Showing posts with label 4. Show all posts
Showing posts with label 4. Show all posts
Thursday, November 20, 2014
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. Ive 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 "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 do. 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 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 do. 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.
Saturday, September 20, 2014
4 × 40 W BTL quad car radio power amplifier
FEATURES:
Requires very few external components
High output power
Low output offset voltage
Fixed gain
Diagnostic facility (distortion, short-circuit and temperature pre-warning)
Good ripple rejection
Mode select switch (operating, mute and standby)
Load dump protection
Short-circuit safe to ground and to VP and across the load
Low power dissipation in any short-circuit condition
Thermally protected
Reverse polarity safe
Electrostatic discharge protection
No switch-on/switch-off plop
Flexible leads
Low thermal resistance
Pin compatible with the TDA8568Q, except for the gain.
GENERAL DESCRIPTION:
The TDA8571J is a integrated class-B output amplifier contained in a 23-lead Single-In-Line (SIL) plastic power package. It contains four amplifiers in a BTL configuration, each with a gain of 34 dB. The output power is 4 × 40 W (EIAJ) into a 4 Ω load.
APPLICATIONS:
Primarily developed for car radio applications
Circuit Diagram:
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| 4 × 40 W BTL quad car radio power amplifier |
Friday, August 22, 2014
Audio 4 5Mhz notch filter Wiring diagram Schematic
Audio 4.5Mhz notch filter Circuit Diagram. Component value sensitivityis 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. To illustrate, the quality factor Q is very high as amplifier gain approaches 1 with all components matched (in fact, theoretically it approaches «) but decreases to about 12 with the amplifier gain at 08.
Audio 4.5Mhz notch filter Circuit Diagram
Sunday, August 17, 2014
4 x 46 W quad bridge car radio amplifier TDA7384A
Features
■ High output power capability:
– 4 x 46 W / 4 max.
– 4 x 27 W / 4 @ 14.4 V, 1 kHz, 10 %
■ Low distortion
■ Low output noise
■ Standby function
■ Mute function
■ Automute at min. supply voltage detection
■ Low external component count:
– Internally fixed gain (26 dB)
– No external compensation
– No bootstrap capacitors
■ Protections:
– Output short circuit to GND, to VS, across
the load
– Very inductive loads
– Overrating chip temperature with soft
thermal limiter
– Load dump voltage
– Fortuitous open GND
– Reversed battery
– ESD
Description
The TDA7384A is an AB class audio power amplifier, packaged in Flexiwatt 25 and designed
■ High output power capability:
– 4 x 46 W / 4 max.
– 4 x 27 W / 4 @ 14.4 V, 1 kHz, 10 %
■ Low distortion
■ Low output noise
■ Standby function
■ Mute function
■ Automute at min. supply voltage detection
■ Low external component count:
– Internally fixed gain (26 dB)
– No external compensation
– No bootstrap capacitors
■ Protections:
– Output short circuit to GND, to VS, across
the load
– Very inductive loads
– Overrating chip temperature with soft
thermal limiter
– Load dump voltage
– Fortuitous open GND
– Reversed battery
– ESD
Description
The TDA7384A is an AB class audio power amplifier, packaged in Flexiwatt 25 and designed
for high end car radio applications. Based on a fully complementary PNP/NPN configuration, the TDA7384A allows a rail to rail output voltage swing with no need of bootstrap capacitors. The extremely reduced boundary components count allows very compact sets.
Circuit Diagram
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| 4 x 46 W quad bridge car radio amplifier |
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