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How to make a computer (in particular, my laptop (Acer Extensa 5220)) to perform some mechanical movements without buying anything >$5, soldering things inside computer or creating big sophisticated circuits?

Traditionally CD-ROM tray is used to make computer do some movement IRL by, for example, SSH command, but in laptop tray is one-shot (unless manually reloaded) and also not very comfortable [mis]usage.

Some assistance circuits can be in use too, but not complex. For example, there is a little motor that can work on USB power.

Devices in my computer:

  1. DVD-ROM tray: one-time push.
  2. USB power: continuous power to the motor or LEDs or relay that turns on something powerful.
  3. Audio card. 3 outputs (modprobe alsa model=test can set Mic and Line-in as additional output). One controllable DC output (microphone, 3V, 1+1 mA, can also modulate external DC which is applied to the port (with clicking side effects to laptop speakers) /* Poor soundcard, it is still working. */) that can power up LED and some electronic (may be even mechanic?) relay. Also with sophisticated additional circuiting can control a lot of devices with a good precision. Both input and output support. Probably the most useful object in computer for radio ham.
  4. Modem. Don't know about this much, it doesn't work because of hsfmodem crashes kernel if memory is >= 1GB. May be it's "pick up" and "hang up" can turn on and off power taken from USB port?
  5. Video card. VGA port? S-Video port? Can them be useful?
  6. Backlight. Tunable, but probably unuseful.
  7. ExpressCard (or some) slot, 4 pin Firewire. Nothing interesting for the task probably (is it?).
  8. AC adapter and battery. Probably nothing programmable here. /* My AC adapter already have additional jacks to connect extra devics */
  9. Keyboard. No use.
  10. Touchpad. Good sensor (synclient -m 1), but no output.
  11. Various LEDs inside laptop. Probably too weak and requires soldering.
  12. Fans inside laptop. Poor control over them, requires soldering and dangerous to tinker.
  13. HDD (internal and external) that can be spin down and up (hdparm -Y, cat /dev/ubb). But connecting anything serially with it's power line makes HDD underpowered... And too complex.
  14. Ethernet port. Can weakly blink up a LED in disconnected operation (between green and white-green wires), can be conrolled ifconfig eth1 {up,down}. Simple, but limited usage - power is too weak.
  15. Modulating the power consumption of laptop itself. Probably nothing good here.

Is something are missed? Any ideas how to use described components? Any other ideas?

May be there are easily available /* in developing countries */ cheap devices like "enhanced multimeters" that are controllable from computer and can provide configurable output and measure current and other things? Things to aid pushing many physical buttons with computer. Isn't this a simple idea and implementation and a lot of use in good hands?

P.S. Ability to turn on and off the power of USB ports is almost what's needed. /* In my laptop USB port can give more than 1A for several seconds without triggering short-circuit state and can be used to handle rather powerful devices */. The only way I imagine to control USB is setting up RTC to wakealarm and turning off computer (not to suspend-to-ram). But this is slow and interferes with normal computer activity.

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What are you trying to accomplish? –  Stephen Jennings May 19 '10 at 2:40
    
@Stephen Jennings No particular task now. One example: charging 12 serially connected AA NiHM batteries using laptop's power adapter. Current is a bit too much to charge them safely, so I need something to connect and disconnect charger periodically and finally go to something like "1 second connected 9 seconds disconnected" mode. It will be DiY dumb NiHM charger. A relay that is controlled from USB or audio would be fine for this. Actually there can be many situations where you need to do something many times or by timer or remotely and don't want to do it manually. –  Vi. May 19 '10 at 16:08
    
Wait, serially connected? Or do you mean in 6 parallel sets of 2 in series? –  Ignacio Vazquez-Abrams May 20 '10 at 1:01
    
@Ignacio Vazquez-Abrams No, I use 16 AA NiMH batteries to power my laptop (internal battery is degraded to the half of capacity - more than 2 years of work). But to charge all that pack quickly I need to reduce number of batteries in that pack (and charge the remaining somewhere else (in normal charger)). Such battery pack handles about additional 1.5 hours of laptop function. –  Vi. May 20 '10 at 6:36
    
12 AAs in series need about 15V of electromotive force to charge. USB only provides 5.2V. Charging them in series is going to present a challenge without a step-up DC-DC converter. –  Ignacio Vazquez-Abrams May 20 '10 at 7:46
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4 Answers

up vote 1 down vote accepted

Can you execute remote commands that will spin a disk in the DVD drive? On a laptop that should give some vibrations at least.

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Don't know (when it without a disc). I definitely know I can use laptop's DVD-ROM with tray opened (and even tried to slow down the spinning by hand during burning - it works, no failures). Main use there will be to make tweaked disc that will move something. Does someone know how control DVD-ROM at low level (start motor, stop motor, turn of laser, turn off laser)? –  Vi. Jul 24 '10 at 9:48
    
Experimented a bit using "special" disc: vi-server.org/vi/d/disc_misuse Now need to find a way to reliably start and stop the spindle. P.S. That disc is still readable. –  Vi. Jul 24 '10 at 11:27
    
(Accepted to increase answer percentage. Acquired Arduino now, so the question resolved.) –  Vi. Dec 8 '11 at 19:24
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ok gotta really mcyver this one don't I, less then 5 dollars and no internal soldering right? if you don't mind used parts then use the display as a decoupled switch get a light sensing device turn the display on and off have the light sensor control a relay.

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If using some complex additional circuit then I have a plenty of variants: 1. Headphones output + oscillatory circuit, 2. IR output, 3. any led or display/light sensor, 4. radio (tinkle with Wi-Fi). But I want to do it as simple (and lazily) as possible (but safely). –  Vi. May 20 '10 at 6:41
    
Do you know which input is needed for typical relays (that can control about 20V/2A)? If 2mA @ 3V is enough to control it, audio variant will work. –  Vi. May 20 '10 at 6:49
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Normally you would connect the serial port to a relay that operates some other device which performs the physical work.

As for your battery charger idea, you can either build your own or buy one.

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USB charger is not enough to charge 12-16 batteries simultaneously. So buying and using some relay is inevitable for the task. And I don't want to stick with charging task but be able to do various in situ things quickly (each time different ones). Charging is just an example. –  Vi. May 20 '10 at 6:46
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Not really sure what your trying to accomplish but maybe you could use the sound card output to
control a motors speed using PWM, there are a few applications such as this one that can produce a variable frequency square wave.

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Yes, I'm planning to use sound card, but in other way: Mic jack can be controlled to some "50p, 80p, 100p" which is enough to power on a LED. I hope there can be some solid state relay (or similar parts) that can be controlled by such little power, e.g. connect SSR to Mic jack and ready to go. Usual headphone output is too low voltage to control something (without making serious circuits). And I want to listen music too, so headphone jack is better be reserved. –  Vi. May 29 '10 at 1:43
    
You have a number of options, none of which involve too much work. Use a regular relay, although you will need a relay driver circuit for this option which is a small circuit just to supply enough current and voltage to turn on the relay it consist of a resistor, transistor and a diode, the diode is for protection from inductive kick back from the relay, leave that out and you could probably say good bye to your sound card. Another easier option would be to use an opto-isolator en.wikipedia.org/wiki/Opto-isolator which would require no other circuitry for interfacing –  volting May 29 '10 at 15:49
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