Controlling servos with PIC16F84A

Firstly, I didn't exactly know where to post my topic, so please move it if necessary.

I'm planning to build a kind of motorized panning and tilting head for a camcorder crane, and apart from the main construction, this is what I?ve planned this far:

The camera unit is supposed to be controlled by two servos (modified to "motors" if necessary (especially the panning unit)). I'm hopefully using a PIC16F84A micro controller to control the two servos, unless this makes the project (even) more complicated. My problem is to find a way to accomplish this project. Since my programming skills are somewhat limited, I need help to program the micro controller, making it possible to control the servos via some kind of input. I have a compiler for the PicBasic programming language, if it would help anybody. I have also a modified servo for continuous rotating available, and I can modify another if that would be preferable. I already have a circuit from a robot (featured in the book "Insectronics" by Karl Williams I hopefully can use instead of using money and time constructing a new circuit. However, if anyone has suggestions to a very low-cost, extremely simple circuit to make it possible for the micro controller to communicate with the servos, please let me know. Since I already have an applicable circuit, it would be great if anyone could se if they could help me programming the micro controller to make the servos respond to a certain input (e.g. a simple switch). If you know the language, you can use the .bas-files at the page mentioned above to help you understand the circuit. The perfect solution to my project would be some sort of input-controls (pot-meters?) that makes it possible to determine the amount of rotation / rotation speed on the (prospective modified) servos.

I hope someone understands this jumble. If you have any questions, please ask me. Thanks in advance!

You don't want to modify the servo's, they are ideal for your purpose as they are - you can always increase the amount of movement by mechanical methods, although servos will generally move a good bit further than their specs actually say.

The only connections required from the PIC to the servo are a 0V connection and the input pulse to the servo, you then use the PIC to generate the require pulses to position the servo.

A simple google will find LOTS of sites showing you how to do this.

I would also suggest you use a more modern PIC, rather than the long obselete 16F84!.

I'm planning to use the 16F84 since I don't want to fund too many new components and equipment. Moreover, my programmer only accepts this chip. You say there are lots of sites concerning this topic, but since I left my interests in this a year ago, I probably need some help finding info. Feel free to post me links to sites with related projects.

By the way, how am I supposed to pan a camera (lets say nearly 180 degrees) with an unmodified servo? I can't figure out a solution that don't needs a lot of gears, which I really try to evade.

Ostekjeks said:

I'm planning to use the 16F84 since I don't want to fund too many new components and equipment. Moreover, my programmer only accepts this chip. You say there are lots of sites concerning this topic, but since I left my interests in this a year ago, I probably need some help finding info. Feel free to post me links to sites with related projects.

Click to expand...

Have a look at which has a number of servo projects, you might also try **broken link removed**. Or a quick google for '+servo +pic' produces loads of hits, including this one **broken link removed**

By the way, how am I supposed to pan a camera (lets say nearly 180 degrees) with an unmodified servo? I can't figure out a solution that don't needs a lot of gears, which I really try to evade.

Click to expand...

You can use a crank to extend the movement range, from a large diameter on the servo, to a smaller diameter on the target - this will give a larger movement on the target. Or use the servo movement to slide a rack, which rotates the camera via a gear. Or use a gear on the servo and a gear on the camera, or a chain drive with two sprockets?. You only need to extend the movement a small amount - servo's will commonly move far further than their spec says - it might even manage 180 degrees!, the positioning pot is capable of 270 degrees.

No solution is going to require more than two gears, which is hardly 'a lot of gears' :lol:

The advantages of using an unmodified servo far outweigh the slight mechanical difficulties - but test your servos first!, they might well move enough fed from a PIC.