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Senin, 04 Januari 2010

Guitar Control

Stand-alone, 9V battery powered unit

Three-level input selector, three-band tone control


P1,P2_________100K Linear Potentiometers
P3____________470K Linear Potentiometer
P4_____________10K Log. Potentiometer

R1____________150K 1/4W Resistor
R2____________220K 1/4W Resistor
R3_____________56K 1/4W Resistor
R4____________470K 1/4W Resistor
R5,R6,R7_______12K 1/4W Resistors
R8,R9___________3K9 1/4W Resistors
R10,R11_________1K8 1/4W Resistors
R12,R13________22K 1/4W Resistors

C1____________220nF 63V Polyester Capacitor
C2,C8___________4µ7 63V Electrolytic Capacitors
C3_____________47nF 63V Polyester Capacitor
C4,C6___________4n7 63V Polyester Capacitors
C5_____________22nF 63V Polyester Capacitor
C7,C9_________100µF 25V Electrolytic Capacitors

IC1___________TL062 Low current BIFET Dual Op-Amp

J1,J2__________6.3mm. Mono Jack sockets

SW1______________1 pole 3 ways rotary or slider switch
SW2______________SPST Switch

B1_______________9V PP3 Battery

Clip for PP3 Battery

Device purpose:

This preamplifier was designed as a stand-alone portable unit, useful to control the signals generated by guitar pick-ups, particularly the contact "bug" types applied to acoustic instruments. Obviously it can be used with any type of instrument and pick-up.
It features a -10dB, 0dB and +10dB pre-set input selector to adjust input sensitivity, in order to cope with almost any pick-up type and model.
A very long battery life is ensured by the incredibly low current consumption of this circuit, i.e. less than 800µA.
Circuit operation:

IC1A op-amp is wired as an inverting amplifier, having its gain set by a three ways switch inserting different value resistors in parallel to R4. This input stage is followed by an active three-band tone control stage having unity gain when controls are set in their center position and built around IC1B.
Technical data:

Frequency response:20Hz to 20KHz -0.5dB, controls flat.

Tone control frequency range: ±15dB @ 30Hz; ±19dB @ 1KHz; ±16dB @ 10KHz.

Maximum input voltage (controls flat): 900mV RMS @ +10dB input gain; 7.5V RMS @ -10dB input gain.

Maximum undistorted output voltage: 2.5V RMS.

Total Harmonic Distortion measured @ 2V RMS output: <0.012% @ 1KHz; <0.03% @ 10KHz.

THD @ 1V RMS output: <0.01%

Total current drawing: <800µa.

Sabtu, 02 Januari 2010

4 Digit Keypad Switch

This is a universal version of the Four-Digit Alarm Keypad. I've modified the design of the output section - to free up the relay contacts. This allows the circuit to operate as a general-purpose switch. I used a SPCO/SPDT relay - but you can use a multi-pole relay if it suits your application.

Do not use the "on-board" relay to switch mains voltage. The board's layout does not offer sufficient isolation between the relay contacts and the low-voltage components. If you want to switch mains voltage - mount a suitably rated relay somewhere safe - Away From The Board.

Schematic Diagram:


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 "A B C & D" in the right order. When you do so - pin 10 of the IC goes high - and it turns Q4 on through R8. Q4 connects the base of Q6 to ground. This unlatches the complementary pair - and the relay drops out.

Any keys not wired to "A B C D & E" are connected to the base of Q3 by R7. Whenever one of these "Wrong" keys is pressed - Q3 takes pin 1 low and the code entry sequence fails. If "C" or "D" is pressed out of sequence - Q1 or Q2 will also take pin 1 low - with the same result. If you make a mistake while entering the code - simply start again.

The Keypad must be the kind with a common terminal and a separate connection for each key. On a 12-key pad - look for 13 terminals. The MATRIX TYPE with 7 or 8 terminals WILL NOT WORK. With a 12-key pad - over 10 000 different codes are available. If you need a more secure code - use a bigger keypad with more "Wrong" keys wired to "F". A 16-key pad gives over 40 000 different codes.

The Support Material for this circuit includes a step-by-step guide to the construction of the circuit board, a parts list, a detailed circuit description and more.