Would a solenoid work?

1 solenoid per key * how many keys?

You might be able to extend the stroke of a solenoid by using a lever.

Then again, I think I'd go with a pneumatic solution. Use a solenoid valve to open/close air flow to a cylinder that presses the keys. It's easy to find pneumatic cylinders with the right stroke & power combination you'll need.

Instead of 1 "presser" per key, how about some smaller number that get moved around using something similar to a X-Y table? It might be fun to build 9 key pressers that emulate human fingers in the same finger- to-key assignments used in normal touch typing (4 home keys on each hand, plus a thumb on the space bar). This could consist of 2 moving modules, with 4 pressers on the left & 5 on the right. I think that would be fun to watch in action, & I wouldn't be surprised if somebody else hadn't done it already. Make it programmable, so that any character gets translated to a sequence of X-Y movements followed by a press (2 presses if you need to hold down the Shift key) & you can use it to type anything you want.

Is this going to be used on a manual or electronic typewriter? If manual, you'll need to add a carriage return as well. I think pneumatics would work fine for this as well, using a 3rd (fixed) unit. If it's only supposed to work on an electronic typewriter, then just pressing the "Return" with the RH "little finger" would do.

JM

Wow, deja vu! I wanted to do this in about 1980, and I think I even bought a load of surplus solenoids to do it, but never went beyond that. Instead I bought a dot-matrix printing mechanism, built a driver board and made a printer driven by my Z-80 CP/M system. Hint on that one - buy lots of extra printhead pins to replace the ones you break while debugging the software!

Theoretically it is certainly possible. If you use stiff wires or rods between the keys and the solenoids that should make your physical construction a lot easier. And make sure your power supply, drivers and circuitry can all handle the current spikes (and resultant noise). Use a short-timeout watchdog or gate the firing pulses with an external signal (555?) to assure that you don't hold a solenoid down too long by mistake. Make sure all your solenoid drivers power up in the OFF state (imagine all 50 trying to fire on power-up!).

And be sure and post a video to youtube when you've got it working. :-)

Little robot hands, typing. What a cool thought.

--
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Manual typewriters take a lot of force, over that 1" stroke you mention. That's going to take a _big_ solenoid. Yes you can do it, and you can probably find one off the shelf, but you'll fill the underside of that desk with all the solenoids.

The electric typewriters that I used to mess with had a motor that rumbled away when the thing was on; I assume that the mechanism involved a one-turn clutch to make the ball actually strike the paper.

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Well, I should probably have expanded a bit more. Not only do I want the keyboard to type on itself, I'd like to be able to type on it as well. I thougt I'd make a kind of a 'manual' word processor. You could type a page, it would store the text info, and you could print it back. I wonder if I can't adapt an X Y solution under the keyboard if the solenoids are too cumbersome.

I think it has 45 keys, I'll have to count again tonight.

Lonlaz

Heh, look for it on You Tube in about 15 years. ;)

Lonlaz

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ed text -

I don't want the whole apparatus to too large. I'll have to test the force it takes tonight.

Lonlaz

So put the button-pusher in a box that can register its position to the typewriter, so you can easily lift it away.

I still vote for robot hands that look like hands, probably because I'm not the one who has to make it work...

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Yep, couild work. I'd aim for 15 solenoids (a 7 x 7 button array and a single for 'shift' key.

Each key would be connected by tensile wire to a T bar, one branch of the T to the row solenoid, one to the column solenoid. Fire two solenoids, and one row of 7 buttons gets the wire pulled taut (but not quite depressing any key) while one column of 7 buttons gets the same treatment. The single key that is both in the targeted row AND the targeted column gets full depression.

I seem to recall a Selectric interface that was simply and literally a plate of solenoids clamped over the keys. Ick.

I had to think about this for a bit to invison it, it looks somewhat like an inverted marionette. I like the idea of reducing solenoids, though it seems like the solenoids involved have to work a bit harder than a solenoid-per key solution. I'm guessing the trade off ends up being advantageous anyway.

The only possible problem I can see with this at the moment is all the partially pressed keys causing the hammers to stick.

I did end up measuring the force necessariy using highly sciency means, by pressing down with my finger on a scale approximately with the same force needed to press a key. It ended up being somewhere between 1 1/2 to 2 1/2 lbs of initial force. I think anything over 3 might be damaging. The travel needed is .75". Although if I grid it out I can split the distance between the solenoids (I believe).

Thanks.

Lonlaz

The internals of an IBM Selectric boil down to six or seven bars that are pulled in various combinations, then a 'print' bar is pulled and the character types. Oddly enough, the bars have a 1:1 correspondence with the bits in EBCDIC - I can't _imagine_ how that could be.

So you can modify a Selectric into a printer with a few solenoids underneath on a plate, and an interface box, and still use it as a typewriter.

--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

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"Applied Control Theory for Embedded Systems" by Tim Wescott
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a 2

ed text -

*gag* I am a COBOL programmer by profession, I do electronics to get *away* from EBCDIC.

Unfortunately it won't be that easy, I have a typewriter that I have in mind, a LC Smith Super Speed purchased from a Thrift store for $15. Still mulling over a design. I am going to wind up a solenoid, just to find out how boring an ineffective it is and convince myself to just buy some.

Lonlaz

You should get one of those toy typewriters, if they still make them, that had a knob that you had to turn to select the letter, and then a single something to press on to actually type the later. It was never that much slower than when I first tried to use a real typewriter.

Then you'd use a stepper motor to rotate the letter selector, and then only a single solenoid to get it to print that letter.

I bet they don't make those anymore, likely they don't even have toy typewriters. It's so much easier to make things in electronics that I imagine all you can get now are toy computers for your juvenile typing needs.

Michael

Look at the surplus places to see just how cheap solenoids can be if you're not picky about mounting features. Herbach & Rademan, All Electronics and M.P. Jones & Associates all come to mind.

Winding your own will be _very_ tedious, and you won't get the same force out of them that an off-the-shelf one will until you've _really_ learned a lot about it.

--
Tim Wescott
Control systems and communications consulting
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...

I envision this, and the idea of a pair of disembodied hands (and maybe forearms) seems like it would look a little creepy, like some of the "mechanisms" in "Animusic":

But it would be fun, if you have a proper machine shop and stuff. :-)

I'm thinking solenoids like from an old "ding-dong" doorbell, or from a pinball machine. I was once going to buy 88 "drop target reset" solenoids to electrify my piano, but the approx. $3.00 a pop price tag kind of slowed me down on that.

With a jig and some proper cores you could make them yourselves, but there must be solenoids on the market somewhere.

And yes, I think it's a cool idea, also using it for input, albeit then you'd need to figure out how to mount all those contacts.

Cheers! Rich

Nah. If you've got the parts and access to a decent shop, you could slap something like this together in just a few months, assuming you already have the micro and know how to program it. :-)

Cheers! Rich

Should be easy enough to fit - just remember that you can use longer and shorter rods to connect the solenoids to the keys, so all 45 don't need to be in the same vertical plane - then you should have plenty of room. You might consider pushing at the far end - depending on the layout, that may provide better spacing, as those are often arranged in a radial pattern, so things would fan out.

You may have an interface problem for manual use, however - I think the solenoid space is going to eat up the knee room for sitting at the thing.

It's definitely in the crazed project zone, given the relative ease of getting the same result out of an electronic typewriter, if the typewritten (and automatically typewritten) aspect was more important than the antique manual (but not manual) typewriter. So long as you recognize that going in, crazed projects are OK. Enjoy yourself. I'd seriously consider starting with a Selectric(tm), but it would be a very different end result.

The automated hands would be a very interesting and artistic approach.

--
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