Servo controlled TV arm

[Asellith]

I am looking at buying something like this



Now I want to attach servos to the joints and make it remote controlled. I might just program some preset positions into it so that I can have like three buttons and each one moves the TV to a new position. This is to hold my nice 32" LCD Tv. It weights 38.8 lb. The mount supports up to 70 Lb. Now all I need is to determine how much the servos would cost. I took statics and dynamics in college but I can't find my book and changed to electrical engineering because I wasn't good at that stuff. I don't know the exact dimensions yet but just a rough estimate of the size of servo I might need would be ok for the planning stages. I'll actually run the numbers later. (I'm not going to do this if it is going to cost me loads of cash in motors or servos.)  My first impression is that because the weight of the TV is supported vertically by the arms the horizontal force required to move the arms should be that much. Just wanted to get everyones thoughts on it.

[HDL_CinC_Dragon]

Your best bet IMO would be to just get some motors rated for a minimum of like 6 volts and give them a big gear ratio like 100:1 so you get a lot of torque and just put 1 at each of the 2 joints with a remote receiver that takes 1 nibble(4 bits) binary commands to be able to discern what motor is being told to do what. Ill post a little table at the bottom here because ive got the time

Nibble | Hex |  Dec | Wall Joint Motor Function | Middle Joint Motor Function
0000  |  0    |  0    | Dont Move                      | Dont Move
0001  |  1    |  1    | Spin Clockwise                | Dont Move
0010  |  2    |  2    | Spin Counter Clockwise    | Dont Move
0011  |  3    |  3    | Spin Clockwise                | Spin Clockwise
0100  |  4    |  4    | Spin Clockwise                | Spin Counter Clockwise
0101  |  5    |  5    | Spin Counter Clockwise    | Spin Clockwise
0111  |  6    |  6    | Spin Counter Clockwise    | Spin Counter Clockwise
1000  |  7    |  7    | Punch Nearest Person     | Point And Laugh
1001  |  8    |  8    | Take Over Planet            | Point And Laugh
1010  |  9    |  9    | Black Mail Owner             | Point And Laugh
1011  |  A    |  10  | Mug Nearest Person        | Kick Them In Kidneys
1100  |  B    |  11  | Save Kitteh From Tree     | Pet Teh Kitteh

Oh, and dont forget limit switches so you dont burn out the motors. Those are extremely simple to add in... that or have a current sense IC to detect when the motors are being hindered more than they usually should be when not moving anything more than the TV (Like if it tries to go through a wall, the motors will draw more current than usual. Simply make it so that if the motors draw more than the normal current for more than 1000ms to shut them off or maybe even reverse them for like 2s

Hope this helped a little tiny bit
I can post pseudo-code too if you like
Real pseudo-code too, not with the crazy joking stuff up there ^

[Trumpkin]

yeah that's going to take loads of torque, you probably won't be able to use servos unless you wanna spend big bucks.

[Mcrich113]

Hey guys!
     Trumpkin is sorta right, even with a good servo this is hard, you should try making your own, go to this page.



http://www.societyofrobots.com/robot_arm_tutorial.shtml

[kd5kfl]

This looks like a task for a linear actuator

[Mcrich113]

How big exactly is this robot arm?

[Admin]

I would say use my robot arm calculator . . . but that includes gravity . . . give it a try anyway and it will tell you worst case scenario.

You don't need statics, just dynamics. Equations here:
http://www.societyofrobots.com/robot_arm_tutorial.shtml#velocity