Advice on a wheelchair control design 2

[Catch22]

I am trying to build a flexible system to control my brother’s power wheelchair. The chair has 6 power functions that control the seat and we may add more (lumbar etc). I need to provide 10 relay control outputs to the main chair controller and I want to have room for more (Lights - alarm - PC button interface) - say 16 to 20 total.

I want to make a flexible interface for both my brother (He has ALS like Stephen Hawking) and can only use two buttons with his head. He needs to control all 6-8 degrees of freedom from a graphical interface.

I know ladder logic and can use PLC's but they draw a fair amount of power. I was also thinking about a touch screen so he knows what mode he is controlling with the buttons and it would also give the attendant clear control over the chair.

I could just use a Koyo 06 with a 6" touch screen but now I am up at $1000 and I would like to spend less. I am also worried about power drain (The chair is 12V)

Does anyone have any thoughts on a cost effective integrated controller interface?

Thanks,

Catch22

 

[honjohnest]

Hello Catch,

If your brother has the capability of answering or dialing a telephone, I might suggest a DTMF controlled relay box. We manufacture DTMF controllers for video surveillance applications and I would be happy to assist you. Your brother could switch between regular telephone and DTMF control of his environment.

Regards,


John Dustman
switchone.com
johnd@switchone.com

 

[ROBERTDAY]

I recently ran across these neat little guys.

http://www.tri-plc.com/t100md.htm

They look like they may be useful in your application. They have a built in LCD display and are low profile. They also look like they have serial comms. I don’t know much more about them but I have requested some info. If they are priced fair they might work out good in applications that are more suited to embedded controllers but require more flexibility.
Hope this helps.

 

[ve7brz]

On the basis of operating either of two buttons with one's head, I would be inclined to go with a code system similar to morse code. Instead of dots and dashes we use right switch / left switch. I'll do my best to describe what I envision.

The concept involves putting the switch operations within a time frame; that is, following the first switch operation each succeeding operation must fall into a timed sequence. Lack of a response within a time frame indicates the end of an instruction. A 'confirm?' query is then presented, which requires a yes/no (right/left) response. This could be followed by a 'how much / how many?' query, requiring alternating operations of the switches.

I realize this is a bit disjointed (the way my mind works) so I'll give some examples. For the two most used commands, a left or right bump. Multiple bumps in a short period of time are read as one only. An acknowledge indicator comes on with the first bump. After a suitable delay a 'next' indicator comes on. If no further response is made within the next timed period a confirmation is requested and upon an affirmative the action is executed, or with a negative you go back to step one.

If a second switch operation is made within the time frame following the first (multiple bumps again ignored) the second part of the code is acknowledged. If no operations take place during the third interval then the two bumps are interpreted as a one-of-four command and the confirmation and action proceeds.

Similarly three bumps (close multiples ignored) within three time frames give you eight more instructions, and so on.

As to how to do it, I would recommend a microcontroller such as the 'Stamp':

http://www.parallaxinc.com/html_files/products/Basic_Stamps/stamp_modules.htm

I've not used one (I build my own) but this is probably far better suited to this task than a PLC. For a visual readout and an external operator interface there are a number of keyboard/keypad/LCD display units which easily interface with units such as the 'Stamp'.

 

[skills]

The basic stamp suggested above is probably the cheapest and fastest solution. Any Microchip or Atmel can be programmed to easily do this job. Use power transisters to interface to motors. Basic compilers exist for both of these.