DRM Down-Converter For 455kHz IF Receivers

This project came about
due to my interest in a new form of radio transmission called DRM, which stands for “Digital Radio Mondiale” (see http://www.drm.org).
This is a new form of digital shortwave transmission. A few devices are
available from Europe for decoding the digital signals but are
expensive. I decided instead to modify an existing circuit, using a
stable purpose-built 470kHz ceramic resonator as the oscillator, rather
than the original unstable L/C version. The 455kHz IF signal from a
shortwave receiver is fed into the input (pin 1) of a double-balanced
mixer and oscillator (IC1) via a level adjustment pot (VR1). The NE506’s
output (pin 4) is then AC-coupled to a PC’s sound card input for
processing. With the capacitor between pins 5 & 7 set to 150pF, the
oscillator frequency should be around 467.5kHz. You can check if the
oscillator is working by putting it near a receiver tuned to 467kHz. You
should hear a beat frequency.

DRM DownConverter Circuit For 455kHz IF Receivers

DRM DownConverter Circuit Diagram For 455kHz IF Receivers

The IF signal of 455kHz is mixed with 467kHz, giving an output with a
centre frequency of 12kHz. Sound cards should have no trouble sampling
the 10kHz-wide DRM signal. A number of
software-defined radio applications were found to work well with this
converter. These applications perform all of the demodulation (SSB, AM, FM, etc) and various other DSP
functions. If all is well, connect your 455kHz IF to the input and your
computer sound card to the output. Run the Dream software (see http://drm.sourceforge.net), and tune to 6095Khz (RNZI), or 1440Khz (SBS). You should see the Dream software lock onto the DRM
transmission and audio should start playing from the computer speakers.
The NE602AN mixer/oscillator and 470kHz resonator are available for a
cost of $12.50. A CD with various software defined receivers as well as the latest Dream software decoder is also available.

Author: John Titmuss
Copyright: Silicon Chip Electronics


12V to 250V Converter

A very simple portable
12 to 250V converter can be designed using this circuit diagram. This 12
to 250V converter is designed for portable use with a 12 V car
battery.A built astabil multivibrator T1 and T2 generates a rectangular
wave at a frequency of 50 Hz. As T1 and T2 drive alternative exit stage
system also works in “push-pull”. When T1 lead by passing a current T3:
T5 and that it engages the latter transistor connects to a half battery
of 12 V secondary winding of the transformer Tr When T2 network drive,
T6 transistor coupled to the battery the other half of the network

12V to 250V Converter

12V to 250V Converter

If it is used for output stages 40 411 RCA
transistors, the current through secondary winding can be up to 10 A,
giving a power output of 180 watts. If you use 2N3055 transistors, power
output will be about 90 watts. Since the output transistors are driven
to saturation, they have very high mounted radiators.Although circuit is
simple construction and has high efficiency disadvantage is rectangular
output voltage which, in the absence of a regulator is dependent on
task: small loads, the output voltage is 250 V ac (not working properly
for the engine speed control, light dimmers, televisions, hi-fi


Balanced-Unbalanced Converter For Audio Work

If you work in the
professional audio field, you need to use balanced lines for long signal
runs to prevent hum and noise pick-up. This Balanced/Unbalanced
Converter is really two projects in one. It can convert an unbalanced
input to balanced outputs and vice versa.


  • Signal to noise ratio: -100dB with respect to 1V output, 4.7kW input load.
  • Frequency response: -3dB at 2Hz and 200kHz.
  • Total harmonic distortion: less than .001% from 20Hz to 20kHz with a 1V input.
  • Signal handling: supply dependent; requires 30VDC or ±15V for 9V RMS signal handling.

Professional audio gear invariably has balanced inputs and outputs.
However, what if you want to connect standard audio equipment that has
unbalanced outputs to equipment that has balanced inputs? Alternatively,
what if you want to connect a balanced output signal to an unbalanced
input? Either way this Balanced/Unbalanced Converter project can do the

The reason professional audio equipment utilises balanced inputs and
outputs is quite simple. It’s done so that audio connections can be
made over quite long distances without adding extra noise to the signal.
These balanced connections use 3-pin XLR plugs and sockets and screened twin-core cable.

Block Diagram

Block diagram shows the basic arrangement. Basically, the audio
output signal is coupled to two separate amplifiers and these drive the
two signal leads in the cable in anti-phase (ie, the signals have
opposite phases). In this case, Amplifier 1 has an output signal that’s
in phase with the input, while Amplifier 2 has an output that’s opposite
in phase with the input.

Circuit looks like:

The output impedance of each amplifier is the same and the twin-core
cable carries the signal to the equipment at the other end. However, in
some cheaper balanced line drivers, one core does not carry any signal
but is grounded instead. So in this case, Amplifier 2 is left out and
the left hand side of resistor R2 is grounded.

In operation, there will be some noise and hum pickup over the
length of the cable even though the cable is shielded. However, because
the cores in the cable are close together, any signal that is picked up
will be common to both.

Parts Layout

At the receiving end, the signal in each of the two cores is
subtracted to produce the original audio signal. At the same time, this
also removes most of the noise and hum that was picked up in the leads,
since the same noise signal is present in both.

Circuit diagram:

Balanced/Unbalanced Converter

Balanced/Unbalanced Converter

If one of the cores is grounded, as in the cheaper type of balanced
driver, then the signal level after subtraction will be the same as the
signal in the main core. Alternatively, if anti-phase signals are
applied to both cores, the subtraction process produces an audio signal
level that’s twice the level in the individual cores.

Source: Silicon Chip 09 June 2008

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12V From USB Port – 5V to 12V Converter

Using this circuit we can convert 5V DC from the computer USB port to 12V DC and a circuit like this will find a lot of application in USB
powered systems. The heart of this circuit is IC LT1618 which is a
constant current, constant voltage boost converter. The IC has a wide
input voltage range of 1.8 to 18V DC and output voltage can be up to 35V

In the circuit resistors R1, R2 sets the output voltage. Pin number 9
is the shutdown pin, less than 0.3V to this pin will shut down the IC.
Pin number four is the current sense adjust pin. The current sense
voltage can be reduced by applying a DC voltage to this pin. If this
adjustment is not needed connect this pin to ground and you can omit
components R3, R5 and Q1.


  • C2 and C3 must be rated at least 15V.
  • Less than 0.3V at the shutdown pin will shutdown the IC.
  • Output voltage is governed by the following equation R1 = R2 ( (Vout /1.263V) -1).
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Buck-Boost Voltage Converter

Sometimes it is desired
to power a circuit from a battery where the required supply voltage lies
within the discharge curve of the battery. If the battery is new, the
circuit receives a higher voltage than required, whereas if the battery
is towards the end of its life, the voltage will not be high enough.
This is where the new LTC 3440 buck/boost voltage converter from Linear Technology (http://www.linear.com)
can help. The switching regulator in Figure 1 converts an input voltage
in the range +2.7 V to +4.5 V into an output voltage in the range +2.5 V
to +5.5 V using one tiny coil.

Circuit diagram:

The level of the output voltage is set by the voltage divider formed
by R2 and R3. The device switches as necessary between step-up (or
‘boost’) operation when Vin is less than Vout , and step-down (or
‘buck’) operation when Vin is greater than Vout. The maximum available
output current is 600mA. The IC contains four MOSFET
switches (Figure 2) which can connect the input side of coil L1 either
to Vin or to ground, and the output side of L1 either to the output
voltage or to ground. In step-up operation switch A is permanently on
and switch B permanently off. Switches C and D close alternately,
storing energy from the input in the inductor and then releasing it into
the output to create an output voltage higher than the input voltage.

Circuit diagram:

Buck Boost Voltage Converter Circuit

Buck-Boost Voltage Converter Circuit Diagram

In step-down operation switch D is permanently closed and switch C
permanently open. Switches A and B close alternately and so create a
lower voltage at Vout in proportion to the mark-space ratio of the
switch ing signal. L1, together with the output capacitor, form a
low-pass filter. If the input and output voltages are approximately the
same, the IC switches into a pulse-width modulation mode using all four
switches. Resistor R1 sets the switching frequency of the IC, which with
the given value is around 1.2 MHz. This allows coil L1 to be very
small. A suitable type is the DT1608C-103 from Coilcraft (http://www.coilcraft.com).

The IC can be shut down using the SHDN/SS
input. A ‘soft start’ function can also be implemented by applying a
slowly-rising voltage to this pin using an RC network. The MODE pin allows the selection of fixed-frequency operation (MODE connected to ground) or burst mode operation (MODE=Vin).
The latter offers higher efficiency (of between 70% and 80%) at
currents below 10 mA. At currents of around 100 mA the efficiency rises
to over 90 %. A further increase in efficiency can be obtained by
fitting the two Schottky diodes shown dotted in the circuit diagram.
These operate during the brief period when both active switches are open
(break-before-make operation).

Author: Gregor Kleine – Copyright: Elektor July-August 2004


12V to 9V DC Converter

To get a more precise
output voltage, replace zener diode Z1 with 10V and R1 with a 1Kilo ohm
potentiometer. A Coolrib for Q1 is optional but highly recommended. You
can replace Q1 for a more robust type to get more output amps depending
on your requirements. Simple circuit to power your 9 volt cassette
recorder and other stuff.

Parts List:
R1 = 560 ohm
C1 = 1000uF/40V, Electrolytic
C2 = 10uF/25V, Electrolytic
C3 = 330nF, Ceramic
Z1 = 9.1V, 1watt zener
Q1 = ECG184, NTE184


Cheap Switch-Mode DC-DC Converter

This circuit is based on
mobile phone chargers. These chargers are based on the Motorola MC34063
switchmode IC. By changing the values of the feedback resistors (R1
& R2), the output voltage can be varied over a wide range. Just
modify R1 and R2 according to the formula: Vout = 1.25 (1+R2/R1). The
values shown give an output of 3V.

Cheap Switch mode DC DC Converter Circuit

Cheap Switch-mode DC-DC Converter Circuit Diagram

Author: Timo Mahoney – Copyright: Silicon Chip Electronics Magazine


DC/DC Converter From +1.5V To +34V

An interesting DC/DC
converter IC is available from Linear Technology. The LT1615 step-up
switching voltage regulator can generate an output voltage of up to +34V
from a +1.2 to +15V supply, using only a few external components. The
tiny 5-pin SOT23 package makes for very compact construction. This IC
can for example be used to generate the high voltage needed for an LCD
screen, the tuning voltage for a varicap diode and so on. The internal
circuit diagram of the LT1615 is shown in Figure 1. It contains a
monostable with a pulse time of 400 ns, which determines the off time of
the transistor switch.

If the voltage sampled at the feedback input drops below the
reference threshold level of 1.23 V, the transistor switches on and the
current in the coil starts to increase. This builds up energy in the
magnetic field of the coil. When the current through the coil reaches 350
mA, the monostable is triggered and switches the transistor off for the
following 400 ns. Since the energy stored in the coil must go
somewhere, current continues to flow through the coil, but it decreases
linearly. This current charges the output capacitor via the Schottky
diode (SS24, 40V/2A). As long as the voltage at FB remains higher than
1.23V, nothing else happens.

As soon as it drops below this level, however, the whole cycle is
repeated. The hysteresis at the FB input is 8mV. The output voltage can
be calculated using the formula Vout = 1.23V (R1+R2) / R2 The value of
R1 can be selected in the megohm range, since the current into the FB
input is only a few tens of nano-amperes. When the supply voltage is
switched on, or if the output is short-circuited, the IC enters the
power-up mode. As long as the voltage at FB is less than 0.6V, the
LT1615 output current is limited to 250mA instead of 350mA, and the
monostable time is increased to 1.5µs.

These measures reduce the power dissipation in the coil and diode
while the output voltage is rising. In order to minimize the noise
voltages produced when the coil is switched, the IC must be properly
decoupled by capacitors at the input and output. The series resistance
of these capacitors should be as low as possible, so that they can short
noise voltages to earth. They should be located as close to the IC as
possible, and connected directly to the earth plane. The area of the
track at the switch output (SW) should be as small as possible.
Connecting a 4.7-µF capacitor across the upper feedback capacitor helps
to reduce the level of the output ripple voltage.

The selection of the coil inductance is described in detail in the LT1615 data sheet at http://www.linear-tech.com.
Normally, a 4.7µH filter choke is satisfactory for output voltages less
than 7V. For higher voltages, a 10-µH choke should be used. In the data
sheet, the Coilcraft DO1608-472 (4.7 µF) and DO1608-100 (10 µF) are
recommended. The Schottky diode must naturally have a reverse blocking
voltage that is significantly greater than the value of the output
voltage. The types MBR0530 and SS24 are recommended. The shutdown input
(/SHDN) can be used to disable the step-up regulator by applying a
voltage that is less than +0.25V.

If the voltage at this pin is +0.9 V or higher, the LT1615 is
active. You must bear in mind that even when the IC is disabled, the
input voltage still can reach the output via the coil and the diode,
reduced only by the forward voltage drop of the diode. The second
circuit diagram for the LT1615 (Figure 2) shows how you can make a
symmetric power supply using this switching regulator. Here the switch
output of the IC is tapped off and rectified using a symmetrical
rectifier. The voltage divider at the positive output of the rectifier
determines the output voltage.


RMS to DC Converter

In order to measure the RMS value of an alternating voltage an accurate converter is required to produce the true RMS value of its alternating input as a DC output. With simple sinewave inputs the RMS
voltage can simply be calculated as 0.707 times the peak AC voltage,
but with complex waveforms the calculation is not nearly as
straightforward. The RMS value is defined as the DC voltage that would give the same heating effect in a resistor as the alternating voltage. The LTC 1966 from Linear Technology (http://www.linear-tech.com)
uses a new form of delta-sigma conversion and is designed for battery
operation, drawing only 170µA from the supply. The new technique is
accurate to 0.02 % between 50 mV and 350 mV and is highly linear. It can
operate from 50 Hz to 1 kHz (with an error of 0.25 %) and up to 6 kHz
with a 1 % error.

The input voltage range on the differential inputs IN1 and IN2
extends to the supply rails, and so in the non-symmetrical circuit shown
here the voltage on IN1 can swing between 0 V and the supply voltage.
If the signal to be measured is AC only, then another coupling capacitor
will be required. The input impedance is many megohms. The output
voltage at the OUT pin can be offset by applying a DC voltage to the OUTRTN pin. This is particularly helpful when using the device with LCD
multimeter ICs such as the 7106. A further capacitor is connected to
the output which is charged up to the required voltage by the
switched-capacitor circuit in the converter. The capacitor required is
ten times smaller than that demanded by previous RMS to DC converter designs. The LTC1966 is not temperature sensitive and is available in an 8-pin MSOP package. It allows a tiny RMS to DC converter to be constructed using just four components.

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Sine Wave To TTL Converter

As the title implies,
the present circuit is intended to convert sinusoidal input signals to TTL
output signals. It can handle inputs of more than 100 mV and is
suitable for use at frequencies up to about 80 MHz. Transistor T1,
configured in a common-emitter circuit, is biased by voltage divider
R3–R5 such that the potential across output resistor R1 is about half
the supply voltage. When the circuit is driven by a signal whose
amplitude is between 100 mV and TTL level
(about 2 V r.m.s.), the circuit generates rectangular signals. The
lowest frequencies that could be processed by the prototype were around
100 kHz at an input level of 100 mV, and about 10 kHz when the input
signals were TTL level.

Circuit diagram:

Sine Wave To TTL Converter Circuit

Sine Wave To TTL Converter Circuit Diagram

Resistor R6 holds the input resistance at about 50 Ω, which is the
normal value in measurement techniques. It ensures that the effects of
long coaxial cables on the signal are negligible. If the converter is
used in a circuit with ample limits, R6 may be omitted, whereupon the
input resistance rises to 300 Ω.