Simple Scratch and Rumble Filter

This is 12 dB per octave and the beginning of the add-on Rumble filter, which can be connected to "Tape" or the institution responsible for the amplifier.

And 'the usual quadratic filter circuit having a passive high pass filter formed by the ability of C3 and C4 series and parallel resistor R2 and R3 (the latter is also used to bias the transistor Q1 source follower). Passive filter of this type gives only very slowly to the original roll, and the final reduction was only 6 dB per octave. Boot Strapping resistance is then used to improve performance. Above the cutoff frequency, where profit is the district would otherwise drop slightly, R1 is the effect of strengthening the signal. Well below the cutoff frequency, the loss of C4 leads to the signal emitter of Q1 is significantly below the junction of C3 and C4. This leads to some of the signals at the intersection of C3 and is pushed through the R1 and R1 with C3 effectively forming a second network-pass filter. This eliminates the sluts, the number of the original film (in fact, is a small and insignificant in a maximum of about 05dB above the cutoff frequency) and accelerates the depreciation rate for a nominal 12 dB per octave.

The low pass filter works the same way that the high-pass, except, of course, the elements of R and C of the filter have been implemented to provide the correct action of the filter.

With the component values ​​specified for Rumble filter response drops below unity at about 45 Hz, where -6 D13 just above 30 Hz, then drops to a nominal 12 dB per octave. The filter response from zero to unity gain points around 6k5Hz time 6dB points at about 10 kHz, then drops to a nominal 12 dB per octave.

Lie Detector

Here is a simple lie detector that can be built in minutes, but can be incredibly useful when you want to know if someone is really telling you the truth. It is not as sophisticated as those that the pros use, but it works. It works by measuring skin resistance, which goes down when you are lying.

Parts :

R1    33K 1/4W Resistor

R2    5K Pot

R3    1.5K 1/4W Resistor

C1    1uF 16V Electrolytic Capacitor

Q1    2N3565 NPN Transistor

M1    0-1 mA Analog Meter

MISC1Case, Wire, Electrodes (See Nots)

Notes

- The electrodes can be alligator clips (although they can be painful), electrodes (like the kind they use in    hospital), or just the son and bands.

- You can use the circuit, connect the electrodes to the back of the hand subjects, approximately 1 cm intervals. Then adjust the meter reading 0 Applications. He knows the subject is lying when the meter changes.

Car/Bike USB Charger

Looking for a USB charger that can effectively operate from a 12V car battery? This device operates at 89% efficiency and can charge USB devices at currents up to 525mA. Best of all, it will not face battery when it is permanently connected, as long as you remember to unplug the USB device. There are lots of USB chargers on the market, but this unit has two stand-out features: high efficiency and low consumption in standby mode. In fact, his only 160μA standby current, a figure that is well below the self-discharge of most lead-acid batteries. This means you can leave the unit permanently connected, and it will not cause the battery to go flat (or at least not much faster than it would by itself).

While this may seem a very specific application, there are many other uses for low quiescent current 5V DC 12V DC. For example, remote monitoring stations often operate with a 12V SLA complemented by a solar panel. These stations are invariably a microcontroller and other circuits, which needs a supply of 3.3 V and 5V. Energy consumption in these devices is low most of the time, but sometimes the microcontroller wakes up and turn on a radio module and other circuits, which can draw more current. This charger can provide power - up to 500 mA - while being stingy with the battery when the battery is low. In addition, because of its effectiveness is high (89%), almost no battery is spent, even when the load is drawing 500mA.

USB Audio Interface

This circuit is the quality of a preamplifier with a built-in USB DAC Leachamp my power amplifier. The system is PCM2902 Datasheet. Circuit includes DAC and ADC, SPDIF input and output of HID and 3 + button to the MUTE, VOL-and VOL.


For playback of high quality requires an external low-drop voltage regulator for the DAC. LP2951CM DAC is used, which were easily available in local stores. Output voltage is fixed at about 3.7 V, with two resistors. The circuit was designed for the placement of the well and the separation of digital and analog ground. This land is connected to a certain point of the USB connector.

PCM2902 data sheet recommends connecting the low pass filter the DAC output to filter out frequencies above the audio band produced by the conversion of oversampling. Digital integrated circuits, which includes frequencies above 100 kHz LPF. Notes application filter sites recommended by the manufacturer of the first order LPF (simple RC), or 2 Amps order preamp works, it works well. I am a simple RC LPF with the recommended values ​​for R and C. 4N7 1k It 'best to use the scroll-ceramic capacitor in place. I did not hear the sound difference between the filter or not, but in relation to other components of the audio chain is best to use. The best cut-off frequency, which can change the value of the capacitor 3N3