element14 Community
element14 Community
    Register Log In
  • Site
  • Search
  • Log In Register
  • Community Hub
    Community Hub
    • What's New on element14
    • Feedback and Support
    • Benefits of Membership
    • Personal Blogs
    • Members Area
    • Achievement Levels
  • Learn
    Learn
    • Ask an Expert
    • eBooks
    • element14 presents
    • Learning Center
    • Tech Spotlight
    • STEM Academy
    • Webinars, Training and Events
    • Learning Groups
  • Technologies
    Technologies
    • 3D Printing
    • FPGA
    • Industrial Automation
    • Internet of Things
    • Power & Energy
    • Sensors
    • Technology Groups
  • Challenges & Projects
    Challenges & Projects
    • Design Challenges
    • element14 presents Projects
    • Project14
    • Arduino Projects
    • Raspberry Pi Projects
    • Project Groups
  • Products
    Products
    • Arduino
    • Avnet Boards Community
    • Dev Tools
    • Manufacturers
    • Multicomp Pro
    • Product Groups
    • Raspberry Pi
    • RoadTests & Reviews
  • Store
    Store
    • Visit Your Store
    • Choose another store...
      • Europe
      •  Austria (German)
      •  Belgium (Dutch, French)
      •  Bulgaria (Bulgarian)
      •  Czech Republic (Czech)
      •  Denmark (Danish)
      •  Estonia (Estonian)
      •  Finland (Finnish)
      •  France (French)
      •  Germany (German)
      •  Hungary (Hungarian)
      •  Ireland
      •  Israel
      •  Italy (Italian)
      •  Latvia (Latvian)
      •  
      •  Lithuania (Lithuanian)
      •  Netherlands (Dutch)
      •  Norway (Norwegian)
      •  Poland (Polish)
      •  Portugal (Portuguese)
      •  Romania (Romanian)
      •  Russia (Russian)
      •  Slovakia (Slovak)
      •  Slovenia (Slovenian)
      •  Spain (Spanish)
      •  Sweden (Swedish)
      •  Switzerland(German, French)
      •  Turkey (Turkish)
      •  United Kingdom
      • Asia Pacific
      •  Australia
      •  China
      •  Hong Kong
      •  India
      •  Korea (Korean)
      •  Malaysia
      •  New Zealand
      •  Philippines
      •  Singapore
      •  Taiwan
      •  Thailand (Thai)
      • Americas
      •  Brazil (Portuguese)
      •  Canada
      •  Mexico (Spanish)
      •  United States
      Can't find the country/region you're looking for? Visit our export site or find a local distributor.
  • Translate
  • Profile
  • Settings
Personal Blogs
  • Community Hub
  • More
Personal Blogs
John Wiltrout's Blog Hacking a Lift Chair
  • Blog
  • Documents
  • Mentions
  • Sub-Groups
  • Tags
  • More
  • Cancel
  • New
  • Share
  • More
  • Cancel
Group Actions
  • Group RSS
  • More
  • Cancel
Engagement
  • Author Author: jw0752
  • Date Created: 7 Jul 2015 5:40 AM Date Created
  • Views 6317 views
  • Likes 7 likes
  • Comments 11 comments
  • handicapped
  • lift
  • chair
Related
Recommended

Hacking a Lift Chair

jw0752
jw0752
7 Jul 2015

The day before yesterday I was told that my mother had slipped from her reclining lift chair at the nursing home where she lives and had lain for an hour on the floor before she was discovered. Mom who is very clear in her mind suffers from Parkinson's and has lost  most of the movement in her body muscles. She spends all of her time either in a wheel chair which she can't move or in her Lift Chair Recliner with a hand held remote. She still has enough control of her hands so that with great effort she can use the remote to raise, lower and adjust the chair to suit her comfort. This seemingly minor control that she still has is very important to her. The cause of her falling from the chair was a combination of the design of the chair and her inability to let go after she has grabbed something with her hand. Here are three pictures of the chair which is designed primarily for elderly people who have trouble getting to their feet from a sitting position.

 

image

 

Chair is in the up right position.

 

 

image

The Chair in the fully reclined position. This is where she sleeps.

 

 

image

 

This is the full lift position that produced the fall.  She was trying to adjust the recline position, slightly, at 2AM when she found that she could not release her grip on the "UP" button of the chair. With no ability to move her feet or legs, or to stand, the chair dumped her onto the floor much as a dump truck dumps its load of material on the ground. Fortunately, she only received minor bumps and bruises.

 

Her caretakers at the nursing home however were afraid that she would hurt herself the next time and so they took the remote control away from her. They were correct in taking it away but I could see that the loss of the remote was going to be a serious blow to her generally happy and healthy attitude.

 

The chair is powered by an external power supply that converts the 120VAC Main to 12 Volts DC. If you look closely in the above pictures you can see it hiding behind the wrung of the folding chair against the wall. The circuitry of the chair includes a Main Board with attachments to the single motor drive actuator, the heating pad, two massage motors, and the remote control. I knew if I was going to be able to put the remote control back in her hands I would have to find a way to allow her to control the movement of the chair from the Upright Sitting Position to the Full Recline Position but block any movement to the Full Lift Position. The problem was slightly complicated as the Full Lift Position was still needed by the nursing home staff for getting her out of the chair and onto a hydraulic lift that is used to change her from chair to wheel chair and for other needs.

 

An examination of the mechanics of the chair revealed that the frame of the seat stayed within 4 cm of the floor for the Upright and Recline positions but rapidly lifted for movement to the Lift Position.

 

image

 

The black L shaped metal bar that goes out to the wood frame stays within 4 cm of the floor during Upright and Recline Positions.

 

image

 

The same black bar is raised out of the picture in this photo of the Full Lift Position.

 

 

It was decided that the best solution would be to attach a limit sensor switch to the structural bar so that as long as the chair was in the Upright or Recline Positions the switch would be closed and signals from the Remote Control to the Main Board would pass normally. Once the chair began to go to the Full Lift Position however the limit switch would open and break the UP signal from the remote control stopping the upward travel. I returned to the shop with measurements and the remote control so that I could make a limit switch for the chair frame and determine which of the 9 wires from the remote was being used to make the chair go up.

 

image

 

This is the back side of the remote control circuit board. I was really surprised at the level of technology in the Lift Chair. The IC at the top of the picture is a PIC 16F505 microcontroller. A data sheet for the PIC was pulled from the internet. The power supply for the chair was 12 volts but it was not known if the voltage regulation to 5.5V or less to supply the PIC was being done on the main board or on the remote board. The Vcc and Vss of the PIC was determined and traced back to the proper wires. I found it convenient to feed power to the control by clipping onto a small bypass capacitor. The voltage was slowly raised while watching the voltage at the Vcc and Vss pins of the PIC. When the input voltage arrived at 5.5 volts the PIC was also at 5.5 volts and it was assumed that the regulation was being accomplished at the Main Board and the 5 volts was being supplied to the remote from there.

 

image

 

With the remote control powered up it was easy to push the UP and Down buttons and watch the changes on each of the wires leading from the remote. Experimentation revealed that the White wire carried the signal for the UP movement of the chair. In this case 0 volts or LOW was normal. 2 volts or High was the signal to the Main Board to run the motor actuator in the direction to raise the chair. The White wire in the remote cord would be my target for control of the Upward movement of the chair.  By now the solution to how the staff of the nursing home would be able to use the Full Lift Position had also revealed itself. A momentary normally open push button would be wired across the limit switch in the base so that anyone who could reach the push button would be able to hold it down while simultaneously pushing the UP button of the remote control. The momentary push button would complete the circuit and the chair would continue up to the Full Lift Position.

 

image

 

Here is a schematic of the simple modifications that would be needed.

 

As soon as possible the next day I returned to the nursing home with the following items:

 

image

 

Limit Switch for the Base

 

image

 

Momentary pushbutton in a small box. Incidentally the push button was salvaged from a Gendex Panoramic X-Ray Machine and the Limit switch came from a Pin Ball machine that was salvaged out 50 years ago. The small black box housing the momentary switch came with a KaVo dental handpiece turbine.

 

image

 

Here is the limit switch installed on the frame of the chair.

 

 

image

 

This is the wire harness from the remote with the White Wire prepared for connection to the Limit and Momentary switches.

 

image

 

Finally here is the Lift Override Button attached to the back of the chair out of reach of anyone except the caregivers.

 

 

I would have wished to include a picture of Mom happily using the Chair without any further fear of being dumped on the floor but she is a little shy and would not consent.  Suffice it to say that things are back to normal at the Nursing Home at least until tomorrow or the next day when her progressive illness will present its next challenge.

 

Thanks John

  • Sign in to reply

Top Comments

  • mcb1
    mcb1 over 10 years ago +2
    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…
  • Workshopshed
    Workshopshed over 10 years ago +2
    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
  • mcb1
    mcb1 over 10 years ago in reply to Workshopshed +2
    Workshopshed What a fantastic concept. There are many retired professional who have services to offer, and it benefits all parties. Mark
  • jw0752
    jw0752 over 9 years ago in reply to Former Member

    Hi Albert,

    Thanks for adding your adventure to my post. When I first opened the control board on Mom's chair I was hoping for the type of control circuit that you mentioned. Unfortunately this company decided to go modern and had designed a board that was difficult to hack. Whenever her chair went down it was always a serious problem that had to be addressed immediately as she spent most of her days in the chair even to the extent of sleeping there. As you mentioned the quality always seems to be marginal on things like these chairs and this makes them prone to failure in situations of heavy use. I wish I could say that she is still using it but her condition has deteriorated so that she is spending more time in the bed now and less in the chair. I liked your comment about Saving money and doing things ones self. This is good advice and usually the problem is a simple one that can be remedied or like in your case made better than the original.

    John

    • Cancel
    • Vote Up +1 Vote Down
    • Sign in to reply
    • More
    • Cancel
  • Former Member
    Former Member over 9 years ago

    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.

    • Cancel
    • Vote Up +2 Vote Down
    • Sign in to reply
    • More
    • Cancel
  • mcb1
    mcb1 over 10 years ago in reply to Workshopshed

    Workshopshed

    What a fantastic concept.

     

    There are many retired professional who have services to offer, and it benefits all parties.

     

    Mark

    • Cancel
    • Vote Up +2 Vote Down
    • Sign in to reply
    • More
    • Cancel
  • jw0752
    jw0752 over 10 years ago in reply to Workshopshed

    Hi Andy,

    Thanks, I took a look at the UK website. Pretty cool!

    John

    • Cancel
    • Vote Up +1 Vote Down
    • Sign in to reply
    • More
    • Cancel
  • jw0752
    jw0752 over 10 years ago in reply to mcb1

    Hi Mark, Yes it would be nice if the manufacturer would provide this as an option. All they would have to do is put in a position sensor and write the code for the PIC to track the position. A programmable soft limit could then be set. I have seen this technique used on dental chairs so that the dentist can automatically position the patient chair to the desired position for procedures. When dealing with individual disabilities there are so many variations that the need to modify becomes quite important.

    John

    • Cancel
    • Vote Up +1 Vote Down
    • Sign in to reply
    • More
    • Cancel
>
element14 Community

element14 is the first online community specifically for engineers. Connect with your peers and get expert answers to your questions.

  • Members
  • Learn
  • Technologies
  • Challenges & Projects
  • Products
  • Store
  • About Us
  • Feedback & Support
  • FAQs
  • Terms of Use
  • Privacy Policy
  • Legal and Copyright Notices
  • Sitemap
  • Cookies

An Avnet Company © 2025 Premier Farnell Limited. All Rights Reserved.

Premier Farnell Ltd, registered in England and Wales (no 00876412), registered office: Farnell House, Forge Lane, Leeds LS12 2NE.

ICP 备案号 10220084.

Follow element14

  • X
  • Facebook
  • linkedin
  • YouTube