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Robotics material
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Robotics material

by laurentn on Sun Feb 10, 2019 7:12 am

Hi from France!
I'm an engineering teacher and I would like to switch from Arduino-based robots to Feather-CircuitPython ones.

Here's the little DIY robot I'm working on: https://photos.app.goo.gl/FTQJqgRq4mXUZCu66

Several questions here (sorry for the noob's ones...):

1- I have the Feather M0 Express in mid to replace my Arduino Uno: could you confirm me that 2 servos and 2 line sensors would fit on this board?
2- If yes, could you give me a compatible line sensor reference?
3- The continuous servos I use need quite a lot of current, so I'm using a lab power supply connected to the Arduino card. What about the Feather?
4- What I do like with the Arduino cards is the way the kids can change the code, upload it and directly see the behaviour change of the robot. Is this way of debugging also possible with CP and Feather?

Hope that I haven't bother you with my questions. Au revoir!

laurentn
 
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Re: Robotics material

by adafruit_support_bill on Sun Feb 10, 2019 8:03 am

1: Yes, the Feather M0 should have enough pins for that.
2: Pololu carries a large selection of reflectance sensor arrays that are good for line-following applications: https://www.pololu.com/category/123/pol ... ce-sensors
3: Microprocessors are not power sources. You would power your servos directly from a battery pack or other power supply. If your battery pack or power supply is in the 3.3v-5v range, you can use the same pack to power the feather. Good battery choices are: 4x NiMH pack (4.8v) or 3x alkaline cell pack (4.5v)
4: Yes, that is possible to do with CicuitPython. In fact, 'uploading' is even simpler with CP and the Feathers.

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Re: Robotics material

by laurentn on Sun Feb 10, 2019 8:07 am

Thanks a lot!
So, I can power the Feather using the micro USB port but how can I upload the program at the same time?

laurentn
 
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Re: Robotics material

by adafruit_support_bill on Sun Feb 10, 2019 8:15 am

In that case, you may want to use a small LiPo for the Feather and a larger battery pack for the servos. The LiPo will automatically charge when the feather is connected via USB and provide power to the Feather when USB is un-plugged.

The servo battery pack can provide power directly to the servos. You will just need to a jumper from the negative battery terminal to GND on the Feather for a signal reference.

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Re: Robotics material

by laurentn on Sun Feb 10, 2019 8:32 am

OK for the Lipo.

But (sorry), I don't get it with the program/battery pack...

1- the kid works on his program using Mu
2 - he wants to test it so he uploads it to the board using the usb port
3 - he then has to unplug the usb cable to plug the battery pack instead

Is there a switch on the board to start the program and give the kid time to plug the battery pack?

laurentn
 
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Re: Robotics material

by adafruit_support_bill on Sun Feb 10, 2019 9:56 am

he then has to unplug the usb cable to plug the battery pack instead

No. The Feather will be powered by the LiPo. The battery pack is for the Servos.
The only connection between the battery pack and the Feather is a ground wire.

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Re: Robotics material

by laurentn on Sun Feb 10, 2019 1:10 pm

And if I want to use a powerbank on the USB port of the Feather?

laurentn
 
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Re: Robotics material

by adafruit_support_bill on Sun Feb 10, 2019 2:11 pm

Just plug it in to the USB port. It will power the Feather and charge any LiPo that is connected to the Feather.

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Re: Robotics material

by laurentn on Sun Feb 10, 2019 2:35 pm

Sorry but I need the powerbank to stay plugged in to power the servos.
So how can the kid upload his program?

laurentn
 
Posts: 9
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Re: Robotics material

by adafruit_support_bill on Sun Feb 10, 2019 3:42 pm

Once again: The Feather is not a power source. Servos should be powered DIRECTLY from the battery.

If you have a Lipo attached to the Feather, it will recharge when you are connected to a USB port. There is no need to power the Feather from the PowerBank.

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Re: Robotics material

by laurentn on Sun Feb 10, 2019 3:49 pm

Ok, let's say I use this one:
https://www.adafruit.com/product/2928

Will the servo power supply also supply the Feather M0 or do I need to use an extra LiPo?

laurentn
 
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Re: Robotics material

by adafruit_support_bill on Sun Feb 10, 2019 4:22 pm

The servo power on that board goes to the servos only. You would need a separate LiPo for the Feather,
The LiPo does not need to be very big - since the Feather draws only a little current. And it will automatically recharge when connected to USB.

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Re: Robotics material

by laurentn on Sun Feb 10, 2019 5:48 pm

Thank you so much for your help!

laurentn
 
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