Showing posts with label up. Show all posts

Friday, October 31, 2014

Digital Isolation up to 100 Mbits Diagram Circuit

When it is necessary to send a digital signal between two electrically isolated circuits you would normally choose an optoisolator or some form of transformer coupling. Neither of these solutions is ideal; optocouplers run out of steam beyond about 10 MHz and transformers do not have a good low frequency (in the region of Hertz) response. The company NVE Corporation (www.nve.com) produces a range of coupler devices using an innovative ‘IsoLoop’ technology allowing data rates up to 110 Mbaud. The example shown here uses the IL715 type coupler providing four TTL or CMOS compatible channels with a data rate of 100 Mbit/s. Inputs and outputs are compatible with 3.3 V or 5 V systems. The maximum isolation voltage is 2.5 kV and the device can cope with input transients up to 20 kV/µs.

Circuit diagram:

The company produce many other configurations including bidirectional versions that would be suitable for RS485 interfacing. The IsoLoop coupler is based on relatively new GMR (GiantMagnetoResistive) technology. The input signal produces a current in a planar coil. This current generates a magnetic field that produces a change in resistance of the GMR material. This material is isolated from the planar coil by a thin film high voltage insulating layer. The change in resistance is amplified and fed to a comparator to produce a digital output signal. Differences in the ground potential of either the input or output stage will not produce any current flow in the planar coil and therefore no magnetic field changes to affect the GMR material. Altogether the circuit provides a good electrical isolation between input and output and also protects against input signal transients (EMV).
Author: Gregor Kleine - Copyright: Elektor July-August 200

Thursday, October 30, 2014

Mp3 Booster Pump it up Diagram Circuit

MP3 players are all the rage these days. The smaller ones in memory-stick format are particularly easy to take with you; your very own ‘personal sound system’ on the move! It’s when you want others to share your taste in music that you ﬁnd these players to have a lack of power. You can get round this problem with the help of the MP3 booster, a small amplifier that can be used to connect your MP3 player directly to your Hi-Fi. When you next invite your friends to a party you can ask them to bring their ‘personal music’ as well as the usual drinks!

But ﬁrst we have to build this booster! The small battery-powered players have an output signal that is more than sufﬁcient to drive a set of 32 Ohm headphones. You’ll often ﬁnd that with an output of 1mW the sound pressure level (SPL) produced can reach up to 90 dB. This would be sufﬁcient to cause permanent damage to your hearing after only one hour! The maximum output voltage will then be around 200mV. This, however, is insufﬁcient to fully drive a power amplifier. For this you’ll need an extra circuit that boosts the output voltage.

Power amps usually require 1 V for maximum output, hence the signal has to be ampliﬁed by a factor of ﬁve. We will also have to bear in mind that quieter recordings may need to be ampliﬁed even more. We’ve used a simple method here to select the gain, which avoids the use of potentiometers. After all, the MP3 player already has its own volume control. We decided to have two gain settings on the booster, one of three times and the other ten times. Ampliﬁers IC1A and IC1B (for the right and left channels) are housed in a single package, a TS922IN.

The output signal of the MP3 player is fed via a stereo cable and socket K1 to the inputs of the amplifiers. The gain depends on the relationship between resistors R2 and R1 (R6 and R5 for the other channel) and is equal to ten times. When you add jumper JP1 (JP2), resistor R3 (R7) will be connected in parallel with the negative feedback resistor R1 (R6), which causes the gain to be reduced to about three. When you start using the booster you can decide which gain setting works best for you.

Circuit diagram:

MP3 Booster Circuit Diagram

Resistor R4 (R8) takes the ampliﬁed MP3 signal to the output socket K2 (K3). A cable then connects these phono sockets to the input of your power amplifier. The resistors connected in series with the output (R4 and R8) are there to keep the booster stable when a long cable is connected to its output. Cables have an unwelcome, parasitic capacitance. This capacitive effect could (due to phase shifts of the signal) affect the negative feedback of the booster in such a way that a positive feed back occurs, with the result that the booster oscillates and possibly damages the power amplifier!

The resistors (R4 and R8) effectively isolate the output of the booster from the parasitic capacitance of the output cable. They also protect the booster outputs from short circuits. We’ve used a TS922IN opamp in this booster because it can operate at very low supply voltages (the maximum is only 12 V!), but can still output a reasonable current (80 mA max.). For the supply we’ve used rechargeable batteries (e.g. NiCd or NiMH cells) so that we don’t need a mains supply.

To keep the number of cells required as small as possible, we’ve chosen a supply voltage of 5 volt; this can be supplied by four rechargeable batteries. It is also possible to use four ordinary, non-rechargeable batteries; it’s true that the supply voltage then becomes a bit higher (6 Volts), but that won’t cause any harm. Since we’ve used a symmetrical supply for the booster (2 x 2 batteries), it will be easiest if you use two separate battery holders, each with two AA cells. The two holders are connected in series.

Make sure that the batteries are connected the right way round; the positive of one always has to be connected to the negative of the next. This also applies to the connection between the two battery holders. S1A/B is a double pole switch, which is used to turn both halves of the battery supply on or off simultaneously. If you can’t ﬁnd the (dual) opamp we’ve used (or an equivalent), you could always use standard opamps such as the NE5532, TL082 or TL072. These do need a higher supply voltage to operate properly. In these cases you should use two 9 V batteries and replace resistor R9 with a 15 kΩ one.

Do take care when you connect the circuit to your power amplifier because the output signal can be a lot larger and you could overload the power amplifier. (Although you’re more likely to damage the loudspeakers, rather than the amplifier!) (Please note that these two 9 V batteries can’t be used as a supply for the TS922IN!) In our circuit we’ve used a stereo jack socket for the input and phono sockets for the output because these are the most compatible with MP3 players and power amplifiers respectively. If you wanted to, you could solder shielded cables directly to the circuit instead, with the correct plugs on the ends. You’ll never ﬁnd yourself without the correct connection leads in that case!

Wednesday, October 22, 2014

High Current Step Up Converter Using MAX641

High Current Step-Up Converter Using MAX641 integrated circuit, manufactured by Maxim IC, can be designed a very simple step-up converter using few electronic components. This step-up high voltage converter electronic projects allows a maximum output current up to 1A.

High Current Step-Up Converter Circuit Diagram

Low battery voltage detector input compare LB1 with internal reference of 1.31 V. LBO output goes in low state when the voltage at pin 1 falls below 1.31 V. The threshold voltage for "low battery", is determined by voltage divider R1-R2.

LED D1 illuminates the LBO output when the input voltage falls below 2.62 V.
Input voltage must remain below 5 V. The maximum effectiveness is 80% conversion.

Wednesday, October 8, 2014

Door Alarm Hangs up on the door handle Beeps when someone touches the door handle from outside

Door Alarm

Hangs up on the door-handle

Parts:

R1______________1M   1/4W Resistor R2______________3K3 1 or 2W Resistor (See Notes) R3_____________10K   1/2W Trimmer Cermet (See Notes) R4_____________33K   1/4W Resistor R5____________150K   1/4W Resistor R6______________2K2 1/4W Resistor R7_____________22K   1/4W Resistor R8______________4K7 1/4W Resistor C1,C2__________10nF   63V Ceramic or Polyester Capacitors C3_____________10pF   63V Ceramic Capacitor C4,C6_________100nF   63V Ceramic or Polyester Capacitors C5______________2µ2   25V Electrolytic Capacitor C7____________100µF   25V Electrolytic Capacitor D1,D2,D4_____1N4148   75V 150mA Diodes D3_____________5 or 3mm. Red LED Q1,Q2,Q3,Q5___BC547   45V 100mA NPN Transistors Q4____________BC557   45V 100mA PNP Transistor L1_________________   (See Notes) L2_____________10mH miniature Inductor Hook_______________   (See Notes) BZ1___________Piezo sounder (incorporating 3KHz oscillator) SW1,SW2________SPST miniature Slider Switches B1_______________9V PP3 Battery Clip for PP3 Battery

Device purpose:

This circuit emits a beep and/or illuminates a LED when someone touches the door-handle from outside. The alarm will sound until the circuit will be switched-off.
The entire circuit is enclosed in a small plastic or wooden box and should be hanged-up to the door-handle by means of a thick wire hook protruding from the top of the case.
A wide-range sensitivity control allows the use of the Door Alarm over a wide variety of door types, handles and locks. The device had proven reliable even when part of the lock comes in contact with the wall (bricks, stones, reinforced concrete), but doesnt work with all-metal doors.
The LED is very helpful at setup.

Circuit operation:

Q1 forms a free-running oscillator: its output bursts drive Q2 into saturation, so Q3 and the LED are off. When part of a human body comes in contact with a metal handle electrically connected to the wire hook, the body capacitance damps Q1 oscillations, Q2 biasing falls off and the transistor becomes non conducting. Therefore, current can flow into Q3 base and D3 illuminates. If SW1 is closed, a self-latching circuit formed by Q4 & Q5 is triggered and the beeper BZ1 is activated.
When the human body part leaves the handle, the LED switches-off but the beeper continues to sound, due to the self-latching behavior of Q4 & Q5. To stop the beeper action, the entire circuit must be switched-off opening SW2.
R3 is the sensitivity control, allowing to cope with a wide variety of door types, handles and locks.

Notes:

    L1 is formed winding 20 to 30 turns of 0.4mm. diameter enameled copper wire on R2 body and soldering the coil ends to the resistor leads. You should fill R2 body completely with coil winding: the final turns number can vary slightly, depending on different 1 or 2W resistor types actual length (mean dimensions for these components are 13-18mm. length and 5-6mm. diameter).

    The hook is made from non-insulated wire 1 - 2mm. diameter (brass is well suited). Its length can vary from about 5 to 10cm. (not critical).

    If the device is moved frequently to different doors, Trimmer R3 can be substituted by a common linear potentiometer fitted with outer knob for easy setup.

    To setup the device hang-up the hook to the door-handle (with the door closed), open SW1 and switch-on the circuit. Adjust R3 until the LED illuminates, then turn slowly backwards the screwdriver (or the knob) until the LED is completely off. At this point, touching the door-handle with your hand the LED should illuminate, going off when the hand is withdrawn. Finally, close SW1 and the beeper will sound when the door-handle will be touched again, but wont stop until SW2 is opened.

    In regular use, it is advisable to hang-up and power-on the device with SW1 open: when all is well settled, SW1 can be closed. This precautionary measure is necessary to avoid unwanted triggering of the beeper.

Friday, September 26, 2014

Power up down Sequencer

Whether you’re talking about a home cinema or a computer system, it’s very often the case that the various elements of the system have to be turned on or off in a quite specific order, or at least, automatically. Constructing this sort of automation system is well within the capability of any electronics enthusiast worthy of the name, but in this ‘all-digital’ age, most of the circuits of this type to be found in amateur electronics magazines or web-sites use a microcontroller. Even though that is indeed a logical solution (in more ways than one!), and you might even say the easiest one, it does pose problems for all those people who don’t (yet) have the facilities for programming these types of IC. So we decided to offer you now an approach that’s very different, as it only uses a simple, cheap, commonly-avail-able analogue integrated circuit, which of course doesn’t have to be programmed. Our project in fact uses as it’s ‘brain’ an LM3914, a familiar IC from National Semiconductors, usually used for driving LED VU (volume unit) meters.

Circuit diagram :
Power-up-down Sequencer Circuitw

Power-up/down Sequencer Circuit Diagram

Before taking a look at the circuit for our project, let ’s just remind ourselves that the IC has one analogue input and ten out-puts intended for driving LEDs. It can operate in ‘point’ mode, where the LEDs light up in turn, from first to last, depending on the input voltage, but only one LED is lit at any given time. Alternatively it can operate in ‘bar’ mode (this is the mode normally used for VU meters), and in this case, the LEDs light up one after the other, in such a way as to create a strip of light (bar) that is longer or shorter according to the input voltage. This is the mode selected for the LM3914 in the circuit described in some detail below.

So as to be able to control the AC powered equipment our sequencer is intended to manage, we are using solid-state relays — four, in our example, though you can reduce or increase this number, up to a maximum of ten. Since the input devices in solid-state relays are LEDs, they can be driven directly by the LM3914 outputs, since that’s exactly what they’re designed for. As only four relays are available, these are spread across out-puts L2, L4, L6, and L8, but you can choose any arrangement you like to suit the number of relays you want to use.

Resistor R7 connected to pin 7 of the LM3914 sets the current fed to the LEDs by the LM3914 outputs. Here, it’s been set to 20 mA, since that is the value expected by the solid-state relays chosen. The input voltage applied to pin 5 of the LM3914 is none other than the voltage present across capacitor C1 — and this is where the circuit is ingenious. When the switch is set to ‘on’, C1 charges slowly through R5, and the LEDs of the solid-state relays on the outputs light one after another as this voltage increases; in this way, the units being controlled are powered up in the order you’ve chosen. To power-down, all you have to do is flip the switch so that C1 discharges through R5, and the LEDs go out in the reverse order to that in which they were lit, in turn powering down the units connected to the solid-state relays. Easy, isn’t it? If you’re not happy with the sequence speed, all you need do is increase or reduce the value of R5 in order to alter the speed one way or the other.

The circuit needs to be powered from a volt-age of around 9 to 12 V, which doesn’t even need to be stabilized. A simple ‘plug-top’, ‘wall wart’ or ‘battery eliminator’ unit will be perfect, just as long as it is capable of supply-ing enough current to power all the LEDs. As the LED current is set by R7 to 20 mA per LED, it’ll be easy for you to work out the current required, according to the number of solid-state relays you’re using.

In our prototype the type S216S02 relays from Sharp were used, mainly because they proved readily available by mail order. They also have the advantage of being compact, and their switching capacity of 16 A means you can dispense with a heatsink if you’re using them for a computer or home cinema system, where the current drawn by the vari-ous units can be expected to remain under 1 A. These solid-state relays must be protected by a fuse, the rating of which needs to be selected according to the current drawn by the devices being powered.

Also note the presence across the relay terminals of a VDR, also known as a GeMOV or SiOV, intended to protect them from any spurious voltage spikes. You can use any type that ’s intended for operation on 250 VAC without any problem. The values of fuses F1 to F4 are of course going to depend on the load being protected.

Construction of the circuit shouldn’t present any particular difficulty, but as the solid-state relays are connected directly to AC power, it is essential to install it in a fully-insulated case; the case can also be used to mount the power outlet sockets controlled by the circuit. Note that sockets are female components.

Let’s just end this description with the sole restriction imposed by our circuit — but it’s very easy to comply with, given the intended use. In order to remain triggered, the solid-state relays must carry a minimum holding current, which is 50 mA in the case of the devices we’ve selected. In practical terms, this just means that each of the devices powered by our sequencer must draw at least 50 mA, or in other words roughly 12 VA at 230 VAC, or 25 VA at 120 VAC.

Author :Christian Tavernier