Help with a PC controlled Robotic arm

[mechanicus82]

Hi,

As a novice in the field of robotics, I am looking for help build a relatively straightforward robot.

I want to design a fixed robotic arm when can press a "push button" for a specific duration. The arm needs to be controlled from a PC. The push button in portable and can be placed flat on the ground near the arm.

From my hunt on the internet I understand that I will need the following:
1. A servo motor (HS-311)
2. A servo controller (?)
3. A software (???WinAVR???)

Can you please help validate if I am on the right track? Will be great if you can also help suggest the components I should go with.

Thanks in advance.

Regards,
mechanicus

[newInRobotics]

Hi...

If I were You, I'd use microcontroller to get data via USART (USB or Serial) from PC and then actuate servo. This way, You need 1x microcontroller, 1x low power servo (preferably lower power that what USB can supply, then everything can be driven from USB port) and 1x USB to TTL chip (if You desire everything to be handled via USB). You will need to write simple software for microcontroller (if it's Atmel uC, then AVRstudio will be OK) and another piece of software for Your PC.

[Soeren]

Hi,

I want to design a fixed robotic arm when can press a "push button" for a specific duration. The arm needs to be controlled from a PC. The push button in portable and can be placed flat on the ground near the arm.

If that's all you want it to do, a push solenoid with a spring arrangement is the simple and reliable way and it is used in arrays for "keyboard robots" (for testing purposes).

How you're gonna interface it depends on what ports your PC has got.

In case you just need a circuit to run or similar, another option is to interface the electronics directly (i.e. bypassing the button).

[mechanicus82]

Hi Soeren !

Thanks for your reply and suggestions.

A push solenoid sure sounds interesting for the task at hand, but I also see this as a good opportunity to start with something that can be later scaled if required. Hence would like to go with servos.

Your idea to directly interface with the electronic circuit bypassing the button was my first preference but the device is a sensitive device and am not allowed to hook into its electronics

Regards,
Mechanicus

[mechanicus82]

Hi...

If I were You, I'd use microcontroller to get data via USART (USB or Serial) from PC and then actuate servo. This way, You need 1x microcontroller, 1x low power servo (preferably lower power that what USB can supply, then everything can be driven from USB port) and 1x USB to TTL chip (if You desire everything to be handled via USB). You will need to write simple software for microcontroller (if it's Atmel uC, then AVRstudio will be OK) and another piece of software for Your PC.

Thanks for your reply !

Your point about using a servo powered from the USB is good one and I would like to go that route to avoid the need for a distinct power supply.

Instead of using a microcontroller and 1x USB to TTL chip, I was thinking of using a Servo Controller with USB & TTL Interface....something like http://probots.co.in/index.php?main_page=product_info&cPath=55_56&products_id=395

My queries:

1. Can you please suggest a servo which can operate from the USB? If this is not possible can you please point out what options do I have to power the servo ?
2. Will HS-311 give me enough torque to cause the "push" on the button ? I know this one is tricky to answer since it depends on how tough is the button to push. But to give you an idea the button would be similar to the one you see on a scientific calculator.

Regards,
Mechanicus

[newInRobotics]

Instead of using a microcontroller and 1x USB to TTL chip, I was thinking of using a Servo Controller with USB & TTL Interface....something like http://probots.co.in/index.php?main_page=product_info&cPath=55_56&products_id=395

That's not a servo controller, that's a development board, which, in my opinion, is an overkill to drive one servo (unless You're willing to use it for other projects as well), but hey - You're the one paying money 

1. Can you please suggest a servo which can operate from the USB? If this is not possible can you please point out what options do I have to power the servo ?

I'll leave it for You to find a suitable servo; stall current has to below of what USB port can provide. If you are unable to find servo to suit USB power output, then using external power supply is an option as well.

2. Will HS-311 give me enough torque to cause the "push" on the button ? I know this one is tricky to answer since it depends on how tough is the button to push. But to give you an idea the button would be similar to the one you see on a scientific calculator.

Have a look at torque value of the servo 

[Soeren]

Hi,

A servo is gross overkill for this and an unnecessary complication. If you want a learning experience, you can always take up something that includes a servo, but here it's totally inappropriate.

Apart from that, any servo will be able to push the button and so will most solenoids.
I doubt that you'll find a servo that you can power from the USB port and you're risking the USB port and its host controller - better go with 4 AAs from the start.

Whatever you use to activate the button, you need a bit of spring or other means toavoid damaging the button - a servo could probably push the button through it's housing.