Life saving idea - need advice

Projects General Guidance
1

Hello everyone!

At beginning I want to say that my knowledge about Arduino and microelectrics is at real beginner level. I can handle code for my project but hardware I need is mystery for me.

The project - Life saving scream actived switch for my electric wheelchair. No joke! Can trust my hands when it is cold outside and when they stop listening me I drive uncontrolable till I hit something. I have safety switch to turn off engines but like I said when it is cold it is uselles. So my crazy idea is to write program which stop my wheelchair when I scream stop. Android, Windows I can handle it and write working code send signal to Arduino via USB. What I don't know is how to connect Arduino to wheelchair to simulate the switch.

The switch - normaly I can turn off wheelchair using switch for disabled people plugged in to it. It can be any of dozens available on market switches which looks like that:

It has minijack plug which solve a lot of problems with connecting Arduino.

So overal idea is to send signal thru USB to Arduino when to stop wheelchair then make Arduino work like the switch plugged thru minijack to wheelchair.

I will be really thankful for advices, sample projects to look at, tutorials or whatever could be helpful to make it.

Michal

2

these switches are cloing ones, so you can attach a relais in series with them. Arduino opens relais --> stop.

3

Yes... driving a relay with an arduino is pretty much the same as iperating a LED. I could easily provide you with a diagram but im not on my pc so... There are lots of people here that will do that for you though.

The way i see it, you will need a miceophone connected on an arduino board and a mosfet, two resistors and a relay that can handle the current supplied by your chair to its motor. If you put the relay in series with the motor then the arduino will be able to opeb the relay contacts killing power to the motor when you need it to.

4

Won't need to handle motor current, just intercept the joystick or what ever device is used for steering. Playing with the actual electric comonents of the chair will leve you in a bad position when something happens.

5

“I have safety switch to turn off engines but like I said when it is cold it is uselles.”

What makes you think your hardware modifications will work when the safety switch doesn’t?

What hand/arm mobility do you have?

Not kidding, stay inside when it’s too cold, we do.

6

Interesting concept. I have been looking for an inexpensive voice input device for my Telephone AI project and I may have found exactly what you are looking for.

The Grove Speech Recognizer is a simple device that responds to 22 pre-programmed commands. Including start, stop, left, right and reverse. In fact as your project advances you may be able to make your chair voice controlled. It wouldn't work for my project because it requires a wake word, "hicel".
Advantage: it's cheap.

This one on eBay also sounds promising, but I haven't purchased one yet.

Radio Shack used to sell a VCP200 Voice Recognition chip designed for controlling model cars. You can find them on e-bay, but it's just the bare chip that needs a preamp.

You may find that the joystick is low-voltage and you could parallel the switches in it with relays driven by the Arduino. Look for a schematic from the manufacturer.

7

Excuse me if this sounds negative, but I’d be thinking about a 2-part trigger of any sort.

What happens if you’re crossing the road, a car brakes suddenly with screeching tyres. Perhaps smarter voice recognition, and a bump bar which you can hit with your arms or feet?

8

larryd:
“I have safety switch to turn off engines but like I said when it is cold it is uselles.”

What makes you think your hardware modifications will work when the safety switch doesn’t?

What hand/arm mobility do you have?

Not kidding, stay inside when it’s too cold, we do.

He stated that he can't move his hands when too cold.

Okay maybe instead of cutting the motor power he can safely use the relay to engage the kill switch.
I don't see how that can pose any danger.

Though I have to admit that without knowing your true condition it is very hard to advice you. Specially on such thing. Also driving uncontrollably can be a real danger not only for you.

9

Maybe a quality microswitch with a wind paddle to actuate it. No screaming required, just blow - as I think Lauren Bacall once said. Probably no Arduino either.

10

Hello again everyone!

Thank you for so many answers!

HellasT:
Yes... driving a relay with an arduino is pretty much the same as iperating a LED. I could easily provide you with a diagram but im not on my pc so... There are lots of people here that will do that for you though.

I would love to see diagram so I could imagine what exactly I'm building. Like I said I can code but hardware part I just start to learn. So if you or anyone could provide me with that it could be great. I don't want to burn anything :slight_smile:

zwieblum:
Won't need to handle motor current, just intercept the joystick or what ever device is used for steering. Playing with the actual electric comonents of the chair will leve you in a bad position when something happens.

I don't want to mess with stering device just buton connected shru jack to it.

larryd:
Not kidding, stay inside when it’s too cold, we do.

When I say cold I mean less then 15C. It is enough to stop my hands listen me.

SteveMann:
Interesting concept. I have been looking for an inexpensive voice input device for my Telephone AI project and I may have found exactly what you are looking for.

I want use microphone in my phone or laptop and just send stop signal to Arduino thru USB. This way I have more programming flexibility, can program city sounds filtering or even send SMS that I'm stucked somewhere.

lastchancename:
Excuse me if this sounds negative, but I’d be thinking about a 2-part trigger of any sort.

What happens if you’re crossing the road, a car brakes suddenly with screeching tyres. Perhaps smarter voice recognition, and a bump bar which you can hit with your arms or feet?

I have first line of defense, safety button under my thumb but I can use it when it is cold. Hour spent outside and in temperaturę like 15C and I can't move my finger. I need something other to make me stop if something happened.

HellasT:
Okay maybe instead of cutting the motor power he can safely use the relay to engage the kill switch.
I don't see how that can pose any danger.

Though I have to admit that without knowing your true condition it is very hard to advice you. Specially on such thing. Also driving uncontrollably can be a real danger not only for you.

The switch I want simulate don't cut power of motors. It turn off whole wheelchair like simple on off button.

My condition: I can minimal move only my thumbs, one I use to drive using mini joystick, second one I can push button. When it is cold my fingers can move uncontrolable or don't move at all. Me and wheelchair together weight 200kg and speed up to 10km/h. It could kill me or someone if I lost control over it that is why I want make 'scream safety buttons' and I will be thankful for help :slight_smile:

11

“I can handle code for my project but hardware I need is mystery for me. “
Assume you have a voice interface to help in writing the code.

Assume you wear insulated gloves to keep your hands warm.

Can you explain this statement:
“I have safety switch to turn off engines but like I said when it is cold it is uselles”

If your arms move can they could operate a switch paddle?

12

larryd:
“I can handle code for my project but hardware I need is mystery for me. “
Assume you have a voice interface to help in writing the code.

Assume you wear insulated gloves to keep your hands warm.

Can you explain this statement:
“I have safety switch to turn off engines but like I said when it is cold it is uselles”

If your arms move can they could operate a switch paddle?

I have bunch of hardware for disabled people which let me write code. Voice commands software as well.

I have car heater to warm one hand. It consume a lot of power and don't work enough long. Gloves blocks movement so are useless for me.

My arms don't move, only thumbs move.

13

Can you explain this statement:
"I have safety switch to turn off engines but like I said when it is cold it is uselles"

Is it useless because of your hands or the hardware switch?

Can your head operate a switch?

Edit.
Can your jaw opening operate a switch?

14

The last thing i can personaly think of is to use an arduino with a microphone to give the voice command and a relay to engage the kill switch contacts.

But you have seriously consider the fact that it may not be reliable enough.

For example ambient noise may clutter the microphone and the arduino may never "hear" the shutdown command or the arduino may receive ambient noise and preceive it as a shutdown command...

It really is a big deal building something reliable.

15

try eye blink detection with a raspberry pi:

a certain unusual sequence of eye blinks = stop the chair
another sequence = start the chair
some other sequence = fire rocket propulsion unit
yet another = eject parachutes

Or, voice recognition with a raspberry pi.

16

Please check your safty switch: is it normal-open or normal-closed?

17

Reading the progress of this thread, I sympathise with OP, bit also concerned that this idea may be adding several levels of complexity to what could be seen as a last-chance life-saving device.

This brings many more problems than reliability - like insurance coverage etc.
I’d go back to the standard factory fitted plug, and the simplest device possible to get your ‘intent’ into the kill circuit.

Gadgets are cool and often useful, but this may not be the project.

18

“Gadgets are cool and often useful, but this may not be the project.”

I would agree with this full heartedly.

Let a wheel chair outlet help.

19

zwieblum:
Please check your safty switch: is it normal-open or normal-closed?

Either way he can use the No or Nc contacts of the relay to "switch" it so it can be done both ways.

20

In professional systems, the kill switch in circuits like this should be wired n/c - so that if the plug is pulled, or wire is broken, it goes
Open-circuit.

One reason they use ‘cheap’ 3.5/6.5 mm plugs & sockets - they can use the ‘plug-removed’ contact to close the circuit if there’s no lead present.
Also potential to use a ‘resistor-ladder’ of switches for same reasons. Open circuit/hi-R == no operation.