The Particle Lab

Redesigning interfaces: learn from the old before you throw it away

By Ben, 09 Mar 2010

Central heating, as a domestic utility, has not changed much over the decades. We burn fuel, our homes stay warm when its cold outside, and we generally regulate the service in one of two ways — either it's thermostatically controlled to maintain a constant room temperature, or scheduled according to rudimentary on/off time programming.

The interfaces to the latter control system however, have changed considerably over the years. Here's an old control interface, still in use in many homes (but I would guess no longer manufactured for sale in any new systems today), based on a mechanical rotary time switch.

A timeswitch interface for a central heating system

To set the on/off periods, you move the small plastic tappet switches to either an inner (on) or an outer (off) position. The example here is set to run constantly from 10am to 10pm (hour 10 to hour 22). You can set the current hour simply by turning the inner dial, and you can switch between timed, and constantly on or off with the large switch in the lower right.

Compare this to a more modern interface, with an LCD display, and multi-function buttons.

Control panel for a Horstmann H47XL heating programmer

These are just some of the buttons on this system. If you slide down the face plate, a further five are revealed which are used for actually modifying the schedule.

If you compare the manuals for these two systems, the manual for the rotary timeswitch is about as extensive as my description of it above. Just set the time by turning the dial, then put the switches into position corresponding to your desired on and off times, set the thing to timer mode, then go and get on with your life.

The manual for setting up a schedule on the digital system involves ten pages of A4, including (I kid you not) no less than four flow charts. This system supports per-day scheduling, so to set it you start with the current day, then you're forced to set up four discreet active periods of heating operation (if you want fewer than four, you have to set some of them back to back). Times are set (and the clock) using Plus, Minus and Enter keys, and when you're done setting one day you can copy and paste the times (no really) to other days, or set them individually. It's not hard once you've got the hang of it, but even the most basic schedule set up will involve about 20 key presses.

Now let's say that winter is passing into spring, but it's still pretty cold at the start and the end of the day so you want the heating on at those times but off while the sun is radiating you nicely during the day. If you have the timeswitch control, you can reach straight for the day time tappets and nudge them all to the off position with a swipe or two of one finger and then go back to training your cat to make a Reuben sandwich, or whatever it is you enjoy doing when you're not programming central heating systems. If you have the newer digital system, first switch the system to Edit mode, push enter repeatedly until the blinking digits represent the day, and then the time you want to change, then use the Plus and Minus keys to ... well you get the idea.

The timeswitch interface is perfectly simple, both aesthetically and in terms of functionality. When you come back to it months after setting a programme and needing to make an alteration, you can see at a glance the current schedule on the familiar clock face layout, and even complete reconfiguration will take a few touches and mere moments. It does have its downsides of course. You don't get per-day scheduling, and with moving clock parts inside it's neither as silent nor as reliable as its digital replacement, but its certainly a lot easier to actually use.

As far interface design goes, we've taken a big leap backwards with the digital heating control. When you're redesigning an interface for anything, please make sure you look at (and use!) what you're replacing to make sure you're not throwing away something that did the job far better than your proposed solution. You may have newer technology to hand which makes the old design look antiquated, but there will always be lessons to learn from any design you're inheriting and hopefully improving upon. Ignore them, and our lives will be full of endless Edit/Run mode, Plus, Minus and Enter button experiences, supplemented by multi-page manuals stuffed with flow charts.

Photo of Ben Bodien, who wrote this blog post

Ben Bodien is Principal & Co-Founder at Neutron Creations, where he oversees product design and front-end development. For a somewhat balanced mixture of ranting and raving follow Ben Bodien on twitter.

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