Sorry if posted in wrong section!

Hey guys, I have a few questions! I need to make a few robots for different competitions in my college, and they need to be manually controlled. So I was wondering if using a transmitter/receiver RC would be a viable option.

I don't have much access to a variety of different RCs and stuff. The only RC I can purchase is this one. Would it be possible to purchase 3 servos, and connect it to that RC and immediately control them? I watched the SoR video (http://www.societyofrobots.com/remote_control_robot.shtml) and it seems like that's all that has been done.

Now, servos. I just did a bit of research and found out that most servos only rotate 90 to 180 degrees, so I would need to find one that rotates 360 degrees right? And servos come with 3 output wires, that just need to be plugged into the receiver correct? Dont need a ESC (electronic speed controller) for servos right?

Also, would I need to program the RC, or like in the video will the servos be controlled as soon as they're plugged in?

I might be paranoid here, but I am afraid of spending quite a bit of money of this hardware, and worried that it might fail or something might go wrong.

If your robots will be manually controlled... and that means you will control them with moving your fingers (and NOT by running any preprogrammed code), then you can use a basic RC TX with RX and servos to build a remotely controlled robot with applicable limitations.

Search this forum to see how a servo can be tweaked to turn 360 degrees, it has already been discussed.

Obviously you have a lot of reading up to do in terms of what the capabilities and limitations of such a setup would be, but the basic idea is plausible.

The page you posted itself is a good start.

Quote from: Cycloned on February 14, 2014, 08:02:09 AM
.....
I might be paranoid here, but I am afraid of spending quite a bit of money of this hardware, and worried that it might fail or something might go wrong.

Hi 'Cycloned', you are being rational and not paranoid.
In my early years with this hobby, all the excitement made me buy and plug-in the stuff before I could read about and understand its workings. Looking back, I realize how much time and money I could have saved if I had read first.
Be patient and equip yourself with all the knowledge about everything you want to work with before you pour in the money.

For my final year project, I made a  'Simultaneous Localization And Mapping' robot using continuous rotation servos. They can be directly plugged in to the receiver of an aeromodelling radio set. Using an arduino will give you a lot more options.

Here's some links to CR servos:

http://www.rhydolabz.com/index.php?main_page=product_info&cPath=155_157&products_id=1288

http://www.nex-robotics.com/index.php?page=shop.product_details&flypage=flypage.tpl&product_id=817&category_id=217&option=com_virtuemart&Itemid=45   

May i ask you the target application of your robot.
If it doesn't need to look like a humanoid, likely that you can complete it without servos.

Also a RF transmitter module costing 400rs and a development board for 400rs is enough instead of a RC grade TX and RX and lot of hacking needed. also the RF tx rx is opensource and compatible with all Embedded devices.

If you want 360 rotation go with geared motors. no need to mess with servos.

Ashok.P 

hey cycloned you can use any normal 9gm servo for continuous rotation+you have to add an extra geared motor(any type) and a bit of hard work and modification is needed.I don't know how I did but I did and it worked.

If its for college competitions that requires manual control of the robot, stay away from rc servos. They are just too slow. You need atleast 200 rpm motors to be competitive.

RC servos are slow ? Do you mean while they are used in speed competitions (purely as drivers for wheels on vehicles) ?

Otherwise many servos (especially tail / swash servos on helis) are super fast !

servos are at least a bit speed than dc geared motors when it comes to response,depends on your input.

Sir the video Is super cool good one !!!

   As mentioned by V2 EAGLE, you can opt for a RF Tx Rx  pair which is little cheaper.... (rather lot more cheaper than the RC stuff). but the range would be around 75 to 100 meters

   Selecting the motors depends on your application. If you need some rotational mechanisms (like 360 degree rotating tyres) then you can go for the geared DC motors which are available in 10, 30, 60, 90, 200,500 etc RPMs. If at all you need TO n FRO motion (say 180 degrees) then go for the servo motors.

   You can use a programmable control board (8051, arduino, msp etc etc) to control the motors, servos n whatever u wanna control

Anwar, direct drive using servos will be slow Super expensive servos may have fast response times but the op's purpose will not be served by them. The main reason we roboteers ( ) modify rc servos for continuous rotation and use them for locomotion is because a servo provides a geared dc motor along with a motor controller in a small package.

Now back to the original problem, Cycloned , if you are entering a event where they allow wired control, don't mess around with wireless control. Instead focus on the mechanical construction. Make the robot as small and as light as possible.

I still don't get the slow part, unless this is a distance race type of competition.

Robotic competitions include ROBO wars too... where you have to destroy the opponents robot.

Anwar Ji, Let me explain.

The torque and speed of servos are well below when compared with geared motors.
a few plus of geared motors:
Price: 220rs max for a good metal geared 300rpm motor(5 rotations per sec!)
Torque:has Metal gear and can move a load equivalent to 2x12v 7AH UPS battery(I did that already in robowars) since it works with 12v not 7.4 volt
Easy interfacing with MCU no hacking required interfacing circuits too cost less for best quality.
we do not need a positional feedback system in a geared motor used just for mobility other sensors handle the part(This is where the servo wins)

Ashok.P

Well, what you say makes sense, but you are explaining the advantages of cost, torque, ease etc.

The speed aspect of servos per se does not seem to be the hindrance, which was the original contention.

Ill try to make it simple:
Each one has their own advantages, servos operate at much lower voltage and thus they are slow. also for RC application these servos may appear faster since they cover only 90degree. even if it moves 4 times in 1 sec it might look faster. but it actually covers 1 rotation in a sec(90x4 deg), ie just 60rpm. wherein the hobby grade DC geared motors having the same torque can go around 300rpm. cost and torque comparison are a different story altogether.

hope this helps
Ashok.P

True, and useful if you are racing (which I mentioned in my very first post).

Not for other tasks that demand accuracy and control.

Use a fairly fast servo, and you can get close to 180rpm and all the control you want (60degrees in 0.06secs at 6V).

http://www.servodatabase.com/servo/align/ds420

I guess in most robot competitions, there is a "distance to be covered in a specific amount of time" aspect, so what you are suggesting is probably the better choice.

Did someone mention robowar? I am an addict Things get a bit expensive when you get into robowar. Puny 350bucks motors wont cut it
Servos are really not designed to be used in locomotion, thus not suited for it. The 28$ for the align servo will get you very good geared motors. RC servos are not good for robotics. They are used only for the fact they are relatively inexpensive and easier to control. But a serious robot servo looks like this:

http://www.trossenrobotics.com/p/mx-64t-dynamixel-robot-actuator.aspx

This servo has more processing power than an APM and more resolution than the best helicopter servos out there.