Fun with Arduino micro-controllers. engineering questions

[jeff0520]

Hello all,
A visit to our local hackerspace introduced me to the Arduino and the great stuff you can do with one. I'm thinking it would be fun to have the bed that folds into a couch be electric and remote controlled. (Based on Cracker39's Squidget design.) I'm thinking the jack screw mechanism from a garage door opener to pull the foot section of the bed backward, and perhaps a couple of linear actuators to give the center sections an upward shove as the jack screw starts pulling to begin the fold. A couple of magnets and a reed switch to act as a travel limiter, and a couple of relays would do it. Anyone see any problems with the concept?

[Dale M.]

You don't need any sophisticated electronics to do that... Just a actuator or two, couple of relays, a few micro switches and hope it does not decide to fold up while you are still in it.....

Dale

[jeff0520]

Hey Dale,
Just to make the bed move I wouldn't need the micro-controller. The part that requires that is the remote control. The Arduino monitors an IR sensor for signals from a remote salvaged from an old A/C unit that died and closes the proper relays in response . I'm also going to have the TV on a vertical drawer that slides out from the upper cabinets. Press a button on the remote and the bed folds into a couch. Press another and the TV extends from the cabinet. :-)

[jeff0520]

The drive mechanism for the TV drawer will be based on a piece of threaded rod. It doesn't need to develop nearly as much force as the bed fold mechanism

[desertmoose]

A good reversible geared drive unit is a cordless drill. even has a chuck to connect to the drive screw.

You will have to open it and connect to the reversing switch, and run power to the old battery contacts.

Sam

[asianflava]

I was just looking at Arduino hacks for the quadcopter I've got on order.

[jeff0520]

A good reversible geared drive unit is a cordless drill. even has a chuck to connect to the drive screw.

You will have to open it and connect to the reversing switch, and run power to the old battery contacts.

Sam

Do you think a cordless drill motor would have the torque for a jackscrew drive? Folding the bed up will take a fair amount of force. The mattress is actually in 4 pieces to facilitate folding, but still, that's a lot of lumber to move around. I might also want to move the mechanism with me sitting on it as a way to adjust recline angle. I don't know a lot about reversable DC motors.

[jeff0520]

I was just looking at Arduino hacks for the quadcopter I've got on order.

Cool. Pics please :-D

[desertmoose]

Do you think a cordless drill motor would have the torque for a jackscrew drive? Folding the bed up will take a fair amount of force. The mattress is actually in 4 pieces to facilitate folding, but still, that's a lot of lumber to move around. I might also want to move the mechanism with me sitting on it as a way to adjust recline angle. I don't know a lot about reversable DC motors.

I use a cordless drill to run down the jackscrew stabilizer jacks on my 30' toyhauler. 11,000 pounds of trailer. I don't know what load the jack takes before the drill stalls, but it actually raises the corner of the trailer a bit.

I'm sure it's a lot more force that your application would need, even with you sitting on it.

Sam

[droid_ca]

This is a cool idea, can't wait to see where this thread goe...I know there is a trailer on her that has a power hatch with slide-out stove

[PubUltraStar]

I've used the Teensy 2.0 with Teensyduino to send keyboard commands to a PC from Arcade Buttons in a DIY Photo booth I created for a wedding a couple of years ago. The scripting language is pretty intuitive with good documentation form Arduino, or you can google pretty much what you need for code. My Y6 Multi-copter uses arduino for it's source, but I don't muck around with the settings too much for that since it's pretty much honed in. Sounds like a fun project. Post pics and code.

[Bogo]

As an old hack at amateur robotics and other things electromechanical, forget the threaded rod for a jack screw unless your load is light. They will gaul up in no time when put under moderate loads. Yeah, you can find super smooth ones made for motion control, but they will cost more than non precision acme lead screws. Go find non precision acme lead screws, or use a different type of drive mechanism. Think carefully about your drive mechanism and how it will or won't intrude into the interior, and other spaces.

On acme threaded lead screws. You may be able to scavenge them out of old hospital beds, or other equipment. A big issue will be getting ones long enough. You might have to design leverage into your system. Hum, non precision 6' and 12' ones are now available at McMaster-Carr: http://www.mcmaster.com/#general-purpos ... ds/=lgtx9i so I guess length won't be an issue. Plain steel ones are cheap enough to ignore threaded rod. I wish they handled them a couple decades ago.

A cordless drill will be powerful enough. If needed it is easy to gear it down some with a simple chain drive. Look on craigs list for a 12V or 14.4V drills with dead batteries. Hook it to your house battery with some stout wires. Use a high current relay to control the power it. Those drills can suck down the amps when loaded. Note, some higher end battery operated drills already have gear boxes in them for higher torque output.

Ball screws have an advantage in the turning load pressure is across ball bearings, and thus are easier to turn. They have the disadvantage of not have that great deal of friction to resist being pushed so a brake of some sort is needed. You could use a magnetic brake. There are ones where you provide power to release the braking force. In the past I've found them at electronics salvage places. If you scavenge a ball screw, don't remove the ball nut from the lead screw unless you like the nightmare of reinstalling a large number of ball bearings into it again.

[jeff0520]

http://m.grainger.com/mobile/search/ecatalog/N-?Ntt=acme+thread+rod&tab=search&Nty=1
Gotta love Grainger. Same day local pickup from the branch 6 blocks from my door :-)