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                     Timer (Bleeper) Boxes
                     Video Inserter

Firstly, it is useful to note that in timekeeping  we can usually easily find the correct date, hour and 'identification' of the minute  with a regular wristwatch.  Any additional 'Local Clock' (including a bleeper), needs to give us precise Second Markers and start of the new Minute Markers.

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For single events, a stopwatch can be carried to the observing site, used there and later compared with a standard time signal from a primary source.  Alternatively, some users prefer to first synchronise the stopwatch with the primary time source and then later use the 'lap' timer for discrete events.

For e.g. visual minor planet occultation timing it is necessary to have a source of time, accurate to about 0.1 second ‘on site’, where we typically record on tape the time signal plus the observer's voice.  The observing ‘site’ can be a well equipped observatory, in which case we can use a radio receiver tuned to a standard time and frequency station (e.g. WWV / WWVH), or a high quality local master clock synchronised to a known accurate telephone signal, or a GPS receiver interfaced with a computer running suitable software.

In the case of a grazing occultation we may have numerous (3 - 5 - 10, etc.) observing sites or ‘stations’ that all need reasonably accurate time ‘on site’, but we may not have the required number of communication receivers or GPS units and computers.  Working in the field, away from the observatory, and far from power and telephone lines creates a situation where each station has to be independent, using simple, low cost solutions.

A good source of cheap temporary time keepers is Quartz clocks, which keep time to within about a second a day.  They typically ‘drift’ less than 0.1 sec per hour, so they can be used to transfer time from a “master” clock (radio, telephone, GPS) to another occultation site.  Such a device, once set correctly, puts out audible marker bleeps that are usable for occultation work, and it will keep reasonable time for about 1 to 2 hours.

The best loved example of the local clock is the
An excellent tool to maintain moderate accurate time for a few hours and use this for timing one event or, if the (stop-)watch has multiple lap timer modes, a small number of events.  Today, even very cheap digital watches with a 'stopwatch mode' work very well.  "Get to know" your stopwatch, how much it runs fast or slow, and for field work try to work out its temperature sensitivity.

Another excellent approach to recording Time and Date together with an event is the use of a
These devices connect between a video camera and the recorder/monitor and electronically imprint the time and date along a (chosen) edge of the video frame.  Most versions use an internal quartz clock, but they can also be synchronised with an accurate external time source, such as GPS.

The next section describes some of the many ways to build a
'Timer Box'  or  'Bleeper (Box)'
Once set, these put out audible Second Markers and Minute Markers that are usable for recording, and will keep reasonable time for about 1 to 2 hours.
(and you could have a  GPS  Bleeper  that goes forever.....)


Recently Pauline Loader in New Zealand has developed a current technology "Timer Box".  It is based on the PIC16F84 microprocessor and generates a series of audio pips (beeps) close to the fundamental VNG sequence.   This PBB is extremely simple in terms of hardware because all timing, counting, pip coding etc. is done in software.  The 16F84 is the only active component, and it is programmed through a PC interface and can be reprogrammed when a software update becomes available.  The stability of the PBB is typical for a clock crystal that is not temperature controlled and thus provides acceptable stability for visual observations over a 1 hour period.  The component cost is about  NZ$50 or A$45.  The power consumption is extremely low; the complete circuit draws 6 mA, so it will run for many days on AA penlight batteries.

An important feature for field use of such bleepers is the option of a direct synchronisation process.  The PBB can be synchronised electronicaly by the  'KIWI'  GPS Time Receiver or the 'VNG Users Consortium' GPS Time Receiver  (see the GPS section elsewhere on this web site) and also has a manual reset/synch button.   For further information and email contact follow this link

From early 2005 the Royal Astronomical Society of New Zealand Occultation Section is now supplying  these "beeper box" portable timebases, as described here:
These boxes use the design principles of Pauline Loader, Geoff Hitchcox and Bill Parkin, and are being built by John Priestley and can be ordered for  NZ$ 60.

We know of quite a few working prototype bleepers, which all contain:

In principle, we can also use a 'GPS Hybrid', which, if kept powered up, will keep correct time forever (or until the next GPS anomaly caused by unusual satellite positions or reflections.....):  we can follow the above scheme, but use the 1 PPS from a GPS receiver as the 'clock'.  Then use this to drive the counter, etc. to obtain the minute marker, and manually start / reset this on a full minute,  An example of a 'Bleeper' using GPS input is the  Japanese "GHS Clock"  (hope you can read this..... ), which was a forerunner of the more sophisticated  Japanese "MICON - GHS Clock"

Useful Bleepers put out regular second markers plus a useful long “Minute Marker” bleep every full minute.  Firstly we synchronise the short Second Markers against the UTC master clock.  Next we synchronise the Full Minute Marker.  For the microprocessor versions or digital clock version, only one reset action is needed.  It will keep then going with the audio output within about 0.1 second of UTC for an hour or so.

Given this, it will be easy to speak the correct minute onto the tape recording once on site.  This version is a realistic option for field work, and some have been used on grazes in the past.

All Bleeper Boxes contain (some of) these elements and functions:

Source of 1 pulse per Second: Generate the Minute Marker:
GPS  1 PPS output, or
Microprocessor based clock, or
Digital or Analogue Quartz Clock
Seconds start or adjust button
Divider chips (e.g. 4017 CMOS)
Pulse shaping chip(s)  (e.g. 555), or
Small Microprocessor chip (e.g. PIC)
Full Minute start / reset button

Detailed practical comments:

GPS 1 PPS output:  interface with care to protect the receiver.  Depending on the make and model, the pulse may need to be lengthened (and/or inverted) with the aid of a timer IC (e.g. 555) or monostable multivibrator (e.g. 74123).

Microprocessor based {clock, divider and tones generator} all in one:   we have seen examples using a single chip microprocessor such as the (older) '6805' or the current PIC16F84 (see yellow text box above) plus an external crystal and (very) few other components.  The microprocessor performs multiple functions, eliminating many discrete components.  The use of a microprocessor also has the advantage that complex tone sequences with short and long pulses, ticks and blanks can be generated.

Digital Quartz Clock:  If a microprocessor design can not be sourced, another option is to base a 'divider train' unit on a battery operated digital clock with Large Digits (about A$20 in K-Mart or Target in Australia) which needs to be the type that has setting a 1PPS flashing colon, and time set buttons labelled "Hour" and "Min" (we can not use the type with "Fast" and "Slow" setting buttons).  It would be even nicer to use a digital clock with hours, minutes and seconds display, but these do not have a 1PPS flashing colon.  An important advantage of this type of clock is that pressing the "Min" button also resets the seconds to zero (before purchase confirm this for your sample by waiting 60 seconds).  If a clock with 24 hour time display mode is used, this can be conveniently set to UTC as well.  The reason for choosing a clock with Large Digits is the larger size of the copper tracks running between the circuit board and the LCD display.  In smaller clocks, these tracks tend to be very narrow.  If we need to (a) locate the 1 PPS track, and (b) solder wires onto selected tracks, it is nice to have the largest tracks possible.  After opening the clock, locate the track(s) leading to the (1 PPS) flashing colon between the hour digits and minute digits.  It should be possible to find on one of these 'colon' tracks a pulse each second.  These pulses may have very small amplitude (e.g. 50 mV), requiring a preamp before this can be used to drive the bleeper and dividing circuit.

Analogue Quartz Clock:  this needs to have a second hand that you can see move each second.  Locate the solenoid and measure the pulses on it.  Some clocks generate a positive pulse each second, and they are then fed into the divider ICs (see The Circuit Diagram of the 1987 'Classic' Bleeper as an early example ).  Other clocks generate alternating positive and negative pulses, which need to be turned into consistent polarity to drive the counters.  When using an analogue clock, there is a need for  Divider ICs:  we have seen this done with one 4017  IC dividing by 10, and a second 4017 IC dividing by 6.  The final output is the Minute Marker.  In principle, the '9' output of the first divider IC could also be used to suppress or shorten every 10th second marker.  These ICs use low power and tolerate a range of supply voltage.  (If a microprocessor is used, there is no need for these dividers).

Full Minute and Second Start / Reset  -  Automated (e.g. from KIWI) or Manual Reset Button(s):  these have to be clear in their function and operation for field use.  With digital clocks and microprocessor versions (preferred), only one reset is needed.  With an analogue clock, first the clock (source of second pulses) needs to be synchronised with UTC, then the dividers resent on the full minute.


The simplest imaginable version is described below.  It puts out a regular stream of one bleep every two seconds or every second, but without minute information, and is therefore fairly difficult to use.  The best method is to use it together with a watch or stopwatch which also has been carefully synchronised with ‘true’ time at the base station master clock, and then on site with the help of that (stop )watch speak or tap markers onto the tape recording giving the correct minute and start of minute information.

If this is not possible, then, in the hands of a skilled and very patient (!) observer, we could in principle keep recording continuously, beginning with a calibration against another time source - to get the correct minute information - and then do a lot of counting when reading out the tape.  Hard work....   However, these things are dead easy to make for under A$10, so if you are really stuck......:


Quartz clocks keep time to within about a second a day.  They ‘drift’ less than 0.1 sec per hour, so that we can use them to transfer ‘time’ from a “master” clock (radio, telephone, GPS) to another site.  To make the clock suitable for tape recording we use an analogue clock with a moving second hand, then hook up one or two piezo bleepers to the connections that drive the coil (solenoid) that drives the mechanical hand movement.  This device, once set correctly, puts out “second marker” bleeps that are usable for occultation work for about 1 to 2 hours.  Note that this 'super simple' device has no minute marker, so that it is most important that you carefully mark on your tape the precise start of the correct minute.

1.   Get a battery operated Analogue Quartz Clock with a second hand that you can see move each second.  These normally work on a penlight AA 1.5 volt battery.

2.   Buy one (or two - see later) small “piezo buzzer” or bleeper, or “piezo alarm”, or “electronic buzzer”, with “built in driver”.  Small, round, about 2 cm in diameter and 1 cm thick.  Two thin leads (red and black) come out the side of the base.  Get the type that will work on Direct Current (DC).  While the Catalogues say they work from 3 or 6 volt up to as much as 30 volts, most will work OK on 1.5 volt.  Ask the shop to show you it works on one AA Penlight battery (1.5 V DC).  You can get these in electronics parts stores.  Try for example:
 ¤  Jaycar “Mini Piezo Buzzer”, 3 -16 V DC (15 mA at 12 V)  (cheapest in Australia; works OK)
 ¤  Dick Smith “Slim Piezo Alarm” In-built driver, 3 - 30 volt DC (2.5 - 19 mA)
 ¤  Tandy “Electronic Buzzer with Leads”, 4 - 28 V DC (5 mA at 12 V DC)

3.  Take the battery out of the clock, and carefully unscrew or un-clip or pull off the back cover until you see the coil, or solenoid, or electromagnet, made of fine copper wire, wound around a core.  When you take off the cover the small gears will fall out, and it will be difficult to put them back.  For our purpose this is no problem, but it is likely the clock mechanism can not be used as a “normal” clock any more.  Now find the two points on the circuit board where the wires to the coil are attached.  It is OK to break these wires to the coil, but remember where they were attached.

4.  Disconnect the wires to the coil and instead connect the red and black leads of your piezo buzzer to those same spots on the circuit board.  You need (a friend with) a small soldering iron for this.

5.  Put the battery back in the clock and listen:

6.  Synchronise with a reliable time source (WWV/H, GPS, Telstra 1194) by putting the battery in at the right moment, or by briefly disconnecting the battery a few times until you get a ‘perfect match’.  Leave it running for a few hours to check how well it keeps time.  However, also appreciate that these quartz clocks are temperature dependent, so you may have to check at different temperatures.

Quartz clocks are inherently pretty stable (limited by temperature and supply voltage effects) but cheaper models are often not well adjusted at the factory as a cost cutting measure.  As a result, many cheaper quartz clocks may run consistently a couple of second per day fast or slow, because the manufacturer judges this "good enough' for the expected market.  Such clocks 'could' do better, but only in rare cases can a trimming capacitor be found allowing the user to perform the final adjustment.  Even then we find that the clock rate will vary slightly over the life of the battery, when the voltage slowly decreases from 1.6 V when new, down to about  1.2 V  when the clock stops.

Most quartz clocks can be made to run better by regulating and altering the supply voltage.  Cheap clocks normally run off a 1.5 Volt AA penlight dry cell, but will work from about 1.2 to 2.0 Volts.  Typically, they run a little bit faster at a higher supply voltage.  Using an adjustable voltage regulator, with a 10 or 25 turn trimpot in the adjustment leg, we can fine tune the supply voltage.

Start with a low value, e.g. 1.3 Volt and check how much it runs fast or slow over a few days against a primary source of time (if the voltage regulator will not go down to a sufficiently low voltage, place one or more rectifier diodes in series with the clock).  Next set the supply to 1.7 Volt and repeat.  Now a first estimate can be made of the optimum supply voltage for that temperature.  Refine the procedure by repeating with smaller voltage steps above and below the estimated optimum voltage.  In this way many clocks will run to better than 0.5 second per day (at one temperature....).  The bad news is that using a voltage regulator means we need to start with a higher voltage and also accept much higher current drain (the regulator uses much more power than the clock).

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