Linear Remote Control Servo

[camerarobot]

I am new to robot construction and electronics in general.  Before I jump into making a full robot I want to make a remote control cable release for my old camera.  I have a few ideas but am not sure how to implement them. 

I have been reading a lot here and it seems that if I use a servo motor then I can get a linear motion adapter kit for it.  But I am confused as to how to control the servo.   I want to use a simple on/off one or two button RF remote control that trips a relay whch trips the servo.  The RC needs to be small, about the size of a keyless remote, and the servo has to move forward about 1-2 inches to depress a cable release button.

First, what happens to a servo motor if it is hooked up to power?  Does it stay still.  I have read that you use a "pot" to control the pulse of the servo.  How do I wire up this  simple operation.  I should be able to figure it out but cannot on my own.  Thank you in advance for your help.

I attached a picture to help explain.

[Trikky2]

I'm sure others here will be better to help with the servo question, but when I saw your idea I immediately thought of using a linear actuator ?

Should be able to find something that suits at :
http://surplussales.com/Motors/Motors-6.html

Hope that helps.

All the best.

Richard

[izua]

I'm pretty sure that if the trigger for the camera doesn't require too much force, you can get away with it by using the servo horn to push it.

As for control method, you don't cut out the power via a relay, power to the servo controller is always on. you just change the signal (there is no pot). The signal should be between 1ms and 2ms wide, to give you the required angular position.
Since you made a little shiny thing on your picture instead of an antenna, it just popped into my mind that you could actually use IR for triggering the servo, instead of RC, which is expensive.

But you will need a microcontroller, anyway.

[camerarobot]

I'm pretty sure that if the trigger for the camera doesn't require too much force, you can get away with it by using the servo horn to push it.

What is a servo horn?

As for control method, you don't cut out the power via a relay, power to the servo controller is always on. you just change the signal (there is no pot). The signal should be between 1ms and 2ms wide, to give you the required angular position.
Since you made a little shiny thing on your picture instead of an antenna, it just popped into my mind that you could actually use IR for triggering the servo, instead of RC, which is expensive.

Now I am confused about how I change the signal.  I would like to use an IR remote control but I feel the distanse will be too far. I can by a RF remote control that trips a relay for about $40.  I am really new at this os I am sorry that I don't understand you 1ms to 2ms suggestion.

But you will need a microcontroller, anyway.

I have no experience with a microcontroller.  This is what i fear having to use.  I want to make a simple on/off switch that presses the cable release button when I hit the remote control.

I'm sure others here will be better to help with the servo question, but when I saw your idea I immediately thought of using a linear actuator ?

I too thought of a linear actuator but I am confused about them as much as I am about servos.  Could I wire a switch to a linear actuator to have it move forward?  How does it work?  Thank you again.

[izua]

A linear actuator (solenoid) might be much simpler in your case, since it simply requires DC with polarity reversal (so no signals or microcontroller needed).
The servo horn is the servo's arm, that black/white round/cross/line/circle thing you stick on the output gear.

[camerarobot]

A linear actuator (solenoid) might be much simpler in your case, since it simply requires DC with polarity reversal (so no signals or microcontroller needed).
The servo horn is the servo's arm, that black/white round/cross/line/circle thing you stick on the output gear.

Yes, after initially seeing pictures of servo motors with what I now know is the horn, I thought it would be fairly simple to have the whit plastic arm depress the cable release.

Now the idea of a linear actuator seams promising.  I need to ask simple questions though.  If I have a linear actuator and I introduce power to it does it extend?  If I continue to apply power does it stay in the extended position?  If I take the power away, what happens?  I ask this because of my limited electronics knowledge.  If I can wire a simple switch to it and flip the switch to have the actuator extend, that would be great.  I do not understand how to implement polarity reversal.

Thank you again.

[Trikky2]

A linear actuator (solenoid) might be much simpler in your case, since it simply requires DC with polarity reversal (so no signals or microcontroller needed).

Actually even simpler when using a cable release it is usually sprung ( in otherwords returns after you have pushed it ) so with a linear actuator all you need to do is switch the power on to make it push the cable release then when power is removed the 'spring' will be enough to reset it so no need to reverse the polarity .... Just simple on or off.

All the best.

Richard

[Trikky2]

Now the idea of a linear actuator seams promising.  I need to ask simple questions though.  If I have a linear actuator and I introduce power to it does it extend?  If I continue to apply power does it stay in the extended position?  If I take the power away, what happens?  I ask this because of my limited electronics knowledge.  If I can wire a simple switch to it and flip the switch to have the actuator extend, that would be great.  I do not understand how to implement polarity reversal.

Thank you again.

No problem they are quite simple ... Apply power and the rod in the middle extends out. Whilst power is applied it will remain extended. When you remove the power most will stay in that position but have no pushing force so the sring from your camera release would be enough to push it back in.

Hope that explains it.

All the best.

Richard

[camerarobot]

No problem they are quite simple ... Apply power and the rod in the middle extends out. Whilst power is applied it will remain extended. When you remove the power most will stay in that position but have no pushing force so the spring from your camera release would be enough to push it back in.

This is great news.  How fast does the rod push out?  The spring on the cable release will not have near enough force to press the solenoid back in.  Can I press it back in by hand?  I will have to wind the film on each shot anyway.  Or could I use a separate relay trigger to bring it back into position?  How does one reverse polarity?  Is there danger of the actuator overheating form power being applied too long? 

Are there many 12v models? 

Thank you again for your patience.

[Trikky2]

Really working from memory, used to do a lot of photography many years ago and had a set up like this with a solenoid for photographing birds ( The feathered variety I hasten to add ).

Once activated they are pretty fast, certainly in the fractions of a second time.

On mine the cable release did have enough power to reset it because once power is removed it is basically a rod of metal lying in a tube so does not take much pressure at all. If you have an electronics store nearby nip down and ask if you can see one and youll see what I mean.

Main thing is to check it has enough power and travel to activate your release.

It could overheat if you applied power for a REALLY long time I suppose but I have never come across that problem, especially on your project as you would only be applying a 'pulse' to activate it .... The rest of the time it takes no power.

All the best.

Richard

[camerarobot]

You made a camera setup like this?  I would love to see a picture.

Just to double check my idea before I start buying parts.  Should I use an IR or a RF remote control?  I found what I think is an IR remote control for a reasonable price here:
http://www.dealsurprise.com/gigain87chul1.html
But I don't know if it will have a very far range.  I want to go at least 100ft.  I could get a set up using a transmitter like this:
http://www.hobbytron.com/ce-ck1617.html

In addition to those decisions I noticed that some of the solenoids advertised on the internet mention a pulling power.  Does that mean that some solenoids pull in rather than push a pin out?  How does one tell the difference?

You mention that I need to make sure that it is strong enough and has enough travel to move the cable release.  Are small solenoids not that strong? 

I attached an image of my improved plan for error checking.  Di you think that this new idea will work? 

Thank you so much. 

[izua]

I'm not sure, but solenoids need current in one way to open and the other way to close. So you'll probably need an H-bridge to open/close it.

[camerarobot]

I'm not sure, but solenoids need current in one way to open and the other way to close. So you'll probably need an H-bridge to open/close it.

What is an H-bridge and how do I use one?

[izua]

a H-bridge is a circuit which aids in conducting current both ways through a load. a motor may be run both ways, or a solenoid, opened and closed.

you can check the tutorials on more details about h bridges. basically, you have two pairs of transistors, each pair has the top collector to +, middle emitter tied to output and middle collector, while lower emitter tied to ground (for npn). the outputs are connected together, and activtating diagonal transistors changes current direction through the outputs

[camerarobot]

Thank you for everyone's help.  I am going to order parts and read up on the various tutorials.  I just did not know here to start.  I will post a picture of my progress when I make some and I am sure I will have a some more questions, but for now I am going to dive  in.

[ed1380]

instead of a n h-bridge you could get an ESC. it's pretty much the same but it's designed to take servo signals and transform them into DC power needed by motors and actuators

[Trikky2]

Sorry for delay

Sorry, no pictures as was built over 20 years ago really just a piece of wood with a solenoid taped to one end and the shutter release to the other so they lined up No remote .... Instead about 20 feet of wire

Most of the smaller / cheaper solenoids you will be looking at will be either pull or push.

What I would suggest is just taking the camera and release to your nearest electronics store and telling them you just need something to activate it.

All the best.
PS
By the way I still think you will find that solenoids with the pressure you need to close the shutter will easily be reset by the reverse pressure once the current is removed.