Tag Archive: supply


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This circuit Tone Control Stereo you can ajustable bass , mid range and treble. It use IC NE5532.
Supply Volt min 12V 80mA. Easy to build, PCB small.

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ImageLM324N  Connection Diagram
    Transmitter operation. Operating power for the transmitter circuit is derived directly from the ac line. The dc power to operate the circuit is generated in two stages, one for an RE power-amplifier stage, and the second for the remainder of the circuit.

    The ac line voltage is applied to D1 , which half-wave rectifies the ac input . The resulting dc voltage (approximately 30V under load) is fed across an RC filter (comprised of R1 and C1) and used to operate amplifier, Q1. The second stage of the power supply (composed of LED1, R2, D2, D3, C2, and C3, which forms a regulated +13.6-V, center-tapped supply) feeds the remainder of the circuit. LED1 is connected in series with R2 and is used as a visual power-on indicator for the transmitter.

    An electret microphone element (MIC1) is used as the pick-up. The output of the microphone is ac coupled through C5 to UI-a (a noninverting op amp with a gain of about 100). The output of U1-a at pin 1 is ac coupled through C4 to the noninverting input of UI-b (which provides an additional gain of 48) at pin 5. The output of UI-b at pin 7 is then fed through D4 and RIO, and across R11 and C6 to the inverting input of UI-c which is biased to a positive voltage that is set by SENSITIVITY-control R19. This represents a threshold voltage at which the output of UI-c switches from high to low.

    During standby, the output of UI-c at pin 8 is held at about 12 V when the voltage developed across C6 is less than the bias-voltage setting at pin 10. When a sound of sufficient intensity and du-ration is detected, the voltage at pin 9 of UI-c exceeds the threshold level (set by R19), causing UI-c’s output at pin 8 at go low. That low is applied to pin 2 of U2 (a 555 oscillator/timer configured as a monostable multivibrator). This causes the output of U2 to go high for about one second, as de-termined by the time constant of R12 and C7. The output of U2 at pin 3 is applied to pin 4 of U3 (a second 555 oscillator/timer that is conftgured for astable operation, with a frequency of about 125 kHz). That causes U3 to oscillate, producing a near square-wave output that is used to drive Q1 into conduction. The output of Q1 is applied across a parallel-tuned circuit composed a T1’s primary and C8. The tuned circuit, in turn, reshapes the 125-kHz signal, causing a sine-wave-like signal to appear across both the primary and the secondary of Tl.

    The signal appearing at T1’s secondary (about 1 or 2 V peak-to-peak) is impressed across the ac power line, and is then distributed throughout the building without affecting other electrical appli-ances connected to the line. Transient suppressor D7 is included in the circuit to help protect Q1 from voltage spikes that might appear across the power line and be coupled to the circuit through T1.

    Receiver operation. Power for the receiver, as with the transmitter, is derived from a tradi-tional half-wave rectifier (D5). The resulting dc voltage is regulated to 27 V by D6 and R20, and is then filtered by C11 to provide a relatively clean, dc power source for the circuit. A light-emitting diode, LED2, connected in sGries with R20 provides a visual indication that the circuit is powered and ready to receive a signal.

    The 125-kHz signal is plucked from the ac line and coupled through R21 and C12 to a parallel-tuned LO circuit, consisting of C13 and L1. That LO circuit passes 125-kHz signals while attenuating all others. The 125-kHz signal is fed through C14 to the base of Q2 (which is configured as a high-gain linear amplifier), which boosts the relatively low amplitude of the 125-kHz signal. The RE out-put of Q2 is ac coupled to the base of Q3 through C15. Transistor Q3 acts as both an amplifier and detector. Because there is no bias voltage applied to the base of Q3, it remains cut off until driven by the amplified 125-kHz signal. When Q3 is forward biased, its collector voltage rises.

     Capacitor C16, connected across Q3’s collector resistor, filters the 125-kHz signal so that it is essentially dc. When the voltage at the collector of Q3 rises, Q4 is driven into conduction. That causes current to flow into piezo buzzer BZ1, producing a distinctive audio tone that alerts anyone within earshot that the baby needs attention.

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This one has a supply current of 70 mA at 1.5V and a LED current of 25 mA at 3.3V (actually 25 millivolts measured across the 1 ohm [2 resistors] in series with the LED’s green wire).  This calculates to an efficiency of 78.6 percent.  The frequency is 250 kHz.

The circuit is almost as simple as the conventional Joule Thief; it requires a diode and 680 pF capacitor in addition to the 1k resistor.  The end of the feedback winding that was normally connected to positive is instead connected to the 1k and 680 pF as shown in the picture.  I used a SS8050 transistor, which is a Fairchild equivalent to the C8050.  It can handle up to 1.5 amp collector current.

The circuit will give more LED current for about the same supply current, or the resistor can be increased to 1.5k to give about the same LED current for less supply current.  The two current sensing resistors that are in parallel on the lower right are optional and can be removed, and the LED’s green wire connected directly to the heavy negative wire.

 ImageMost people’s idea to improve the power of a USB device is to replace the USB power with an external linear supply. Although this kind of mod would improve the incoming power to the device, the ultimate noise performance is determined by the local regulators that directly feed the chips.

Additionally, because I value the convenience of using USB power, I took a different route: I decided to replace the local regulators with low noise types. The factory regulators are  AMS1117. The ones I am upgrading are LT1963. Noise density figures for the AMS1117 is approx 990 nV (3.3v regulator) and for the LT1963 is approx. 125 nV (3.3v regulator).

The AMS 1117 regulators are similar in noise performance as the very popular LM317 types. The LT 1963 are cousins of the LT 1763 used in Buffalo II. They have higher noise (but are still low noise) due to their higher current carrying capability.