I’m absolutely new to this, so I just wonder if someone knowledgeable can see if I’m missing anything crucial from my parts list. I want to build an autonomous mower - maybe use my existing EGO 21" electric mower. I’ve already got an old wheelchair that I’m taking apart for the motors and drive wheels. I want the best in navigation, so I want to model it on the excellent work done by Yuri (https://www.youtube.com/c/YurisHomebrewDIY/videos) and Kenny (https://www.youtube.com/c/KennyTrussell/videos), both well known here, I believe.
So the main parts I think I want and need are:
HEX Cube Orange, on a ADS-B Carrier Board, and power supply
Three of simpleRTK2B GPS boards (for base, rover-main & rover-moving) + antennae
Motor controller for the wheelchair motors - I was thinking maybe the Dual H-Bridge L298N, which can control 2 motors
Hey Rick - I’m on the road now but might be able to help a bit once home tomorrow. I’m sure Kenny and Yuri will also chime in at some point as they are the experts on their excellent set-ups.
What telemetry range do you need?
Are you setting up “permanent” RTK and telemetry systems?
Hi Steve. Thanks for taking the time to respond. The total distance from base station to the furthest extent the mower would go is only about 155’ to cover the crucial area, and as a bonus if I can do a more remote small section of land I have, the distance from base to mower would max out at about 385’.
The RTK & Telemetry would be semi-permanent, meant to stay at my cottage, and could be mounted on the cottage, if that’s advisable. However, at some point I might want to try it out at home in the city, just for laughs, but my home is only about 5,500 sf to mow. Thanks in advance.
You can save a few dollars on a fixed base installation if there is a public NTRIP station nearby.
It might be better to use a good motor controller from a known vendor like the Sabretooth series from Dimension Engineering.
Seems you don’t need anything too fancy for telemetry. I like the 900MHz radios from mRo for somewhat short range needs like you describe.
The Radiomaster TX16S gets a lot of good press for its price. Pair it with just about any SBus receiver. If you do a little more research, you can probably find a receiver that will support Yaapu’s telemetry scripts on the TX16S, making it a mini-GCS of sorts.
You don’t need any relays for now. Most of our relays are used to control combustion engine features that you won’t have. You can always add them later if you find the need.
Hi Yuri. I’m honoured & grateful for your response. Your YT videos and work are excellent and helpful to all of us.
I’m still working on the NTRIP research, but I don’t think there are any public stations nearby. The closest fee-based station is about 16 miles away. I’ve heard the Sabertooth name but didn’t know it was a motor controller, so thanks, I’ll track one down.
Thanks for the suggestion on telemetry and Radiomaster radios. I’ll check into them.
With respect to the GCS (Gate Controlled Switch, I’m assuming), what function would that give me ?
Got it. Thanks.
Wow, if I understand it correctly, I’d need the 25A Sabertooth MC, and they’re out of stock until November. Any other suggestions for an MC ? My wheelchair motors are 24v, 1000W peak, 275W continuous.
I’m getting into some detail here, but what about turning the electric mower on & off, and maybe monitoring the mower’s battery status. Do I need a special module for that ? Thanks again.
I don’t have any other recommendations - I’ve only used the Sabretooth ones. Everything is low/out of stock lately! I’m sure there’s a comparable brand, but I’m probably not the guy to ask.
Your method for mower blade control will depend on the motor/drive system you choose. Another motor controller might work well, or you could just tie it to a relay if it’s a simple on/off brushed motor.
Forgot to mention - basic battery voltage can be monitored via the Cube’s own power module. I prefer Mauch’s line of power modules for that task. They are a little more fully featured.
FYI, seeing as there is no public NTRIP around me, I enquired with a commercial provider - wow - they want $295 (Canadian) as a 1-time setup fee, and $1,500/yr (Canadian) subscription !!
I ordered the Cube Orange + Carrier Board, and should have it by week’s end. If I may, a few more questions as I get into shopping for other parts:
All Sabertooth motor controllers are back-ordered until at least September, and some until November. Looking at alternatives, most DO NOT have direct R/C functioning. Do I need that in a motor controller ? Is control through the HEX Cube Orange flight controller good enough ?
Going with the three simpleRTK2B GPS boards, do I need the Xbee modules on them ? I’ll have a separate telemetry module for the Cube Orange.
Naive question, I’m sure, but, if the Cube Orange / Mission Planner does all the controlling, why do I need an R/C transmitter like the Radiomaster ?
Thanks in advance, once again. I really appreciate the help. Rick
Not sure what you’re asking here, but I’ll take a stab at it. ArduPilot outputs RC PWM for throttle control. Your motor controller should be able to accept that as an input.
You can either use the XBee modules to transmit RTCM3 from the fixed base to the moving base or you can connect the fixed base to a computer running Mission Planner and inject RTCM3 over the telemetry stream. Either works. I don’t know what kind of range to expect from the XBee radios - I don’t use them.
You don’t technically need an RC transmitter. I think, though, that you’ll find for testing, tuning, and manually positioning your mower, an RC transmitter is almost essential.
This motor controller is a little expensive and perhaps more fully featured than you need, but it’s in stock as of this post:
Wow, thanks Yuri. You’re fast (and thorough) to respond. Regarding your answers:
On the RC capability of the motor controllers - yes, that’s what I was asking, and what I suspected.
If I understand you correctly, as I want my son to run the mower when I’m not there, perhaps the Xbee’s might be useful, so that he doesn’t have to have a computer running Mission Planner.
I thought as much, that an RC is advantageous, but not essential. I’ll get one, for the benefits.
I should mention that XBee is far from the only direct transmission option for RTCM3. You can use LoRa, WiFi, ESPNow, or any number of other means, so long as the endpoint input and output are serial data.
It’s also possible to use a microcontroller and H Bridge to roll your own motor controller, but that may prove more frustrating than useful.
I bought 2 Cytron ESC’s for motor control, but their wiring terminology confuses me. Their 3 outputs to the flight controller are labelled: DIR, PWM and GRD
whereas the Hex Cube Orange carrier board has them labelled as: Signal, Power & Ground
I assume GRD is the same as Gound, but my question is, how do the other 2 Cytron outputs match up to the Cube inputs ? Thanks in advance.
EDIT: See my next post below for the solution to the problem at hand.
I found this datasheet for a Cytron controller with those inputs.
The DIR pin is a logic high/low input for selecting motor direction. Our autopilots do not typically provide a compatible output when configured for ESC output.
The PWM pin expects a duty-cycle based PWM signal.
This is a common source of confusion. When we talk “PWM” with respect to autopilot servo/ESC output, we are speaking specifically about a hobby/RC servo PWM signal that encodes position information by varying pulsewidth across a very narrow band. That servo PWM signal does not have enough duty cycle variation to be useful as a duty cycle bound PWM output like these types of motor controllers expect.
Yuri, your help is priceless. I just spent the last hour looking for another motor controller, ready to throw these in the garbage, I don’t really know what to look for anymore. I’ll have a look at the documentation you found - can’t say I’ll understand it, but I’ll have a look. Thanks ever so much for the time you put into responding to me. Without you, I might have given up by now, even though I’ve sunk over $1,000 into this already.
I use the AUX OUT pins on the carrier board, instead of the MAIN OUT’s
I set MOT_PWM_TYPE = 3 for “BrushedWithRelay”
I connect ESC ground to carrier board ground; and connect ESC DIR to carrier board “S” pin
Does that mean I connect the remaining pin, the ESC PMW to the +pin of the carrier board ?