Missing Features

Microwaves have notoriously poorly designed interfaces. From setting the clock to picking the power level, microwaves just aren’t easy to use. Which is odd, because all your correspondent really wants to do is nuke last night’s mushroom pasta for 2 and half minutes so I can eat. But I can’t.

Take this example microwave:

The major fault of this microwave is the designer tried to make the interface better by including more buttons. But the designer wasn’t that smart, and made really bad assumptions. What bad assumptions?

For starters, what do all of those food buttons do? If you press popcorn, does the microwave read the recommended popping time on the bag of popcorn? What power level does popcorn use? How does it know if I have a full page of popcorn, or the new mini bags?

How about the pizza button? Does it count the slices I have and adjust the time accordingly? Does it know when a user is reheating triple sausage pizza, and that you might need more microwave time?

Every time you add a button to an interface you increase the complexity of the device and the time required to learn the control system. A designer has to make a careful trade-off: if I add this button, does it really make the system better, knowing I’ve just made my device harder to use?

It’s a hard, delicate balance to get right, but it can be done. On this example microwave, they got the balance all wrong. Too many ambigious buttons that the user spends too much time thinking about how they might work, only to not use out of fear that the task might go awry.

If a control requires a description to be understood most of the time by most of the users, it probably isn’t a good control.

Of Time, and Keypads

And why does a microwave need a keypad? Your correspondent can think of two reasons why you need a full keypad:

1. You need to set the clock; and,
2. You need to microwave a frozen sausage for exactly 3:28s.

Having a clock on a microwave is a useless feature. The clock is always a pain to set and you have to set it every time the power goes out. You already have to set the stove and bedroom clocks, so why add one more to the work list?

Though the consistent inclusion of clocks in microwaves signals otherwise, knowing the current time is not a factor needed in calculating microwave cooking time.

The worst argument a designer would make for having a full keypad is the “need” for a user to microwave something for an arbitrary length time. Think about it. When have you ever you needed to microwave for a length of time that wasn’t a 15sec interval? You can’t think of anything because there is never a need.

Building a Better Microwave

A great microwave UI would have exactly four controls

1. +15sec
2. +1min
4. a power knob
5. start

Control 1: +15sec

This is a button that adds 15 seconds to the current cook time. If you press this when the microwave isn’t on, it turns on. If you press this while the microwave is on you add exactly 15 seconds to the microwave time.

Control 2: +1min

This is a button that adds 1 minute to the current cooking time. Like the +15sec button, if you press this when the microwave isn’t on the microwave starts.

Control 3: Power Knob

To control defrost and low, medium and high power level we use a static, 4 point knob that clicks into position. Default value should be high.

Control 4: Start

The start button is really a resume button. If you open the door to check your item, the microwave stops. Close the door and you press start to resume any remaining time.

Why wouldn’t we have the microwave autostart on door close? This would be helpful from a purely usability perspective, but a technology limitation proves tantamount in this design decision. The problem is that microwaving an empty chamber is dangerous, so we don’t autostart on door close.

Wait! You Forgot the Stop Button!

What does a user do after pressing stop 95% of time? They open the door. So why have a stop button that gets in the why of the action the user wants?

So how do you stop this microwave? Open the door.

Is Our Microwave Faster?

Your correspondent’s favorite classroom anecdote about usability was written by Bruce Tognazzini of AskTog fame:

…which of the following takes less time? Heating water in a microwave for one minute and ten seconds or heating it for one minute and eleven seconds?

The answer is one minute eleven seconds. How? Because it takes a user more than a second longer to press 1, 1 and find and press 0 then it does to simply press 1 three times.

Using this metric, is our microwave design faster? You bet. Our microwave can boil water in exactly two button presses! All you have to do is press the +1min and +15sec. The microwave has already started by the time you press +1min, so we gain even more efficiency by starting the microwave before the user is even finished entering in the desired time.

About the Controls

It’s vital for controls to show clear intention and provide feedback to the user when acted upon. So our theoretical microwave needs buttons that feel and make a sound when depressed and our power knob ought to click or beep when adjusted. Run a few lab tests with real users to find out.

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