go_away

Author Topic: Automated lcd retractable arm  (Read 2667 times)

0 Members and 1 Guest are viewing this topic.

Offline teddyTopic starter

  • Beginner
  • *
  • Posts: 4
  • Helpful? 0
Automated lcd retractable arm
« on: June 15, 2008, 10:26:41 PM »
Hey, anyone has any idea on how to built a h-bridge and connect it to a Dc motor to power an automated arm that holds a 15-17 inch lcd screen? it needs to be able to move to the user's desired position. In this case, how much torque should my dc have?

I am now doing my final year project. and i really need some help here. Thanks a million! (:

Offline shlodo

  • Jr. Member
  • **
  • Posts: 30
  • Helpful? 0
Re: Automated lcd retractable arm
« Reply #1 on: June 16, 2008, 03:00:44 AM »
hello check out this schematic from this site > http://www.societyofrobots.com/schematics_h-bridgedes.shtml for the H-Bridge. Just plug ur 4 outputs from Microcontroller into A, B, C, D. Or u can find chips have H Brigdes integrated. So to make 1 motor go foreward and backwards u need 4 outputs.

But if u dont want microcontroller just use a switch instead of HBridge. Wire the switch so if u press it one way it goes up, other way goes down - simple. Have this hooked up to ur power supply,which will depend on your motors and desired speed.

I would use a gearbox, like a cheap Tamiya one. Probably want metal gears for long life. U cant just stick ur motors onto the LCD, it will spin around a thousand times a second... Worry more about speed than Torque. I guess u would want to design it to lift a force of 1kg at the end of the arm
Torque= Force x Length of Arm.    Length of arm is the distance from the rotatingshaft to the point where the Force is acting.

Say u get a motor that has rated 1000rpm and torque of 100g.cm.....

U put that through a gearbox with a ratio of 500:1. So it slows it down 500 times... This gives u an rpm of 2rpm (1000/500=2) on the output shaft. This will multiply your torque however (100g.cm x 500= 50,000g.cm = 50kg.cm) so that will be your torque - Divide this by length of moment arm (lets say 10cm) - 50kg.cm/10cm = 5kg of force. More than what we need (5kg>1kg).

U would probably want an rps of say 0.25 - or 15rpm on the output shaft. So in 1 sec the arm moves 90degrees. Nice and slow for accuracy.

Offline teddyTopic starter

  • Beginner
  • *
  • Posts: 4
  • Helpful? 0
Re: Automated lcd retractable arm
« Reply #2 on: June 16, 2008, 10:40:28 PM »
ok. Thanks alot! but do you have any other recommended sites that i can refer to for my current project? thank you

Offline Admin

  • Administrator
  • Supreme Robot
  • *****
  • Posts: 11,632
  • Helpful? 169
    • Society of Robots

Offline teddyTopic starter

  • Beginner
  • *
  • Posts: 4
  • Helpful? 0
Re: Automated lcd retractable arm
« Reply #4 on: June 23, 2008, 05:52:44 AM »
ok. Lets say if i were to use a SN754410 motor driver. Do i need to programme the driver to move my retarctable arm? or i can just power the arm using a switch? Any recommended sites i refer to for the codes if i need to programme the driver?

Thanks (:

Offline teddyTopic starter

  • Beginner
  • *
  • Posts: 4
  • Helpful? 0
Re: Automated lcd retractable arm
« Reply #5 on: June 23, 2008, 06:17:04 AM »
Or is there any other motor drivers recommended for this project?

Offline shlodo

  • Jr. Member
  • **
  • Posts: 30
  • Helpful? 0
Re: Automated lcd retractable arm
« Reply #6 on: June 29, 2008, 08:49:43 AM »
just use a switch

Offline Admin

  • Administrator
  • Supreme Robot
  • *****
  • Posts: 11,632
  • Helpful? 169
    • Society of Robots
Re: Automated lcd retractable arm
« Reply #7 on: July 05, 2008, 08:54:30 PM »
hmmmm you will need some sort of position feedback (like an encoder or limit switch), or the arm motor won't know when/where to stop . . .

 


Get Your Ad Here

data_list