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LED Clock - Using 72 led bulbs

Galaxy 10:45 AM

In the circuit below, 60 individual LEDs are used to indicate the minutes of a clock and 12 LEDs indicate hours. The power supply and time base circuitry is the same as described in the 28 LED clock circuit previously posted. The minutes section of the clock is comprised of eight 74HCT164 shift registers cascaded so that a single bit can be recirculated through the 60 stages indicating the appropriate minute of the hour. Only two of the minutes shift registers are shown connected to 16 LEDs. Pin 13 of each register connects to pin 1 of the next for 7 registers. Pin 6 of the 8th register should connect back to pin 1 of the first register using the 47K resistor. Pins 2,9,8, 14 and 7 of all 8 minutes registers (74HC164) should be connected in parallel (pin 8 to pin 8, pin 9 to pin 9, etc.). The hours section contains two 8 bit shift registers and works the same way as the minutes to display 1 of 12 hours. Pin 9 of all 74HCT164s (hours and minutes) should be connected together. For 50 Hertz operation, the time base section of the circuit can be modified as shown in the lower drawing labeled "50 Hertz LED Clock Time Base". You will need an extra IC (74HC30) to do this since it requires decoding 7 bits of the counter instead of 4. The two dual input NAND gates (1/2 74HC00) that are not used in the 50 Hertz modification should have their inputs connected to ground.

When power is applied, a single "1" bit is loaded into the first stage of both the minutes and hours registers. To accomplish this, a momentary low reset signal is sent to all the registers (at pin 9) and also a NAND gate to lock out any clock transitions at pin 8 of the minutes registers. At the same time, a high level is applied to the data input lines of both minutes and hours registers at pin 1. A single positive going clock pulse (at pin 8) is generated at the end of the reset signal which loads a high level into the first stage of the minutes register. The rising edge of first stage output at pin 3 advances the hours (at pin 8) and a single bit is also loaded into the hours register. Power should remain off for about 3 seconds or more before being re-applied to allow the filter and timing capacitors to discharge. A 1K bleeder resistor is used across the 1000uF filter capacitor to discharge it in about 3 seconds. The timing diagram illustrates the power-on sequence where T1 is the time power is applied and beginning of the reset signal, T2 is the end of the reset signal, T3 is the clock signal to move a high level at pin 1 into the first register, T4 is the end of the data signal. The time delay from T2 to T3 is exaggerated in the drawing and is actually a very short time of just the propagation delay through the inverter and gate.

Two momentary push buttons can be used to set the correct time. The button labeled "M" will increment the minutes slowly and the one labled "H" much faster so that the hours increment slowly. The hours should be set first, followed by minutes.

LED Clock Timer - using 28 leds

Tools n Meisurement

Galaxy 10:43 AM

This is a programmable clock timer circuit that uses individual LEDs to indicate hours and minutes. 12 LEDs can be arranged in a circle to represent the 12 hours of a clock face and an additional 12 LEDs can be arranged in an outer circle to indicate 5 minute intervals within the hour. 4 additional LEDs are used to indicate 1 to 4 minutes of time within each 5 minute interval.

The circuit is powered from a small 12.6 volt center tapped line transformer and the 60 cycle line frequency is used for the time base. The transformer is connected in a full wave, center tapped configuration which produces about 8.5 volts unregulated DC. A 47 ohm resistor and 5.1 volt, 1 watt zener regulate the supply for the 74HCT circuits.
A 14 stage 74HCT4020 binary counter and two NAND gates are used to divide the line frequency by 3600 producing a one minute pulse which is used to reset the counter and advance the 4017 decade counter. The decade counter counts the minutes from 0 to 4 and resets on the fifth count or every 5 minutes which advances one section of a dual 4 bit binary counter (74HCT393). The 4 bits of this counter are then decoded into one of 12 outputs by two 74HCT138 (3 line to 8 line) decoder circuits. The most significant bit is used in conjunction with an inverter to select the appropriate decoder. During the first eight counts, the low state of the MSB is inverted to supply a high level to enable the decoder that drives the first 8 LEDs. During counts 9 to 12, the MSB will be high and will select the decoder that drives the remaining 4 LEDs while disabling the other decoder. The decoded outputs are low when selected and the 12 LEDs are connected common anode with a 330 ohm current limiting resistor to the +5 volt supply. The 5th output of the second decoder (pin 11) is used to reset the binary counter so that it counts to 11 and then resets to zero on the 12th count. A high reset level is required for the 393 counters, so the low output from the last decoder stage (pin 11) is inverted with one section of a 74HCT14 hex Schmitt trigger inverter circuit. A 10K resistor and 0.1uF cap are used to extend the reset time, ensuring the counter receives a reset signal which is much longer than the minimum time required. The reset signal is also connected to the clock input (pin 13) of the second 4 bit counter (1/2 74HCT393) which advances the hour LEDs and resets on the 12th hour in a similar manner.
Setting the correct time is accomplished with two manual push buttons which feed the Q4 stage (pin 7) of the 4020 counter to the minute and hour reset circuits which advance the counters at 3.75 counts per second. A slower rate can be obtained by using the Q5 or Q6 stages. For test purposes, you can use Q1 (pin 9) which will advance the minutes at 30 per second.
The time interval circuit (shown below the clock) consists of a SET/RESET flipflop made from the two remaining NAND gates (74HCT00). The desired time interval is programmed by connecting the anodes of the six diodes labeled start, stop and AM/PM to the appropriate decoder outputs. For example, to turn the relay on at 7:05AM and turn it off at 8:05AM, you would connect one of the diodes from the start section to the cathode of the LED that represents 7 hours, the second diode to the LED cathode that represents 5 minutes and the third diode to the AM line of the CD4013. The stop time is programmed in the same manner. Two additional push buttons are used to manually open and close the relay. The low start and stop signals at the common cathode connections are capacitively coupled to the NAND gates so that the manual push buttons can override the 5 minute time duration. That way, you can immediately reset the relay without waiting 5 minutes for the start signal to go away.
The two power supply rectifier diodes are 1N400X variety and the switching diodes are 1N914 or 4148s but any general purpose diodes can be used. 0.1 uF caps (not shown on schematic) may be needed near the power pins of each IC. All parts should be available from Radio Shack with the exception of the 74HCT4017 decade counter which I didn't see listed. You can use either 74HC or 74HCT parts, the only difference between the two is that the input switching levels of the HCT devices are compatible with worst case TTL logic outputs. The HC device inputs are set at 50% of Vcc, so they may not work when driven from marginal TTL logic outputs. You can use a regular 4017 in place of the 74HCT4017 but the output current will much lower (less than 1 mA) and 4 additional transistors will be required to drive the LEDs. Without the buffer transistors, you can use a 10K resistor in place of the 330 and the LEDs will be visible, but very dim. Using the 4017 to drive LEDs with transistor buffers is shown in the "10 Channel LED Sequencer" at the top of this page.

Time Interval Relay Circuit for the clock circuit above

Speed-Limit Alert

Tracking Devices

Galaxy 5:50 AM

Speed-limit Alert

Wireless portable unit

Adaptable with most internal combustion engine vehicles

Parts:

R1,R2,R19 1K 1/4W Resistors

R3-R6,R13,R17 100K 1/4W Resistors

R7,R15 1M 1/4W Resistors

R8 50K 1/2W Trimmer Cermet

R9 470R 1/4W Resistor

R10 470K 1/4W Resistor

R11 100K 1/2W Trimmer Cermet (see notes)

R12 220K 1/4W Resistor (see notes)

R14,R16 68K 1/4W Resistors

R18 22K 1/4W Resistor

R20 150R 1/4W Resistor (see notes)

C1,C7 100µF 25V Electrolytic Capacitors

C2,C3 330nF 63V Polyester Capacitors

C4-C6 4µ7 25V Electrolytic Capacitors

D1,D5 Red LEDs 3 or 5mm.

D2,D3 1N4148 75V 150mA Diodes

D4 BZX79C7V5 7.5V 500mW Zener Diode

IC1 CA3140 or TL061 Op-amp IC

IC2 4069 Hex Inverter IC

IC3 4098 or 4528 Dual Monostable Multivibrator IC

Q1,Q2 BC238 25V 100mA NPN Transistors

L1 10mH miniature Inductor (see notes)

BZ1 Piezo sounder (incorporating 3KHz oscillator)

SW1 SPST Slider Switch

B1 9V PP3 Battery (see notes)

Clip for PP3 Battery

Device purpose:

This circuit has been designed to alert the vehicle driver that he has reached the maximum fixed speed limit (i.e. in a motorway). It eliminates the necessity of looking at the tachometer and to be distracted from driving.

There is a strict relation between engine's RPM and vehicle speed, so this device controls RPM, starting to beep and flashing a LED once per second, when maximum fixed speed is reached.

Its outstanding feature lies in the fact that no connection is required from circuit to engine.

Circuit operation:

IC1 forms a differential amplifier for the electromagnetic pulses generated by the engine sparking-plugs, picked-up by sensor coil L1. IC2A further amplifies the pulses and IC2B to IC2F inverters provide clean pulse squaring. The monostable multivibrator IC3A is used as a frequency discriminator, its pin 6 going firmly high when speed limit (settled by R11) is reached. IC3B, the transistors and associate components provide timings for the signaling part, formed by LED D5 and piezo sounder BZ1. D3 introduces a small amount of hysteresis.

Notes:

D1 is necessary at set-up to monitor the sparking-plugs emission, thus permitting to find easily the best placement for the device on the dashboard or close to it. After the setting is done, D1 & R9 can be omitted or switched-off, with battery saving.

During the preceding operation R8 must be adjusted for better results. The best setting of this trimmer is usually obtained when its value lies between 10 and 20K.

You must do this first setting when the engine is on but the vehicle is stationary.

The final simplest setting can be made with the help of a second person. Drive the vehicle and reach the speed needed. The helper must adjust the trimmer R11 until the device operates the beeper and D5. Reducing car's speed the beep must stop.

L1 can be a 10mH small inductor usually sold in the form of a tiny rectangular plastic box. If you need an higher sensitivity you can build a special coil, winding 130 to 150 turns of 0.2 mm. enameled wire on a 5 cm. diameter former (e.g. a can). Extract the coil from the former and tape it with insulating tape making thus a stand-alone coil.

Circuit's current drawing is approx. 10mA. If you intend to use the car's 12V battery, you can connect the device to the lighter socket. In this case R20 must be 330R.

Depending on the engine's cylinders number, R11 can be unable to set the device properly. In some cases you must use R11=200K and R12=100K or less.

If you need to set-up the device on the bench, a sine or square wave variable generator is required.

To calculate the frequency relation to RPM in a four strokes engine you can use the following formula:

Hz= (Number of cylinders * RPM) / 120.

For a two strokes engine the formula is: Hz= (Number of cylinders * RPM) / 60.

Thus, for a car with a four strokes engine and four cylinders the resulting frequency @ 3000 RPM is 100Hz.

Temporarily disconnect C2 from IC1's pin 6. Connect the generator's output to C2 and Ground. Set the generator's frequency to i.e. 100Hz and regulate R11 until you hear the beeps and LED D5 flashes. Reducing the frequency to 99 or 98 Hz, beeping and flashing must stop.

This circuit is not suited to Diesel engines.

Soft Musical Telephone Ringer

Tele-phone

Galaxy 8:09 AM

Soft Musical Telephone Ringer

The normal telephone bell, at times (specially during night when one does not want to be disturbed), appears to be quite irritating. The circuit shown here converts the loud sounding bell into a soft and pleasing musical tone.

The incoming ring is detected by transistor T1 and components wired around it. In absence of ringing voltage, transistor T1 is cut off while transistor T2 is forward biased as resistor R2 is returned to the positive supply rails. As a result collector of transistor T2 is at near-ground potential and hence IC1 (UM66) is off. Also capacitor C2 is charged to a slightly positive potential.

During positive half of the ringing voltage, diode D1 forward biases transistor T1 and rapidly discharges capacitor C2 to near ground potential and cuts off transistor T2 which, in turn, causes IC1 to be forward biased and music signal is applied to base of transistor T3 which drives the speaker. During negative half of the ringing voltage, capacitor C2 cannot charge rapidly via resistor R2 and hence transistor T2 remains cut off during the ringing interval. Thus the soft musical note into the loudspeaker sounds in synchronism with the ringing signal. When handset is lifted off the cradle, the ringing voltage is no more available and hence the soft musical note switches off

Telephone amplifier

Tele-phone

Galaxy 8:03 AM

Telephone amplifier

While talking to a distant subscriber on telephone, quite often we feel frustrated when the voice of the distant subscriber is so faint that it is barely intelligible. To overcome the problem, circuit of an inexpensive amplifier is presented here. It can be assembled and tested easily. There is no extra power source needed to power up the circuit, as it draws power from the telephone line itself. The amplifier will provide fairly good volume for the telephone conversation to be properly heard in a living room. A volume control is included to adjust the volume as desired.

The circuit is built around IC LM386. Diodes D6 and D7 are used to limit the input signal strength. Transformer X1 is a transistor radio's output transformer used in reverse. Asoriginal secondary (output) winding is connected in series with the telephone lines, the speech signals passing through the lines cause change in the magnetic flux in the core of transformer and thereby induce signal voltage across the primary winding. This audio signal is used as input for IC LM386. Diodes D2 through D5 connected in bridge configuration constitute a polarity guard so that the amplifier is powered with correct polarity, irrespective of the line polarity, Zener diode D1 may have any breakdown voltage between 6 and 12 volts range. e.

There is no need of a separate power switch as the circuit energises (via the normally open contacts of the cradle switch) when one lifts the handset.

The circuit may be wired on a general-purpose PCB or by etching a PCB for this circuit.

The circuit can be easily tested by connecting a 6 volts supply to line terminals 1 and 2. A hissing sound will be heard from the loudspeaker. Now connect 6V AC from a transformer to terminals 1 and 2 and observe hum in the loudspeaker. The volume of the hum can be changed through potentiometer VR1. Diodes D6 and D7 limit the input below ± 700 mV.

The circuit is to be connected to the telephone lines in series with the telephone instrument, as shown in the figure

Dark-activated LED or Lamp Flasher

Sensor Powered

Galaxy 7:59 AM

Dark-activated LED or Lamp Flasher

Simple photo-sensitive circuit
3V battery supply

Parts:
R1 Photo resistor (any type)
R2 100K 1/2W Trimmer Cermet
R3,R4 10K 1/4W Resistors
R5 470R 1/4W Resistor
R6 47R 1/4W Resistor
C1 220µF 25V Electrolytic Capacitor
D1 1N4148 75V 150mA Diode
D2 LED Any type and color (See Notes)
Q1,Q2 BC337 45V 800mA NPN Transistors
SW1 SPST Switch
B1 3V (Two 1.5V AA or AAA cells in series, etc.)

Circuit operation:
This circuit adopts the rather unusual Bowes/White emitter coupled multivibrator circuit. The oscillation frequency is about 1Hz and is set by C1 value. The LED starts flashing when the photo resistor is scarcely illuminated. The onset of flashing can be set by trimming R2.

Notes:
Best results in flashing frequency can be obtained using for C1 a value in the 100 to 1000µF range.
To drive a filament lamp the following changes must be made:
Use a 2.2 to 3V, 250-300mA lamp in place of the LED
R2 = 10K 1/2W Trimmer Cermet
R3, R4 = 1K 1/4W Resistors
R6 = 1R 1/4W Resistor
C1 = 470 to 1000µF 25V Electrolytic Capacitor
In LED-mode operation the stand-by current consumption is less than 400µA.
In Lamp-mode operation the stand-by current consumption is about 3mA.

Touch Sense Door Alarm

Sensor Powered

Galaxy 7:53 AM

Touch Sense Door Alarm

Hangs up on the door-handle

Beeps when someone touches the door-handle from outside

Parts:

R1 1M 1/4W Resistor

R2 3K3 1 or 2W Resistor (See Notes)

R3 10K 1/2W Trimmer Cermet (See Notes)

R4 33K 1/4W Resistor

R5 150K 1/4W Resistor

R6 2K2 1/4W Resistor

R7 22K 1/4W Resistor

R8 4K7 1/4W Resistor

C1,C2 10nF 63V Ceramic or Polyester Capacitors

C3 10pF 63V Ceramic Capacitor

C4,C6 100nF 63V Ceramic or Polyester Capacitors

C5 2µ2 25V Electrolytic Capacitor

C7 100µF 25V Electrolytic Capacitor

D1,D2,D4 1N4148 75V 150mA Diodes

D3 5 or 3mm. Red LED

Q1,Q2,Q3,Q5 BC547 45V 100mA NPN Transistors

Q4 BC557 45V 100mA PNP Transistor

L1 (See Notes)

L2 10mH miniature Inductor

Hook (See Notes)

BZ1 Piezo sounder (incorporating 3KHz oscillator)

SW1,SW2 SPST miniature Slider Switches

B1 9V PP3 Battery

Clip for PP3 Battery

Device purpose:

This circuit emits a beep and/or illuminates a LED when someone touches the door-handle from outside. The alarm will sound until the circuit will be switched-off.

The entire circuit is enclosed in a small plastic or wooden box and should be hanged-up to the door-handle by means of a thick wire hook protruding from the top of the case.

A wide-range sensitivity control allows the use of the Door Alarm over a wide variety of door types, handles and locks. The device had proven reliable even when part of the lock comes in contact with the wall (bricks, stones, reinforced concrete), but doesn't work with all-metal doors.

The LED is very helpful at setup.

Circuit operation:

Q1 forms a free-running oscillator: its output bursts drive Q2 into saturation, so Q3 and the LED are off. When part of a human body comes in contact with a metal handle electrically connected to the wire hook, the body capacitance damps Q1 oscillations, Q2 biasing falls off and the transistor becomes non conducting. Therefore, current can flow into Q3 base and D3 illuminates. If SW1 is closed, a self-latching circuit formed by Q4 & Q5 is triggered and the beeper BZ1 is activated.

When the human body part leaves the handle, the LED switches-off but the beeper continues to sound, due to the self-latching behavior of Q4 & Q5. To stop the beeper action, the entire circuit must be switched-off opening SW2.

R3 is the sensitivity control, allowing to cope with a wide variety of door types, handles and locks.

Notes:

L1 is formed winding 20 to 30 turns of 0.4mm. diameter enameled copper wire on R2 body and soldering the coil ends to the resistor leads. You should fill R2 body completely with coil winding: the final turn's number can vary slightly, depending on different 1 or 2W resistor types actual length (mean dimensions for these components are 13-18mm. length and 5-6mm. diameter).

The hook is made from non-insulated wire 1 - 2mm. diameter (brass is well suited). Its length can vary from about 5 to 10cm. (not critical).

If the device is moved frequently to different doors, Trimmer R3 can be substituted by a common linear potentiometer fitted with outer knob for easy setup.

To setup the device hang-up the hook to the door-handle (with the door closed), open SW1 and switch-on the circuit. Adjust R3 until the LED illuminates, then turn slowly backwards the screwdriver (or the knob) until the LED is completely off. At this point, touching the door-handle with your hand the LED should illuminate, going off when the hand is withdrawn. Finally, close SW1 and the beeper will sound when the door-handle will be touched again, but won't stop until SW2 is opened.

In regular use, it is advisable to hang-up and power-on the device with SW1 open: when all is well settled, SW1 can be closed. This precautionary measure is necessary to avoid unwanted triggering of the beeper.