Electric bed custom hand controller

Project  / Project number: 26-20 and 31-20  /  Status:

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The challenge

The client has a Volker 2080 electric powered bed and has been able to get hold of replacement plug in hand controllers in the past, these do not last too long it seems. He has had to adapt these using a large wad of bandage stuck to the back with surgical tape and was then able to move the controller in a way that allowed him to pick it up from the surface of his bed and then manipulate it so that he could press the two buttons he uses (up and down) with his chin. More recently the controller design has been changed by the manufacturer to use lower profile buttons and he cannot use these in the same way. His last working controller was getting unreliable and, if it stopped working altogether, he would need help to adjust the bed. He called Remap for help.

The solution

The client gave me an old controller that no longer worked and in my workshop I dismantled this (using a hacksaw) and found that the printed circuit contacts for the two push buttons he used were almost burned out. I also discovered that the printed circuit board included a Hall effect sensor that was operated by a magnet in the rotating “lock” wheel on the back of the case. I was not keen to try to replicate the electronic circuitry as it was not trivial and, in particular, I had no information on what was happening inside the bed electrics. The client had given me some ideas for a better design with the buttons on the top and I set to work with SolidWorks to make some 3D design ideas for him to review. After a few cycles we settled on a design and I went ahead to complete it. The circuit board from the non-working controller was incorporated into the handle of the controller and two micro-switches were wired across the contacts of the damaged buttons (these have a much higher current rating than the simple carbon pill switches that were originally used). A small magnet was arranged to set the Hall effect switch into the unlocked position. The push buttons and case were all 3D printed and then assembled. Without access to the client’s bed I could not test it so I went to visit him (during a more relaxed Covid restrictions period) and plugged it in and, to my great relief, it worked. I left it with him to see how it went. After a while he contacted me to say that, although it was a great improvement, he now had a better idea of what would really be nice. So we closed the first job and set up the second job.

Me holding the first version of the controller

This picture shows how the first version was picked up (on my hand).

For the second version, the client sent me one of the newer controllers that he had bought but could not use. I opened the case (again with a hacksaw, these are sealed devices to prevent moisture ingress) and found a much simpler design with a simple switch for the lock mechanism and relatively simple interconnections of the switches using diodes. Having seen this I was confident that I could replicate it without the need to incorporate the circuit board into the new controller. The modification to the design involved having the switches side by side with a central column to hold onto. Again. I produced some trial designs for approval and, once approved, I completed the design and 3D printed the parts. As the design was now symmetrical, I printed the two push buttons in different colours. Again I could not test the unit but this time, due to Covid restrictions, I decided to post the unit to the client. the client reported back after a few days that the controller was good although he’d added a bit of weight to the handle, presumably to stop it moving about too much when picking it up.

   

Various ideas looked at.                                         Inside the case top showing the buttons.                           The micro-switches are located by the right angle plate.

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The final design.

The benefit

The benefit to the client is that he is able to control his bed independently and much more easily than before. He also has the first version of the unit as a backup if ever required.

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