Switch Toys, Devices and Computer Input
Tip: Read everything and look at the diagrams before feeling overwhelmed. People often tell me it was much easier than they first thought. Confused? I would be glad to offer free pointers over email.
Adding or Replacing a Switch
Battery powered toys can be adapted to replace the small, inaccessible switch with an accessible adapted 1/4" switch. Never attempt to adapt any device that plugs into the wall. Batter powered devices and toys also need to have particular behaviour to work once adapted. To adapt a device it usually needs to be controlled by just one switch that you can access. The rule of thumb is one switch for one adapted switch. For example, If a device does two things with two switches, each must be adapted separately. I have rarely needed to use more than one switch. You must also consider if the individual can physically access two switches with their mobility.
The dog pictured on the left has a switch in its paw that I could get at and the wires ran inside and out the base to keep the device tidy and safe. The basic concept is to hijack the two wires that run to the switch. The adaptation will channel the two wires through a convenient connection port so you can plug in an adapted switch that will act to close the circuit from those two hijacked wires.
A device must do one of the following:
Run when just one switch is depressed and stop when it is released. This will allow for direct activation by the switch. (Press on, release off)
Run when just one switch is depressed and released and keep running throughout its purpose, then stop on its own, e.g., a dancing toy with music. This will allow for timed activation. (Press on, runs through its cycle and stops)
Run when just one switch is depressed and released, then stop running when the switch is depressed again. This is latch behaviour. (Press on, runs, press off)
Another possibility for adapting a battery powered toy is to use a device called a battery interrupter. This adaptation stops the flow of current for a device by diverting the current that is about to leave the battery's terminal to a port (connected to the switch). Closing the switch sends the current back to the battery terminal on the device, completing the circuit. Think of it as a detour up a wire and back.
The device must have certain behaviour to work properly with this adaptation. The device must have a switch that can remain closed. Take note of the button on the nose of the lady bug toy pictured. It presses in and stays in. If this switch did not remain closed the circuit would be broken. Our goal is to have the circuit run continuously so we can divert the current at the battery. If the device's redundant switch cannot be closed permanently, it may be necessary to remove the switch and tie the two wires together, covering them with some electrical tape and enclosing them safely inside again.
This adaptation is tricky due to the lack of durability of the tinfoil. Handle the terminal with care. I am open to suggestions to improve it but have found the materials must be very thin to work.
The music interruption adaptation channels a mono music signal from a portable device with a 1/4" mini jack, like a phone, through a switch to interrupt the signal.
The device takes just one of the two stereo channels of the stereo signal (to keep things simple) and sends it through one path. That single path is created by linking three 1/4" mini jacks. One receives the signal, one provides a connection to the switch and the last one provides the connection to the jack for the output. The devices can be plugged in any order. A mono to stereo adapter can be placed in the plug that is being sent to the speakers.
With portable devices like phones, I tend to use amplified speakers to boost the weak audio signal from the device.
I have tested this effectively with no issues, however, I do suggest it for use with low powered, portable devices and it is to be used at your own risk to your device.
Adapted RC Car Integration Activity
This adapted activity was designed to be a co-operative activity that an individual with very limited mobility can do with a peer. Integrated activities with individuals who have very limited mobility can be a challenge and are often unbalanced because their peer often has to take on a guiding role for the individual to be successful. With the adapted RC car both individuals work at the same level.
The activity consists of a radio-controlled (RC) car that has its forward button on the controller adapted to an assistive switch. The individual with limited mobility presses the switch to propel the car and their peer controls the steering of the car with the other buttons on the controller.
Adapting the controller is a project for people with a fairly good knowledge of circuitry or the adventurous like me who simply short circuited every soldering point I could find until the car sprang to life. Once I found the two points that made the car go forward I soldered speaker wire to the points and connected them to a 1/4" mini jack. I also chose a car that had a controller with buttons instead of analog controls because I wasn't sure if I could short-circuit the analog sticks.