Mutchus

A 4-Digit Keypad Controller Switch Circuit This is a universal version of the Four-Digit Alarm Keypad . I have modified the design to free up the relay contacts. This allows the circuit to operate as a general-purpose switch. It also means that it can be used to control all of my Alarm Circuits. I've used a SPCO/SPDT relay - but you can use a multi-pole relay if you wish. The relay is energized by pressing a single key. Choose the key you want to use - and connect it to terminal "E". Choose the four keys you want to use to de-energize the relay - and connect them to "A B C & D". Wire the common to R1 and all the remaining keys to "F". The Circuit is easy to use. When you press "E" - current through D2 & R9 turns Q6 on - and energizes the relay. The two transistors - Q5 & Q6 - form a "Complementary Latch". So - when you release the key - the relay will remain energized. To de-energize the relay - you need to press keys ...

Overview: The TB2904H (o) is 4-ch BTL audio amplifier for car audio applications.  This IC can generate higher power: POUT MAX = 43 W as it includes the pure complementary P-ch and N-ch DMOS output stage. It is designed to yield low distortion ratio for 4-ch BTL audio power amplifier, built-in standby function, muting function, and various kinds of protectors.  Circuit Diagram: Circuit diagram for  43 W BTL × 4-ch Audio Power IC Datasheet for TB2904H:  Download

The HA13151/HA13152 are high output and low distortion 4 ch BTL power IC designed for digital car audio. At 13.2 V to 4 W load, this power IC provides output power 14 W with 10% distortion. Circuit Diagram: 14 W 4-Channel Audio Amplifier Datasheet for HA13151: Download

The operation of the converter is based on the weighted adding and transferring of the analogue input levels and the digital output levels. It consists of comparators and resistors. In theory, the number of bits is unlimited, but each bit needs a comparator and several coupling resistors. The diagram shows a 4-bit version. The value of the resistors must meet the following criteria: R1:R2 = 1:2; R3:R4:R5 = 1:2:4; R6:R7:R8:R9 = 1:2:4:8. The linearity of the converter depends on the degree of precision of the value of the resistors with respect to the resolution of the converter, and on the accuracy of the threshold voltage of the comparators. This threshold level must be equal, or nearly so, to half the supply voltage. Moreover, the comparators must have as low an output resistance as possible and as high an input resistance with respect to the load resistors as feasible. Any deviation from these requirements affects the linearity of the converter adversely. 4-Bit Analogue to Digital Co...

Apple finally launched iPhone 5, 2012’s most awaited gadget, at a highly anticipated event in San Francisco. The iPhone 5 is 18% thinner and 20% lighter than the iPhone 4S. It is the thinnest smartphone in the world with a casing made from glass and aluminium, according to Apple. iPhone 5 will run on Apple’s new operating software iOS 6. With a four-inch Retina Display screen, the iPhone 5 allows for five rows of apps — one more than previous versions of the device, which sported a 3.5-inch screen. Apple iPhone 5 features a retina display and the screen will have a 1136 x 640 screen resolution, with a 16:9 aspect ratio. Apple has also unveiled a brand new chipset for the iPhone 5: the quad-core Cortex A6 processor, which Schiller says is a full two times faster than the A5 chip in the iPhone 4S. There are also now three microphones in the mix: one on the front, one on the back, and another on the bottom. It sports an 8MP rear camera with panorama mode, backside illumination, hybrid IR ...

Component value sensitivity is extremely critical, as are temperature coefficients and matching of the components. Best performance is attained when perfectly matched components are used and when the gain of the amplifier is unity. 4.5 Mhz Notch Filter Schematic To illustrate, the quality factor Q is very high as amplifier gain approaches 1 with all components matched (in fact, theoretically it approaches infinity) but decreases to about 12.5 with the amplifier gain at 0.98.

This circuit provides an FM modulated signal with an output power of around 500mW. The input Mic preamp is built around a couple of 2N3904 transistors, audio gain limited by the 5k preset. The oscillator is a colpitts stage, frequency of oscillation governed by the tank circuit made from two 5pF capacitors and the inductor. ( Click here for Colpitt Oscillator Resonant Frequency Equation.) Frequency is around 100Mhz with values shown. 4 Transistor Transmitter Circuit Diagram Audio modulation is fed into the tank circuit via the 5p capacitor, the 10k resistor and 1N4002 controlling the amount of modulation. The oscillator output is fed into the 3.9uH inductor which will have a high impedance at RF frequencies. The output stage operates as a class D amplifier, no direct bias is applied but the RF signal developed across the 3.9uH inductor is sufficient to drive this stage. The emitter resistor and 1k base resistor prevent instability and thermal runaway in this stage.

LCD Module in 4-bit Mode Circuit diagram. In many projects use is made of alphanumeric LCDs that are driven internally by Hitachi’s industry-standard HD44780 controller. These displays can be driven either in 4-bit or 8-bit mode. In the first case only the high nibble (D4 to D7) of the display’s data bus is used. The four unused connections still deserve some closer attention. The data lines can be used as either inputs or outputs for the display. It is well known that an unloaded output is fine, but that a floating high-impedance input can cause problems. So what should you do with the four unused data lines when the display is used in 4-bit mode? This question arose when a circuit was submitted to us where D0-D3 where tied directly to GND (the same applies if it was to +5 V) to stop the problem of floating inputs. The LCD module was driven directly by a microcontroller, which was on a development board for testing various programs and I/O functions. There was a switch present for turnin...