QUASAR PROJECT KIT # 3148T9 - PROGRAMMABLE DOWN TIMER (UP TO 99 MIN 59 SEC)
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This is a 4-digit programmable down timer with output and
reset. The uC is marked
T9
. Timing is in
minutes
and
seconds
with a maximum programmable time of 100
minutes (00.00) which is 1 hour 40 minutes. It has
five
operating modes
that control the output function when the
timer reaches zero.
HARDWARE SPECIFICATIONS
Timing range
00.00 to 99 minutes 59 seconds
Starting at 00.00 gives 100
minutes (1h 40m)
Inputs
Start, Stop and Reset
Active low (see text)
Output
Open collector NPN transistor,
100mA @ 30V
Supply voltage
9 to 12V DC
Supply current
30 to 50mA, depending on the
number displayed.
Display
4-digit 7-segment with decimal
point, 14mm RED LED
Physical size
51mm x 66mm (2.0” x 2.6”)
Connection
10-way right-angle SIL header
pins 0.1” spacing. Male or female
PROGRAMMING THE TIMER
The two buttons marked
START
and
STOP
are used to
program the operating time
(4 digits) first, and
select the
operating mode
(1 digit) second.
The Stop and Start button are also bought out to the SIL
header for connection to your own switches along with
Power input, Reset (switch not included) and the Output.
When you apply power, you will see
00.00
on the display.
If you press the
START
button now you will start to count
down from 100 min. Do not do that yet. If you did,
reconnect the power and start again at
00.00
Programming the countdown time is done
one digit at a
time
starting with the leftmost x10-minutes digit. The
decimal points are used to indicate which digit to its left is
being set.
Press the
STOP
button once to enter programming mode.
The leftmost decimal point will come and show
0.000
Now
use the START button to set the value required from 0-9.
When you have selected the 1st digit you want (say 2) press
the STOP button and you will see
20.00.
The “2” has been
set and you are now ready to program the minute-units
digit. Press the START button to set the 2nd digit to say 7.
Press the STOP. You will see
270.0
Repeat the steps above for the x10-seconds and Seconds-
units digits.
After you set the units digit and press STOP the display will
switch to allow the
operating mode
to be set. The current
operating mode, probably
1
will be displayed. Use the START
button to set which of the 5 operating modes you want (see
below for a description of each.) After you have selected the
mode you want then press the
STOP
button. The display will
blank momentarily to indicate that programming mode has
ended and the 4 digits you set to count down from will be
displayed. For example,
27.30
if you want to count down from
27 minutes 30 seconds. The timer is now programmed ready
to go.
STARTING THE TIMER
Press the
START
button or apply a ground to the start input
and the timer will start counting down towards zero. The
STOP button or input has no affect while the timer is
counting down.
Accuracy
. Timing will be accurate to /- 1.8 sec per
hour (3600 seconds.)
STOPPING THE TIMER
The only way to stop the timer is via the reset input. Short
the Reset pin to ground. The timer will reset to its
programmed value and the operating mode is not affected. If
the timer loses power it will restart in Mode 1 with a preset
value of
00.00
(100 minutes).
OPERATING MODES
There are five operating modes that control the timer and the
output. The RESET input does not affect the operating mode.
Mode 1. Timer Stop, Output Hold (default)
This is the default mode at power up. The timer stops when
it reaches zero and the Output goes low and stays low. You
have to press Reset (short the Reset pin to ground) to
continue.
Mode 2. Timer Overrun, Output Hold
Same as Mode 1 except the timer continues counting down
past zero, wraps around to 99.59 and starts counting down
from there. The Output pin goes low and stays low. Short the
Reset pin to ground to return to the preset timer value.
Mode 3. Auto Reset, Pulse Output
When the timer reaches zero the Output pulses low for 20mS
and the timer resets itself to the programmed value and
stays there. You can start to count down again from the
preset value by pressing START.
Mode 4. Timer Overrun, Pulse Output
Same as Mode 2 except the output pulses low for 20msec
instead of staying low. Counting wraps to 99.59 and starts
counting down. Short the Reset pin to ground to return to
the preset timer value.
Mode 5. Output On, Timer Run
