Good, that makes more sense. Looks like you are half way there…
If this is for an entertainment cabinet, you’re probably OK going the direction of just timing the duration of the actuator motor.
If this is for a kitchen cabinet, people are going to expect that if the door hits their hand it will stop or reverse and this one won’t.
Also, if you have a power outage when the cabinet is partway open. You’re going to have a problem when the power comes back on. Whether you then open it or close it, with a duration base design it’s going to keep running too far. This might break the door or damage the motor depending.
If you don’t make the device smarter, about the only additional factor you can tweak for these situations is the stroke length. You want to be really careful that it’s not possible for the actuator to push farther than the door can handle if you’re only relying on duration to manage it.
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The actuator I linked above actually has a built-in limiter, so running it too long won’t damage it, and the 6" length is exactly the distance of travel I need. And it’s going into an entertainment center cabinet, so nobody should be interfering with the operation of the door.
Edit: For anyone curious, it’s because one of my IR devices is behind this entertainment center door, and I want it to open when I switch to “Watch TV” mode instead of having to get up and walk over to open it myself. And it’s mostly just a nifty first DIY project.
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Just remember that in a power outage situation where the cabinet is left partway, you’re not exceeding any set time limits when the power comes back. You’re starting from a different starting point. This is a big issue with motorized casement windows, where force applied to the fully open window can break it.
It’s just something to think about. 
Not actually true. Because the actuator has a built-in limiter, it can be supplied power for a half hour without a problem, so returning from power outages should be no issue.
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You may want to add one of these to your project… Logitech Harmony Remotes with the hub use RF to talk to the hub and the hub then emits the IR so you could have the hub inside or outside of the cabinet as long as at least one of the IR blasters is inside where you have equipment you want to control. This would eliminate the need to open the cabinet to just control devices.
Regardless… cool project! I hope you can share a picture of project done so as to inspire others 
in similar projects.
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Already did, but my Harmony Hub is further away from the TV so that all devices can see it. Plus I still need to volume up/down and navigate the menus and such, which the Harmony Hub isn’t particular good at.
Edit: I guess it does have it’s own remote which doesn’t require IR, but the line-of-sight to all devices is still an issue.
“…cool project.” And thanks! I will share as soon as that project is completed.
Hmm. Well apparently you can buy these pre-built for practically nothing. 12V, 10A, 2-relays. Exactly what I need.
At least by going through the exercise of putting one together on paper, I learned something I may need next time.
FYI to anyone who might be watching this thread, I’ve now selected and ordered my bill of materials. Each item is pasted below. I’ll update as I make progress on this project.
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And apparently, as my first mistake, I grossly underestimated the maximum physical dimensions of short-throw linear actuators.
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It’s a 15 inch tube with a 6 inch stroke. The product dimensions in the “product details” section of the Amazon page are wrong. That’s actually unfortunately really common with actuators and machine parts . I usually go back to the manufacturer’s own site and get the dimensions there.
Lesson learned. Are linear actuators the wrong mechanical part for this project? I guess I was picturing something more along the lines of this, though slightly faster and more inline than this…
But clearly the part I have in hand is significantly larger. Should I be looking at something smaller and simpler? What are my options?
Edit: Also, my door is opening downward instead of upward, if that makes a difference.
Linear actuator is the right device class, just got to get the right size. The ones you want are probably marketed under the term “mini.” Just check the specs for strength.
How heavy is the door you’re pushing?
Also, slower is safer with actuators. Don’t go for a rush on these.
Also, as one of my professors used to say, “you have to understand the physics before you can select the right electronics.”
The following is a good place to start for determining how to place the actuators and what size you’ll need:
http://www.progressiveautomations.com/selecting-the-appropriate-linear-actuator/
Very small door, similar to what is pictured in the YouTube link, but opening downward. Otherwise a similar amount of space inside the cabinet. Picture with dollar bill to scale included below.
Ok, opening downward is the same as opening upward, just upside down, and the unit shouldn’t care.
Not sure I understand what you meant by “more in line”
It will be installed on the side wall just like in the YouTube video.
And, for the third time, how heavy is the door? Seriously, it matters if it’s a 2 pound door or a 5 pound door.
If you’re going to do projects like this, get used to questions like this. 
Physics again. For anything with lift, know exactly how much force you’re going to require.
By “more in line”, I just thought that a “bullet”-style linear actuator would be easier to fit than the other styles. And it’s less than a 2-pound door. Very lightweight.
I get it. Or…I’m starting to get it. Keep in mind that I’m a programmer trying to incorporate mechanics. I don’t actually know what info is important yet. But when we get to the point of where I’m writing the scripts, I can probably be a huge help to other people coming after me.
Edit: And all I mean by that is that, for home automation projects in particular, I know that it often requires a combination of electrical engineering, mechanical engineering, and software engineering, and as a primarily software engineer, I need help.
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This is exactly why I sent you the link to the firgelli automations site…
They have full and accurate dimensions for all the actuators they sell, in addition to the largest selection I’ve ever seen in one place…
Have a look at this one:
If you mount the clevis very close to the door hinge you can probably get away with a 1" throw, also this actuator will stop if it encounters an obstruction, net length on the 1" throw is less than 8", and its an inch in diameter.
Time to open/close will be a little more than 1 second, which is fast enough to not be annoying, and or alarming…
By placing the door clevis correctly you will be able to utilize the built in limit switches…
Yes, it’s more money than the beast in your picture, but is much more appropriate for the job.
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So on with a few other tips.
Should you decide on an actuator with a 1" throw, the location of the rod clevis in relation to the door hindge can be calculated using the following:
Center of door hindge to center of rod clevis = actuator travel /(door opening angle * PI / 180)
Assuming 90 degrees that you want the door to open we get:
1 / ((90 * 3.14159) / 180) or apx .637" call it 5/8"…
Mount both clevises to the cabinet with mounting tape until you get the positioning just right after cycling the actuator. Make sure the actuator is fully extended with the door open to 90 degrees when mounting.
Mount the actuator clevis as high up as possible to maximize it’s leverage against the door when open.
Also it looks like the door has an existing magnetic catch on it, if so you’re going to want to remove its strike plate else the actuator will wind up a bit while it over comes the magnet force, this will not produce good WAF…
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