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This infrared object counter can be installed at the entry gate to count the total number of people entering any venue. For example, it can be used at the railway stations or bus stands to count the people arriving per day or week.

The counter uses an infrared transmitter-receiver pair and a simple, low-cost calculator. It works even in the presence of normal light. The maximum detection range is about 10 metres. That means the transmitter and the receiver are to be installed (at the opposite pillars of the gate) not more than 10 metres apart. No focusing lens is required. If an 8-digit calculator is used the counter can count up to 99,999,999 easily, and if a 10-digit calculator is used the counter can count up to 9,999,999,999.

Powered by a 9V battery, the transmitter circuit (see Fig. 1) comprises IC 555 (IC1), which is wired as an astable multivibrator with a centre frequency of about 38 kHz, and two infrared light-emitting diodes (LEDs). The receiver circuit (see Fig. 2) is powered by a 5V regulated power supply built around transformer X1, bridge rectifier comprising diodes D1 through D4 and regulator IC2. It uses an infrared receiver (IR) module (RX1), optocoupler (IC3) and a simple calculator.

When switch S1 is in ‘on’ position, the transmitter circuit activates to produce a square wave at its output pin 3. The two infrared LEDs (IR LED1 and IR LED2) connected at its output transmit modulated IR beams at the same frequency (38 kHz). The oscillator frequency can be adjusted using preset VR1.

In the receiver circuit, IR receiver module TSOP1738, which is commonly used in colour televisions for sensing the IR signals transmitted from the TV remote, is used as the sensor.

The IR beams transmitted by IR LED1 and LED2 fall on infrared receiver module IR RX1 of the receiver circuit to produce a low output at its pin 2. This keeps transistor T1 in non-conduction mode.

Now when anyone enters through the gate to interrupt the IR beam, the IR receiver module produces a high output pulse at its pin 3. As a result, transistor T1 conducts to activate IC3 and its internal transistor shorts key ‘=’ of the calculator to advance the count by one.

Both the transmitter and the receiver can be assembled on any general-purpose PCB. Place the transmitter and the receiver around one metre apart.

For calibration, press switches S1 and S2 followed by ‘on’ key of the calculator. Now press ‘1’ and ‘+’ keys sequentially to get ‘1’ on the screen of the calculator. Then, place a piece of cardboard between the transmitter and the receiver to interrupt the IR rays two times. If the calculator counts ‘2,’ the counter is working properly for that range. Repeat this procedure for higher ranges as well. If there is any problem, adjust VR1.

For installation, switch off the transmitter, receiver and calculator, and mount the transmitter and the receiver on the opposite pillars of the main entry gate such that they are properly orientated towards each other. Mount the calculator where you can read it easily. Connect pins 4 and 5 of IC3 across ‘=’ key connections on the PCB of the calculator.

Now switch on the transmitter and the receiver by pressing switches S1 and S2, respectively. Thereafter, switch on the calculator and press ‘1’ followed by ‘+’ key of the calculator to initialise it. Now your counter is ready to count.

The calculator reads ‘1’ after one interruption, ‘2’ after second interruption and so on.

Sourced By : EFY Author  Rambir Singh

Build a Simple Digital Electronic Lock Circuit Diagram. This is a Build a Simple Digital Electronic Lock Circuit Diagram. The digital lock shown below uses 4 common logic ICs to allow controlling a relay by entering a 4 digit number on a keypad. The first 4 outputs from the CD4017 decade counter (pins 3,2,4,7) are gated together with 4 digits from a keypad so that as the keys are depressed in the correct order, the counter will advance.

Simple Digital Electronic Lock Circuit Diagram

As each correct key is pressed, a low level appears at the output of the dual NAND gate producing a high level at the output of the 8 input NAND at pin 13. The momentary high level from pin 13 activates a one shot circuit which applies an approximate 80 millisecond positive going pulse to the clock line (pin 14) of the decade counter which advances it one count on the rising edge.

A second monostable, one shot circuit is used to generate an approximate 40 millisecond positive going pulse which is applied to the common point of the keypad so that the appropriate NAND gate will see two logic high levels when the correct key is pressed (one from the counter and the other from the key). The inverted clock pulse (negative going) at pin 12 of the 74C14 and the positive going keypad pulse at pin 6 are gated together using two diodes as an AND gate (shown in lower right corner). The output at the junction of the diodes will be positive in the event a wrong key is pressed and will reset the counter.

When a correct key is pressed, outputs will be present from both monostable circuits (clock and keypad) causing the reset line to remain low and allowing the counter to advance. However, since the keypad pulse begins slightly before the clock, a 0.1uF capacitor is connected to the reset line to delay the reset until the inverted clock arrives. The values are not critical and various other timing schemes could be used but the clock signal should be slightly longer than the keypad pulse so that the clock signal can mask out the keypad and avoid resetting the counter in the event the clock pulse ends before the keypad pulse.

The fifth output of the counter is on pin 10, so that after four correct key entries have been made, pin 10 will move to a high level and can be used to activate a relay, illuminate an LED, ect. At this point, the lock can be reset simply by pressing any key.

The circuit can be extended with additional gates (one more CD4011) to accept up to a 8 digit code. The 4017 counting order is 3 2 4 7 10 1 5 6 9 11 so that the first 8 outputs are connected to the NAND gates and pin 9 would be used to drive the relay or light. The 4 additional NAND gate outputs would connect to the 4 remaining inputs of the CD4068 (pins 9,10,11,12). The circuit will operate from 3 to 12 volts on 4000 series CMOS but only 6 volts or less if 74HC parts are used. The circuit draws very little current (about 165 microamps) so it could be powered for several months on 4 AA batteries assuming only intermittent use of the relay.

 
In the last few years, the available range of operating systems for PCs  has increased dramatically. Various free (!) operating systems have been  added to the list, such as BeOS, OpenBSD and Linux. These systems are  also available in different colours and flavours (versions and  distributions). Windows is also no longer simply Windows, because there  are now several different versions (Windows 95, 98, ME, NT, XP, Vista  and 7). Computer users thus have a large variety of options with regard  to the operating system to be used. One problem is that not all hardware  works equally well under the various operating systems, and with regard  to software, compatibility is far from being universal. In other words,  it’s difficult to make a good choice.

Hard Disk Selector Circuit Diagram

Switching from one operating system to another - that’s a risky business, isn’t it? Although this may be a bit of an exaggeration, the safest approach is still to install two different operating systems on the same PC, so you can always easily use the ‘old’ operating system if the new one fails to meet your needs (or suit your taste). A software solution is often used for such a ‘dual system’. A program called a ‘boot manager’ can be used to allow the user to choose, during the start-up process, which hard disk will be used for starting up the computer. Unfortunately, this does not always work flawlessly, and in most cases this boot manager is replaced by the standard boot loader of the operating system when a new operating system is installed.

In many cases, the only remedy is to reinstall the software. The solution presented here does not suffer from this problem. It is a hardware solution that causes the primary and secondary hard disk drives to ‘swap places’ when the computer is started up, if so desired. From the perspective of the computer (and the software running on the computer), it appears as though these two hard disks have actually changed places. This trick is made possible by a feature of the IDE specification called ‘CableSelect’. Every IDE hard disk can be configured to use either Master/Slave or CableSelect. In the latter case, a signal on the IDE cable tells the hard disk whether it is to act as the master or slave device. For this reason, in every IDE cable one lead is interrupted between the connectors for the two disk drives, or the relevant pin is omitted from the connector.

This  causes a low level to be present on the CS pin of one of the drives and  a high level to be present on the CS pin of the other one (at the far  end of the cable). The circuit shown here is connected to the IDE bus of  the motherboard via connector K1. Most of the signals are fed directly  from K1 to the other connectors (K2 and K3). An IDE hard disk is  connected to K2, and a second one is connected to K3. When the computer  is switched on or reset, a pulse will appear on the RESET line of the  IDE interface. This pulse clocks flip-flop IC1a, and depending on the  state of switch S1, the Q output will go either high or low. The state  on the Q output is naturally always the opposite of that on the Q  output. If we assume that the switch is closed during start-up, a low  level will be present on D input of IC1a, so the Q output will be low  following the reset pulse.