Flipping a display physically without using stepper motor?

[pavjayt]

The task is to flip a display panel 90deg CW and CCW with min delay (on other words as instantaneous as possible). The display itself is about an Ounce with dimensions of (2.9" x 5.86" x 0.076"), so it is pretty lightweight and I am making a frame for it which will be 3D printed while making sure it is as lightweight as possible as well, yet sturdy enough not to break the display.

This is integrated into a visual experimental setup where the display lays flat and flips to vertical into the view path of the observer.

Looking at bi-stable rotatory solenoids for example here and here , wondering if you guys have any ideas or suggestions on this?

Let me know if you need any more details.

thanks

 

[unclejed613]

you can do it in software.... requires no additional mechanical parts

 

[pavjayt]

you can do it in software.... requires no additional mechanical parts

Thanks for your feedback, I updated my OP to reflect more about what the setup is going to be.

 

[Pommie]

Rotary solenoids look like an expensive solution. If you add a crank to the 3D printed frame then a linear solenoid could be used. Does it need to maintain it's position when power is removed?

Mike.

 

[pavjayt]

Rotary solenoids look like an expensive solution. If you add a crank to the 3D printed frame then a linear solenoid could be used. Does it need to maintain it's position when power is removed?

Mike.

Saw those as well, but not sure how to do 90deg though at the moment. If you have some examples or even a sketch to do a 90deg flip with a linear solenoid, can go from there. When not in use it always stays flat and only flip up during experiment sessions for brief moments.

 

[Les Jones]

If you biased the mechanism to the center position with springs and drove it with a DC motor (PM) powered with a current limited supply you could drive it against mechanical stops to the + /- 90 degree positions. (The current would be limited to a value that did not damage the motor when it was stalled against the mechanical stops.)
Another way would be to have a disk attached to the motor shaft with three notches in the perimeter that could trigger a micro switch or slotted optical sensor to stop the motor on each of the three positions. I slightly better variation on this method would be to have a single notch and three micro switches or optical sensors. This would make the control logic simpler as you would know the existing position without the logic having to keep track of it.

Les.

 

[rjenkinsgb]

I'd use a radio control type servo motor.
They are readily available in various size & power ratings, from tiny to very high torque & typically operate from around 5V

The position is set by the width (duration) of a pulse, usually between 1.5 to 2.5mS over the full range of movement.
That can come from microcontroller or just a 55 timer with the appropriate values around it & switching in resistors to change the position.

You could either attach the servo shaft to the end of the hinge, or put it below the display carrier and use a wire pushrod from a servo arm to part way up the back of the display, to give the appropriate range of movement.

For info & reference, these are around the extremes - the little ones have nine grams force at one cm from the shaft centre, the big one 25Kg at 1cm from the shaft centre; 25 Kg-cm torque, almost 2.5NM

1-20PCS SG90 9G Gear Micro Servo Motor Tower RC Robot Helicopter Plane Car Boat | eBay

Specification: - 100% brand new - High Quality Features: - Color: As shown. - Size: 2.3 x 1.2 x 2.9 cm. - Material: Plastic. - This is the most popular mini servo. - Only weighs 9 gram and gives you a 1.2-1.4 kg/cm torque. - Pretty strong regarding its size. - Suitable for beam type robots.

www.ebay.co.uk

**broken link removed**

Or a typical mid-range type, around 3Kg-cm which should be fine for what you need:

4pcs Standard High Torque Servo For S3003 Futaba Helicopter RC Car Plane Boat | eBay

4 x S3003 Standard Servo (with accessories). Stall Torque: 3.2 kg / cm (4.8V), 4.1 kg / cm (6.0V). Great for Racing Car, Helicopter and Airplane. Temperature range: -30°C -- +60°C.

www.ebay.co.uk

Just search ebay for "RC Servo" to find other examples.

ps. Operating time for 90' movement is typically under a quarter of a second.

 

[ClydeCrashKop]

A regular solenoid and bellcrank would do it.

 

[djsfantasi]

I agree with rjenkinsgb that a hobby RC Servo will do what you want. This video shows how I do that with RC Servos and an Arduino. The arms are 5mm plywood and about the size of your display

One thing you haven’t specified is how your going to control the display position. A momentary switch or two? A toggle switch? Output from another circuit?

If you or a member of your team have programming skills, this could be done simply with an Arduino. Either a Nano or a Uno. The Arduino includes built-in functions for controlling a servo. A few lines of code are all that is needed.

 

[pavjayt]

thanks for all your replies. They all sound good from sophisticated to more basic implementation. To make clear, the setup should be invisible to the subject, so there shouldnt be anything above the display when it is flat.

I currently have a USB to SPI interface that I use to control other stuff in the system and has few GPIOs left unused which I am planning to make use of. But if it needs to be Arduino, that is fine as well since I use Mega on our other project. Have to look a bit more into RC servos to get some understanding on their response times and operation in our scenario.

Meanwhile if you have any resources that you dont mind sharing that would be helpful

 

[rjenkinsgb]

This is part of a device I designed a few decades back; it produces a pulse train suitable for driving an RC servo, with the 5K preset defining the position.

For two or more positions, you can either set the preset to the highest value position and switch other presets across it to set shorter pulse values, or set it for the lowest value / shortest time and have other presets in series that are normally bypassed & are switched in to give longer pulses.

Or you can just use it for a test rig to run a servo manually while you are working on the hardware..
It will work on the same 4.5V ... 6V power as the servo itself. Add a reasonable size decoupling cap across the power supply, eg. 470uF.

 

[pavjayt]

Great, thanks rjenkinsgb for sharing your sketch. Good to have this to try it out on a bench. Eventually I would like to use the unused GPIO pins on our SPI interface (MCP2210) to set a pulse train for required position.

 

[pavjayt]

Ordered a Fatuba S3004 from amazon, should be delivered by this Saturday which I can quickly try with my mega board. Meanwhile, will 3d print a frame to hold with this servo.

 

[gophert]

The Futaba servo can only rotate 60° so you'll need some gears or bell cranks.

 

[rjenkinsgb]

The Futaba servo can only rotate 60° so you'll need some gears or bell cranks.

I think you will find it actually has a rotation of something more than 180'
The 60' angle mentioned is a standard used to compare operating speed across servo types.

Even it it were a small angle, it would just need the pushrod link attached to the display holder somewhat nearer the hinge than the distance out it attaches to the servo disc or arm.
That will increase the angle moved by the display for a given servo movement.