Building a hobby robot (on Mini DFRobotShop Rover Kit chassis that comes with motor, battery and shield based on L298). All fine and dandy, except the connection to Arduino is done by adding it as a HAT on top of the arduino, and it uses/blocks the Serial ports for some Xbee interfaces (that I don’t think I need, I don’t even know what they are). But I will need the serial port for RPi integration. And it wants to power the arduino as well.
So two problems. I don’t want to serials to be blocked by Xbee AND i want to supply my own power to arduino.
So, my question is can I just add the connections from arduino to pins to the same new motor shield pins I use (pin 5 &6 for E1 & E2 speed control, pins 7 & 8: M1 & M2 direction control), not connect the other pins(Xbee, Vin, 5V, 3V3 etc), add the battery to the motor shield to supply the power only to the motors by connecting the GRD between arduino & motor shield?
What I’m not sure of is apparently the motor shield supplies power to arduino as well, not sure through what pins, so if I only connect the 4 digital motor control pins → arduino and the ground it should not power arduino (planning to power arduino in a different way)? From what I have understood, if you want to use different voltages on the same circuit to power the motors they should be connected by GRN.
Also to not block the serials can I just skip connecting the Xbee Tx pin / Rx pins to arduino?
What I’m not sure of is apparently the motor shield supplies power to arduino as well
Yes it does. The 3.7V LiPo battery is connected to the shield, which has an onboard 5V regulator which then provides the 5V pin to power the microcontroller.
Although not great, you can bend the 5V, 3.3V and Vin pins outward so they don’t provide power to the microcontroller. You’d need to keep the GND pins for common ground.
Also to not block the serials can I just skip connecting the Xbee Tx pin / Rx pins to arduino?
Sure, but… if there’s no XBee module plugged in, the D0 and D1 serial pins are free.
If you didn’t already purchase the kit and don’t need the Arduino:
If you’re using a Raspberry Pi, note that there’s a chassis only kit:
If you end up using a battery of up to 7.4V, to ensure you don’t burn the low voltage motors which are included with the Tamiya gear motor kit, you can upgrade them to 6V nominal motors:
Ok thanks for the info! Very helpful. I actually already have the shield so I’m going with it. Maybe just one more clarification, can I still keep the Arduino connected with USB while the motor shield is powering the Arduino, if I would choose to use the LiPo battery and motor shield to provide the power to Arduino? Yes they both have regulators but would it damage the Arduino if it’s getting power from the motor shield with battery and the USB connection at the same time? Because my Arduino Uno will be constantly connected to USB when running the motor shield so I can’t turn it off.
So I actually got everything running very nicely. What I’m now experiencing is the lack of torque on my motors. The motors you recommended @cbenson (Brushed DC motor &V, 11500) are the totally compatible with the gear box meaning are they the same size? Also do the have more torque? I’m stacking such a massive amount of stuff on the machine it’s lacking the capacity to turn properly. What is the best motor I can use with this kit while still supplying the motors with the RobotShop 1000mAh, 3.7V LiPo Battery that came with the kit?
Indeed. They are drop-in. That motor size seems to be pretty common on the market. You’d need to increase the input voltage though (might work using a 7.4V LiPo despite being 6V nominal).
It’s less about the capacity and more about the voltage, current and gear ratio.
Higher current for the same voltage tends to provide higher torque output
Higher voltage tends to provide higher rpm
Higher gear ratio lowers the rpm and increases the torque
Although we have not tried it on our end, the default configuration for the Tamiya gearbox is configuration A, which (if I remember correctly) provides a 58:1 gear down (same as configuration B). Configuration C (again, if I recall correctly) provides a 207:1 gear down. However, this moves the shaft by around 1cm, so the tracks will be loose. It may be possible to offset that by using a medium sized wheel on the front instead of the small one. You may be able to play around and achieve something… just brainstorming. Note that the gearbox would need to be completely disassembled as a lot changes in the assembly between the two ratios.
Last, do you really have a lot stacked on it? It should have no problem even in a configuration like the kit below. Is there a chance the battery is too discharged?
Thanks for the brainstorming and help @cbenson very helpful! I was thinking about lowering the gear but was actually concerned about the tracks. Maybe I could try that. I do have actually a massive amount of stuff stacked on top (Arduino, the LiPO battery, Grove base shield, motor shield, 7 sensors, Raspberry Pi 4 and still need an extra battery for the Pi) soo yeah. The battery is fully charged so no worries there. Can the motor shield on board charger charge batteries with higher voltage the LiPO 3.7 V batteries that came with the pack or will it work with only that? Also I saw there were not a single larger LiPO battery on robotshop.com that would work with the motors you suggested… Any ideas that would come to mind?
Thanks!
Here is a picture of my still incomplete messy setup:
Regarding alterative sprocket and track setups using a different gear ratio - honestly, just play around.
Large sprocket at the back and large sprocket at the front might work with a different combination of track segments
Large sprocket at the back and medium sprocket at the front
Medium sprocket front and back
I was not expecting that many devices. Wow. Hopefully you had an idea of the size of the base before purchasing it?
Can the motor shield on board charger charge batteries with higher voltage the LiPO 3.7 V batteries
No - it’s a specific chip for a 3.7V LiPo, single cell.
I saw there were not a single larger LiPO battery on robotshop.com
RobotShop’s selection of Lithium based batteries is currently sparse (an understatement) because of issues with shipping them cross-border and by air (considered “dangerous goods”.
Honestly the one thought would be to optimize and perhaps abandon almost everything Arduino-related and only use the Raspberry Pi and a DC motor HAT with enough IO. If you can somehow work with one battery that may save weight too (7.4V and a pair of voltage regulators maybe?)
However, the base is far from expensive, so simply opting for a larger one might be good too since the DFRobotShop Rover base was intended to be small, inexpensive and versatile, but definitely not a “heavy hauler”.
Yeah, I mean my prototype has been growing since I first envisioned it and it was supposed to have much less stuff in the beginning I think I will build on top of this to validate my solution and once I get my code side of things running (RPi facial recognition & Speech recognition) I could maybe order a bigger chassis w/ motors. But I would love it if I could. use the same motor shield to control the motors (I don’t see why, since I’ve separated the motor voltage from the arduino for this exact reason), and I would like to have a charger/battery combo. Any robot chassises you could recommend? My specs would be that it can be controlled with the current motor shield, can carry more stuff and has more room, has a battery and charger for just running the motors. I was looking at the devastator for instance which could be big enough and has only 2 motors and I guess I could control with the same motor shield.
If you want a platform to be able to use the motor shield, the max current per motor will need to be 2A. Not certain the Devastator platform’s motors are more powerful than the ones on the DFRobotShop Rover mini.
The reason I was pondering about the devastator is that it has a newer version with metal gear motors that says ”increases load capacity from 1.5kg to 3kg” Devastator Tank Mobile Robot Platform (Metal DC Gear Motor) - RobotShop. Do you think this could work? For this i assume i could still use the dfrobot shield and buy new 7.4V LiPO battery with charger that’s on robotshop.com?
I checked out the lynxmotion and man that looked like the perfect platform!! I think if i get my code side of things running i would opt for this platform.
My concerns are, after checking the specs, it needs 12V power for the motors so I would need a new shield. The lynxmotion product page listed a shield (Sabertooth dual 5A regenerative) but that is not directly compatible with my arduino setup (my serial is in use or needs analog input/rc filter). Also could not find battery+charger combo to power the lynxmotion. Could you(sorry to ask for so much!) recommend a shield that works with the lynxmotion that is arduino compatible (would the arduino motor shield v3 work?) and what kind of battery charger setup would be enough to power the lynxmotion motors?
I understand if this was a tall order but I got pretty exited about the Lynxmotion chassis! Thanks again @cbenson !
Good catch - the other model had the normal plastic gears. Yes - good chance that version can work with the equipment you currently have. However, hard to say if the payload capacity stated is moving forward and backward as well as rotating on the spot.
If you opt for the Lynxmotion Tri-Track, then it might actually be best to conserve the DFRobotShop Mini and shield separately for future projects.
You might just want to opt for a Raspberry Pi setup unless you really need the Arduino? Raspberry Pi Motor HAT:
Ex: Cytron 2x10A Motor Driver HAT For Raspberry PI - RobotShop (there are others)
Although RobotShop does not seem to carry one at the moment, your ideal would be a DC motor HAT with RC servo control.
There are currently issues shipping Lithium batteries which explains the almost complete lack of lithium batteries on the RobotShop website. Staff are doing their best to try to find solutions to this. You can still opt for a NiMH pack like:
6V for the servos:
Wiring harness:
Note that depending on the size of the chosen battery, it can be placed either between the top and bottom frame, or above it. The mounting pattern at the rear is for an SSC-32U or BotBoarduino as opposed to a Pi:
The issue is really powering the Pi (the external 5V battery bank is certainly an option).
These are all great ideas thanks @cbenson , but I do actually need the arduino for my setup so i can’t get rid of it.
I’m quite exited with the lynxmotion tri-track so with your battery recommendation(12v nimh) I just need a motor driver shield that plays well with arduino. Could i use the arduino motor shield? That should support the lynxmotion motors and work well with them (2A, 12V) right?
Any other shields that play well with arduino and lynxmotion tri-track motors?
The motors used on the Tri-Track are the following:
They have a stall current (which you should not reach) of 1.5A while at maximum power they consume around 0.8A. You only need a DC motor controller which can ideally provide around 1.5A or more continuously (though it will not reach this, it avoids the chip getting too hot).
The shield you mention seems to be able to provide up to 2A continuously, so yes, in theory it should be fine. Any DC dual motor shield which can provide around 1.5A or more should work. https://www.robotshop.com/eu/en/arduino-shields.html
I think I will build on top of this to validate my solution and once I get my code side of things running (RPi facial recognition & Speech recognition) I could maybe order a bigger chassis w/ motors. But I would love it if I could. use the same motor shield to control the motors (I don’t see why, since I’ve separated the motor voltage from the arduino for this exact reason), and I would like to have a charger/battery combo. Any robot chassises you could recommend? My specs would be that it can be controlled with the current motor shield, can carry more stuff and has more room, has a battery and charger for just running the motors. I was looking at the devastator for instance which could be big enough and has only 2 motors and I guess I could control with the same motor shield.