Where to begin? Needing switch help.

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Quentin.Lynn

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I have some electronics experience, not a whole lot and have been tasked to figure out a solution. We have a PTZ camera that will go onto a sliding rail systems. We want to use the camera's internal output to drive a servo to move the camera on the slider back and forth. The issue is that the output is only limited to either on or off @ 3 volts DC. My thought is to use some type of 3 stage switch (this is where I am at a loss as to what type of switch) to turn the power "on" "off" and to reverse polarity to reverse the motor. I have not figured out what size motor I will use yet. I'm trying to work through the logic on how it will work before. So in my perfect world, when i press the "on" button, on the camera we slowly start sliding one way. I press "off" we stop. I press "on" again, we go the opposite direction.
Any ideas?
Thanks in advance..
Quentin
 
What limitations does this "output" have in terms of maximum current, frequency? Is it gnd+V or is it two independent outputs? When the output is zeero voltage, is it a short between terminals?

Any pictures of device/camera?
 
I set the "switch" on the camera to on and got 3 volts from my meter. Here is some documentaion with scematic of the camera.View attachment 61885 maybe this will answer some of the questions. I appreciate all your help.
 
First thing is that it seems that you're equiped with 12V, not 3V.

Another thing is that there is no information at all about how fast it can switch. I doubt that the camera output is suited for pmw control at all. More documentation is needed.
 
When you say how fast does it switch, what do you mean? When I select on, it stays on until I choose the "Off". What other information can I provide you?
 
I see my answer wasn't specific enough.
I should have stated first that slow motor start is best achieved using pwm technique. Then I was about to state that the camera of yours is probably not likely to control PWM pulses, so that means you need aditional circuitry to achieve that.

What type of dc-motor do you have. Or have you yet about to buy one. To move a camera with precise speed, a step motor is recomended.
 
I thought I would match the motor to the circuitry. Step motor would be fine. They are relatively inexpensive and have a good amount of torque.
 
As I understand you don't need to vary the speed of the motor.
PWM is needed if you want different speeds...
Step motor needs special driver.
I'll go with brushed DC motor.
To get started you need H-bridge (like L298), flipflop and some logic (74xx).
 
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Your camera has an open collector output, so either the output is disconnected to anything when its off, or shorting to ground when its on.

The issue is that you want 3 conditions, forward, backward and stopped, but you only have 1 output.

One way to do it is to make a circuit that closes 1 relay on one 'click', and closes another relay on a 'double click', pretty much how a mouse button can perform 2 functions.

This would require a little circuit and some design work, a microcontroller would make it easy but it'll be possible with some simple electronics too, maybe a 555 and a 4027.
 
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in my mind I picture single electronic 3 way "toggle" type switch, on, off, on(reverse polarity). Yes, I only have one ouput when ON gives out 12v and when off, is shorting to gnd. Sorry to be a pain, I thought this would be an easy item to come up with.
 
Looks doable. Give me a day or so and I'll see what I can come up with.
 
That was a quick day! Here's a suggested circuit simulation. I've assumed a 12V motor drives the camera traverse, the circuit has a separate supply from the camera, and that pressing the camera 'on' switch pulls the open collector output (pin 3) low. The circuit includes an opto-isolator for camera protection, two optional limit switches for the traverse, and a power-on-reset function to ensure the traverse motor is off when the circuit supply is first connected.
 
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Thank for such a quick turn around. I appreciate the circuit design. Would you mind attaching a larger picture of the diagram? Or... if you can tell me what program you used to display the *.asc file?
Thanks again for all the help!
 
Right-click on the attached. Better?
The asc file was generated with the simulator LTSpice, a free download from Linear Technology. Recommended.
 
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Thats a good idea, push to forward, then stop, then reverse then stop.
Free design and drafting service too.
The only thing I'd add is some suppression for the motor, 3 x 0.1uF ceramic caps, one across the motor terminals, and one from each terminal to the metal case of the motor.
 
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I agree with Dr Peppers re adding the motor suppression components.
 
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