Hello ! Another newbie here needs some coaching...

caesar

Hello,
·· I hope this was the correct place to post my 1st question.
Looking for some advice with a project using 1 or 2 servos. (not sure)
I'm hoping that everyone has seen those fancy automotive in-dash DVD players.
The ones where the screen ejects horizontally then·angles up to a 90* degree angle for viewing.

·My challenge is to make my 17"·LCD computer monitor slide horizontally out from·under the desk, pause, then flip upward for viewing. (Then reverse when finished)
I thought I'd start with·using heavy duty cabinet drawer slides. But flipping up a monitor from it's bottom edge has me baffled, and I guess it's going to require lots of servo torque.
Any thoughts on the servos & controller type or maybe a different approach altogether???·
Thanks!
·

SRLM

If I read this correct, you are using this in a office, not a car? If so, here are some ideas. You can counter balance the LCD so that about half of it is above the track, and half is below. Hower, this is probably too low for convient use. So if we go on the counterbalancing again, you can make the whole track rotate so that the LCD is lifted higher in an arc. Just make sure that you lock it in place before the lift so the whole thing doesn't go sliding!

This setup would require 4 servos: 1 continuous rotation to move the LCD in and out, 1 standard to flip the LCD at the end of the line, 1 servo to lock it in place, and one to rotate the LCD up. Keep in mind that the whole system relies on counterbalace to reduce the load on the servos.

caesar

Hello,
Yes, this is for home use.
I like the counter-balance idea.·I would be ok with having the axis point being midway up the side·of the monitor. The viewing height isn't really an issue.
·· I could use 2 servers just for the monitor rotation(if need be), one mounted on LH side & RH side. Sharing the load·will be easier on the servos.
The monitor servos wouldn't travel more than 90·degrees from a horizontal position.
Any suggestions for the push/pull mechanism of the drawer slides?
I think the lifting part is too advanced for me at this point. (Thanks for the suggestion though)

Will the servos hold the monitor firmly at·the predetermined angle, or (not that I want too) be able to push the monitor horizontal.
Can you explain the "1 servo to lock it in place? Do I need to lock the monitor once it's in the desired position?

Parallax Futaba standard servo(s) for the monitor?
Parallax Futaba continous servo for the slide mechanism?
What type of controller do you recommend for this application? Basic Stamp?

Sorry for so many questions...
Thanks!

Post Edited (caesar) : 8/10/2008 1:59:11 AM GMT

SRLM

Where to start?

c said...
Any suggestions for the push/pull mechanism of the drawer slides?

You have three choices: a continuous rotation servo, a stepper motor, or a regular DC motor. Your best bet will probably be the continuous rotation servo since it is the easiest to interface with the BS2, and powerful enough to do the job. Now, to move the LCD in and out using this servo you can do it several ways. I think that the most reliable system for you would be to have a long threaded rod. On the LCD or attached to it is a nut. As the rod turns, it causes the screw action to move the nut up and down. To connect the rod to the servo remove the horn and place a short length of tubing over the ends of each. Whatever your motor choice, you'll need to have some sort of feedback to tell the BS2 when the monitor is at it's destination.

c said...
Will the servos hold the monitor firmly at·the predetermined angle, or (not that I want too) be able to push the monitor horizontal.

What do you mean about the horrizontal? I thought that was half the project: to make it go in and out automatically. Anyway, I your monitor is counterballanced well enough then yes, the internal resistance should be good enough. Standard servos...

c said...
Can you explain the "1 servo to lock it in place? Do I need to lock the monitor once it's in the desired position?

This was to prevent the monitor from sliding down the rail if you raised it above the desk level. You mentioned that the height isn't an issue, so neither is this. Plus a threaded rod would serve if you keep the drawer pieces horrizonatal.

c said...
What type of controller do you recommend for this application? Basic Stamp?

Sorry for so many questions...

The Basic Stamp would probably be the best. You don't need the power of the propeller, and the BS2 is easier for new programmers.·As far as code is concerned, your project is actually rather simple. The difficulties lie in the hardware.

And no need to be sorry.

Let me know what you think.

Zoot

You can purchase linear actuators at servo city if you have some $$. Non-servo versions are about $100 (but include limit switches for end-of-travel feedback). Servo versions with full positioning capability are about $200. Very powerful, though, with great holding position.


servocity.com/html/12v_linear_actuators.html
servocity.com/html/servo_actuators.html

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When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php

SRLM

Why spend more than you need to? My vote is use the cheapest system that will work reliably. It's your LCD though...

caesar

Hello,
I'm liking the screw rod method ·for push/pull of the drawer slides.
Just hoping that a standard servo will be fast enough. I don't want to want over 1 min just to·push/pull the lcd.

I created a short generic·3D·.gif of the project's main 2 functions.(push/pull & rotate)
The LCD travel distance & overal scale is no where correct. It's just the best way for everyone to·have a clearer view of·what I'm trying to do.

SLRM: I totally agree, it's not a complicated idea or application, it's the hardware selection that's been the most challenging for a robo newbie.

Zoot: Thank you for the parts supplier link, I'm in the process of building a resource list for future projects.

I'm sure more questions will develop soon, I was more concerned about posting the .gif file.

Thanks again!





Post Edited (caesar) : 8/10/2008 4:50:29 PM GMT

SRLM

Well, if you want something fast then that might be a problem. I realized that after posting when thinking about the project. The servo rotates at most maybe 120 rpm. I have not measured this, it's simply a qualitative observation. Anyway, I'll use the number. If you use a #6 bolt, and it has 32 threads per inch (memory here). That gives you a movement speed of four inches per minutes. Assuming that your monitor is about 18 inches tall, that gives you five minutes just to get the thing in and out. These are really rough numbers, but more or less acurate.

So, what next? I first saw the thread idea in an article about how to built your own CNC machine. They used a Stepper motor. Personally, I don't like the things because they take up to many I/O pins. However, this may work for your project. My other idea for movement is this: use the servo with a mounted wheel. The wheel is pressed against the upper side of the desk/shelf (a spring assembly would be best), and the setup works exacly like any other wheeled vehicle. This has the advantage of being easily moved by hand. With the screw setup, you'll have to turn it yourself. With the wheel, you can pull the wheel away from the surface and slide at will.

Both systems have their pros and cons, and like anything else youy have to make tradeoffs.

SRLM

One more thing: in your animation, you have the monitor rotating CCW. If you change that to CW, then you can begin flipping the monitor before it is fully extended and it won't hit the desk. It would look really cool that way: a second, more organic motion and feel. Just a thought.

Franklin

I second the idea of rotating the screen the other way 'cause then it will store face down and be less prone to getting dirty. Also consider using mechanical means of swinging the screen up like a rod attached to the screen so when the drawer extends the rod stops extending and pulls the screen upright.

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- Stephen

caesar

Hello,

I wasn't sure...but I·thought that·a·continuous servo was going to be way to slow ejecting the slide mechanism. I was aiming for under·20 secs.

I have a old 12v cordless drill. (dead NiCad) The drill's·1000 rpms & torque will definetly be high enough.·Using a DC Drill motor will definetly eject the drawer under a minute. Or possibly use a Remote Control·car motor. I would just need to incorporate some type of travel·limit switches.

I initially tried to·utilize a mechanical linkage system to pull up the LCD when the slides were fully extended. But no·successful concepts yet.

I agree it would be more dramatic...So I'm considering the the idea of starting the LCD in the face down position, then CW direction to the final viewing position.

Thanks!

SRLM

The drill motor would work well. However, keep in mind that the full current for the motor may be routed through the switch and so you'll want a transistor or relay to protect the BS2. As for mechanical linkages, I think that the servo to tilt the monitor would be easier. Plus, with the servos you could change the angle of viewing.

A thought: Is this for watching TV? If it is, you could hijack some of the buttons on the remote to be used just for your project. Your buttons could make it go in, out, and tilt up and down. For information on programming using a remote there are several great sources, including IR Remote for the BOE-BOT and Understanding Signals. The best part is that it only costs you about $2.

caesar

Hello,
·· It was originally for my desk PC, but I thinking about upgrading to a PC/TV monitor...
I definitely would like to activate the unit by using an IR remote (plenty of old tv remotes around).
To take advantage of your experience, what should I purchase from Parallax that is best for my project?
Thanks!

SRLM

I won't list a complete shopping list, but here are some components that you'll probably want:

servos (continuous, standard)
microcontrolers (a single BS2 would be fine)
BOE-BOT Wheel (If you use the wheel idea...)
a couple sets of IR emitters and recievers (these are to locate the LCD and recieve the IR Remote signals)
an oscilloscope (If you don't know the pattern of the remote that you want to use)
A development board(Obvious...)
A power supply(5-12 volts would be best, depending on the board)
Lots of wire (Radio shack/electronics store. Probably don't want to have to chain together 20 three pin extension cables.

Thats pretty much it for the neccesities. Some additional features that you may want are some LEDs and a piezo speaker. If you are really going for a highly functional system, you can have the BS2 monitor the LCD, and if it's turned off for a long time and the slide is out, it can make the system go back in automatically. Personally, I'd do this by hijacking the little LED on the monitor that indicates power. Monitor that and you should be able to do closings automatically. Now that I think about, you could make it open automatically too by monitoring when the LED is on. Hmm... Just lost the need for the remote... Best keep in just in case you want to customize while in your chair.

A few buttons might be useful for when you lose the remote or simply don't want to go get it.

I think thats about it. Any other supplies?

caesar

Hello,

I'm thinking since this would be my first robo type project I was considering the

BASIC Stamp Discovery Kit (USB) $159.99

"Build over 40 Hands On Projects"

It may be overkill for my project but I believe·the included projects will be beneficial to my learning curve.

Your thoughts?

Thanks to you, I already have a better understanding of the hardware I'll be using. And some cool·modifications to my project.·

·

SRLM

Yep. The discovery kit is the perfect way to learn. Not only do you get all those gadgets, you get the yellow book, the most important reference in the BASIC Stamp world (my opinion...) Anyway, since your project is going to be permanent you'll probably also want to get a carrier board for the permanent part of the project and not use the BOE for long term:

Carrier board

Super Carrier Board

This way you have the BOE for later experiments and short term projects.

caesar

I like the super carrier...

Thank You!·

SRLM

Good choice. I forgot to mention it, but you may want to get a few extra 5 volt regulators to power your servos with. Calculate how many amps you'll need and check if the onboard regulator is enough. It probably is, but might as well be safe by checking.

Zoot

I would not run more than one servo (maybe two) from the onboard regulator which is rated at ~1amp. Most regulators like the venerable 7805 or 3940 are rated at about 1amp, 1.5amp with a big heatsink.

If you really want to regulate servo voltage I would use an LM350 or LM317 depending on your requirements. Remember too that if the battery voltage is, say, 9.6v, and the servos draw .75amp each at stall, with 4 servos that's 3 amps x ~4v voltage drop = 12watts. Get a big heatsink!

However, if you are doing home-brew (like cordless drill motors), then I would run those straight from battery power.

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When the going gets weird, the weird turn pro. -- HST

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sam_sam_sam

caesar

This idea is a good one from SRLM and if one·you have· is variable speed drill motor you can change the trigger switch with a pot and set you speed

I have done this before but you have be very careful to get the + and -

right to the speed controller or you fry it this also has happen to before




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··Thanks for any··that you may have and all of your time finding them

·
·
·
·
Sam

Post Edited (sam_sam_sam) : 8/12/2008 2:15:57 AM GMT

sam_sam_sam

Zoot

Thank You For sharing these Links

I have been looking for some thing like this


servocity.com/html/12v_linear_actuators.html
servocity.com/html/servo_actuators.html

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··Thanks for any··that you may have and all of your time finding them

·
·
·
·
Sam

SRLM

With one of those actuators caeser could lift his whole desk up, never mind just the monitor. Anyway,

Zoot

Do you have any recomendations on where to get one of those LM voltage regulators? I'm working on a project designed for 7.2 volt batteries with 12 volt batteries. I've looked and it seems that they're mainly sold in 1000+ quantities.

Zoot

Digikey.com sells 'em. So does Jameco.com, mouser.com, and others.

e.g. search.digikey.com/scripts/DkSearch/dksus.dll?Detail?name=LM350TNS-ND

2.29 for 1.

Digikey is doing USPS first class on low-weight packages these days, no minimum. I've been getting handfuls of parts with shipping costing 42 cents and getting in the mailbox in just a few days.

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When the going gets weird, the weird turn pro. -- HST

1uffakind.com/robots/povBitMapBuilder.php
1uffakind.com/robots/resistorLadder.php