oscillators
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A very STABLE 40khz generator
(From Rodney Radford)
A circuit that I have used before is based on the CD4060 (14stage
binary counter) and a 640Khz ceramic
resonator. The CD4060 is basically an oscillator and a ripple counter
to divide the 640khz down to something
more usable.
Here is the pinout of the CD4060 (frequencies are assuming a 640khz
input signal into pins 10/11/12 - circuit
shown below):
+-\/-+
160hz 1 | | 16 Vcc
80hz 2 | | 15 625hz
40hz 3 | | 14 2.5khz
10khz 4 | | 13 125hz
20khz 5 | | 12 \
5khz 6 | | 11 >---- see sub-circuit below
40khz 7 | | 10 /
GND 8 | | 9 NC
+----+
Sub-circuit for a 640khz ceramic resonator:
12 >
+
740pf | (you may be able to obtain
11 >
+----+---|(----+ a resonator with builtin
| | | capacitors and three leads)
640khz --- \ |
res. O / 1Mohm |
--- \ |
| | |
10 >
+----+---|(----+
740pf |
GND >
+
A nice part about this circuit is that it delivers a STABLE 40khz
signal, as well as delivering several other
frequencies that can be used to modulate the 40khz carrier. For
example, the person that designed this
circuit (Ken Boone, member of Triangle Amateur Robotics) used it to
build several beacons in his yard to serve
as navigation points for a robotic lawnmower. By diode-OR'ing the
results of the 40khz carrier and one of the
lower frequencies (such as the 125Hz) line to drive a ring of IR-LEDs,
he could locate the beacon and tell
which, of several, beacons he had found.
This circuit has proven to be VERY stable, and is fairly inexpensive
(about $1.50 for the CD4060 and 640Khz
ceramic resonator).
(From Rodney Radford)
A circuit that I have used before is based on the CD4060 (14stage
binary counter) and a 640Khz ceramic
resonator. The CD4060 is basically an oscillator and a ripple counter
to divide the 640khz down to something
more usable.
Here is the pinout of the CD4060 (frequencies are assuming a 640khz
input signal into pins 10/11/12 - circuit
shown below):
+-\/-+
160hz 1 | | 16 Vcc
80hz 2 | | 15 625hz
40hz 3 | | 14 2.5khz
10khz 4 | | 13 125hz
20khz 5 | | 12 \
5khz 6 | | 11 >---- see sub-circuit below
40khz 7 | | 10 /
GND 8 | | 9 NC
+----+
Sub-circuit for a 640khz ceramic resonator:
12 >
+
740pf | (you may be able to obtain
11 >
+----+---|(----+ a resonator with builtin
| | | capacitors and three leads)
640khz --- \ |
res. O / 1Mohm |
--- \ |
| | |
10 >
+----+---|(----+
740pf |
GND >
+
A nice part about this circuit is that it delivers a STABLE 40khz
signal, as well as delivering several other
frequencies that can be used to modulate the 40khz carrier. For
example, the person that designed this
circuit (Ken Boone, member of Triangle Amateur Robotics) used it to
build several beacons in his yard to serve
as navigation points for a robotic lawnmower. By diode-OR'ing the
results of the 40khz carrier and one of the
lower frequencies (such as the 125Hz) line to drive a ring of IR-LEDs,
he could locate the beacon and tell
which, of several, beacons he had found.
This circuit has proven to be VERY stable, and is fairly inexpensive
(about $1.50 for the CD4060 and 640Khz
ceramic resonator).