Vaygr Wrote: [ -> ]
(05-08-2018 03:30 AM)nikola-wan Wrote: [ -> ]I just got my latest EVO2 Off-Road MEGA 2560 working tonight.

Great work, Monty! You've done quite a lot of modifications. The extra pins of the MEGA can always come in handy to connect more components, such as additional servos, etc. For example, it would be cool to attach a small/simple robot arm on top of the B-Robot to pick up stuff. Could you post some close-ups of the wiring on your MEGA or maybe some schematic if you made one? Maybe you could even consider sharing your work on GitHub. Big Grin

What is the diameter of your bigger size wheel? I also realized that the 83 mm wheels didn't leave much space between the bottom of the chassis and the ground surface, especially for off-road. I ordered some new wheels: https://www.aliexpress.com/item/2pcs-Wil...0.0.US6LXX
Diameter 125mm
Width 70mm
Hexagon adapter 12mm
Brand: GWOLVES (since it's branded, i'm hoping that the quality will be better)
I'll post some pictures and video of my upgraded B-Robot setup when i receive the new wheels in a few weeks.
I also have some larger wheels but with 17 mm hex and i just ordered these adapters (although you can design and 3D print your own): https://www.aliexpress.com/item/12-17mm-...40979.html


Thanks for the kind comments.

I have now posted my modifications to the EVO2 Arduino code on github:
I have included my TOUCHOSC file. My mods include getting the PID sliders to report the adjusted PID values, plus a working battery voltage and battery percentage display with a background RED LED that lights below the low battery threshold.

The secret to getting the EVO2 telemetry back to the TOUCHOSC application was only sending one message - immediately after the TOUCHOSC app pings the EVO2 Wifi. There is a short window where TOUCHOSC listens, then closes its connection to the Wifi.

I reworked my first attempt - bending the shield serial pins out made the shield too sensitive and it would pop off if the robot fell over. My suggestion to JJROBOTs- if they are redesigning the shield would be to put jumper headers for the Wifi serial to the shield pins 0 and 1. This would have allowed me to remove the jumpers and connect the Mega serial1 pins to the Wifi - bypassing the shield pins.

My rework was to unsolder pins 0 and 1 from the shield and resolder them to the top side of the shield - making sure the pins did NOT make contact with the arduino pins 0 and 1 when the shield was plugged in.

I also decided to change out the inline 6x AA battery box and created a 2 row 3x AA battery box by cutting off a larger 2 row AA box. This allowed me to put the batteries between the two stepper motors to further reduce the EVO2 MEGA center of gravity.

I've got several photos of my latest modifications - I'll post those in separate messages in this thread to keep from being banned again.



My tire info is in post #9:

My github site also includes my stretched "Stealth" EVO2 front and back bumpers, stretched electronics platform and stretched stepper motor platform. The platforms are now 130mm long - just enough to bolt the Arduino MEGA and fit inside the side panels.


Here are some photos:

First the relocated Serial pins to the top of the shield:


MEGA Serial1 to shield Serial1

Gyro i2c cabling

New battery box between stepper motors

I added an external power switch on the side

I soldered red wire to the +9V terminal on the battery pack - but didn't check which wire was center conductor (plus) to the Arduino. So I reversed the power leads from the Arduino - now I'm switching on/off the ground lead.


I took your suggestion and purchased a 17mm to 12mm metal hex adapter on Amazon - I didn't want to wait for the shipment from China Smile

I did have to use my grinding wheel to shave off some of the adapter so the washer would fit flush with my big wheels. I also cut off the captive washer on the bolt that came with the brass coupler and smaller wheels - otherwise I would have had to find longer bolts to attach the big wheels to the coupler.

I forgot to post a photo of my EVO2 MEGA Off-Road Smile
Great work :-)

I`m building my own "Off road" version - how does it handle obstacles (not flat surface) when you have a low center of gravity? Does it not need to lean forward and use a top weight when trying to "climb" angled surface..?
(05-16-2018 07:04 AM)@mundsen Wrote: [ -> ]Great work :-)

I`m building my own "Off road" version - how does it handle obstacles (not flat surface) when you have a low center of gravity? Does it not need to lean forward and use a top weight when trying to "climb" angled surface..?

Great question!

I have tile and throw rugs in my house. I found the original wheels with an O-ring had difficulty transitioning to the throw rugs from the tile.

The larger 1:8 scale wheels can easily handle the transition.

I am using the "Pro" mode which has more aggressive 'angles'. I have found that I can easily turn the MEGA Off-Road in either direction on a fairly deep pile carpet - but if stopped on the carpet - I need to drive backwards to get off. Sometimes with 'shag' pile carpet I need to jog the robot forward and then back to begin to move. I believe the backwards angle in the code is larger than the forward angle - has something to do with that.

I haven't tried driving outside on any surface other than concrete. I think the aggressive off-road treads will help here.

I'm still experimenting with changing the PIDs - although I've found that reducing the Stability P to 0.200 helps a lot with the changed center of gravity.

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