3000+ Free Electronic Schematic

AT89S51 Programming Schematic

2011-12-30T08:36:00.000-08:00

The AT89Sxx learning board features,

Designed for new ISP chips, 89S51, 89S52, and 89S53, 40-pin DIP,
In System Programmable (ISP) through the 6-pin header and a jumper, (no need external programmer),
TxD and RxD serial port for communicating with serial devices,
32 bit GPIO,
Onboard rectifier and +5V DC voltage regulator,
Single Sided PCB design.

Part List

R1                          330 1/4W +/-5%
R2                          10K 1/4W +/-5%
R3-10                     10K 1/4W +/-5% (for pull up on P0)
C1                         1000uF/16V electrolytic capacitor
C2                         100uF/16V electrolytic capacitor
C3                         100nF multilayer or ceramic
C4                         10uF/16V electrolytic
C5,C6                    33pF ceramic
D1                         1N4001 / 1N4002 silicon rectifier diode
D2                         LED
U1                         LM7805, voltage regulator
U1                         AT89S51, AT89S52 or AT89S53
X1                         Crystal 1MHz – 33MHz (11.0592MHz is suitable for standard BAUD rate generator using timer1, says 9600 )

DB25 parallel port, 25pins connector

Original from: http://www.kmitl.ac.th/~kswichit/tahan/boards51/Board S51.htm

Simple Audio Limiter Schematic

2011-12-30T08:23:00.000-08:00

Technical specifications
Supply voltage: 10-14 V stab.
Supply currents: 20 mA
Audio input: impedance 20 kOhm, optional preemphasis
Output voltage: 0,4 V rms
Dynamic range: >50 dB

Parts list
Resistors:
R1 - 68 k
R2 - 22 k
R3 - 180 k
R4 - 10 M
R5 - 10 k
R6 - 47 R
R7 - 240 k
R8 - 1,5 k
R9 - 820 R
Capacitors:
C1 - 100 p (ceramic)
C2 - 1 n (plastic)
C3, C6, C12 - 100 n (ceramic)
C4, C11, C13 - 100 u (electrolytic)
C5 - 0,33 u (tantalum)
C7, C8 - 10 u (electrolytic)
C9 - 220 n (plastic)
C10 - 47 n (ceramic)
C14 - 470 n (plastic)
Misc.:
T1 - BF245C
T2 - BC556B, BC307
IC1 - LM386
Don't place the C8 if you don't want to use whole dynamic range. Then you will get much better S/N ratio.
You may adjust release time by C7 and R4 values.
PCB layout

Original from : http://pira.cz/enlter.htm

High Quality 60 Watt 8 Ohms Power Amplifier Schematic

2011-12-30T08:17:00.000-08:00

Basic specs on the amp are as follows .

Input sensitivity for 60 W output - just under 1V (1V gives 66W)
Gain - 27dB
Frequency response (-3dB) - 10Hz to 23kHz @ 1W
Harmonic distortion @ 1kHz - 0.05% (maximum typical)
Open Loop Gain - 125dB (no load), 80dB (8 Ohm load)
Input Impedance - 22k Ohm
DC Offset - Less than 100mV (< 20 mV typical **)
Noise - < 2mV at output (-80dB ref 50W unweighted)

Original from : http://sound.westhost.com/project03.htm

Basic Uninterruptible Power Supply (UPS)

2011-12-30T08:08:00.000-08:00

This circuit is a simple form of the commercial UPS, the circuit provides a constant regulated 5 Volt output and an unregulated 12 Volt supply. In the event of electrical supply line failure the battery takes over, with no spikes on the regulated supply.

Note:

This circuit can be adapted for other regulated and unregulated voltages by using different regulators and batteries. For a 15 Volt regulated supply use two 12 Volt batteries in series and a 7815 regulator. There is a lot of flexibility in this circuit.
TR1 has a primary matched to the local electrical supply which is 240 Volts in the UK. The secondary winding should be rated at least 12 Volts at 2 amp, but can be higher, for example 15 Volts. FS1 is a slow blow type and protects against short circuits on the output, or indeed a faulty cell in a rechargeable battery. LED 1 will light ONLY when the electricity supply is present, with a power failure the LED will go out and output voltage is maintained by the battery. The circuit below simulates a working circuit with mains power applied:

Between terminals VP1 and VP3 the nominal unregulated supply is available and a 5 Volt regulated supply between VP1 and VP2. Resistor R1 and D1 are the charging path for battery B1. D1 and D3 prevent LED1 being illuminated under power fail conditions. The battery is designed to be trickle charged, charging current defined as :-

(VP5 - 0.6 ) / R1

where VP5 is the unregulated DC power supply voltage.

D2 must be included in the circuit, without D2 the battery would charge from the full supply voltage without current limit, which would cause damage and overheating of some rechargeable batteries. An electrical power outage is simulated below:

Note that in all cases the 5 Volt regulated supply is maintained constantly, whilst the unregulated supply will vary a few volts.

Standby Capacity
The ability to maintain the regulated supply with no electrical supply depends on the load taken from the UPS and also the Ampere hour capacity of the battery. If you were using a 7A/h 12 Volt battery and load from the 5 Volt regulator was 0.5 Amp (and no load from the unregulated supply) then the regulated supply would be maintained for around 14 hours. Greater A/h capacity batteries would provide a longer standby time, and vice versa.

From : http://www.zen22142.zen.co.uk/Circuits/Power/ups.htm

1 GHz Frequency Counter

2011-12-29T07:38:00.000-08:00

This simple counter is useful for frequency measurements of various wireless equipments, especially transmitters, receivers and signal generators in VHF/UHF band.

Features

Display range: 0,0 to 999,9 MHz, resolution 0,1 MHz
Correct rounding, reduced blinking of last digit
Over-range indication
Fast measurement - short measuring period
High input sensitivity in VHF/UHF band
Switchable intermediate frequency offset for use with receiver
Technical specifications

Supply voltage: 8-20 V
Supply current: typ. 80 mA, max. 120 mA
Input sensitivity: max. 10 mV in 70-1000 MHz range
Measuring period: 0,082 sec.
Display refresh rate: 49 Hz

Schematic diagram

Parts list

R1 - 39 k
R2 - 1 k
R3-R6 - 2,2 k
R7-R14 - 220

C1, C5, C6 - 100 n mini
C2, C3, C4 - 1 n
C7 - 100 u
C8, C9 - 22 p

IC1 - 7805
IC2 - SAB6456 (U813BS - different pin layout, not tested, also maybe R1 value need to be changed)
IC3 - PIC16F84A programmed + socket
T1 - BC546B
T2-T5 - BC556B
D1, D2 - BAT41 (BAR19) - may be ommited
D3 - HD-M514RD (red) or HD-M512RD (green), 4-digits multiplex driven LED display from HP, or four standard 1-digit LED displays
X1 - 4.000 MHz crystal
BNC input connector

To use with a receiver as a digital scale, close the -10,7 pins.

IC3 program download: counter.hex
Programmer settings: Oscillator: XT, WDT: on
For additional changes (eg. IF frequency offset change): counter.asm

The SAB6456 description

The SAB6456 is a prescaler for UHF/VHF tuners. The circuit has an input frequency range of 70 MHz to 1 GHz, has high input sensitivity and good harmonic suppression. With lower sensitivity it's usable down to 3 MHz.
The circuit comprises an input amplifier, a divider stage and an output stage. The divider stage may oscillate during no-signal conditions but this oscillation is suppressed when input signals are received. The voltage-edges of the output signals are slowed internally to reduce harmonics in the television intermediate frequency band.

Printed circuit board

Important!
There are two pin connection versions of the SAB6456. In the schematic diagram there is drawn a standard pin connection as provided by Philips datasheet. The PCB is proposed for both versions.

Level indicator with 10 LED

2011-12-29T06:32:00.000-08:00

Technical specifications:

Supply voltage: 12 V
Supply current: 10 mA in stand-by, max. 80 mA
Input voltage: min. 20 mV rms
Indication range: 30 dB
LED currents: 7 mA
Ref. voltage of IC2: 5 V

Schematic diagram

Parts list

R1 - trimmer 100 k mini
R2 - 2,2 k
R3 - 1 M
R4 - 2,7 k
R5 - 6,8 k

C1 - 0,47 uF
C2 - 10 uF
C3 - 47 nF
C4 - 4,7 uF
C5 - 0,1 uF
C6 - 100 uF
C7 - 100 nF

IC1 - LM386
IC2 - LM3915
D1 - 1N4148
D2-D11 - bargraph or LED's

PCB layout