Build Log: Robotising a RC tank (first attempt)

[ecat]

From my experince a few (read many) years back of creating an autonomous robot, keeping the drive motor control seperate from the servo control is critical for reliability. Personally I'd use a multi-way PWM output shield to drive the servos and two channels of that to drive external PWM controllers for the motors. That way you can keep the Arduino and low curent systems away from the high current and position the motor controllers to optimise (e.g. shorten) the high current wiring. Also motors controllers have a habit of going pop and keeping them seperate can save money in the long run.

Wise words indeed. Never underestimate the latent malice of electric motors.

A bit of easy reading for when random failures occur:
http://modelsolutions.ca/articles/Da...eMarch2006.pdf
http://www.fightingrobots.co.uk/docu...Guidelines.pdf

I'm quite new to all this motor stuff but my feelings are:

1) If you can use a servo then use a servo. Servos are designed to be mechanically and electrically robust while playing nicely with the rest of your electronics.

2) If you can use a brushless motor + electronic speed controller then do so. Expensive but efficient and while the ESC will generate electrical noise it is easier to manage than the all-out circuit frying shotgun blasts of...

3) Typical, cheap brushed motors. There are two at the front of the tank in the first post picture. Use caution, read the links and good luck.

At the risk of stating the obvious, all of these models are designed to be powered by batteries, batteries that are designed to deliver massive amounts of current as and when required. Even a small electric motor may pull 1Amp while running under load, and more when changing direction. Stick 5 such motors in model and a typical 'made for models' battery will handle the 5A or more current with ease, the same cannot be said of the typical wall/mains adapter you may use in place of the battery while messing about - expect random resets. And don't even think about running the whole shooting match from a USB port!

But you, yes, you random reader who I know won't listen to that last bit, will you? You watched a clip on YouTube of some random running their motor(s) from an arduino + USB connection. It worked for them so it will work for you, obviously. They also know a lot more than I do too, obviously, they have a video! Good luck, USB should protect itself and limit the current to about half an Amp after which things may randomly stop working or reset or your PC may start smoking.

Last bit, honest.
So you have your motors running off a battery supply and you have wired your arduino to run from the same batteries. Is it ok to plug in the USB connector, or one of those neat 6 pin breakout boards? The battery is supplying voltage and the USB connector wants to supply 5V so what happens when the two meet up? The answer is, I don't know. Perhaps it depends on the flavour of arduino, perhaps it doesn't matter, perhaps... On my 6 pin Mini Pro I just don't connect the 5V pin, in general I think it a good idea to always disconnect the arduino battery/external supply before using USB.

[Fivetide]

Wise words indeed. Never underestimate the latent malice of electric motors.


Last bit, honest.
So you have your motors running off a battery supply and you have wired your arduino to run from the same batteries. Is it ok to plug in the USB connector, or one of those neat 6 pin breakout boards? The battery is supplying voltage and the USB connector wants to supply 5V so what happens when the two meet up? The answer is, I don't know. Perhaps it depends on the flavour of arduino, perhaps it doesn't matter, perhaps... On my 6 pin Mini Pro I just don't connect the 5V pin, in general I think it a good idea to always disconnect the arduino battery/external supply before using USB.

Thanks ecat, yes thats why I have all the baords powered, and I to dont know the effect of having power and pluging in the 5v USB, but I hope that once all the wireless stuff is up and running I can swap to total independant and use the wireless to program the board (as seen on youtube :) )

One of the things I want to attempt is to switch between two cameras using a relay, in theory it should be easy, but I bet it wont be.