hey all
this is the project idea.
I will take an ordinary webcam and want to fix it to 2 suitable mechanisms which will enable me to rotate the camera left/right and up/down.
This will be controlled by a PIC and will eventually be linked to the computer.

The problem i have is i dont know what to use to turn/rotate the camera..

should i use stepper motors/servos...or what?
id rather not use stepper motors as this would be an expensive option and i want to make it as cheap/simple as possible.

Any ideas?

Thanks Guys
Kane

 

Use servo's, they are cheaper and more powerful than steppers, also they provide 'absolute' positioning, whereas steppers are only 'relative'.

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PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

thanks...
do servos need any special type of drive? or do you just supply a voltage?

Kane

 

They just require an HT supply (about 6V or so), and a variable width pulse - between 0.5mS and 1.5mS wide on the input, every 20mS or so. The width of the pulse tells the servo where to position it self.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

No Nigel,

I'm not agree with you in this case. For a auto-camera, we should use the stepper. The holding torque of a stepping is stronger than servo motor, because the magnetic field inside the stepping is constant when you hold it.

And if we use a big servo, it will bigger than a stepping to get the same holding torque.

In fact, they used stepping for auto-camera like in this application. And Douglas W. Jones is one of the professors who build those kinds of auto-camera.

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Falleaf
mail@falleaf.net
English forums at PIC Vietnam - Vietnamese Electronics forums
R&P Trading and Forwarding Co. Ltd.
Distributor of Microchip in Vietnam

 

I would disagree there, a servo has loads more power than a stepper, and likewise loads more holding power, also how do you know where the stepper motor is positioned? - it hasn't got absolute positioning like a servo.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

Because the camera need a slow speed to turn, therefore, the stepping give strong torque at low speed. And we well know exactly the position of the stepping. And if we need a feedback, we can add an encoder to the motor.

The fact that the servo creat strong torque because of its gear box inside the motor. It's not the real torque from the motor. Therefore, if we also use the gear box to the stepper, we will get stronger torque than the servo. The servo hold the rotor buy continuously changed magnetic field, however, the stepper hold the rotor by constant.

And I saw in most of auto-camera, like this application, they used steppers.

yes, perhaps, for a small webcam, for example, a servo will be good. But I don't think it's good for heavier camera. Because it will vibrate with the magnetic field.

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Falleaf
mail@falleaf.net
English forums at PIC Vietnam - Vietnamese Electronics forums
R&P Trading and Forwarding Co. Ltd.
Distributor of Microchip in Vietnam

 

That's the point, you DON'T know the absolute position of a stepper motor, only a position relative to where it last was (and even then, only if it didn't miss any steps) - with a servo you know it's absolute position at all times.

__________________
PIC programmer software, and PIC Tutorials at:
http://www.winpicprog.co.uk

 

RC servo's would do fine, as they're cheap and readily available. If you need to see the images on screen as the camera moves, you can slow the servo down by "stepping" successively in software untill the position is reached.

To implement the sync & signal pulses should be easy as normal RC rx's use 4.8V anyway, so you should be able to drive the signal line of the servo straight from the mc port. No stepper control IC etc. You just have to get the timing right.

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Stef

 

The name escapes me at the moment but do recall a singles bar/cafe
where every table has a webcam with servo mount. The system seemed to work quite well and comercial hardware and webcam freeware / project info are to be found on the web.

 

hi,
i am going to prpare a project on topic " Industrial Robo". Have you any idea on this topic which will make my project more applicable in Industries.
my mail is
yogeshwar_ade@yahoo.co.in

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Hi friends,
i am the student of Engineering & i am in Final year & belongs to branch Electronics & Telecomm.I am going to prepare a project related to topics like Robotics, PC based projects.