Sometimes all that digital stuff is just too bland.

If you want to display a time-of-day clock in LabVIEW, it takes three seconds to plop down a TIMESTAMP indicator, and 10 more seconds to enter ADVANCED EDITING mode, and skip the month, day and year, and format it the way you want. Piece of cake.

And it looks just exactly like every other digital clock out there: six digits, two colons, everybody knows what it means. And that’s fine for a lot of purposes.

But sometimes you like to decorate your work a little bit. If you’ve got space on a front panel, and a few cycles of execution time in your run loop, then consider an analog clock.

The visual part of this is pretty simple: a custom control with a cluster of three gauges, all with their scales stretched to a full 360° and both ends of the scale at the top:

• A gauge indicator in the back: single dark red needle, and the scale set to 0..12.
• A gauge indicator with an INVISIBLE scale of 0..60, and a bright red needle for minutes.
• A gauge indicator with an INVISIBLE scale of 0..60, and a gray needle for seconds.

The three indicators are sized identically and lined up identically, with transparent backgrounds, so the needles show through.

An analog is an analogy

You might think it’s straightforward to use this thing – just pass a cluster of hours, minutes, and seconds to the indicator, and you’re done.

You’d be wrong.

Consider what would happen: at 9:22:10, as shown above, the hour hand would be EXACTLY on the 9, the minute hand EXACTLY on the 22. Not exactly what you would expect from an analog clock. It’s even worse 35 minutes later: the minute hand would be on the 57, but the hour hand is still EXACTLY on the 9. It looks for all the world like it’s three minutes before nine, but it’s actually 9:57. If you’re going for the analog, then you’ve got to do better than that.

The gauges accept floating point numbers, so we’re in luck. If you think of how an analog clock works, it’s not the same as a digital clock (and you can quote me on that!). The second hand may move smoothly around the dial, or it may snap from one second to the next. We choose the snap idea, as it’s easier. But the minute hand definitely does NOT snap – it moves smoothly.

So we have to incorporate the position of the SECOND hand into the position of the MINUTE hand. Namely, we add SECONDS / 60 to the MINUTES value given, so that 6:30 will be halfway between 6 and 7, and 6:57 will be just before 7. Similarly, we have to incorporate the position of the MINUTE hand into the position of the HOURS hand so that 6:30:00 puts the hour hand at 6.5, halfway between 6 and 7.

Download

Click to download the example (about 12kB ZIP), containing the typedef indicator you can put on your panel, and a VI to do the above math for it. You can display the CURRENT time by leaving the TIME input unwired, or display a specific time by supplying a timestamp.

Enjoy.