Zoe required a grabber to be able to pick things up from the floor or other places. The grabber had to be able to grasp large items, such as her teddy bear, as well as small items, such as pencils. Various commercially available grabbers had been tried, but she did not have the strength to pull their actuators or to maintain the pressure while the object was picked up. Some grabbers had a lever to lock the jaws, but she struggled to operate the actuator and the locking lever at the same time.
A grabber was made using a motorised claw from a toy robotic arm. The only control was a centre-biased lever switch mounted just under the handle. Pushing the switch one way closed the claw, the other way opened it. With no pressure on the switch, the claw stayed in its last position. She could now operate the switch to grab the item and then use both hands to pull the item up to her level. Velcro bands on the stem and a Velcro strip on the arm of the wheelchair allowed for stowing while not in use.
The claw was powered by a built-in power block of the type used for “on the go” mobile phone charging. This device could be re-charged from any mobile phone charger and switched itself off automatically when not in use.
Some plastic parts of the claw were replaced by stronger aluminium parts to improve robustness.
These rechargeable batteries are very useful and have been appearing recently in other Remap jobs, but some thought should be given to safety if they are not being used for the manufacturer’s intended purpose of charging mobile phones. Two safety checks were made in this case. The maximum current taken by the claw with the motor in the stall condition was measured at 700mA. The stated maximum output current of the power block was 1000mA. A check was also made to see what would happen if a short circuit developed in the wiring or in the claw itself. Under short circuit conditions, the power block behaved perfectly by instantly switching itself off.
The BBC TV broadcast this interview with the client.
Zoe is more independent now that she can pick up items herself.