Hacking a Lift Chair

RE: Hacking a Lift Chair

e14 Contributor — Mon, 04 Apr 2016 02:05:38 GMT

On my MegaMotion brand lift chair (LC500) the pc board was located underneath between the 2 lift motors on a plate welded onto the frame. The chair just stopped working. I turned it over and found the plastic covering the pc board was hot to the touch so I figured the problem was there. Once I got the board off I was able to jumper out the voltage (24v) from the transformer to the motor and make the chair work. When I priced out the replacement board I got price ranging between $205 plus shipping to $225 plus shipping. Knowing the basic logic on the board I decided to take 2 - 24 volt relays with double pole double throw contacts and build my own control system. Total cost was $12. Essentially it is necessary to wire both motors to go up or down at the same time. The need to isolate the circuits was done by using one relay for up and one for down. Reversing the polarity, reverses the direction on a dc motor. I used one relay to power the motors in one direction and the other to power the motors with the opposite polarity. The up button is wired to energize the up direction relay and the down button on the remote is used to energize the down direction relay. I could have gone further to prevent both buttons from operating the motors at the same time but I use the chair myself and felt I could just be careful not to push both buttons at the same time. 2 extra relays could be used as a way to prevent both motor relays from being energized at the same time.

The chair is working fine again with the one caveat mentioned above regarding the need to be careful not to push both up and down buttons at the same time. Plus the relays used will outlast the rest of the chair with ease as they are heavy duty heat/a-c type. (Amazon had them for $6 per each with shipping included).

It seems the parts on these chairs are not of quality necessary to provide long life. Made in China stamped on everything. Save yourself some money and do it yourself.

RE: Hacking a Lift Chair

Workshopshed — Fri, 10 Jul 2015 13:41:06 GMT

Fantastic job John. For those in the UK who don't feel up to this kind of challenge there's a charity that does similar kinds of thing Remap Custom Made Equipment For People With Disabilities

RE: Hacking a Lift Chair

mcb1 — Fri, 10 Jul 2015 11:13:04 GMT

John

While the accident with your mother was regretable, you've provided a really useful solution that could be incorporated into any of these chairs.

Hopefully the manufacturer will see the benefit and offer it.

Otherwise you might get called on by the home to modify other chairs.

Mark

RE: Hacking a Lift Chair

DAB — Tue, 07 Jul 2015 20:08:34 GMT

Nice fix John.

I know how much independence means to my 87 year old mother.

She would rather die that lose her independence and privacy.

DAB

RE: Hacking a Lift Chair

shabaz — Tue, 07 Jul 2015 18:37:07 GMT

Hi John,

I'm sorry to hear about your mum. Thousands of papers have been written on Parkinson's over the years, I really hope some breakthroughs can be made to

lessen the effect of it. Someone I know has the illness too, although at a relatively young age of late 40's.

On the technical points, what an excellent and very informative post and reverse-engineering effort, the solution is excellent with the microswitch position detection and the override switch.

I tried an all-singing advanced robotic massage chair a few months ago (I was walking past a store!), and it was disconcerting for the first few minutes because I could see no accessible 'stop' button : )

The control panel was nearby at head height but with the arms secured all I could do in an emergency was probably stick my tongue out to see if I could reach the button ; )