PIC Project - Martian Clock

Mars Clock

Main

Construction

Operation

Schematics

Code

HowTo

This section has some examples for setting up the clock, as well as links to various useful tools and sites. And, because I called this a Mars clock, we start with...

Setting the Timer Cycle Length, or how to answer the "What time is it on Mars?" question

By default each of the 16 timers runs on a standard 24-hour cycle. If you wish to have a timer tracking a different time period (for example, have it run on Mars time), you have to change the timer's cycle length. The timer will still show numbers from 00:00:00 to 23:59:59, but it will run faster or slower, depending on the cycle length setting. (If you wish to have a timer running at regular speed, but resetting before it reaches 23:59:59, this is another issue - use alarm setting for this timer, along with a Reset action. See the Alarm Settings section on how to do that.)

Useful Links
	MarsBase dot net Everything about Mars: current Mars time, charts, maps, images, and another Martian clock with full schematic.
	Sky & Telescope magazine Jupiter satellite position and GRS transit times, other astronomical info.

Below you will find a table of commonly used values for the cycle length. If you need to set up a timer to something that is not shown in the table below, calculate the value to use by multiplying the number of seconds in the cycle by 4 and rounding the result to the nearest integer. For example, take the Mars day in the table below - a day on Mars is 24 hours 39 minutes and 35.24 seconds long. This gives us

4 * ( 24*60*60 + 39*60 + 35.24 ) = 4 * 88 775.24 = 355 100.96 ≈ 355 101
To set a timer cycle length, select the timer, choose Adjust Timer → Set Cycle Length and enter the new value.

Name	Time	Cycle length
Earth day	24:00:00	345 600
Earth sidereal day	23:56:04.1	344 656
Mars day	24:39:35.24	355 101
Mars sidereal day	24:37:22.66	354 571
Moon synodic period	29.53059 days	10 205 772
Moon sidereal period	27.32166 days	9 442 366
Jupiter's Great Red Spot rotation period	approx. 9 hr 53 min	142 320

Once you configure the correct cycle length, you can set the timer to Mars time. You can get the current Mars time from NASA's Mars24 Sunclock. An excellent resource for all things Martian is MarsBase dot net.

Sky and Telescope's website has information on Jupiter's Great Red Spot transit times. If this link has expired, go to http://www.skyandtelescope.com and search for "GRS".

What is Julian Time?

The second row on the clock's LCD is a decimal number that represents the time of the day in Julian format. The number is 0.0 at 12:00 at noon, and then starts increasing toward 1.0 until it 12:00 noon on the next day. Midnight is 0.5. Representing the time this way makes it very convenient to calculate time differences and is generally easier to work with than time expressed in hours, minutes, and seconds.

Julian time is used in astronomy. There, the number does not roll back from 1.0 to 0.0 each day, but keep increasing. The result is a unique number for each moment of time. Because this clock does not have date, we always show zero-point-something.

What about Moon Phase?

Well, this is one place where the Julian time comes into play. After setting a timer's cycle length to 10 205 772 (the moon phase cycle in quarters of seconds), you can set the timer so its Julian time portion represents the phase. For example, 0.0 might mean new moon, 0.25 - first quarter, 0.5 - full moon, and 0.75 third quarter. So, if you see a number like 0.58, you will know it is short after a full moon. Note that because the Moon does not rotate in a perfect circle, the values that you will see from the clock will fluctuate around the actual phase. If you see the clock showing moon phase a few percent ahead of the real thing, don't worry, pretty soon they will get in sync again.

Find the current moon phase here, then use the calculator on the right to set up the timer (make sure JavaScript is enabled in your browser). Enter the moon phase as percent value on the third row and select if the moon in the waxing or waning phase - this will give you the correct value in HH:MM:SS format for the timer. The calculator also lets you convert between Julian and HH:MM:SS time.

The same principle applies for other periodic events, such as the GRS transit times, Jovian satellite motions and so on. Once you have the correct value in Julian format, enter it in the converter to get the HH:MM:SS value for your timer.

How about something more down to Earth? I want to time my exercise/music practice/etc.

Set a timer to regular Earth day (this is the default for all timers). Select the timer and press ENT

. The display will show Adjust Timer. Pause the timer, set the time to 00:00:00. Go back to Adjust Timer. Use the

button to start and pause the timer to track how much time you exercised, played the banjo, or whatever you are doing.

Can it work as an cooking timer?