School "Mars Rover" Project

Hi, I'm new to arduinos and I have to make a "Mars Rover" using an arduino that can navigate around and retrieve materials (ping pong balls). I will need 4 motors and 1 servo. I was provided with an arduino uno and a motor shield. I'm really confused what kind of motors and servo I need to buy and the vehicle also has to be wireless, so I need to provide power as well. Right now, I was thinking of using a "8 AA battery holder" for the power, so about 12V and 4000mAh. Is that enough to run 4 motors and a servo? Also, for the motors (DC, correct?), how much voltage should they be? And for the servos, is this alright: http://www.amazon.ca/MG995-Micro-Servo-Degree-Digital/dp/B00ESC510A/ref=sr_1_4?ie=UTF8&qid=1450647127&sr=8-4&keywords=servo+motor (I just need it for steering) I would really appreciate if anyone can help, I am really stuck

They gave you an an Uno and a motor shield, and you have to buy/build everything else? That is a quite challenging project for a beginner!

a "8 AA battery holder" for the power, so about 12V and 4000mAh

Actually, AA batteries have capacity in the range of 1200 - 2500 mAh and no, that won't be enough power for 4 motors and a servo.

RC battery packs are what most people use, and I've been happy with ones from Tenergy, for example these packs.

[u]Always[/u] power the motors and the Arduino separately, but connect all the grounds together. Never try to power either a motor or a servo by the Arduino.

You might look on youtube to get some ideas. Often continuous rotation servos are used for the wheel drives on simple bots.

http://www.foxytronics.com/learn/robots/how-to-make-your-first-arduino-robot/introduction

Hi guys, thanks for helping, and I also feel that this project isn't quite suited for a grade 10.

jremington: Actually, AA batteries have capacity in the range of 1200 - 2500 mAh and no, that won't be enough power for 4 motors and a servo.

So the voltage is enough, it's just that the battery will run out very quickly? And also, I checked out the website you suggested, most of the batteries were around 1500mAh, so shouldn't mine have more power? (8x2000=16000mAh) Do you think that we will need a rechargeable battery pack?

jremington: [u]Always[/u] power the motors and the Arduino separately, but connect all the grounds together. Never try to power either a motor or a servo by the Arduino.

Does this mean that I will need 2 power sources; one for the arduino itself, and one for the motors and servo? If so, how would you supply power for the other one? I only know that you can put in power from the 2.1mm pin on the arduino (doesn't that provide power for the motors and servos as well?)

zoomkat: Often continuous rotation servos are used for the wheel drives on simple bots.

Does "360 degrees servo" mean it is continuous? I was looking at the MG995, which says to be 360 degrees. If the motor is not continuous, does it mean that it will still work, but it can only turn the wheels a little bit.

Hi @kclark!

This is certainly an ambitious project. What is your budget? The quickest way to get a robot is from a kit, so look at something like this that has all the parts except the motors and Arduino:

https://www.pololu.com/product/2509

Hey @ChristTenone, My budget is around $100, so I feel it should be enough to buy the motors and servo, it's just the battery that I'm worried most about, as there are some that cost as low as $15 and some that are over $50. Kits aren't really suited for my project as we need to be able to retrieve materials, and most kits cannot do that

most of the batteries were around 1500mAh, so shouldn't mine have more power? (8x2000=16000mAh)

No, you will have 8*1.5(ish) volts = 12 volts, but still 1.5 Ah.

Does this mean that I will need 2 power sources; one for the arduino itself, and one for the motors and servo?

Yes. Spend some time with Google, there are millions of examples of how to wire a robot.

Ok, I think I understand most of it now, however, I'm still confused with the power supplies. From researching, I found that there are 3 ways to power the arduino, through the USB port, through the "external power source" port (2.1mm) and the "Power pins" (Vin & GND). Is that correct.? So which 2 should I use to power the arduino and motors (I cannot use an outlet, as it has to be wireless). Which one provides power for only the arduino and which one provides power for only the Motors?

Any of the Arduino inputs can be used to power the Arduino. Two of them are "5 volts only".

The [u]motor power supply[/u] should be connected to your motor controller.

Ok, I finished working on the design, now I have a question about the batteries. I can't buy a buy an actual battery pack because it goes a little beyond my budget. So I was thinking of using a 8-AA battery holder (9V), but this time rechargeable, does that work? I'm also wondering how this whole voltage thing works. I am planning to use 4 motors (1.5-4.5V) and a servo motor. Does the voltages add up (4x1.5V=6V), so I need at least 6 volts just to power the motors (excluding the servo)? And also, how much voltage does an average servo use, I couldn't find it on the specifications?

8 x 1.5 = 12V, not 9. Rechargeable batteries should work.
Servos should work from 6V and typically draw as much as an amp.
You need 1.5V to 4.5V for the motors?

CrossRoads:
You need 1.5V to 4.5V for the motors?

Right, I will have 12V, and yes, the motors are 1.5-4.5V

3xAA pack for motors 4xAA pack for servo, unless you find they work from 4.5V okay. 8xAA pack for whatever

CrossRoads: 3xAA pack for motors 4xAA pack for servo, unless you find they work from 4.5V okay. 8xAA pack for whatever

So wait... Does that mean I will need a combined total of 15 AA batteries?

If you insist on powering the motors from that odd voltage, then yes, you do need 15 batteries.

Motors work fine off other voltages, particularly when there's a motor controller and Arduino to regulate the voltage to an appropriate level for the motor. Servos are more sensitive to their voltage although they will run just fine one or two volts below their nominal maximum voltage, just with less torque/power

A simple bot setup using two continuous rotation servos to power the two wheels. The bottom servo is very easy to modify for continuous rotation. About as simple of bot as you can get.

http://inventorartist.com/rolly-bot/

http://www.hobbyking.com/hobbyking/store/uh_viewitem.asp?idproduct=67121

Sorry, I'm a noob, I still don't quite get it... :confused: Why do I need 3 AA batteries for motors,? At the least (1.5V eachx4), shouldn't it be 4 AA batteries? And also, why do I need another 8 AA batteries for "whatever" (I actually don't get it), what is the 8 AA batteries powering? The arduino board itself? Also, Do I need to power the motors and the servo separately, could I not just combine them and just connect a 8-AA pack to the "External Power" on the motor shield? Sorry for my lack of knowledge, I am really confused.

zoomkat: A simple bot setup using two continuous rotation servos to power the two wheels.

That would be perfect, however, we were told that we can only use 1 servo max. :(

1.5x3 = 4.5 That's the value you specified in your previous answer.

Yes, the Arduino board needs 7-12V to power it through the barrel jack.