Automatic sliding door question using linear actuator

Jyetman

Jyetman

Active member
So I have a cat who needs to be let in and out while i'm on vacation. My apartment has a "bolted" sliding glass door with a screen door. I need to open and close that screen door 4" using a actuator connected to my apex eb4 bar. My question is to operate the linear actuator 12+ volts DC to open and 12- DC to close. Can I wire two 12 volt DC power supplies to the actuator one power supply being the "+" the other "-" plugged into 2 separate EB4 outlets for each power supplies? How can I make this work? Any better ideas would be greatly appreciated.
 
You didn't specify which actuator so I can't go look at its specs to read the speed from the specifications for you ;)

Typically you PWM them for speed control.. If you adjust the voltage you reduce its force...
 
mcgyvr said:
You just need single supply and a DPDT relay

First link I found.. I didn't scan for total accuracy.. you don't need the switch.. just plug the 12VDC supply into the eb4 outlet
http://blog.actuonix.com/2017/12/how-to-use-relays-to-control-linear.html
Click to expand...

The one you provided requires a switch unless its a timing switch it wont work for my project. I found this but according to the diagram it requires two power supplies do they sell already made boards?

https://www.dropbox.com/s/kvuxg410gwqcvvr/forward_reverse_relays2.jpg?dl=0
 
Last edited:
For the linear actuator, a single power supply and a single Double-Pole Double-Throw (DPDT) relay is all you need. This power supply should be always on.

But to control the DPDT relay, which will switch the polarity of the power supply and make the linear actuator go the other direction, you'll need another (much lighter duty) power supply.

So get a DPDT relay, then wire it up so it is effectively just switching the polarity of the linear actuator. You can see the example wiring here (https://www.firgelliauto.com/products/12-volt-double-pull-double-throw-relay#ptab-technical-drawings).

Then for the DPDT relay, wire the coil leads to an appropriately sized power supply in your EB4, and when you turn the power outlet on, you'll power the coil and flip the DPDT relay. When you shut the power off, the DPDT relay will flip back and the linear actuator will go the other way.

Just poking around Jameco, it looks like you can get an appropriate relay for $6 and a light duty power supply to go along with it for another $5-6 (though I'm sure you'll have a light duty 12v DC adapter lying around). Then you just need your beefier power supply for the linear actuator and you are good to go.
 
Jyetman said:
The one you provided requires a switch unless its a timing switch it wont work for my project. I found this but according to the diagram it requires two power supplies do they sell already made boards?

https://www.dropbox.com/s/kvuxg410gwqcvvr/forward_reverse_relays2.jpg?dl=0
Click to expand...

Like I said above.. you don't need the switch.. You can just omit it and in case its not clear just connect the 2 ends that would go to each side of the switch together... The schematic I posted above works just fine..
 
sfdan said:
For the linear actuator, a single power supply and a single Double-Pole Double-Throw (DPDT) relay is all you need. This power supply should be always on.

But to control the DPDT relay, which will switch the polarity of the power supply and make the linear actuator go the other direction, you'll need another (much lighter duty) power supply.

So get a DPDT relay, then wire it up so it is effectively just switching the polarity of the linear actuator. You can see the example wiring here (https://www.firgelliauto.com/products/12-volt-double-pull-double-throw-relay#ptab-technical-drawings).

Then for the DPDT relay, wire the coil leads to an appropriately sized power supply in your EB4, and when you turn the power outlet on, you'll power the coil and flip the DPDT relay. When you shut the power off, the DPDT relay will flip back and the linear actuator will go the other way.

Just poking around Jameco, it looks like you can get an appropriate relay for $6 and a light duty power supply to go along with it for another $5-6 (though I'm sure you'll have a light duty 12v DC adapter lying around). Then you just need your beefier power supply for the linear actuator and you are good to go.
Click to expand...

For switch trigger can I use any size DC power supply to the relay's coil terminals? Do I need a resistor in parallel or series?
 
Never mind I got it working with a 8.4 V DC 1.5A Power supply on switch side just hope it don't blow up. Thanks
 
Jyetman said:
For switch trigger can I use any size DC power supply to the relay's coil terminals? Do I need a resistor in parallel or series?
Click to expand...

It depends on the type of relay. Some use AC for the relay coil, some use DC. Some are designed for 12V, some for 24V, etc.

The spec sheet will have all the info, including the minimum voltages necessary to operate along with the expected current. If you have a coil designed for 12V DC, and you supply it 12V DC, you don't need a resistor, the internal resistance of the coil will limit the current to the appropriate levels.

If you using 12V DC on a relay that is designed for 5V, or perhaps 8.4V for a relay that designed for 5V, you would want to put a resister in series to lower the current flowing through the it. The size of the resister would be determined by internal resistance of the relay which you'd find on the spec sheet. There also are probably smarter ways of wiring it up using other components that I don't know because I'm not an electrical expert, but putting the resister is certainly better than nothing (and potentially some fancier way of wiring it up is better than just a resistor).

By far the easiest thing is just make sure the power supply voltage matches what the relay coil expects and then you don't need to worry about anything else... just plug the power supply directly to the coil.
 
You should be careful what linear actuator you use also. If it doesn't have endstop switches the motor will always be trying to close the door and will over heat. The actuators with endstop switches will cut power to the motor when it reaches full return and stroke. You can get around this by using a second eb8 outlet to cut main power after say 1 min

Sent from my SM-G955U using Tapatalk
 
aaronpentz said:
You should be careful what linear actuator you use also. If it doesn't have endstop switches the motor will always be trying to close the door and will over heat. The actuators with endstop switches will cut power to the motor when it reaches full return and stroke. You can get around this by using a second eb8 outlet to cut main power after say 1 min

Sent from my SM-G955U using Tapatalk
Click to expand...

It does shuts off when it reaches both end strokes. It was cheapest I could find on amazon for $38 bucks 12 Volt 4" 220 LBS linear actuator.
 
sfdan said:
It depends on the type of relay. Some use AC for the relay coil, some use DC. Some are designed for 12V, some for 24V, etc.

The spec sheet will have all the info, including the minimum voltages necessary to operate along with the expected current. If you have a coil designed for 12V DC, and you supply it 12V DC, you don't need a resistor, the internal resistance of the coil will limit the current to the appropriate levels.

If you using 12V DC on a relay that is designed for 5V, or perhaps 8.4V for a relay that designed for 5V, you would want to put a resister in series to lower the current flowing through the it. The size of the resister would be determined by internal resistance of the relay which you'd find on the spec sheet. There also are probably smarter ways of wiring it up using other components that I don't know because I'm not an electrical expert, but putting the resister is certainly better than nothing (and potentially some fancier way of wiring it up is better than just a resistor).

By far the easiest thing is just make sure the power supply voltage matches what the relay coil expects and then you don't need to worry about anything else... just plug the power supply directly to the coil.
Click to expand...

Its rated for 12 V DC I assume on coil too the 8.4 V works fine.
 
To make it more fancy someday do they make trigger sensors? I like to put a sensor on the cats collar to automate the door?
 
Jyetman said:
It does shuts off when it reaches both end strokes. It was cheapest I could find on amazon for $38 bucks 12 Volt 4" 220 LBS linear actuator.
Click to expand...
I would check via current readings from the motor. Just because you don't hear or feel the motor running doesn't mean it's not powered. It might just be mechanically bound not allowing it to make noise.

Sent from my SM-G955U using Tapatalk
 
aaronpentz said:
I would check via current readings from the motor. Just because you don't hear or feel the motor running doesn't mean it's not powered. It might just be mechanically bound not allowing it to make noise.

Sent from my SM-G955U using Tapatalk
Click to expand...

Amazon website says has safety switches built in besides motor is cold to touch after being off awhile.

https://www.amazon.com/gp/product/B00VBASRP8/ref=oh_aui_detailpage_o01_s00?ie=UTF8&psc=1#feature-bullets-btf
We designed our linear actuator with pre-lubricated metal gears, pre-installed limit switches, and with an IP65
 
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