Solenoid?

[revjoe]

So I am still working through my head how I want to manage triggering on my scanner. While I was watching TV last night I saw something that peaked my interest. On this show, a gun manufacturer was mounting a pair of handguns onto the bumper of a car. In order to be able to trigger these handguns, they rigged up a solenoid to a switch on the dashboard. Whenever the switch was triggered, the solenoid would retract and then release the handguns trigger. Even though it was on TV, the design seemed really simple, and I was wondering if anyone had looked at using a solenoid to trigger their cameras?

joe

[daniel_reetz]

I don't think I've seen a solenoid used, but the Gigapan panoramic imager uses a hobby servo as a universal shutter-pressing trigger:

[dpc]

This might be of interest to you.

[revjoe]

That's actually perfect!

Thanks for finding that and passing it along.

Joe

[dbmoura]

I am testing a solenoid miniature, quite like the following link. It is an interesting video where they test different voltage applied to see the force generated with the cylinder of the component.
Some sort of support is to be provided.
I am also looking for "latching solenoid" because they can be tiny but enough for the shutter operation.
http://www.sparkfun.com/products/10391

[dbmoura]

The solution to switch the solenoid can be done by a simple and well positioned push button next to the glasses. Is someone testing or had this kind of idea? For me sounds nice the mechanism operating the shutter at the end, when the printed material achieve the proper pressure against the glass. Any contribution I would share it here documented in 3D via Sketchup.

[M@rtijn]

The solution to switch the solenoid can be done by a simple and well positioned push button next to the glasses. Is someone testing or had this kind of idea? For me sounds nice the mechanism operating the shutter at the end, when the printed material achieve the proper pressure against the glass. Any contribution I would share it here documented in 3D via Sketchup.

How about placing a small white colored profile piece / clip, which will slide between the glass panels so it can be placed above the bottom and inner margin of the book. The clip has small and thin switches attached underneath to contact the book pages when it is pressed against the glass. The clip can be made of a plastic / aluminum connection or finishing profile. See the profile shape at http://www.salomons-metalen.nl/en/products/89/aluminium/profiles/finishing-profiles and the illustration below:

illustration

IMG.jpg (121.86 KiB) Viewed 1664 times

I found two ideas for having thin switches underneath the clip for activating the solenoids or servos mounted without damaging the pages:

1: LilyPad Buttons

Two LilyPad Buttons placed under the clip. The button closes when pushed and opens when released (momentary push button). Dimensions: 8x16mm and thin 0.8mm PCB. Maybe it can be setup with two 5v solenoids parallel using conductive thread which is thin enough for under / or in the gap between the glass.

Materials:
- LilyPad Buttons from http://www.sparkfun.com/products/8776
- Conductive thread from http://www.sparkfun.com/categories/204
- Solenoid small 5v from http://www.sparkfun.com/products/11015
- Servo from http://www.sparkfun.com/categories/178

or

2: Conductive Fabric Pressure Sensors

Two small fabric sensors placed under the clip. It will switch with the pressure between the paper and the glass. By minimizing the conductive surfaces on either side of the piezo resistive material, the sensitivity of the sensor can be adjust.

- DIY sample http://www.instructables.com/id/Flexibl ... re-Sensor/

Materials:
- Velostat by 3M from http://www.lessemf.com/plastic.html
- Conductive thread from http://www.lessemf.com/fabric.html
- Conductive fabric from http://www.lessemf.com/fabric.html

Note:
In the DIY sample neoprene is used but is not necessary in this design. One can use any fabric or material as a base substrate, as it is not a functional part of the button/sensor. Fusible interfacing is a fabric glue that comes in sheets and is fused with heat from an iron, one can also use double sided sticky tape. Instead of conductive fabric contacts one can also use aluminum foil. Even the spacer material can be made from a material other than foam. Anything thick enough to keep the two conductive contacts apart when they aren't pushed together.

[dpc]

Is it that much of a burden to press a single button with your thumb or a foot switch to trigger both cameras? You'll likely need some sort of manual trigger like this anyway if you invert the top of the new scanner to scan "normally-closed" books like paperbacks.

[rob]

Well, times the number of pages. The less force your body has to apply, the better. Consumer cameras aren't exactly ergonomic when you have to take hundreds of pictures in the space of an hour.

[dpc]

I must be missing something, Rob. I don't understand what consumer camera ergonomics have to do with this.

I have two cameras mounted to the scanner frame that are triggered by solenoids. They are connected through relays to a single momentary push button switch that takes less effort to press than tapping my finger on this keyboard to type this message right now. I'm not having to press the camera shutter buttons myself.

Hitting that single push button switch with my thumb is nothing compared to the work necessary to lift/lower the platen and turn a page. Heck, (for me at least) the button press is far easier than squeezing a brake lever used to trigger cameras on the current new scanner. I also like the fact that I have the ability to have a look at things on the LCD monitors driven by the output from my cameras before the cameras are triggered.