Sunday, April 19, 2009

LED Sequencer Circuit

Descrete Multistage Light Sequencer Circuit
The drawing below illustrates a multistage light sequencer using

descrete parts and no integrated circuits. The idea is not new
and I hear a similar circuit was developed about 40 years ago
using germanium transistors. The idea is to connect the lights so
that as one turns off it causes the next to turn on, and so forth.
This is accomplished with a large capacitor between each stage
that charges when a stage turns off and supplies base current to
the next transistor, thus turning it on. Any number of stages can
be used and the drawing below illustrates 3 small Christmas lights
running at about 5 volts and 200mA. The circuit may need to be
manually started when power is applied. To start it, connect a
momentary short across any one of the capacitors and then
remove the short. You could use a manual push button to do this.

16 Stage LED Sequencer Circuit
The circuit below uses a hex Schmitt Trigger inverter (74HC14)
and two 8 bit Serial-In/Parallel-Out shift registers (74HCT164 or
74HC164) to sequence 16 LEDs. The circuit can be expanded to
greater lengths by cascading additional shift registers and
connecting the 8th output (pin 13) to the data input (pin 1) of the
succeeding stage. A Schmitt trigger oscillator (74HC14 pin 1 and 2)
produces the clock signal for the shift registers, the rate being
approximately 1/RC. Two additional Schmitt Trigger stages are
used to reset and load the registers when power is turned on.

60 Light Sequencer Circuit using a Matrix

The circuit below illustrates using a 10x10 matrix to sequence up
to 100 LEDs with just three ICs and 20 transistors. The two 4017
decade counters control the 10 rows and 10 columns so that one
LED is selected depending on the output of the decade counters.

The LED circuit is drawn showing 25 LEDs and 10 transistors but
can be expanded up to a 100 by using sucessive stages of the
4017 counters.


LED sequencer
The model 4017 integrated circuit is a CMOS counter with ten
output terminals. One of these ten terminals will be in a "high"
state at any given time, with all others being "low," giving a
"one-of-ten" output sequence. If low-to-high voltage pulses are
applied to the "clock" (Clk) terminal of the 4017, it will increment
its count, forcing the next output into a "high" state. With a 555
timer connected as an astable multivibrator (oscillator) of low
frequency, the 4017 will cycle through its ten-count sequence,
lighting up each LED, one at a time, and "recycling" back to the
first LED. The result is a visually pleasing sequence of flashing
lights. Feel free to experiment with resistor and capacitor values
on the 555 timer to create different flash rates

Saturday, April 18, 2009

led flashing circuit

Transistor LED flasher Circuit

This circuit has a lot going for it. For one thing, it only consists of two

transistors, two capacitors and four resistors. That also means it
consumes very little power. You can control the flash rate by changing
the size of the 100k resistors (100k makes for a pretty slow rate).
You can also control the duty cycle by using resistors of different
values on the two sides. The 470 ohm resistors control the current
through the LEDs. Normally you want to limit this to 20mA, but to
conserve battery power, you may need to limit it even further. You
can also connect several LEDs in series, instead of using only one
for each side. With red LEDs (1 per side) and the values shown,
the circuit draws about 11mA.

Basic LED flasher circuit using NE555 timer IC
This circuit consumes more power, but it's advantage is when
you need a variable flash rate, like for strobe circuits. You can
actually use this circuit as a remote control for strobes that have
a remote input. Of course, it has many other applications
besides strobes.


4 Parallel LEDs flashing circuit
Nominal flash rate: 1.3 Hz. Average IDRAIN e 2 mA

LM3909 LED Flasher/Oscillator
General Description
The LM3909 is a monolithic oscillator specifically designed
to flash Light Emitting Diodes. By using the timing capacitor
for voltage boost, it delivers pulses of 2 or more volts to the
LED while operating on a supply of 1.5V or less. The circuit
is inherently self-starting, and requires addition of only a battery
and capacitor to function as an LED flasher.
Packaged in an 8-lead plastic mini-DIP, the LM3909 will operate
over the extended consumer temperature range of
b25§C to a70§C. It has been optimized for low power drain
and operation from weak batteries so that continuous operation
life exceeds that expected from battery rating.
Application is made simple by inclusion of internal timing
resistors and an internal LED current limit resistor. As
shown in the first two application circuits, the timing resistors
supplied are optimized for nominal flashing rates and
minimum power drain at 1.5V and 3V.
more pdf

12 LED Flasher
LED flasher in this circuit use 12 LED it can show 2 style .
The circuit consist 2 section


1.5 volt dual LED flasher Circuit
This 1.5 volt led fasher runs more than a year on a single 'd" cell
and alternately flashes 2 LEDs at about a 1 second rate. The
circuit employs a 74HC14 CMOS hex inverter that will operate
at very low voltages (less than 1 volt). One section is used as a
squarewave oscillator (pins 1 and 2), while the others are wired
to produce a short 10mS pulse on alternate edges of the square
wave so the LEDs will alternate back and forth.

Thursday, April 16, 2009

Infrared motion detector with Microcontroller Circuit

A simple automatic motion-detection Digital Camera Circuit

When the sensor detects movement in a room it will take a burst of
10 photos with the digital camera. Each photo is taken at 0.5sec
interval. After the 10 photos, the camera waits 3 seconds for further
movement and if it is detected, the process is repeated until 80
photos are taken.
The photos can then be downloaded to your PC (via the USB
connection on the board) for viewing.


The Directional Infrared Detector Module Circuit (DIRM)

Figure shows a block diagram of the DIRM. A Fresnel lens
captures the incident IR and focuses it towards the
pyroelectric sensor increasing the sensitivity of the sensor
and improving its directional response. The resultant signal
passes through a low pass filter, which removes any high
frequency noise generated by mechanical vibration. The
output of the filter is then fed into a differentiator, which
produces an output voltage proportional to the rate of
change of the incident IR. The frequency response of this
differentiator is also rolled off at high frequencies, further
reducing the effects of undesired signals. The window
comparator produces a logic output whenever the rate of
change of incident IR exceeds a given set point.
An 8-bit PIC16F84 microcontroller processes the logic
signals and controls the rotating platform and reports
information to the team leader.


A PIR detector can be made easily with ST7FLITE05 using the
circuit shown in Figure. The sensor interfacing circuit (shown on
the left side of the microcontroller in Figure ) can be divided
into the following modules:
1.Transistor circuit used as an amplifier.
2.Transistor biasing controlled through the microcontroller.
3. Software-controlled transistor output.

more pdf

Infrared, Alarm, and PIC Microcontroller
• Get familiar with an infrared emitter diode and receiver.
• Create an obstacle detector with an infrared emitter and receiver.
• Learn about PIC microcontroller and programming a PIC microcontroller.
• Write a PIC program and build the circuit of a household alarm system.

more pdf

Ultra-low Power Motion Detection using the MSP430F2013

A system capable of detecting motion using a dual element PIR
sensor is shown in Figure 1 using the MSP430F2013
microcontroller. Using the integrated 16-bit Sigma-Delta
analog-todigital converter and built-in front-end PGA (SD16_A),
the MSP430F2013 provides all the required elements for interfacing
to the PIR sensor in a small footprint. With integrated analog
and a 16MHz, 16-bit RISC CPU, the MSP430F2013 offer a great
deal of processing performance in a small package and at a low cost.

Wednesday, April 15, 2009

PIR Infrared motion detector Circuit

Infrared motion detector Circuit
The pyroelectric sensor is made of a crystalline material that
generates a surface electric charge when exposed to heat in the
form of infrared radiation. When the amount of radiation striking
the crystal changes, the amount of charge also changes and
can then be measured with a sensitive FET device built into the
sensor. The sensor elements are sensitive to radiation over a wide
range so a filter window is added to the TO5 package to limit
detectable radiation to the 8 to 14mm range which is most sensitive
to human body radiation.
Typically, the FET source terminal pin 2 connects through a
pulldown resistor of about 100 K to ground and feeds into a two
stage amplifier having signal conditioning circuits. The amplifier
is typically bandwidth limited to below 10Hz to reject high
frequency noise and is followed by a window comparator that
responds to both the positive and negative transitions of the
sensor output signal. A well filtered power source of from 3 to
15 volts should be connected to the FET drain terminal pin 1




Application Schematic of Pyroelectric Infrared Motion
Sensors Circuit
Note: For best results the power supply should be very stable
at a constant +5V DC +/- .2V.This Schematic is offered for reference only without warranty
of any kind. Microsystem Technologies does not support user
designs or implementations that use this circuit


Automatic security lights Circuit
Combination PIR sensor and floodlight units are cheap but
rather inflexible if you want to locate the sensor and light in
different places. In my case, I wanted to detect movement
on the driveway and switch on the lights in the carport around
the corner. Yet another job for the ubiquitous PICAXE-08

A standard PIR sensor is used as the movement detector.
The sensor interfaces to the PICAXE (IC1) on input 2 (pin 5).
This pin is pulled low via isolation diode D3 and the normally
open (NO) output of the sensor whenever movement is
detected. It can also be pulled low by transistor Q1, which acts
as a simple inverter for sensors with normally closed (NC) outputs.

Passive Infrared Motion Detector Circuit

This circuit was originally reverse -engineered from a motion
detecting yard light that I ripped apart. That's still probably the
best way to get the parts at a reasonable price, especially the
pyroelectric sensor and the absolutely necessary Fresnel lens.
The signal at pin 7 of the 324 is very interesting and fooling with
the filtering around the first amplification stage can make it even
more so. The LM324 is a wonderful little bug, and you will find
many uses for the window comparator if you look at it the same
way you would learn a new really useful knot. It all works on a
single 5 volt supply. The sensor is only sensitive to changes
across its surface, so don't expect a signal from a static object
even if it is hot. Yard lights are turning up at flea markets and yard
sales as people find themselves heads up every time the cat walks
past. This circuit is in a machine that sees people moving 40 feet

Thursday, April 9, 2009

4-20mA Current Loop Receiver Circuit

4-20mA Current Loop Receiver with Input Overload
Protection circuit

The RCV420 is a precision current-loop receiver designed
to convert a 4–20mA input signal into a 0–5V
output signal. As a monolithic circuit, it offers high
reliability at low cost. The circuit consists of a premium
grade operational amplifier, an on-chip precision
resistor network, and a precision 10V reference. The
RCV420 features 0.1% overall conversion accuracy,
86dB CMR, and ±40V common-mode input range.


A current-sensing circuit derives its power from the
4-20-mA current loop.

4-20mA Current Loop Receiver with fault protection and
digital-signal recovery circuit

Figure shows one form of flexible fault protection for the 24VDC
power supply of a 4-20mA loop. Also included is circuitry for recovering
a digital signal superimposed on that loop. U1 (a high-side current-
sense amplifier with comparator and reference) senses the loop current
in R1 as an 8-40mV voltage and amplifies it by 100, producing an
output-voltage range of 0.8V to 4V. That output (VOUT) can directly
drive external meters, strip-chart recorders, and A/D converter inputs.

More pdf

Wednesday, April 8, 2009

4-20mA Pressure Transducer Circuit

Complete 4-20mA Pressure Transducer Solution with
PGA309 and XTR117

The XTR117 is a precision current output converter designed
to transmit analog 4-20mA signals over an industry-standard
current loop. It provides accurate current scaling and output
current limit functions.

XTR117 datasheet pdf

The PGA309 is a programmable analog signal conditioner
designed for bridge sensors. The analog signal path amplifies
the sensor signal and provides digital calibration for
zero, span, zero drift, span drift, and sensor linearization
errors with applied stress (pressure, strain, etc.). The calibration
is done via a One-Wire digital serial interface or
through a Two-Wire industry-standard connection. The
calibration parameters are stored in external nonvolatile
memory (typically SOT23-5) to eliminate manual trimming
and achieve long-term stability.

PGA309 datasheet pdf

Tuesday, April 7, 2009

4-20mA Current-Loop Transmitter Circuit

The XTR117 is a precision current output converter designed
to transmit analog 4-20mA signals over an industry-standard
current loop. It provides accurate current scaling and output
current limit functions.

The on-chip voltage regulator (5V) can be used to power
external circuitry. A current return pin (IRET) senses any
current used in external circuitry to assure an accurate
control of the output current.


0-5V To 4-20mA Current-Loop Transmitter Circuit

The AM422 is a low cost monolithic voltage–
to–current converter specially designed for
analog signal transmission. The AM422 is
available in a 3– or 2–wire version, which allows
applications with flexible input voltage
ranges to be used for a standard output current.
Output current range and current offset level
are freely adjustable by external resistors. The
IC consists of three basic sections: an operational
amplifier input stage for single ended
input signals (0.5–4.5V, 0–10V, or other), a
programmable 4.5 to 10V reference for transducer
excitation, and a current output, freely
adjustable in a wide current range (4–20mA,
0–20mA, other). With the broad spectrum of
possible input signals the AM422 is a flexible
and multipurpose voltage–to–current converter
for single ended transducers or voltage transmission.

- Wide Supply Voltage Range: 6...35V
- Wide Operating Temperature Range: –40°C...+85°C
- Adjustable Voltage Reference:4.5 to 10V
- Operational Amplifier Input:0.5...4.5V, 0...5V, other
- Adjustable Offset Current
- Available as Three– (0/4...20mA) or Two–Wire Version (4...20mA)
- Adjustable Output Current Range
- Protection Against Reverse Polarity
- Protected Current Output

AM422 datasheet pdf

Monday, April 6, 2009

Constant Current Battery Charger Circuit

Constant Current Battery Charger

Simple Power Supply and Charger Circuits
Figure 4 shows a simple power supply circuit. I have tested with KABO,

it works fine. For those who have a big capacity rechargeable battery,
the resistance value of R can be selected for approx. 10% output
charging current. DC in can be higher if your battery voltage higher than
8.4V, say. To ensure the output current is within the value calculated by
R, measure DC current before. The maximum supply for LM317 is ~35V.

A Simple Peak-detecting Nicad Charger
The circuit consists of two parts, a constant current generator using
a PNP power transistor (Q2), and a peak-detecting shutoff circuit
using a high-gain opamp (IC1). To start the charge cycle, switch
SW1 is momentarily closed, causing C1 to discharge. As IC1's
inverting input is now higher than its non-inverting input, its output
goes low, turning on Q1. This lights the red "charge" LED (D2) and
provides about 80mA through R6 and R7 to turn on Q2, which starts
charging the battery. Charge current flows through R8 on its way to
the battery. When the voltage across R8 exceeds about 0.6V, Q3
starts to turn on and robs current from the base of Q2. This regulates
the output current to an amount determined by the value of R8.

Saturday, April 4, 2009


The HIP5600 can supply a 450 A (20%) constant current.
It makes use of the internal bias network.

See Figure 27 for bias current versus input voltage.
With the addition of a potentiometer and a 10 F capacitor the
HIP5600 will provide a constant current source. IOUT is given
by Equation 13 in Figure 16.



The LM317 is an adjustable 3−terminal positive voltage regulator
capable of supplying in excess of 1.5 A over an output voltage
range of 1.2 V to 37 V. This voltage regulator is exceptionally
easy to use and requires only two external resistors to set the
output voltage. Further, it employs internal current limiting,
thermal shutdown and safe area compensation, making it
essentially blow−out proof.

The LM317 serves a wide variety of applications including
local, on card regulation. This device can also be used to
make a programmable output regulator, or by connecting a fixed
resistor between the adjustment and output, the LM317 can be
used as a precision current regulator.
-Output Current in Excess of 1.5 A
-Output Adjustable between 1.2 V and 37 V
-Internal Thermal Overload Protection
-Internal Short Circuit Current Limiting Constant with Temperature
-Output Transistor Safe−Area Compensation
-Floating Operation for High Voltage Applications
-Available in Surface Mount D2PAK−3, and Standard 3−Lead
Transistor Package
-Eliminates Stocking many Fixed Voltages
-Pb−Free Packages are Available

Friday, April 3, 2009

Constant-Current Circuit

Booster Constant-Current Circuit
Constant-current circuits can be configured to take
advantage of the fact that CMOS regulators consume
a very low current.

If you wish to set constant current value io to a
larger value, PNP transistor Tr1 and resistor R1 can be
added, as seen in Figure 5. This will improve the
input/output voltage characteristics, allowing you to
increase the said current value as a result.
Consequently, under the same conditions as stated
above, that is, an input voltage VIN of 3 V and a
device voltage VO higher than 1V, for example, the
drive capacity will rise from 10 mA (typ.) to 100 mA

Figure 4. Booster Constant-Current Circuit

Constant Current Battery Charger Circuit

The resistors R1 and R2 determine the final charging voltage
and RSC the initial charging current. D1 prevents discharge
of the battery throught the regulator.
The resistor RL limits the reverse currents through ther
regulator (which should be 100 mA max) when the battery
is accidentally reverse connected. If RL is in series
with a bulb of 12 V/50 mA rating this will indicate incorrect

Transistor constant current Circuit
This is a schematic of the smoke circuit regulator. This is a
constant current regulator. The two 1.5 ohm resistors sense
the current in the smoke elements. If the smoke element
current increases, the base voltage of the 2N3904 increases
and it in turn drags down the base of the TIP122 pass transistor
which reduces the voltage and therefore the current of the
smoke elements. The circuit regulates the current to about 1 amp.
The resulting voltage across the elements is about 6 volts. The
most significant internal voltages are shown in red referenced to
the (-) side of the bridge.

Constant Current for Sensor Excitation Circuit
The MAX1464 can be easily configured to generate constant
current excitation for sensors that is ratiometric to the power supply
voltage for resistive transducer applications. Applications utilizing
sensing elements with high temperature coefficients, TCR, such as
piezo resistive bridges, RTDs, etc. are typically implemented with
constant current excitation. This application note suggests a simple
resistive network that can be implemented to provide a ratiometric
current source for sensor excitation.

Transistor constant current source Circuit
The current source shared by the two transistors is also shown in the
figure. Due to the fact that the forward biased diodes have fixed
voltageVd = 0.7V, the base voltage of the transistor is also fixed at 2.1V
, so is the current Icc, i.e., the circuit can be used as a constant current source

Thursday, April 2, 2009

Ramp Generator Circuit

Dual Ramp Generator
The first circuit is a dual ramp generator where the positive

and negative ramps are generated separately. This circuit
was used as a ramp generator for a transistor curve tracer:
the positive going ramp was used for testing NPN transistors
and the negative ramp for testing PNP transistors.

Generating Triangle Waves
In the circuit to the right, we use a separate integrator to

generate a ramp voltage from the generated square wave.
As a result, we can get both waveforms from a single circuit.
The phase relationship shown between the two output
waveforms is correct

555 ramp generator
Again, we are using a 555 timer IC as an astable multivibrator,

or oscillator. This time, however, we will compare its operation
in two different capacitor-charging modes: traditional RC and

Ramp Generator by Schmitt trigger

The ramp is generated by a constant charging current into
capacitor CRAMP, which is connected between ground and
the noninverting input of op amp IC1, configured as a
voltage follower. The current through RRAMP is the charging
current, kept constant by forcing the voltage across RRAMP
to equal the reference voltage from IC1. One side of RRAMP
is connected to CRAMP, and the other side to the reference
output. In turn, the ground terminal of the reference IC connects
to the op-amp output, which provides a low-impedance replica
of the voltage across CRAMP

Linear Voltage Ramp
To make the ramp of the charging cycle linear with time the
capacitor must be charged from a constant current. R1 is
replaced with another PNP Q3, which implements a constant
current source. Q3's base voltage is fed from a diode drop,
leaving just a single resistor R1 to vary the charging current,
and hence frequency of oscillation.

Wednesday, April 1, 2009

Pulse Generator Circuit

Transistor Schmitt Trigger Oscillator
The Schmitt Trigger oscillator below employs 3 transistors, 6

resistors and a capacitor to generate a square waveform.
Pulse waveforms can be generated with an additional diode
and resistor (R6). Q1 and Q2 are connected with a common
emitter resistor (R1) so that the conduction of one transistor
causes the other to turn off. Q3 is controlled by Q2 and
provides the squarewave output from the collector.

X'tal Oscillator Frequency
This circuit may used as clock frequency for many digital

circuits. I got this circuit from a microcontroller clock generator

555 Pulse Generator
A 555 pulse generator circuit with a difference, the initial
pulse is tailored by additional circuitry to match the duration
of subsequent pulses.

Op Amp Square Wave Generator
This is a square wave generator circuit. The main component
of this circuit is the 741, a general-purpose operational amplifier.
This circuit employs a single power supply Vs that can range
from +5V to +15V.

Changing the pulse width
The previous assembly gives a rectangular signal with a duty
cyclic equal to 50 %. We can need to change it to produce
pulses for example. A simple means is to use a variable RC
circuit and to reshape the signal obtained by means of a
Schmidt trigger , here a CD 4093 which allows to use a wide
range of voltage.