The History and Science of Stairlifts
Part 4 - Stairlift Control
AC and DC power
Early stairlifts mostly had alternating current (AC) drive motors which ran at full mains voltage (around 100 volts in North America, 230 volts in Europe). An "energy cable" ran alongside or through the rail to carry the power from the supply point to the carriage. More recently, domestic stairlifts have been powered from rechargeable batteries and use direct current (DC). One of the selling points is that a DC stairlift will continue to function during a power outage, provided the batteries are sufficiently charged. Most stairlifts have a 'chargepoint' where the unit will 'park' to charge its batteries. Some straight stairlifts have the ability to continuously charge no matter where they are left along the track. With most DC models the batteries are accommodated within the carriage and travel with it.
The power rating of drive motors for domestic straight rail stairlifts may be around 250 watts. The power requirement will be greater for heavy loads, very steep inclines, and wheelchair platform stairlifts.
Stairlift with remote control
Stairlifts are largely operated using a control on the arm of the lift. This is either a switch or a toggle type lever. This larger toggle switch enables users even with limited mobility or painful condition to use stairlifts easily and safely.
Electronic controls are used extensively. Many stairlifts have radio frequency or infrared remote controllers. It is known that radiation from devices such as fluorescent lights can interfere with infrared stairlift controls. Also, heat and incandescent lights can, in some circumstances, have an adverse effect.
Control circuit design varies greatly among the different manufacturers and models. Curved rail stairlifts have more complex controls than those with straight rails.
The seat of a curved rail stairlift may have to be tilted so it remains horizontal whilst going around curves and negotiates different angles of incline. This requires an additional motor and link system. Also, the carriage is slowed down on bends but travels faster on straight runs. This means a more complex control system. Modern controls have small microprocessors which “learn” the characteristics of the journeys and keep the data in memory. They also record the number of journey and direction. This assists service engineers on maintenance calls.
