Time-of-Day routines control On-Off timing to the second by day of week, month or date and/or with holiday omissions. Up to 40 schedules, controlling 16 power circuits, can be set for selected days or times. Daylight/Standard time-adjust and Leap Year are automatic. External inputs initiate timing sequences; e.g., remotely turned on lights will automatically turn off at a specified time, or after a specified period. During a power outage, a back-up battery system maintains schedules and time-count. When power returns, scheduled circuits are energized all at once or in a delay sequence to minimize lighting and motor start-up power surges.

    Interval Timer routines are initiated by one of eight external inputs, a keyboard command or by a Time-of-Day schedule. An interval routine occurs only once when activated, or it can repeat to a preset cycle until stopped by an input or Time-of-day schedule.

    The L-Series models include additional features for building and energy management: latitude-corrected sunrise and sunset times, back-up battery condition display, display of last power outage, and cumulative time of past power outages.

    The 40 schedules for 16 power circuits are entered via a 24-key keyboard. In addition, schedules can be entered or checked over a serial data link or telephone modem from either the ChronTrol Remote Control Unit, or a PC. The ChronTrol Printer/Programmer accessory prints out existing schedules or reloads alternative schedules stored in its memory module.

    Categorically, ChronTrol is a Time Switch. You can program it to turn electricity on and off.

    L-Series Energy and/or Building Management Timers
• All of the XT capabilities plus additional features directed to the needs of building management and control
• 60 user-entered schedules to control separate or combined circuits
• Expandable Wall-mount Model

    L-Series Accessories
• PRO60 Printer/Programmer
• T90 Remote Control Unit
• T50 Telephone Modem

Interval timing changed all that. Instead of telling the ChronTrol to turn its circuits on and off at a particular time, you tell the ChronTrol to turn its ciruits on and off for a designated length of time. This duration of time is what we call an "interval."

The only remaining question is this: when does the interval begin? With no fixed point in time, an interval program just sits there and does nothing. You must start the interval program running by one of three methods: you can have another program start it at a specific time of day, or you can have one of your 8 digital inputs start it, or you can start it yourself with a keyboard command.

    Cycle, on the other hand, has been a feature of every ChronTrol since before the beginning. It is very simply the rate at which an event re-occurs. For example, if a circuit repeatedly turns on for 5 minutes and off for 3 minutes, it must be turning on every 8 minutes, so its Cycle Rate is 8 minutes. If you program a bell to turn on at 7 a.m. and cycle every 50 minutes, you'll find it turning on at 7:00, 7:50, 8:40, 9:30, etc. The following illustration shows the relationship between Interval and Cycle:



        It should be noted that Cycle Length must also be defined as the sum of the time              On and the time Off.

Strictly speaking, a dry contact is a switch which makes and breaks a connection in an open circuit, that is, a circuit which is already disconnected by a switch or other means somewhere else along the line. Since no current can flow in such a circuit, it is essentially "dry." The purpose of a dry contact is to prevent the other switch from completing the circuit. The dry contact has the capacity to conduct the current flow, but it is usually not rated to start or stop the current flow.

ChronTrol uses the term dry contact to emphasize that there is no output voltage from the ChronTrol relay. The relay is not pre-wired to any internal voltage source. That means you are free to use the relay to switch any electrical supply voltage or signal (up to 277VAC) that is wired to it.

     Through an input, you can initiate a timed event that does not have a fixed position in real time. The input signal can come from anyone or anything anywhere, whether it's a guy pushing a doorbell, or a laboratory instrument indicating "operation complete," or a limit switch on an elevator indicating "end of travel." In the end, the signal boils down to a switch (or any conductor less than 1Kohm) making a short circuit between two points on the ChronTrol's input connector. The two points are:

          1. one of eight distinct, individually programmed inputs (electrically "pulled up" to +5 volts DC by a 10Kohm resistor) and
          2. a reference point (0 volts or signal ground) common to all 8 inputs.

     When the switch makes a short circuit between the two points, the input is "pulled down" from 5 volts to zero volts, and the input (if it is enabled, which is a whole nother issue) triggers whatever sequence of events it was programmed to control.

     When the switch opens up again, the input returns to 5 volts and is ready for another activation. This is what makes the input "digital": either the input is at 0 volts or at 5 volts.

     This is in contrast to an "analog" input which can make sense of a continuous range of voltages. For example, as a signal ranges from -10 volts to +10 volts DC on an analog input, it might elicit louder and louder music from an amplifier. An analog input may receive many types of continuous signals and also be of varying frequency or phase. Not so for a digital input - its sees the world only one way or the other, on or off, with no in between.

     That doesn't mean you can't drive a digital input with a slowly varying signal. As the input signal continues to rise and fall, at some point (roughly half way between 0 and 5 volts) it changes abruptly from on to off.

      You can flip-flop back and forth between the two display formats by hitting the TIME key followed by the ENTER key, and all the program settings you have made will change to the corresponding format. For instance, if you set a program to turn a circuit on at 8 a.m. and off at 3 p.m. and then change to 24-hour format, the on and off times will suddenly appear as 0800 hours and 1500 hours respectively. Now if you decide to change the off time to 4 p.m. you should either 1) put it in as 1600 hours or 2) change back to 12-hour am/pm format, because the AM/PM will be ignored and your entry will come out as 0400 hours (4 a.m.).

If you decide to change the program, we advise that you clear the program first. This will remove the sun-relative option. Subsequent program changes will no longer be ignored.

          1.   On XT models manufactured between 1991 and 1997, you must plug the timer into the wall before you connect its battery, because the timer tries to determine the AC line frequency as soon as it sees power, and if it sees battery power before AC power it starts running at top speed, in which a minute goes by in about 6 seconds accompanied by 10 rapid blinks, pause, 10 blinks, pause, etc. To correct this problem, unplug the ChronTrol and disconnect the battery for 2 minutes. Then plug the ChronTrol in first, then connect the battery.
          2.   The first ChronTrols ever made did blink once every second. There is no cure. Your ChronTrol is over 20 years old. Be glad it still blinks.

The XT ChronTrol can use one program to control another. In the school bell application, for example, you see how numerous programs, with only a Turn On time, call an interval program throughout the day to ring a bell for a few seconds.

A program can even control itself, and this is where the trouble begins. Because when the program goes to turn off its circuits, it also turns itself off; hence, the effect of stopping after one cycle.

Correct this situation by carefully reviewing the program's control assignments and clear out any references the program makes to itself.

On models built prior to 1985 this feature was accessed through Master Entry #69.

     But what if you want to get action on the opening of the input instead of, or along with, the closing? Well, you can still have it. The 8 unused inputs (numbered 9 through 16) are internally connected to the inverse of inputs 1 through 8 respectively, so that when inputs 1-8 open, inputs 9-16 close. So whatever you set input #1 to do will occur when input #1 closes and whatever you set input #9 to do will occur when input #1 opens.

           See what the following program steps do:

     Circuit #1 turns on when Input #3 closes, and stays on until 5 seconds after Input #3 opens. This might be useful for changing a traffic signal shortly after a line of cars has finished a left turn.

     There is no "back door" to the unlock code. Either it was put in deliberately, in which case you have to pay off the guy who has it (don't let this happen to you), or it was put in accidentally.

     Before you give up, consider the following:

     The keyboard beeps when you press each key, so if you're not getting a beep, the ChronTrol does not hear you. Keep in mind that when a key is held down it locks out all the other keys, so feel around and see if one of them is being held down. If a key has collapsed, you should send your timer in for factory repair. You can also get prompt temporary relief by lifting the key up with a piece of cellophane tape

     XT models do not require an unlock code, and they have none when first plugged in. To set one, you hit the LOCK key, which makes the display go blank, then enter a number (up to four digits), then hit the ENTER key. Study this table which shows what the LOCK key does:

     If the keyboard is locked and you enter the unlock code, then hitting:

 and when you are at (*) above, you can always hit TIME, which leaves you once again with no unlock code.

     Of the 10,000 possible unlock codes, the one most likely to be set accidentally is 0000. So your first logical step for unlocking the keyboard if it's been locked accidenatlly is to hit LOCK LOCK. If the unlock code was 0000, the display will go blank. You should then immediately hit the TIME key, leaving no unlock code.
      If the display does not go blank, try LOCK 1 LOCK. If the display still doesn't go blank, try LOCK 2 LOCK
     
      If you are still unable to unlock the keyboard, simply pull the plug, disconnect the battery, wait a couple of minutes, then plug it back in with no battery. Then all you have to do is re-program it from scratch.

     If the indicator light comes on, that means that the electronics behind the ChronTrol are sound and the only problem you have is an electrical misconnection, or at worst a broken relay. But if the indicator doesn't come on, then a whole world of possibilities opens up, which our factory-trained technicians are prepared to straighten out. It could be anything from a programming mistake to a total computer meltdown. Your best bet is to pick up the phone and give us a call.

     ChronTrol keeps the date internally in "ordinal date" format; the date runs from day 0 to day 364. Right off the bat, you can see that dates from March 1 onward have a different ordinal date in leap years.

     The ChronTrol XT model is required to do some pretty intensive calculations when it comes to cycles that extend past 24 hours. For instance, if you program a circuit to come on for two days out of every three, starting at 5 p.m. on February 28, will it go off at 5 p.m. on March 2? It helps to know if it's a leap year, because the circuit will actually go off on March 1 if it is.

      The reverse is just as cumbersome - if you say explicitly "Turn on Feb. 28, turn off Mar. 1, and repeat every 3 days," the circuits will do just that. But when will they come on again? On Mar. 2 or Mar. 3? You can't say for sure unless you know whether the program was set in a leap year or not. And if the program were set in a leap year, but after Feb. 29, does that mean the program would apply to the following (non-leap) year? You bet!

     The date of 3/1/99 is the internal represenation of the ChronTrol's date after initialization. Just as the timer also initializes time to 12:00 a.m. (this is the internal representation of 0000 hours which is the internal representation, how the data is stored internally).