REMAP Buggy Development

This blog is a placeholder for various notes, circuits and code for the kid's powered buggy I am developing for REMAP.

REMAP is a UK charity that develops technical aids for the disabled. Specifically, it creates technical solutions to everyday problems where no off the shelf solution exists. This particular project is intended to help very young disabled children to learn how to control a powered wheelchair. They cannot use a full size one because they are too small to fit safely into it. Small ones they would fit safely in are not available.

I have already obtained a pair of half sized motors (scrapped from a medium sized chair). They are DC permamnent magnet types and normaly operate from 24V batteries. To reduce the maximum available speed, the kid's buggy will be operated from a single 12V battery.

In regular electric wheelchairs a joystick is used to set direction and speed and PWM is used to set motor speed and direction. The kid's buggy will use a standard joystick and a new 12V PWM design all controlled by an 8052 variant. The current plan is to base this on a Keil MCB900 evaluation board (see picture) which uses a Philips P89LPC932 microcontroller (an 8052 variant). This device has PWM output capability but no A/D (for the joystick inputs). It has a couple of comparators that could be used to make an A/D at a push but this is unnecessarily complex and may be unreliable. So it has been decided to replace the 89PLPC832 with a P89LPC935 which does have A/D inputs.

The reasons for choosing this board is that it has a convenient breadboarding area and I just happen to already have one. In addition, the code size will be small enough to use the free tools provided by Keil for it.