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Hello everyone,
I have been corresponding with Bruce Robinson on the subject of analog
counters and this has developed into the attached article and circuit.
So with my best wishes for the new year to all
enjoy!
wilf
BEAM SONICS 101
wilf rigter 12/99
Hello everyone,
Goodbye to BEAM silence in 20th and say hello to BEAM sonics in the 21th
century!
The SONIC circuit is a sound processor which generates a chirp if it
receives several chirps (or other sound packets) from external sources
like other chirpers or human whistles.
It's function is based on a concept by Bruce Robinson and it is one of
those projects that is looking for a "killer application".
In the mean time this article is presented here for your enjoyment, for
discussion and a test platform of related ideas eg adding sound sensing
and sound processing to a beam bot.
The project combines several typical BEAM subsystems and components
which have been used for many other applications. The circuit uses a
single 74HC14 available from Solarbotics, etc. and a handful of other
parts readily available from Radio Shack making it easy to get started.
Unlike the SMART HEAD which required careful fine tuning to get results,
the SONIC circuit component values are not particularly critical and you
may substitute or adjust values to suit. This will change some circuit
parameters but nothing's going to "hang up" and cause frustration.
As shown in the attached schematic, a electret microphone signal is
increased by a factor of about 2000 with two AC coupled transistor
amplifiers (Q1-2). The small coupling capacitors provide a high pass
filter function which strips off any low frequency "rumble" sound and
vibration which could cause problems for example on a moving robot.
MICROPHONE AMPLIFIER
The microphone amplifier is a sound receiver, sensitive enough to pick
up a low level sound, ie chirper/beeper, 5 or 6 ft away. Clapping your
hands or whistling can be easily be detected 15 or 20ft away. When the
microphone detects a chirp or a whistle, the pre-amp output is a complex
sound waveform with a mix of analog and clipped signals. This output
signal is large enough to drive the following level detector stage.
SOUND LEVEL DETECTOR
The next section of the SONIC circuit uses a AC coupled Schmitt trigger
(Nv neuron) as a threshold detector which processes the amplitude
information of the incoming sound. Triggered by any sound pulse with an
envelop above a minimum level, the Nv output is a clipped digital
waveform with a duration and frequency of the incoming sound pulse.
SOUND DURATION DETECTOR
The following Nu neuron stage is a dual time constant integrator which
sets a threshold for the minimum duration of and the minimum delay
between sound pulses. The Nu filters clicks and noise pulses shorter
than 10ms from the incoming sound. The Nu stage produces a single
positive output pulse which is at least 10ms and as long as the duration
of the incoming sound pulse.
Resistor RA, in series with diode D1 and in parallel with resistor RD,
sets the Nu "attack" time ie the minimum required input pulse duration.
The parallel resistor RD sets the Nu "decay" time which determines the
minimum Nu output pulse duration and therefore the minimum delay between
incoming sound pulses. Values of RA and RD are nominally 100K. In
general, RA is equal or smaller than RD but values can be adjusted to
suit.
CHARGE PUMP
The following charge pump (diode dump) circuit uses the positive edge of
the Nu output pulse to transfer a single charge on the charge capacitor
(CC) through D3. The charge on CC is reset on the negative edge of the
Nu output pulse through D2. This way discrete pulses are transferred on
the rising Nu output which can be counted by the following charge
counter.
ANALOG COUNTER
The analog charge counter ciruit is closely related to the classic CMOS
oscillator. It is used to accumulate discrete charges from the charge
pump on capacitor CA until the voltage on CA crosses the input trigger
level of the Schmitt trigger. When that happens the counter circuit
output rapidly changes to the active state, and just like a standard
CMOS oscillator, uses positive feedback from the non-inverting output to
dump the charge on CA through the 74HC14 input protection diodes. Next
CA start to rapidly charge in the reverse direction through D4 and the
1M resistor with negative feedback from the invering output. When the
voltage on CA crosses the lower trigger level, the active outputs are
terminated and the charge on CA is again dumped through the 74HC14 input
diodes and the counter is "reset" (CA charge is zero).
The number of charges required to trigger the charge counter is set by
the ratio of the charge cap CC (0.1uF) and the accumulator cap (CA
(1.0uF) as well as the Schmitt input threshold. In this SONIC circuit,
that number is arbitrarily set to 6 which makes the circuit act as a
divide by 6 counter, generating one output pulse for every six input
pulses.
The counter divider ratio can be adjusted by changing the ratio of the
two capacitor values. The charge counter active output pulse duration is
set by the 1M resistor which can be changed to other values if required.
COUNTER MODULATING
The optional PD is a green LED or photodiode which provides a reverse
bias leakage current to charge capacitor CA causing the counter to
dynamically change divider ratio (modulus) with time and light level
requiring fewer pulses to trigger in brighter light. This tends to make
SONIC circuits more active in brighter light. If used on bots this may
be also used to influence group behaviour since the frequency of chirps
in a group will increase exponentially with group size and light level.
SOUND TRANSMITTER
The beeper circuit is a conventional gated Schmitt trigger oscillator
plus inverting buffer with a piezo element driven by the push-pull
outputs at an equivalent 10Vpp signal level. The RC components may be
adjusted to set the oscillator frequency to the piezo resonant frequency
to maximize the sound volume.
APPLICATIONS
The charge counter generates complementary outputs used here to echo a
sound chirp after hearing six incoming chirps but which can be used for
many other things like halting or reversing a bot . With the PD
installed, at low light level and with no input sound pulses, the charge
counter self-generates a chirp after a relatively long time. (Who says
you can't divide by zero!) In bright light the SONIC circuit
self-generates chirps more frequently and triggers after fewer input
sound pulses making the circuit more active and contributing more to
communal chirping.
Bots may be halted when the level of communal chirping increases beyond
a certain level in bright light, happy to bask in the light and chirp
away.
In a colony of chirpers, SONIC transmitters could be tuned to notes of
the musical scale. I would expect some unusual emergent sounds to occur
including the sponaneous generation of BEAM MUSIC (which perhaps only a
Beamer could enjoy).
As I write this, the SONIC project is breadboarded on a workbench 20 ft
away and with a couple of short whistles I get a nice "I'm alright,
you're alright" chirp in response, so I know it's safe for me to
recommend you build this circuit yourself and end the silence of the
bots .....
enjoy!
wilf
[Image]
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boundary="------------B933799ADA1773DCE3CC9E1B"
--------------B933799ADA1773DCE3CC9E1B
content-transfer-encoding: 7bit
Hello everyone,
I have been corresponding with Bruce Robinson on the subject of analog
counters and this has developed into the attached article and circuit.
So with my best wishes for the new year to all
enjoy!
wilf
BEAM SONICS 101
wilf rigter 12/99
Hello everyone,
Goodbye to BEAM silence in 20th and say hello to BEAM sonics in the
21th century!
The SONIC circuit is a sound processor which generates a chirp
if it receives several chirps (or other sound packets) from external sources
like other chirpers or human whistles.
It's function is based on a concept by Bruce Robinson and it is one
of those projects that is looking for a "killer application".
In the mean time this article is presented here for your enjoyment,
for discussion and a test platform of related ideas eg adding sound sensing
and sound processing to a beam bot.
The project combines several typical BEAM subsystems and components
which have been used for many other applications. The circuit uses a single
74HC14 available from Solarbotics, etc. and a handful of other parts readily
available from Radio Shack making it easy to get started. Unlike the SMART
HEAD which required careful fine tuning to get results, the SONIC circuit
component values are not particularly critical and you may substitute or
adjust values to suit. This will change some circuit parameters but nothing's
going to "hang up" and cause frustration.
As shown in the attached schematic, a electret microphone signal is
increased by a factor of about 2000 with two AC coupled transistor amplifiers
(Q1-2). The small coupling capacitors provide a high pass filter function
which strips off any low frequency "rumble" sound and vibration which could
cause problems for example on a moving robot.
MICROPHONE AMPLIFIER
The microphone amplifier is a sound receiver, sensitive enough to pick
up a low level sound, ie chirper/beeper, 5 or 6 ft away. Clapping
your hands or whistling can be easily be detected 15 or 20ft away. When
the microphone detects a chirp or a whistle, the pre-amp output is a complex
sound waveform with a mix of analog and clipped signals. This output signal
is large enough to drive the following level detector stage.
SOUND LEVEL DETECTOR
The next section of the SONIC circuit uses a AC coupled Schmitt trigger
(Nv neuron) as a threshold detector which processes the amplitude information
of the incoming sound. Triggered by any sound pulse with an envelop above
a minimum level, the Nv output is a clipped digital waveform with a duration
and frequency of the incoming sound pulse.
SOUND DURATION DETECTOR
The following Nu neuron stage is a dual time constant integrator which
sets a threshold for the minimum duration of and the minimum delay between
sound pulses. The Nu filters clicks and noise pulses shorter than 10ms
from the incoming sound. The Nu stage produces a single positive output
pulse which is at least 10ms and as long as the duration of the incoming
sound pulse.
Resistor RA, in series with diode D1 and in parallel with resistor RD,
sets the Nu "attack" time ie the minimum required input pulse duration.
The parallel resistor RD sets the Nu "decay" time which determines the
minimum Nu output pulse duration and therefore the minimum delay between
incoming sound pulses. Values of RA and RD are nominally 100K. In general,
RA is equal or smaller than RD but values can be adjusted to suit.
CHARGE PUMP
The following charge pump (diode dump) circuit uses the positive edge
of the Nu output pulse to transfer a single charge on the charge capacitor
(CC) through D3. The charge on CC is reset on the negative edge of the
Nu output pulse through D2. This way discrete pulses are transferred on
the rising Nu output which can be counted by the following charge counter.
ANALOG COUNTER
The analog charge counter ciruit is closely related to the classic CMOS
oscillator. It is used to accumulate discrete charges from the charge
pump on capacitor CA until the voltage on CA crosses the input trigger
level of the Schmitt trigger. When that happens the counter circuit output
rapidly changes to the active state, and just like a standard CMOS oscillator,
uses positive feedback from the non-inverting output to dump the charge
on CA through the 74HC14 input protection diodes. Next CA start to
rapidly charge in the reverse direction through D4 and the 1M resistor
with negative feedback from the invering output. When the voltage on CA
crosses the lower trigger level, the active outputs are terminated and
the charge on CA is again dumped through the 74HC14 input diodes and the
counter is "reset" (CA charge is zero).
The number of charges required to trigger the charge counter is set
by the ratio of the charge cap CC (0.1uF) and the accumulator cap (CA (1.0uF)
as well as the Schmitt input threshold. In this SONIC circuit, that number
is arbitrarily set to 6 which makes the circuit act as a divide by 6 counter,
generating one output pulse for every six input pulses.
The counter divider ratio can be adjusted by changing the ratio of the
two capacitor values. The charge counter active output pulse duration is
set by the 1M resistor which can be changed to other values if required.
COUNTER MODULATING
The optional PD is a green LED or photodiode which provides a reverse
bias leakage current to charge capacitor CA causing the counter
to dynamically change divider ratio (modulus) with time and light level
requiring fewer pulses to trigger in brighter light. This tends to make
SONIC circuits more active in brighter light. If used on bots this
may be also used to influence group behaviour since the frequency of chirps
in a group will increase exponentially with group size and light level.
SOUND TRANSMITTER
The beeper circuit is a conventional gated Schmitt trigger oscillator
plus inverting buffer with a piezo element driven by the push-pull outputs
at an equivalent 10Vpp signal level. The RC components may be adjusted
to set the oscillator frequency to the piezo resonant frequency to maximize
the sound volume.
APPLICATIONS
The charge counter generates complementary outputs used here to echo
a sound chirp after hearing six incoming chirps but which can be used for
many other things like halting or reversing a bot . With the PD installed,
at low light level and with no input sound pulses, the charge counter self-generates
a chirp after a relatively long time. (Who says you can't divide by zero!)
In bright light the SONIC circuit self-generates chirps more frequently
and triggers after fewer input sound pulses making the circuit more
active and contributing more to communal chirping.
Bots may be halted when the level of communal chirping increases
beyond a certain level in bright light, happy to bask in the light and
chirp away.
In a colony of chirpers, SONIC transmitters could be tuned to
notes of the musical scale. I would expect some unusual emergent sounds
to occur including the sponaneous generation of BEAM MUSIC (which perhaps
only a Beamer could enjoy).
As I write this, the SONIC project is breadboarded on a workbench 20
ft away and with a couple of short whistles I get a nice "I'm alright,
you're alright" chirp in response, so I know it's safe for me to recommend
you build this circuit yourself and end the silence of the bots .....
enjoy!
wilf