Sofa bed (Rock and Roll) linear actuator

[GeorgeRad]

I completed the design of the sofa bed linear actuator and almost finished ordering all necessary parts. I was a little surprised about copper wires availability on Amazon. Bulk of automotive wires are copper clad aluminum, to get tinned copper “marine wire” like ANCOR is necessary in searches. Waiting for machined pieces from 80/20 for final testing and installation.

 

[booster]

Looks like you are running it with continuous drive and limit switches off the relays?


Any "just in case it jams" clutches? Or can it handle stalling without breaking something?

 

[avanti]

As a suggestion, you might consider using an H-bridge controller instead of all those mechanical relays. Quite a bit simpler, more robust and cheaper. I use this one for all my actuators:

https://www.amazon.com/gp/product/B06XGD5SCB?th=1

This is a dual unit, but there are single-channel ones available as well. As a bonus, they can be controlled directly by microcontrollers if you ever want to automate. They also support PWM if you need speed control.

 

[GeorgeRad]

Looks like you are running it with continuous drive and limit switches off the relays?


Any "just in case it jams" clutches? Or can it handle stalling without breaking something?

Thank you for your feedback, yes this is direct drive between 2 limit switches. The actuator has its own limit switches at both ends of travel, but not a slip clutch, not good enough for safety. To follow your good suggestion, I could add a couple dollars 3A or 4A fast acting fuse limiting the load to over 100 or over 200 lbs, way lower than max load.

In case of a total failure the bottom of the linear actuator will be accessible through the front sofa doors with quick pin disconnect

 

[GeorgeRad]

As a suggestion, you might consider using an H-bridge controller instead of all those mechanical relays. Quite a bit simpler, more robust and cheaper. I use this one for all my actuators:

https://www.amazon.com/gp/product/B06XGD5SCB?th=1

This is a dual unit, but there are single-channel ones available as well. As a bonus, they can be controlled directly by microcontrollers if you ever want to automate. They also support PWM if you need speed control.

Thank you for suggestion, I am not certain what the advantage of H-bridge would be over wireless polarity switching relay which I use - https://www.amazon.com/dp/B0CYH9QZBW?psc=1&ref=ppx_yo2ov_dt_b_product_details

The reason for relays is to ensure longer life of limit switches which are border line OK for switching inductive DC load. My original design had no relays, just limit switches and polarity switching wireless relay.

I could have a completely programmable actuator with programmed travel limits but this type of design would be outside of my comfort zone, especially after a few glasses of wine trying to get to a stubbornly unresponsive sofa telling me from its sofa position: I told you so, you made me too complicated, did you check with your grandmother?

 

[booster]

Thank you for your feedback, yes this is direct drive between 2 limit switches. The actuator has its own limit switches at both ends of travel, but not a slip clutch, not good enough for safety. To follow your good suggestion, I could add a couple dollars 3A or 4A fast acting fuse limiting the load to over 100 or over 200 lbs, way lower than max load.

In case of a total failure the bottom of the linear actuator will be accessible through the front sofa doors with quick pin disconnect

If you do the fast blow fuses, it will be interesting to see how high of amperage you have to go to so you don't blow them during starting motor inrush.



Most motors will give a fuse rating to use, with many being in the 150% of max rated motor amps. But most of the time they also spec slow blow fuses.


If it was logic controller controlled, it would much easier by simply including a max travel time between the switches, which if gone over it shuts off the motor. I think the same could be done with small timers, also.

 

[avanti]

If it was logic controller controlled, it would much easier by simply including a max travel time between the switches, which if gone over it shuts off the motor. I think the same could be done with small timers, also.

Yes. I resisted going that far in my suggestion, sensing that George's grandmother would not approve. There are advantages to throwing an Arduino or an ESP32 into the mix, though. In addition to the protection-via-timing technique you describe, the limit switches are reduced to signal devices passing negligible current. Magnetic reed switches work fine. There is no high-current circuitry except from the actuators to the H-bridge. Plus, of course, you can program added features, such as "tap to close completely" and so on. This was important in my setup, since I have two sides to control and they need to be continuously positioned in "reclining seat" mode. Also, I have two extra little actuators that "pop" the flat bed upward to get the fold started.

George's situation is simpler, so the tradeoffs are less compelling.

 

[booster]

Yes. I resisted going that far in my suggestion, sensing that George's grandmother would not approve. There are advantages to throwing an Arduino or an ESP32 into the mix, though. In addition to the protection-via-timing technique you describe, the limit switches are reduced to signal devices passing negligible current. Magnetic reed switches work fine. There is no high-current circuitry except from the actuators to the H-bridge. Plus, of course, you can program added features, such as "tap to close completely" and so on. This was important in my setup, since I have two sides to control and they need to be continuously positioned in "reclining seat" mode. Also, I have two extra little actuators that "pop" the flat bed upward to get the fold started.

George's situation is simpler, so the tradeoffs are less compelling.

All true and many ways to handle it all now days.



Probably the best way, IMO, that is relatively simple if you have logic control is to use an actuator that has position feedback in the form of a linear scale. All you do is tell it how far it needs to go and it goes there, and any switches would be a bit further as a fail protector. Using feedback for position and a timer for speed reduction catching is very common in automated equipment, at least it was before retired 10 years ago . Things can change quickly, though.


Would I do any of that in a van for myself, nope, too complex and simpler methods like George is contemplating will work fine.

 

[GeorgeRad]

If you do the fast blow fuses, it will be interesting to see how high of amperage you have to go to so you don't blow them during starting motor inrush.
Most motors will give a fuse rating to use, with many being in the 150% of max rated motor amps. But most of the time they also spec slow blow fuses.
If it was logic controller controlled, it would much easier by simply including a max travel time between the switches, which if gone over it shuts off the motor. I think the same could be done with small timers, also.

It should have sufficient time to stop as 3A will be limiting load to about 25% of max and 4A about 50% of max load. Travel speed is load dependent so timers could be difficult to implement.
https://f.hubspotusercontent40.net/hubfs/7717445/PDF Manuals/Actuator datasheets/PA-10 datasheet.pdf

Yes. I resisted going that far in my suggestion, sensing that George's grandmother would not approve. There are advantages to throwing an Arduino or an ESP32 into the mix, though. In addition to the protection-via-timing technique you describe, the limit switches are reduced to signal devices passing negligible current. Magnetic reed switches work fine. There is no high-current circuitry except from the actuators to the H-bridge. Plus, of course, you can program added features, such as "tap to close completely" and so on. This was important in my setup, since I have two sides to control and they need to be continuously positioned in "reclining seat" mode. Also, I have two extra little actuators that "pop" the flat bed upward to get the fold started.

George's situation is simpler, so the tradeoffs are less compelling.

Ideally, I would use a fully programable system with programmed travel limits, and max allowable load but, this is not my forte. Reed switches are great, I primarily used them in alarm switches on doors and windows. My original design had no relays so I purchased mechanical switches with precise adjustments, and later found them to be limited in current for switching DC inductive loads, but they will be ideal for fine distance tuning. https://www.amazon.com/Omron-WLCA2-2-General-Overtravel-Operation/dp/B008L5Q3S4

 

[mobilelists]

Hi,


Why did you pick the Progressive actuator instead of the Firgelli?


Pat

 

[GeorgeRad]

Hi,


Why did you pick the Progressive actuator instead of the Firgelli?


Pat

I was familiar with Progressive name, but neve dive into in depth evaluation. Decided on hard limit switches, instead of Hall sensors to set limits for simplicity, no calibration ever required. I thin Progressive and Firgelli have similar product portfolio. Here is Progressive bed lift using their control. https://www.progressiveautomations....sion-raising-a-bed-to-uncover-the-living-room

 

[mobilelists]

I see. They do look very similar. Thanks

 

[DonBres]

Sofa Bed

I have a complete sofa bed I removed from my B+ van. All frame,wireing, linear screws, stops and switches. It is white leather and perfect. i've heard it called "jack knife"I redisigned the floorplan. IN Northwest Connecticut, for sale. Reasonable offers considered. Must be picked up.

 

[GeorgeRad]

I see. They do look very similar. Thanks

Since you mentioned Firgelli I look deeper into their portfolio, they have one product which could be a good choice with the externally adjustable limit switches, but it is limited to 200lbs, unfortunately too close to have some margin. https://www.firgelliauto.com/products/adjustable-stroke-linear-actuators?variant=39499596103751

 

[GeorgeRad]

Benchtop test successful.

Wiring to camper van control panel is done, I had an extra 12V spare circuit which I used. Limit switches, electronics, actuator are all installed, wired and tested. I found another remotely controlled polarity changing relay with ability to accept limit positions sensors which dramatically reduced complexity. Turning the system on/off and the actuator are controlled with two remotes.

What is left is to add a new ¼” plywood under the bed storage top to accommodate the actuator, install the sofa bed frame in the van with six bolts, install the upholstered panels and Voilà will be ready to go.

 

[GeorgeRad]

continue with pictures

 

[GeorgeRad]

The actuator works as well as I hoped for, meaning it is almost flawless. System is turn on/off via remote with a very visible LED indicator. Activating the linear actuator is via another remote.

One aspect still needs some attention is checking if the system is ready to be activated. I removed the bed latch – the actuator latches on both ends which is sufficient for the bed position.

I have two sofa latches which must be unlatched before turning the actuator.

My options are:
- Check list, good for me but not so good for others to use
- Another potent LED or buzzer indicator activated after system is turned on warning about latched position and options are:
o Limit switches like electromechanical, magnetic – simple 2 wires,
o Proximity sensors like Hall, inductive, capacitive, optical - power needed.

See the picture of these sofa latches, my plan is to alarm only one of them.

Suggestions are welcome, thank you.

 

[GeorgeRad]

I found many options but am not sure if spending my time on this prewarning feature could be justified. I decide on a simpler route, just a buzzer on a 30 sec countdown timer should suffice to be a good reminder to unlatch the sofa position latches.