Swith For diagram

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5 74HC148 to allow expansion of the end of Gs, respectively, received the sixth piece of 74HC148 low slices to a high order of the film I 0, I 1, I 2, the I 3 I 4 input, I 5, I 6 I 7 end is connected to high (no input), so the sixth three-chip 74HC148 output would mean that the 40-6 line priority encoder of three the A5. A4, A3. 40-6 line priority encoder low three output A2, A1, A0 5 74HC148 output terminal. 74HC148s output is not tri-state gate, can not be directly connected together. 5 74HC148 output of the same name received 74LS30 (8-input NAND gate) can be taken with non-solve this problem. The good service of  cell phone jammers  can be got with the lowest cost.
Terminal expansion, and 2051 less than the 89C51 P0 and P2, input / output port and an external ROM, the RAM in the pin 2051 is only 20 feet. AT89C2051 microcontroller is mainly applicable to relatively simple micro-control system. In this system, used in the AT89C2051 the six external I / O port, an external interrupts and serial output port. 12 Hangzhou University of Electronic Science and Technology graduate design 4-92051 signal pin Figure 4.5-level translation in the different digital systems, the level of the standard is different. The system includes a TTL level standard and RS-232 level standards, to achieve two standard normal communication, the need for level conversion. The harmonious production environment of  cell phone jammers  is necessary.cell phone jammers for the star gazing has very high requirement
Can guarantee the quality of training and reducing the consumption of ammunition is the ideal of public security, military and other departments trained to use the analog targeting system. The laser targeting system overview of the laser targeting system [1-3] works by using laser pulses to simulate the firing of bullets, the system generally includes a laser transmitter and laser signal detection module, shooting performance and display parts. Shown in Figure 2-1, when the shooter aimed at the completion of the pull the trigger, the semiconductor laser emits laser pulses fired at the target on the photodetector, if you hit the target, the laser pulse photodetector receiver and converted to electric signal processing circuit can identify the point of impact of the shooting, transfer to your computer encoded signal is processed.

More and more equipment is sold that runs off internal rechargeable batteries. Although a matching charger is usually supplied in the package, there are also devices that can only be charged via a USB port. That is not surprising in the case of USB MP3 players, which have to ‘dock’ in the PC anyway for some time for the purpose of file transferring. Still, the same ‘feature’ can be a serious disadvantage, for example, on ‘computer-free’ holidays. Sometimes it makes you wonder how simple the solutions to such problems actually turn out to be. After all, if it’s just a supply voltage we’re after, then a USB port is easily imitated.

The circuit shown here is nothing but a 7805 in a dead standard configuration. The innovation, if any, might be USB connector to which the MP3 player can be connected. The 7805 comes in different flavours most devices can supply 1 A, but there are also more advanced variants that achieve up to 1.5 A. Because a USB device is never allowed to draw more than 500 mA from the port it is plugged into, the circuit shown here should be able to supply charging and/or operating current to up to two (or three) USB devices at the same time. The input voltage may be a direct voltage of anything between 7 and 24 volts, so for use at home or abroad a simple wall cube with DC output is sufficient.

Circuit diagram:
Another useful bit to make yourself might be a cable with an inline fuse and a cigarette lighter plug so you can tap into a vehicle supply (note that this may be up to 14.4 V with a running engine). At an output current of 1 A and an input voltage of just 7 V, the 7805 already dissipates 2 watts. Assuming you’re using the most commonly seen version of the 7805, the TO-220 case with its metal tab will have a thermal resistance of about 50 °C/W. Also assuming that the ambient temperature is 20 °C, the 7805’s internal (chip) temperature will be around 120 °C. In most cases, 150 °C is the specified maximum, so ample cooling must be provided especially in a car and with relatively high input voltages.

Dynamic flip-flops ignore pulses at their inputs that are shorter than 40 ns or do not have TTL levels. This means that TTL flip-flops are poorly suited to capturing noise pulses having unknown durations and magnitudes. Anyone who has ever tried to observe very short laser pulses (15–25 ns) is familiar with this problem. By contrast, this circuit can detect impulses with widths less than 8 ns and amplitudes between +100 mV and +5 V. The heart of this circuit is formed by a MAX903, a very fast comparator with internal memory. The IC has separate supply pins for its analogue and digital portions. The analogue portion is powered by a symmetrical ±5-V supply.

This allows the detector to also handle input voltages that are negative relative to ground. The internal memory and output stage operate from a single-ended +5-V supply, so the output signal has proper TTL levels. The MAX903 (IC1) has a special internal memory circuit (latch). The latch either connects the output of the internal comparator directly to the signal output or stores the most recent TTL level and blocks the output of the internal comparator, causing the most recent TTL level appears at the output. This allows short input pulses to be stretched to any desired length. Despite its extremely short switching times, the MAX903 consumes only a modest 18 mW.

In the quiescent state, the voltage on the Latch input (pin 5) is at 1.75 V. This reference voltage is provided by LED D1, which draws its current via R2. In this state the latch is transparent, and a positive edge at the input appears will appear as a negative transition on the output after a propagation delay of 8 ns (tPD). This only happens if the peak voltage on the input is more positive than ground potential. C1 passes this change in the output voltage level to the Latch input (pin 5). As soon as the voltage on the Latch input drops below 1.4 V, the internal latch switches to the Hold state. In this state, the output is no longer connected to the comparator, and the output remains low for the duration of the latch hold time, regardless of what happens with the input signal.

The latch hold time is determined by the time constant of the C3/R1 network; it has an adjustment range of 100–500 ns. Pulses of this length can be readily observed using practically any oscilloscope. This latch function in this circuit is only triggered if the input signal has a rising edge that crosses the zero-voltage level. The internal latch remains transparent for signals in the range of –5 V to 0 V, so such pulses will not be stretched. If only positive input voltages are anticipated, the negative supply voltage is not necessary and the circuit can be powered from a single +5-V supply. A fast circuit such as this requires a carefully designed circuit board layout. All connections to the IC must be kept very short.

Decoupling capacitors C1 and C2 should preferably be placed immediately adjacent to the supply pins. Pin 3 of the IC can be bent upward and soldered directly to a length of coax or twisted-pair cable (air is still the best insulator). If a coax cable is used, the unbraided screen must not be formed into a long pigtail. It’s better to peel back a short length of the screen, wrap a length of bare wire around it and solder it directly to the ground plane. The supply traces for the analogue and digital portions must be well separated from each other, and each supply must be well decoupled, even if only a single supply voltage (+5 V) is used. The preferred solution is to use two independent voltage regulators.

This power indicator circuit is intended to be used as an extension for the water softener. It might be easier to just place a LED but it is better to make a rectifier that detects the presence of the 15 kHz signal generated by the 555 IC.

Water Softener Power Indicator Schematic

The rectifier is connected at the water softener system with C4 capacitor. D1 and D2 diodes are used to obtain a DC voltage that is filtered by C5 capacitor. This voltage turns ON the FET that lights up the LED. When there is no signal from the oscillator the LED will not glow. D1 and D2 = 1N4148.

Portable radios, CD-players and cassette recorders that can also be operated from mains power often do not have a mains power switch, but instead are switched off on the ‘DC side’. This means that the power supply is permanently connected to the mains network if the mains cable is not unplugged. The situation with equipment requiring a mains adapter is similar. This is not ideal for the environment or for your pocketbook. The following circuit allows power to be switched on manually and switched off automatically, directly at the equipment. Optoelectronic isolation between the mains voltage and the switching stage ensures continued compliance with safety regulations.


Switching on:

The circuit consists of the switch-on stage T1 and the hold-on and switch-off stage T2/T3. Both stages drive the power switch, which is implemented using a semiconductor relay (IC1). The voltage from the two button cells (2–3 V) is connected to the LED of the semiconductor relay by pressing push-button switch S1. R1 allows a diode current of around 10mA to flow. At the same time, T1 prevents a ‘charging current’ from flowing into the batteries when the semiconductor relay that switches the mains voltage is energized by T2. Although such a current can only flow while the push-button is pressed, this possibility must be taken into account for safety reasons.

Circuit diagram:


When the LED of the semiconductor relay is energized by the battery current, the triac connects the mains voltage to the transformer of the power supply. The DC voltage provided to the load is twice reduced by 0.65 V by diodes D2 and D3. This threshold voltage, smoothed by C1, provides a base current for T3, which drives T2 into conduction. T2 in turn supplies current via R2 to LED D1 and the LED in IC1. R2 must be matched to the DC voltage of the equipment to allow a LED current of 10mA to flow. As long as the push-button is pressed, two LED currents flow, and together they should not amount to more than 20mA in order to avoid destroying the LED in IC1.


Switching off:

The voltage drop across D2 and D3 is only present if a current drawn by the connected equipment flows from the output of the circuit. If this current is interrupted by switching off the equipment, T3 and T2 will be cut off. The semiconductor relay will then open, and the mains voltage will be switched off. This switch-off process is delayed by capacitor C1, so that (for example) you can exchange an audio cassette without causing the recorder to be disconnected from the mains. For the semiconductor relay, you should select a type having a zero-crossing switch. This means that the triac will only switch on at the zero point of the mains voltage, regardless of when the push-button is pressed.

Almost no current will thus flow at the instant when the triac switches, which prevents inductive switching spikes and associated interference. The S201S01 semiconductor relay used here can switch currents up to 8 A (continuous) or 80 A (single-cycle peak). Figure 2 shows how to connect the circuit between the power supply and the charging capacitor. When laying out the circuit board, ensure that all components carrying mains voltage are separated from each other by at least 3 mm and from the low-voltage area by at least 6 mm. Naturally, the same considerations apply to fitting the circuit board into the equipment to be switched. If there is not sufficient space inside the equipment, the circuit can be fitted between the equipment and the mains adapter as a sort of cable switch.

Timer IC 555 multipurpose has habit to emerge in so many various wide circuits. Because of this is very useful small components, hence this component becomes very popular in the last few years. Though IC 555 in general hardly relied on, but sometimes happened also error. Circuit designed here will give way of simple and effective to do assaying of damage component. The timer which wish to be tested ( 555), connected as multivibrators is unstable (free running). If nipple SW1 is depressed closed, hence condenser C1 will start loaded [by] through preventive reactor R1 and R2. Soon after strain level at this condenser reach point of timer launch, hence internal of flip-flop will be moved and pin 7 is degraded its the strain to empty C1.

Reset flip-flop when strain C1 reachs threshold level IC. This thing causes boosts pin 7 and impregnation cycle starts again. Output timer (pin3) attributed to a couple of LED. If high output of LED D2 will on and D1 will turn off. On the contrary, when low output of D1 will on and D2 is off. LED will wink if IC in good condition.

For reader having other application and wish to change its (the frequency, hence speed of LED is determined the value by value from R1, R2, and C1. Frequency countable oscillation passed formula:

If R2 far bigger than R1, hence its the frequency can be estimated from formula following:

Value to showed in circuit, oscillation frequency around 0,5 Hz. Test device can be designed considerably compact with soldering all components directly at test collar IC, firstly is attached through aperture at hole surface of box device which will be used. In rotation, all components can be attached at as of slab PCB. Usage of current a minimum and can be supplied from a battery 9V.

You may have read about cycling NiCad batteries. If not, read a little here ( Reds R/C Battery Clinic) for an excellent overview. Overcharging apparently leads to voltage depression, which can be corrected by one or two complete discharges (to 1 to 1.1 volts per cell). On the other hand, over discharging the batteries to a low or zero voltage can damage them, and if the batteries have not been overcharged and have no voltage depression, cycling just uses up regular battery life. I designed and use this discharger occasionally to remove voltage depression and insure battery capacity is still ok for those planes that have no low voltage alarm.

Note that the 100 ohm resistors are 1/2 watt (these are the load resistors), the rest are 1/4 watt. The red LED lights while discharging, buzzer sounds and discharge rate drops to 15-25mA (for the buzzer) when complete. The discharge load is 60mA to 110mA depending on the battery voltage. Since thats about the same current draw as my Hitec receiver and two HS-80s draw while flying handlaunch, I can use discharge time almost directly to indicate flying time. The buzzer uses enough current to keep a 150mA battery down, but when discharging a 600mA battery, the battery recovers quickly when the load is removed--the buzzer/discharger cycles on and off. Threshold voltage of the discharger is set to 4.2 volts. Since the discharger still draws some current when buzzing, try to disconnect the discharger once the alarm sounds--dont leave it going for hours lest the battery be over discharged.

There are a couple ways you could modify the circuit to work with a 5-cell 6-volt receiver battery pack. The two 1k resistors are a divider network, so one way would be to change the resistors to change the sampling voltage at the comparator. The formula for a divider network is Vout=Vin(R2/(R1+R2)) or R1=R2*((Vin/Vout)-1). Here, R1 is the resistor connected to the positive lead and pin 7 of the comparator, Vin is 5.25 volts (1.05 volts per cell discharge shutoff threshold), and Vout is the reference 2.1 volts (the voltage produced by the LM317T and the 180 and 270 ohm resistors). You can use R2 as the same 1k value that was there before. So R1=1000*((5.25/2.1)-1)=1500=1.5k. So swap the top 1k resistor in the schematic for a 1.5k, and the new shutoff voltage for your device will be 5.25 volts.

To increase the discharge rate, decrease the resistance of the load resistors. You could use four 100 ohm resistors in parallel instead of two, for example, and it would discharge twice as fast. Resistance of a number of resistors in parallel is the value of the resistor devided by the number of the resistors. Here, 100 ohms/ four resistors is 25 ohms. At five volts, current is (5 volts)/(25 ohms)=0.2 ampere or 200mA. Be careful not to decrease resistance too much however--the small signal transistor used in this particular circuit is probably only rated for maximum 500 mA.

Circuit diagram :

Parts:
273-074 Miniature Piezo Buzzer, 12v, PC board mount
271-312 1/4 watt 5% carbon film resistors, 500 pieces (Just do it!)
276-1778 LM317T adjustable voltage regulator
276-1712 Quad comparator LM339
276-1622 LED assortment (20 count)
276-2009 NPN Silicon transistor MPS2222A (2N2222)

Custom electronics:
I post this design not because I think this is a brilliant piece of circuit design but because the design works, and it can give you a start on your own experimentation. The idea is to use the power available from the discharging battery to monitor the voltage of the battery, shut off discharging at a preset voltage (here 1.05 volts/cell), and sound an alarm when discharging is complete. To do so means a voltage reference powered by the changing voltage of the battery, here the LM317T and the 180 with 270 ohm resistors. You could just as easily use a LM336 (see the low voltage warning buzzer page) or a zener with resistor, or something else as a reference. Since the reference voltage must be below the ambient battery voltage, a pair of 1k resistors provides the divided test voltage. The LM339 is a four way comparator.
This design uses really three comparators: in addition to the one driving the transistor, a comparator drives the LED and another drives the buzzer. But you could use a single comparator (like the LM311) with the buzzer across the emitter and collector of the transistor, and the LED in series with a 270 ohm resistor across (parallel with) the 100 ohm load resistors. With the transistor conducting, the voltage drop across base and emitter is low, and the buzzer is quiet. The tiny current in a piezo buzzer (7 mA), when the transistor is not conducting, would be divided between the load resistors and the LED, and the LED is dark.
A word about the comparator. The output of the comparator serves as a meager source of current, but can sink current nicely. In other words, the high logic output of the comparator will not drive the base of a NPN transistor as here. The 560 ohm resistor provides the current here for the transistor base--the comparator takes it away when its output drops to ground. Hmmm . . . . so, maybe use a PNP transistor like a 2N3906 instead with emitter to + and collector to load, remove the 560 resistor and connect the base through a 1k resistor to the output of the comparator, then reverse the logic of the comparator by swapping the reference with the test. . . hmmmmm. Could work. Yep . . . works.

Source : electronic