Using Servos/Motors to open Side Panel

[Belial88]

I'd like to use a servo or motor to open the side panel (use a button or switch to just push).

I'm not sure where to start with this. I'm not trying to hook it up to the computer, just a switch I'd put on the case. Thanks.

If I can't get this to work, I'll use magnets (no hdd, not that it matters)... but I'd really like to make this work. I am somewhat familiar with servos (model airplane when I was a kid) and motors (various), but not anything like this.

Thanks. Bitfenix shinobi (modded side panel to be mostly an acrylic window).

 

[dma0991]

You will need to place hinges on one side. Could be at the back for a suicide door style or place at the top for a gull wing door style. Any tabs that latches on to the case notches should be removed as it hinders the side panel from closing and opening.

The fact that you've modded the side panel to hold an acrylic panel makes it lose some of its rigidity, even more so if the acrylic panel is only held with double sided tape. If you want it to work properly, the parts that move the side panel must be on a square frame (to give rigidity, possibly made out of 1" flat steel), welded or bonded permanently to the side panel with epoxy.

The final part in making it open is using an actuator. You will need to find where and how to mount it (could be on a rail). How to power it (should be 12V DC actuators) and move it with a flip of a switch.

 

[Belial88]

Yea, I can get hinges from a local hardware store, then just clip the things that hold the door in place normally as well as the piece that slides in at the front (would need to use a dremel on that likely).

The final part in making it open is using an actuator. You will need to find where and how to mount it (could be on a rail). How to power it (should be 12V DC actuators) and move it with a flip of a switch.

Yea I dont know what to do here. Also, it gets a bit more complicated I think with press/switch on/off opening, and then the other motion closing, might need a controller of some kind there.

Like I'm not sure a servo would be strong enough (or I'm sure it would be, if i got a big enough one). So if I got a big servo with a rod long rod attached to it, and that rod hinged to the opoosite end of the hinges, and it moves 90*, and then back 90*, for open/close... would probably need some sliding action involved due to the servo and door being on different fulcrums, unless the arm just pushed the door out by pushing against it, and then closed when the arm retracts and a spring or rubber band pulled the door tight...

 

[monkeydelmagico]

servo tester and a servo for RC car should do the trick. Most of the decent stuff will work with typical voltages from PC. The amperage is going to be more tricky though and you might need to use step down transformer.

From the mechanical engineering perspective some of this also depends on how much of a door opening you want. The length of the servo throw and how far the door ends up opening being will determine the size servo you will need. The servo(s) are going to have less work if you are hinged at the top with the opening facing downward.

Sounds like a cool project! Hobby king online is a great place to find rc parts for cheap.

 

[Belial88]

Thanks, I'm still not sure exactly what to buy though. I don't know much about servos (i just know how to hook them up to an rc plane controller, but that was like over a decade ago...).

 

[Belial88]

Someone on reddit recommended I use a pololu controller.

I'm still not sure about what servo to buy, what rods and stuff to buy, what battery to buy, and execution.

 

[natto fire]

I would look towards linear actuators myself, servos are usually rated in grams with how much weight they can handle, especially the more common ones used in RC applications. As stated, you will probably need a frame around the side panel edges to attach to the arm of your actuator. Determining how much you want the panel to swing away will give you an idea of whether you can just use the throw of the actuator, or have to use a complex hinge setup to trade force for distance.

Another idea is to get a latch and have a gas-charged strut do the throw, and resetting it after you are done. At that point, though you will still have the frame involved so might as well go fully automatic with an actuator or motor and worm gear setup.

 

[Belial88]

wow, linear actuator... that's insane. I'll look into that, it seems like some people have even done that (as opposed to zero search results for servo).

Why would I need a frame around the side panel edges?

Just needs to swing like 90*. I don't see more than that being helpful at all.

I don't think it'd be too heavy to move the side panel though, since it'd be on hinges. I don't really know anything though.

Another idea is to get a latch and have a gas-charged strut do the throw, and resetting it after you are done. At that point, though you will still have the frame involved so might as well go fully automatic with an actuator or motor and worm gear setup.

Looks like a pneumatic thing, like a car strut/shock or those single piston engines they use to throw airplanes off aircraft carriers.

I'm trying to spend less than $50 for this... I mean I'd like to do this right, don't get me wrong, but I think $100+ would start to cross into way too much (still would consider it i guess...). I'd really like to spend more like $20-40.

 

[dma0991]

You need the frame to give the side panel rigidity. Currently it lacks much of its rigidity due to the acrylic panel, which wouldn't be much of a problem if it is mounted with screws/rivets. If you're using a single linear actuator instead of a double at both ends, the side that does not have the actuator will flex/sag due to the weight. Plus the frame gives it a good spot to weld on a bracket.

Its modding. You can't put a strict budget to it because of uncertainties in the build process. I would say for this, $100 is just a start for this particular mod.

 

[monkeydelmagico]

Just needs to swing like 90*. I don't see more than that being helpful at all.

90 degrees is alot. As Cpt Howdy indicates way too much swing for a simplistic RC servo and rod setup. The worm gear idea is a good one though. Would require alot more engineering know how than I have.

Here some food for thought though:

http://rollertrol.com/actuator-for-vent-control-or-window-opener

 

[Saffron]

I did a mechanical hand for a school project a year ago. I purchased a pololu controller and 5 Power HD1501MG High Torque servers from pololu as well. There is a no spec sheet on these servos but I successfully put 5 Amps through them continuously for a 1 hour operation using a 450W PC Power supply. During the testing phase of my project All 5 servos in conjunction broke a 1" X 1/4" ply-board board in half.

I am sure a single HD1501MG servo can swing out a case door just fine if you get the hinges and swing arm right. You can probably use the +5V 2A power from your computer's power supply. Use the Pololu controller for the logic, wire the servos with external power, and put bi-directional switch on the pololu controller and program it for +/-90 degree operation.

In terms of the hinge, just purchase some small hinges for the hardware store. Put an extruding metal bar or something (small U-bolt or Eye-Bolt) on the door for the servo arm to attach too. Find a way to screw down the servo with good alignment (Good Alignment is CRITICAL!) and you should be good.

 

[Belial88]

I dont know what a worm gear is. Why would 90* be hard for a servo?

The hinges shouldnt cost much, a pololu controller is like $20. So the only cost here really is the actuator, whatever i end up using. I dont know if a frame is necessary since it doesnt need to be fast, but if i do ill get to just putting steel rods around the panel.

a bidirectional switch... why not just an spst switch and somehow program do this, then do that, on the pololu, or a dpst switch (or am i thinking spdt... you know what i mean).

 

[Saffron]

You can use whatever flavor of button or switch you want. They will all work if programmed properly.

Another way you can go about doing it is with a continuous servo and a cable. Then all you would need is a self-returning (spring loaded) hinge. You can program the controller to spin the servo say 360 or 540 degrees to pull the door closed. When you open it the springed hinge will provide the opening force while the servo just feeds it slack. But then you would probably need a prop to hold the door open if you had it laying on it's side, maybe not. It just depends on how much spring force you want on the hinge as they are usually adjustable or come in different forces for different applications. This will all rely on what type of servo you use.

Just throwing some suggestions your way

 

[Belial88]

Okay so so far this is what I've got in my mind:

* Buying a Pololu controller. I guess I'll just buy the micro, smallest/cheapest one. It does like 5-6 channels, an even smaller one for just 1 channel would be better, but whatever.

* Buying some ~5v battery, I guess I'd just buy the cheapest 5v battery from ebay. I mean I only need like 1a+ here for just one servo and the controller.

* Buying a linear actuator. I looked into servos, went to a local hobbytown rc store and talked to them about it, and it sounds like servos might not really work well. 90* would be hard to pull off I think.

They recommended that instead of doing like a sweep motion, to do something where the rod was perpendicular to the side panel, and pushes it out.

I don't know what linear actuator to buy (some seem really expensive, I hope to not get that $90 firgelli one that the one guy used who actually did this, pretty sure what he got was insane overkill, when I mentioned 100:1 to the guy at the store he was like yea that's really strong), and if I could go the servo route ($10+, a worm gear box, which i understand is basically just a servo box) that'd really be a lot cheaper...

Then all you would need is a self-returning (spring loaded) hinge.

I'd like to go fully automated.

 

[Belial88]

Okay guys, this is what I've got:

* http://www.ebay.com/itm/Firgelli-Au...552?pt=LH_DefaultDomain_0&hash=item2a30edaeb0
FA-150-S-12-2" Firgelli Actuator 20:1 150lb 2"

Which is 2" just like this guys: http://www.youtube.com/watch?v=0C1yT-QBBr4 another firgelli actuator) His is 100:1 gear ratio, http://www.trossenrobotics.com/p/figelli-L12-50mm-100-1-Linear-Actuator.aspx

Now I don't really understand gear ratios (whats higher/lower, 100:1 or 20:1, what does it mean), but his works, and mine says 150lb, so I'm assuming the one I picked is good brand, and more than powerful enough.

* Micro USB 6 channel controller http://www.pololu.com/catalog/product/1351
I'll go with partial build, to just solder stuff, save space. $19.
I wish I could go smaller/cheaper/less channels, but can't find anything. i also have no friggin clue on what to buy a controller, but I've heard a few people say pololu, I can't see the USB controllers cheaper anywhere, so whatever. I'm guessing what I need, is computer programmable, in that i can set it in the PC, and then it'll run the script once unplugged... so i can basically hit a switch/rocker/button for open, then close, then open operation, then close operation.

*
* I'll need a battery. I think I'll need a 4.8v battery, but a few confusing things - the linear actuator specs say 12v@5A (so 60w), so wouldn't that be a lot of amps for just ~5v? Secondly, the pololu controller says 5v minimum, would a 4.8v battery be okay still? Or do I need to buy that 5v regulator (in which case, it says it can only handle 5v@500ma, that's not good is it?).

Someone mentioned something where I could do something where the battery would charge when the PC was on, and then it'd run off the battery when the PC was off (or psu unplugged if i went by 5vsb, which would just be jamming a wire into the 24 pin on the 5vsb line). It'd be really cool if I could do that, but I'm sure any 5v battery pack will last a lifetime anyways.

* I think I'll need linear actuator mounting stuff - something to attach it to the door, and attach the actuator itself to the pc. I have absolutely no clue on this, hopefully I just buy the actuator, and then I can go to a hobby store full of servo equipment, to get the answer...

 

[Saffron]

Keep this in mind: Voltage is the speed at which things will move and the Amperage is how much weight it can move (Torque).

The spec sheet saying 12V@5A means you are going to need a 12V@5A supply. You can get away +/- of those specs but not too far from it. DO NOT compensate amperage for lack of voltage to meet the power, it will end in disaster. If all you have is a 5V supply then you are going to need to figure out a separate 12V. Wattage is just a measurement of power, or the work that particular component can perform. The 4.8V may be fine with the controller but I would only recommend running it at it's specification. Don't run the 12V@5A through the controller to supply the other component or else you will fry controller PCB.

A 100:1 gear ratio is a lower gear ratio and the 20:1 is a higher gear ratio. 100:1 means the motor gear will turn 100 times for every shaft gear rotation. At 100:1 ratio the movement will be a lot slower but more powerful and the 20:1 ratio will be a lot faster but less powerful.

I would get a 12V battery instead of the 4.8V (just to keep within the spec of everything; 12V being your highest needed supply) and put a 5V regulator in line. Even though the regulator spec says 5V@500mA you can still use any battery with it because current is only pulled and not pushed like voltage. The regulator will only pull the 500mA the regulator is spec'd at in turn the battery will only supply the 500mA that is being pulled.

For charging the battery you will need to hook up a charging regulator between the battery and your computer's power supply. Your computer's power supply has 3.3V, 5V and 12V supply lines.

As for the pololu controller, I purchased the micro 12 channel and it is the size of a quarter so space shouldn't be an issue with a 6 channel. I hope this helps even a little.

 

[Belial88]

The pololu controller says it is 5v-16v, so it should run just fine off 12v. So there's no need to use a 5v regulator or 5v battery source, I can just run off a 12v battery right? I'm not sure exactly what 12v battery to buy here, I see there's some normal batteries called A23 that duracell/etc make, but I don't see an amperage on it.

I would get a 12V battery instead of the 4.8V (just to keep within the spec of everything; 12V being your highest needed supply) and put a 5V regulator in line. Even though the regulator spec says 5V@500mA you can still use any battery with it because current is only pulled and not pushed like voltage. The regulator will only pull the 500mA the regulator is spec'd at in turn the battery will only supply the 500mA that is being pulled.

I'm a bit confused on this part, if I'm using a 12v battery then there's no need for the 5v regulator, right?

For charging the battery you will need to hook up a charging regulator between the battery and your computer's power supply. Your computer's power supply has 3.3V, 5V and 12V supply lines.

I have no clue where to buy a charging regulator, and a bit confused on this wiring here. So something like polulu controller's grnd to battery to regulator to psu, then power from psu to regulator to battery to pololu vin?

Then I'd have to jump vrin and servo power on the pololu, which on the micro you have to solder together as they show.

DO NOT compensate amperage for lack of voltage to meet the power, it will end in disaster.

What do you mean exactly? Don't things just pull however much amperage/wattage they need, and that's that? What's the possible disaster? If anything, lower voltage means more amperage and if you don't have it, stuff just doesn't work right?

I'm a little worried that the actuator ends up being too fast here, I'm not sure how I'd be able to slow it down besides reducing voltage, but 4.8v is a huge step down from 12v.

As for the hinges, I think I'm actually going to mount the hinges on the outside of the case, that way I don't have to cut that fold part on the side panel. The hinges will not attach to the side panel itself, but that fold thing. I'll have to use a very thin hinge, but it should work out.

 

[Belial88]

So if I went linear actuator, i actually have to buy an 'L12' firgelli which is $80+, because that one I was checking on ebay was full sized and wouldn't fit. I need a mini linear actuator to fit between psu and side panel in a normal case (or any other spot really). I didn't realize that model I was checking was the size of my fist, even though it's the same 2" movement.

However, I think I can do this with servos instead!

Basically, I use a rod to push/pull the door. Like have the servo by the hinges, a horn out, and then the rod back towards the hinge to mount to the door behind the servo. The horn/rod would be 'crumpled', and as the horn turned, it would extend and the horn/rod would straighten out.

So now I just need to know:

* What servo to buy (i can get a rod and mounting stuff at a local hobby store). I could even buy it at a local hobbytown USA, but I don't know if their prices are good or not. But the mounting stuff I could just get there.

* I guess that pololu controller micro 6channel

* What 12v battery to buy (I think I'd just buy some cheap nimh or whatever it is, 12@5a or something, the ones that look like a bunch of AA taped together. I'm sure a 9v battery would work too... maybe just use a normal 9v battery lol.

* How to do a charging regulator (i have no idea where to look on this, I've googled and googled but can't figure it out) to do the whole run-off-psu while on, off battery while off that's charged by psu.

I got a dremel coming in the mail, once it's here I'll put the hinges on, and then order the other stuff assuming hinge mod works.

What I'm going to do, is us enormal small hinges (not piano), and attach it via glue to the rear panel behind the side panel 'fold' part, then glue the other side over the other side of the side panel fold. Sort of sandwich the side panel fold with the hinge, if that makes sense.

 

[dma0991]

However, I think I can do this with servos instead!

Basically, I use a rod to push/pull the door. Like have the servo by the hinges, a horn out, and then the rod back towards the hinge to mount to the door behind the servo. The horn/rod would be 'crumpled', and as the horn turned, it would extend and the horn/rod would straighten out.

I'm not getting a clear idea of what you're describing. I'm getting mixed ideas with what you meant with horn. Are you doing something like a worm gear?

 

[Belial88]

Well a worm gear refers to a specific type of straight-gear (forget the pros/cons, I think it saves space or something) and like the worm gear box tamiya sells is essentially just a servo...

Horn is that long arm part.

Anyways, I've dremeled away all the parts that interlock and such on the side panel with the dremel that I bought, that arrived today (i also cut through my fingernail on my pinkie, that thing is no joke). I took a piano hinge and cut it into 3 different pieces, I've spray-primed it but I need to pick up black spray paint for it. Once that dries, put a bit of grease in there (maybe some deoxit d5).

Then I'll use a metal hobby modeler's glue to attach it to my side panel fold and to the case.

Once that's done, I'll order a servo, pololu controller, and momentary SPST switch. I am still unsure of what servo to buy though to power this.

 

[dma0991]

I think its doable if the servo has sufficient torque to push and pull the side panel. For the hinge, its much preferable to rivet it but if I had to use glue, it would have to be slow curing epoxy. Epoxy, if applied correctly, holds extremely well.

Also to note is that the bonding surface must be bare metal or rough surface. Use some sandpaper to remove/scuff the paint layer of the side panel and leave the bonding surface of the hinge to be bare metal.

You might want to add in some small Neodymium magnets or weak ceramic magnets at the other end of the side panel. This should prevent the loose end of the side panel from flopping around.

 

[Belial88]

Yea I was thinking of magnets, but that might not be necessary if the servo is holding it tight, since I believe the way it works, is that it locks in when not in use, rather just being limp in a position.

I have some modeler's glue, but I'll look for epoxy at lowes. The metal modelers glue always holds stuff amazingly well, I've never had to use anything more in any of my projects.

I don't think the servo has to have a ton of torque (relatively), since pushing a side panel, which is basically just a sheet of acrylic since the window mod I did was so big, that's hinged, really isn't much (ie a door weighs a ton, but pushing a door is really easy to do and only requires a pound or so of force).

Whereas pushing a flap open in .01ms under 200mph winds is quite hard to do, and demanding.

I mean I'm not sure here, but this is my understanding of my situation.

 

[dma0991]

Well I don't think it will shut very tight and will leave a small gap, while considering that the servo will be in a locked position. The magnets is only meant to secure it in place, ensuring that it closes much like before its modded.

Its certainly easier to push a door sideways rather than having it open in a gull wing fashion where the weight does have an impact. But since we're not dealing with precision engineering(calculation of weight and minimum amount of force required) and more towards trial and error, over engineering it would be better than having too little and having to purchase another servo just because the first one isn't strong enough.

 

[Belial88]

Yea I mean I might need magnets, I'll just rip them from a hdd, I'm not too worried about it. I'm more worried about the fact that manufacturing imperfections means there's going to be a gap/unevenness anyways (this is the point of the screws on the side panel - oh manufacturing imperfections? Just jam it really tight!). If I need them, I'll use them.

But since we're not dealing with precision engineering(calculation of weight and minimum amount of force required) and more towards trial and error, over engineering it would be better than having too little and having to purchase another servo just because the first one isn't strong enough.

I don't mind having to purchase another servo and just returning the original one. I'd rather use a $10 servo that does the job, and it had to be the 2nd servo I bought and had to return the other one, then overbuy here. A lot of the appeal of this mod, and of the mods I do in general, is how low cost they are.

The mod kinda loses a bit of appeal if it's over $50 all because I decided to overbuy on a servo, you know?

Anyways, I'm going to buy an Adafruit Trinket instead of the Pololu Maestro. Apparently it's just the same thing but smaller/cheaper, it's $8 vs $18.

http://www.adafruit.com/products/1501?gclid=CMvQ8L2VzrkCFZOe4AodSEAAIA

So that leaves the battery, and the charger. I found a charger, but it only uses 4.2v or less batteries and I need 4.8/5v...
And the servo but I'm not worried about the servo atm.

 

[boondocks]

Might pick up something from this build on OCN. http://www.overclock.net/t/1326148/...d-limo-edition-build-log/640_20#post_20640222