Power Buzzer

How often on average do
you have to call members of your family each day to tell them that
dinner is ready, it’s time to leave, and the like? The person you want
is usually in a different room, such as the hobby room or bedroom. A
powerful buzzer in the room, combined with a pushbutton at the bottom of
the stairs or in the kitchen, could be very handy in such situations.
The heart of this circuit is formed by IC1, a TDA2030. This IC has
built-in thermal protection, so it’s not likely to quickly give up the
ghost. R1 and R2 apply a voltage equal to half the supply voltage to the
plus input of the opamp. R3 provides positive feedback. Finally, the
combination of C2, R4 and trimmer P12 determines the oscillation
红包扫雷苹果下载地址 frequency of the circuit.

Power Buzzer Circuit

Power Buzzer Circuit Diagram

The frequency of the tone can also be adjusted using P1. There is no
volume control, since you always want to get attention when you press
pushbutton S1. Fit the entire circuit where you want to have the
pushbutton. The loudspeaker can then be placed in a strategic location,
such as in the bedroom or wherever is appropriate. Use speaker cable to
connect the loudspeaker. Normal bell wire can cause a significant power
loss if the loudspeaker is relatively far away. The loudspeaker must be
able to handle a continuous power of at least 6 W (with a 20-V supply

The power quickly drops as the supply voltage decreases (P = Urms 2 /
RL). The power supply for this circuit is not particularly critical.
However, it must be able to provide sufficient current. A good nominal
value is around 400 mA at 20 V. At 4 V, it will be approximately 25 mA.
Most likely, you can find a suitable power supply somewhere in your
hobby room. Otherwise, you can certainly find a low-cost power supply
design in our circuits archive that will fill the bill!

Author: G. Baars
Copyright: Elektor Electronics

Cash Box Guard

Most thefts happen after
midnight when people enter the second phase of sleep called
‘paradoxical sleep.’ Here is a smart security circuit for your cash box
that thwarts the theft attempt by activating an emergency beeper. The
circuit can also be used to trigger any external burglar alarm unit. The
cash box guard circuit (shown in Fig. 1) is built around IC CD4060
(IC1), which has an inbuilt oscillator and divider. The basic oscillator
is configured by a simple resistor-capacitor (R-C) network. IC CD4060
divides this oscillator frequency into binary divisions, which are
available as outputs.

In light, reset pin 12 of IC1 remains low, which enables the
oscillator built around IC1. However, in the dark, it making all the
outputs low. This also stops oscillations of the internal oscillator.
Working of the circuit is simple. If the cash box is closed, the
interior will be dark. Hence in the dark, the light-dependant resistor
(LDR1) resets IC1 and it stops oscillating and counting. At the same
time, pins 13 and 14 of IC1 go low. So neither the piezobuzzer (PZ1)
sounds, nor the relay (RL1) energises, indicating that the cash box is

Cash box guard circuit

Cash box guard circuit

If someone tries to open the door of the cash box, light-most
probably from the burglar’s pen torch -falls on LDR1 fitted into the
cash box. As a result, LDR1 conducts and pin 12 of IC1 goes low. IC1
starts oscillating and counting. With the present timing R-C components
(at pins 9, 10 and 11), the output timing at pin 14 of IC1 is two-three
seconds. Hence pin 14 of IC1 goes high for two seconds after the door is
opened and goes low for another two seconds. So the piezobuzzer (PZ1)
sounds for two seconds and then falls silent for the following two
红包扫雷苹果下载地址 seconds. This cycle repeats until the cash box is closed.

An optional relay is added for a remotely located audio/visual alert
system. For that, a relay driver circuit built around npn transistor
BC548 (T2) is used. The relay is energised by the output from pin 13 of
IC1 for about four seconds after the door is opened and then
de-energised for the following four seconds. You can use this relay to
activate another remotely located audio/visual alert system. After
assembling the circuit on a small PCB, house
it in a small tamper-proof box (refer Fig. 2) leaving a little window
for LDR1 and a small opening for the piezobuzzer (PZ1). Now fit the unit
inside the cash box (refer Fig. 3) with LDR1 pointing towards the door
红包扫雷苹果下载地址 of the cash box.

Assemble unit

Assemble unit


  • The relay latching facility can be added to the circuit by
    replacing transistor T2 with a suitable silicon-controlled rectifier
    such as BT169.
  • By changing the value of resistor R1, you can adjust the light detection sensitivity of the circuit.
  • If you want to use a 3-pin piezobuzzer device, remove
    buzzer-driver npn transistor T1 and connect trigger pin of the buzzer
    directly to pin 14 of IC1. Also connect the positive and negative
    terminals of the buzzer to respective positive and negative points of
    the circuit.
  • Photo-transistor 2N5777 can be used in place of the 10mm LDR1.

Unit fitted inside the cash box & also connected to an external alarm

Unit fitted inside the cash box & also connected to an external alarm

Salt Taster Circuit Diagram

Detects the amount of salt contained in liquid foods, Three-level LED indicator

This circuit was designed to detect the approximate percentage of
salt contained in a liquid. After careful setting it can be useful to
persons needing a quick, rough indication of the salt content in liquid
foods for diet purposes etc. IC1A op-amp is wired as a DC differential
amplifier and its output voltage increases as the DC resistance measured
across the probes decreases. In fact, fresh water has a relatively high
DC resistance value that will decrease proportionally as an increasing
amount of salt is added.

IC1B, IC1C and IC1D are wired as comparators and drive D5, D4 and D3
in turn, as the voltage at their inverting inputs increases. Therefore,
no LED will be on when the salt content of the liquid under test is very low, yellow LED D5 will illuminate when the salt content is low, green LED D4 will illuminate if the salt content is normal and red LED
D3 will illuminate if the salt content is high. D1 and D2 are always
on, as their purpose is to provide two reference voltages, thus
improving circuit precision.

At D2 anode a stable 3.2V supply feeds the non-inverting inputs of
the comparators by means of the reference resistor chain R8, R9 and R10.
The 1.6V reference voltage available at D1 anode feeds the probes and
the set-up trimmer R4. One of these two red LEDs may be used as a pilot light to show when the device is on.


R1________________470R 1/4W Resistor
R2,R5______________10K 1/4W Resistors
R3,R6_____________220K 1/4W Resistors
R4__________________5K 1/2W Trimmer Cermet
R7________________680R 1/4W Resistor
R8__________________2K2 1/4W Resistor
R9,R10,R11,R12,R13__1K 1/4W Resistors
C1________________100µF 25V Electrolytic Capacitor
D1,D2,D3______3 or 5mm. Red LEDs
D4____________3 or 5mm. Green LED
D5____________3 or 5mm. Yellow LED
IC1_______________LM324 Low Power Quad Op-amp
P1_________________SPST Pushbutton
Probes_________________ (See Text)
B1___________________9V PP3 Battery


It was found by experiment that a good and cheap probe can be made
using a 6.3mm. mono jack plug. The two plug leads are connected to the
circuit input by means of a two-wire cable (a piece of screened cable
works fine).
The metal body of the jack is formed by two parts of different length,
separated by a black plastic ring. You should try to cover the longest
part with insulating tape in order to obtain an exposed metal surface of
the same length of the tip part, i.e. about 8 to 10mm. starting from
the black plastic ring.
In the prototype, three tablespoons of liquid were poured into a
cylindrical plastic cap of 55mm. height and 27mm. diameter, then the
metal part of the jack probe was immersed in the liquid.
Wait at least 30 seconds to obtain a reliable reading.
Wash and wipe carefully the probe after each test.
To setup the circuit and to obtain a more precise reading, you can use a
DC voltmeter in the 10V range connected across pin #1 of IC1A and
negative supply.
Set R4 to obtain a zero reading on the voltmeter when the probe is immersed in fresh water.
You may change at will the threshold voltage levels at which the LEDs illuminate by trimming R4. Vary R8 value to change D4 range and R9 value to change D5 range.
P1 pushbutton can be substituted by a common SPST switch.

Mapping Defects on Integrated Circuits

Mapping Defects on Integrated Circuits

Mapping Defects on Integrated Circuits

The Challenge:

红包扫雷苹果下载地址creating a system to localize failure mechanisms causing abnormal electrical behavior, including those linked to complex parameters (such as frequencies, amplitudes, and digital values contained in registers), in integrated circuits (ics).

The Solution:

improving a conventional faults mapping system using ni pxi hardware and the ni labview fpga module.

fault localization is complex due to decreased individual pattern sizes, increased metallization levels, and decreased voltage supplies. we needed to localize a defect measuring less than a few micrometers in a component of several square millimeters. there are several ways to do this, including using global fault isolation methods.

one method uses a laser to scan an ic surface while measuring current or voltage variations induced by the laser’s photoelectric or thermal effects. with the thermal laser (λ≈1.3 m), the beam locally heats the component to change its electrical behavior. an analog system monitors some parameters (currents or voltages) during scanning. dedicated software running on a pc then creates a map representing the circuit’s heat sensitivity. faults are generally localized by comparing the map obtained for a reference circuit with the one resulting from a faulty circuit. we used a hamamatsu phemos 1000 that can create maps with 1,024 × 1,024 pixel resolution.

Conventional Method Limitations

with the standard optical beam induced resistive-change (obirch) laser thermal stimulation method, we can only measure voltage or current changes under local heating. we extended this method by mapping complex variables such as frequencies, amplitudes, and digital values stored in registers.

Hardware System Setup

we developed and validated our solution by analyzing a failure in a component that manages cell phone energy (battery power and voltage regulation) and conversions (audio, radio frequency, and supervision).

this circuit contains an a/d converter (adc) to measure various currents and voltages during phone operation. on failing components, conversion results shifted several bits (least significant).

红包扫雷苹果下载地址we used an ni pxi-1036 chassis equipped with an ni pxi-8102 controller and an ni pxi-7852r field-programmable gate array (fpga) module. this ni system is inserted between the device interface board and the fault isolation equipment (phemos 1000).

红包扫雷苹果下载地址this assembly ensures the component startup and the adc control. it initiates conversions and collects the results via serial peripheral interface (spi) bus. it performs scale conversion and transmits data to the fault localization equipment.

the laser scans the chip in 72 seconds to build an image made of 1024 × 1024 pixels. each point must be acquired and processed in less than 65 μs (pixel clock period).

we chosed ni hardware because it fully met our requirements. the ni products are low cost, fast enough to process each pixel in less than 65 μs, and programmable with the labview fpga module.

Software System Setup

we created an autonomous system without requiring expertise in complex programming languages. we used labview fpga to program the system because it provides the developer with all the needed layers: drivers, apis, function libraries, graphical interfaces, compilation and synthesis chains.

红包扫雷苹果下载地址we downloaded and customized a free spi controller from ipnet. this block can communicate with various spi peripherals. we simplified it by removing unnecessary options and created a cell optimized for our needs.

we initiated a/d conversions into the fpga algorithm, retrieved the results, performed a scaling, and exported data to the fault isolation equipment (hamamatsu phemos 1000).

红包扫雷苹果下载地址during the mapping construction, the phemos 1000 is autonomous; it controls the scanning laser, makes voltage and current measurements, and builds laser excitation sensitivity maps. an external signal can be monitored by using an analog input of the equipment. we connected one of the analog pxi-7852r module outputs on this input.

the phemos 1000 and pxi chassis can operate asynchronously or synchronously. we validated both methods. the asynchronous method is simple to implement, but the pixel processing must be less than 65 μs. the synchronous mode is more complex and has a longer processing time. in our tests, processing was fast enough to use the asynchronous mode.

Leak Detection

红包扫雷苹果下载地址we used the previous development to the conversion results of a reference unit and a failing one. the two circuits had significantly different results. the laser strongly altered the adc behavior when scanning two capacitors on the defective part. simulations showed that a 100 fa leakage of the identified elements explained the electrical fault. thus, with the method we developed, we could identify two defects: a silicon manufacturing process defect generating an abnormal leakage in some capacitors, and a component design weakness where the converter architecture was too sensitive to a very low leak rate. we made changes at the application level to correct this problem.


the solution we created using ni pxi and labview fpga is economical. we developed it without the help of programmable logic circuit experts. it greatly increases the possibility of classical faults isolation methods, giving capability to analyze complex parameters such as frequencies, amplitudes, and digital values contained in registers. with the fpga, we mapped heat-sensitive areas on an ic in just a few minutes. it would take many hours with a production tester system.

we used this solution to localize a defect in an adc. the obtained mappings were pointing to internal capacitors. these components had a 100 fa leak, which produced a shift in conversion results. we confirmed this mechanism failure using simulations, and corrected the problem at the application level.

we can now use this system in the st-ericsson quality laboratory for all failure-analysis cases involving complex quantities and adapted to thermal laser stimulation.

Optimizing Circuit Performance

Optimizing Circuit Performance

Optimizing Circuit Performance

national instruments introduces multisim 12.0 with specialized editions for circuit design and electronics education. multisim 12.0 professional edition is based on industry-standard spice simulation and optimized for usability. engineers can improve design performance to fit their applications by minimizing errors and prototype iterations with multisim simulation tools that include both customizable analyses developed in ni labview system design software and standard spice analyses and intuitive measurement instruments. multisim 12.0 also provides unprecedented integration with labview for closed-loop simulation of analog and digital systems. using this all-new design approach, engineers can validate field-programmable gate array (fpga) digital control logic alongside analog circuitry (such as for power applications) before leaving the desktop simulation stage. multisim professional edition is optimized for layout routing and rapid prototyping needs, making seamless integration possible with ni hardware such as the ni reconfigurable i/o (rio) fpga platforms and pxi platforms for prototype validation.

红包扫雷苹果下载地址multisim 12.0 education edition incorporates features specialized for teaching and is complemented by a complete solution of hardware, textbooks and courseware. this integrated system helps educators engage students and reinforce circuit theory with an interactive, hands-on approach to investigating circuit behavior. with the addition of new capabilities, multisim 12.0 can now also facilitate student comprehension of topics in mechatronics, power and digital curricula, expanding the use of a single environment throughout engineering education. widely implemented throughout academia, technical colleges and four-year universities choose multisim for its interactive components, simulation-driven instruments and integration to the ni educational laboratory virtual instrumentation suite (ni elvis) and ni mydaq educational hardware platforms.


红包扫雷苹果下载地址“by giving students access to the same tools they will use as professionals, we eliminate the barriers that make engineering overwhelming or abstract,” said dave wilson, director of proficiency programs for national instruments. “the latest version of multisim introduces powerful functionality in an intuitive way so engineers, both in industry and in training, can focus on the application rather than the tool.”

Product Features

红包扫雷苹果下载地址multisim 12.0 professional edition

  • System-level, closed-loop simulation of analog and digital applications with Multisim and LabVIEW saves time in the design process
  • All-new database enhancements including electromechanical models, AC/DC power converters and switch-mode power supplies for designing power applications
  • More than 2,000 new database components from Analog Devices, National Semiconductor, NXP and Phillips
  • 90+ new pin-accurate connector symbols make custom accessory design for NI hardware easier

multisim 12.0 education edition

  • Easier student project facilitation and design with new pin-accurate connectors to NI educational hardware including NI myDAQ
  • All-new power and machine components for teaching mechatronics and power electronics theory
  • Improved support for digital theory curricula with the latest Xilinx FPGA tool support (12.x and 13.x)
  • Analog and digital system-level simulation with LabVIEW for simulating complete laboratories via desktop to teach controls, energy, power and mechatronics theory

learn more by viewing these additional resources:

  • Product Page: ni.com/multisim
  • Webcast Video for Multisim 12.0 Professional Edition: How to Optimize Circuit Design Performance
  • Tutorial and Video for Multisim 12.0 Education Edition: Teach Analog Circuit Concepts From Theory to Experimentation with NI Multisim and NI ELVIS

Plants Watering Watcher-2

Plants Watering Watcher 2


Parts List:

IC1 ……. CD74HC132

R3 ………. 3.9M

……… Two AAA alkaline cells, with holder

R5, R6 ….. 680

C1, C3 … 1nF (0.001uF) or 2.2nF (0.0022uF)

R7 …….… 15

C2 ……… 100uF/16V electrolytic

R8 …….… 47K

C4 ……… 220nF (0.22uF)

D1 …….… 1N4148 or

R1 ……… 470K (all resistors 1/4W, 5%)

D2 ………. MV8191 or

R2, R4 … 100K

Q1, Q2 ….. 2N4403 or 2N3906

Using a Veroboard
mother-board about the same size as the battery holder, a
daughter-board was added to hold the remaining parts:

Plants Watering Watcher 2 #2

Circuit Description:
1) IC1D is a CMOS Schmitt trigger oscillator at about
2KHz. It starts and continues to oscillate with a supply
down to 1.24V (the lowest output voltage of my LM317
variable power supply) or less.
2) IC1A is an inverter.
3) IC1B is a Schmitt trigger NAND gate. Its output is low
only when both inputs are at, or higher than the upper
Schmitt trigger threshold voltage. With 47 ohms or less
between the probes, an input is always low, so the output
is always high. With a resistance of only R8 between the
probes, the voltage across C3 is high most of the time,
so the gate’s output is low for ½ the oscillator’s
period. With a resistance that is halfway, then C3 is
charged high by that resistance when the oscillator’s
output is high, then is discharged when the oscillator’s
output is low. When C3 is being discharged, then pin 12
of the gate is high, and pin 13 is also high until the
discharging voltage of C3 reaches the lower Schmitt
threshold voltage. During this time, the gate’s output is
low. So the low time of the gate’s output depends on the
value of the resistance between the probes. This is
Pulse-Width-Modulation of the low output of the gate.
4) IC1C is another CMOS Schmitt trigger oscillator at
about 2Hz. D1 and R4 discharge C4 quickly so that its
output is low for only about 15ms with a 3V battery, and
about 25ms with a 2V battery.
5) The series connection of Q1 and Q2 performs like a NOR
gate, so that the LED lights only when both inputs to the
transistors are low.
6) R7 is a current-limiting resistor for the 1.8V LED.
With a 3V battery, the LED current is about 35mA.

Circuit Operation:
1) When the soil is very dry, the LED flashes brightly,
since the soil’s resistance is very high.
2) When the soil has been watered a few days before, but
is drying, the LED flashes dimly,
3) When the soil is damp because it has been recently
watered, the LED is off.
Note that different soils have a different resistance.
Also, sometimes, watered soil will continue to have a
high resistance until the soil absorbs the water, a delay
红包扫雷苹果下载地址 of about one hour.

Although the LED’s current is 8mA with a 3V battery, it
is lighted for only a maximum of only about 1/64th of the
time, so its maximum average current is only 550uA. The
remainder of the circuit draws 200uA. The total is 750A
for new batteries, and about 250uA for run-down
batteries. Therefore the exponential current of 300uA
will continue with 1000mA/hr batteries for 2000 hours, or
about 4.6 months.
The LED’s current is logarithmic with the soil’s
resistance, so that when the resistance is one-half, then
the LED’s current is one-tenth. If you water the plants
when they need watering, then the average LED current
will be very low, and the batteries should last for about
one year.

Project Assembly:
1) Try to obtain the very bright and wide-angle LEDs that
are listed. Samples are available from Fairchild.
2) Use tinned copper 1.5mm diameter buss-bar wire about
8cm long for the probes.
3) Use silicone caulking to attach and seal the Veroboard
to the battery holder, and to seal the battery holder’s
contact holes.
4) Perhaps the project can be mounted in a plastic bottle
for pills, available from a pharmacy (chemist?), with the
probes sticking out of its lid.

Additional information:
A list of plants and their watering requirements is here:


Download this project in .doc format

Plants Watering Watcher 2 #3

Also check the conversation about this project at the
community. Post you questions here.


This is a great intercom circuit that can be used in
many ways. It uses 22V to operate and maybe it will work at a lower
voltage (you can try it). For input/output it uses a loundspeaker
红包扫雷苹果下载地址 (20-45 Ohm) on each side.


click to enlarge

Intercommunication #2

componets layout

Intercommunication #3


parts list

R1: 2,2 M

C6: 200uF/40V

R2: 10 Ohm

IC1: PA234

R3,R6: 100K

LS1,2: 20-45 Ohm

R4: 22K

T1: 2N3391 (BC383)

R5: 1M

P1: 5K

C1: 0,2uF


C2: 0,02uF

C3: 0,001uF

C4: 0,05uF

C5: 100uF/40V

*Intercommunication #4

See here how the SW should be. See also the large
theoritical image.


IrOn Off

Turn ON or OFF electrical devices using remote control is
not a new idea and you can find so many different devices
doing that very well. For realization of this type of
device, you must make a receiver, a transmitter and
understand their way of communication.

Here you will have a chance to make that device, but you
will need to make only the receiver, because your
transmitter will be the remote controller of your tv, or
video …This is one simple example of this kind of device,
and I will call it IrOn-Off or Ir-switch.

How it works

Choose one key on your remote controller (from tv,
video or similar), memorized it following a simple
procedure and with that key you will able to turn ON
or OFF any electrical device you wish. So, with
every short press of that key, you change the state
of relay in receiver (Ir-switch).

IrOn Off #2

Memorizing remote controller key is simple and you can do it
following this procedure: press key on Ir-switch and led-diode
will turn ON. Now you can release key on Ir-switch, and press
key on your remote controller. If you do that, led-diode will
blink, and your memorizing process is finished.


To make this device will be no problem even for
beginners in electronic, because it is a simple
device and uses only a few components. On schematic
you can see that you need microcontroller PIC12F629,
ir-receiver TSOP1738 (it can be any type of receiver
TSOP or SFH) and for relay you can use any type of
relay with 12V coil.

IrOn Off #3

IrOn Off #4

Program code for this device is used from IrLightDimmer and it’s
only a subroutine, which is used for memorize and recognize ir-protocol.

I hope you will find a place to use
this simple and usable device.



download hex program code:

hex iron-off-629

红包扫雷苹果下载地址 – program for pic12f629

hex IrOn-Off-675 – program
红包扫雷苹果下载地址 for PIC12F675

红包扫雷苹果下载地址download pcb layout:

IrOn-Off-Protel – pcb file
in Protel 99 SE

红包扫雷苹果下载地址 – pcb file in PDF format

IrOn Off #5
Download full article in

Unusual clock with AT89C2051

Why unusual

Strangeness of this clock is in its expression of
numbers, which is realized using seven Leds.

Unusual clock with AT89C2051

Leds are located inside
a pipe, one above another and if we move Leds enough fast
left or right, we have a space where we can write numbers,
characters or anything else.

All these are possible only if we
turn on specific Leds at precision timing.

Moving LEDs left or right is
achieved using a steel plate, so we have to tense the
pipe in one direction (left or right) and let pipe to
vibrate by itself.

That "virtual display" has
resolution of 30*7 dots or five characters (5*7 with one
empty column).


Unusual clock with AT89C2051 #2

Unusual clock with AT89C2051 #3

To make this device you
红包扫雷苹果下载地址 will need:

A Piece of metal board (I used al-board 150mm*20mm)

Al-pipe in which are located LEDs (fi 10mm *145mm), it can
be of any material, but must be light and firm.

Plate steel 65mm*15mm*0.35mm

Unusual clock with AT89C2051 #4

On al-pipe you must drill 7 holes, where you will place 7
Leds. LEDs are connected with thin copper wire to circuit
board. You must have more patience cutting “piezo” to about
4mm and soldering it or glue it to steel plate.

“Piezo” is
significant piece in this device, as it is used for
triggering and helps us to know the position of Leds.
“Piezo” is a piezoelectric element and you can find it in
clocks, buzzers…


Unusual clock with AT89C2051 #5

Time adjusting

Setting time is not a complicated process, with key “Time” and
“Hour” you can change hours and with “Time” and “Min” – minutes.
The same thing applies also in alarm setting. Time and alarm
setting is possible only when the pipe vibrates with your help.
When the pipe be still, you can’t change time or alarm.

When time is identical to alarm setting you will see one neat
红包扫雷苹果下载地址 effect with LEDs.

Unusual clock with AT89C2051 #6



download hex program code:

program satat89c2051

download pcb/schem layout:

sch, pcb – SatAT89C2051
– pcb file
in Protel 99 SE

红包扫雷苹果下载地址 satat89c2051.pdf – pcb file in pdf format

Unusual clock with AT89C2051 #7
Download full article in