3D Pin Monitor

Hey arduino fans! I just came up with this sweet idea about a 3d monitor made out of pins, like those little office toys where you can make an impression of your face. Here’s my blog post about it: blogs.windwardreports.com/tomasr/2009/06/3d-pin-monitor.html. I would be thrilled if someone out there actually built this thing! And I figure arduino hobbyists are just the type to do it.

I had a blindie friend who read using Braille terminals that were made by using piezo actuators to raise the dots. Unfortunately, they were ferociously expensive: about $100 per character. I don't know how much of that cost was because of the limited market, though.

If I were going to try to tackle something like this (and it would have to be on a very small scale due to cost), I'd probably take some spring-loaded "push" solenoids, and array them behind the panel (much like an old dot-matrix print head). You could use piano wire to make something flexible enough to fan out and accommodate the larger diameter of the solenoids, while being stiff enough to be pushed. By PWMing the solenoids, you could adjust the length of protrusion.

And, as an added plus, you could use the heat from all those hundreds of solenoids to keep your workshop warm in the winter. ;D


By PWMing the solenoids, you could adjust the length of protrusion.

Well I would be very surprised if that worked. I bet you find it either doesn't move or slams against the end stop. Just think about the geometry of the situation. As the solenoid starts to move it moves into a more intense part of the field and therefore is subject to more force and so moves faster. A magnetic field changes as the inverse cube of the distance so it is very sensitive to distance.

As to the first idea it has been done on the input side quite well. See http://create.ucsb.edu/~dano/matrix/

Oh man, that matrix piano thing is so awesome!

You’re right, Mike: I wasn’t thinking of the geometry correctly. I suspect there’s a curve with a sharp “knee” in it: a very small region where you could get a little proportional control, with a sudden transition to “full on”.

It would be possible to make an actuator that does what I was thinking of, by using a coil that pulls the metal toward itself, rather than into itself. But a solenoid won’t do it.


a very small region where you could get a little proportional control

I don't think you get even a small one. The graph would have what is known as a discontinuity in it rather like the graph for an SCR.

What you would need to do this would be something with a strong return force and a position sensor in the same way as you can do the "floating" ball baring suspended from a magnet. Some one here posted one a few months back that was excellent.

Here's a clock in the style you are thinking


It kinda "cheats" though - each segment is on a cam, and the segments go in and out in order pushing a block of pins.

I can't picture in my head how you would practically control each pin individually in a whole matrix (ofcourse that doesn't mean it can't be done!). Maybe if you had a CNC-type device that moved in the X and Y planes, pushing and pulling on the pins.

I think as Ran alluded to a Bowden cable system would help to fan the dense pin grid to an array of bulky actuators. Depending on how much force you want to be able to produce with the pins, you could use motorized linear potentiometers for actuator+feedback in a single off-the-shelf package.

Yeah but still, mapping 1:1 pins:actuators would be a major challenge in terms of space, power and control, almost to the point that I would call impractical.

But hey, people become heros by making the impractical practical!

Ok, so if we just had the pins so that they could be either up or down like the pin clock, could we then use an array of tiny electromagnets? or am I just fantasizing

There is some neat work being done with pneumatically deformable touchscreens. http://gizmodo.com/5230732/step-aside-multitouch-and-haptics-this-touchscreen-has-buttons

but Nokia is on the bleeding edge here http://www.engadget.com/tag/haptikos/ Hopefully Nokia will be shipping product soon...

There is also this tactile display device, with either a serial (RS-232C) or USB interface.