Electrinic and circuit: simple

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Simple Mini Power Inverter

Even robot systems occasionally need a negative supply voltage for some purpose or other, and in this kind of application in particular there is a need for an effective circuit that does not make greater demands then necessary in terms of current or space. If a low current 5 V supply is needed and only +5 V is available, a natural manufacturer to turn to is Maxim, and indeed in this case they do not let us down.The best known integrated circuit made by this company is the MAX232, a level shifter for serial ports with an integrated charge pump that does not need an external inductor.

Simple Mini Power Inverter image:

Along the same lines, although with a more stable output voltage and higher efficiency, is the MAX660. The device can ‘mirror’ any input voltage between 1.5 V and 5.5 V. With a 5 V input the output is typically –4.7 V with a load of 100 mA. Efficiency at 10 mA is around 96 % and at 100 mA is around 88 %. With an open-circuit output the IC draws a quiescent current of just 120 μA.There is little to say about the circuit itself.

Simple Mini Power Inverter Circuit diagram:

The 0 Ω resistor on pin 1 selects the operating frequency. With R1 fitted, the circuit operates at 80 kHz; without it, at 10 kHz. The combination of L1 and C5 slightly reduces ripple on the output voltage; the choice of inductor is not as critical as it would be if it formed part of the switching circuit.Gerber files for the printed circuit board (which uses some SMD components) are available for download from the Elektor website, ref. 070279-11.zip. R1, C1 and C4 are 0603 SMDs and C3 is an SMD tantalum electrolytic capacitor. Either the MAX-660CSA or the MAX660M can be used; both come in SO8 packages. L1 is a 10 μH SMD inductor rated at 300 mA.

Source: http://www.ecircuitslab.com/2011/11/even-robot-systems-occasionally-need.html

Simple 250W Inverter Circuit Diagram

This is a simple 250W Inverter Circuit Diagram. A 555 timer (IC1) generates a 120-Hz signal that is fed to a CD4013BE flip-flop (ICl-a), which divides the input frequency by two to generate a 60-Hz clocking frequency for the FET array (Ql through Q6). Transformer Tl is a 12-/24-V center-tapped 60-Hz transformer of suitable size.

250W Inverter Circuit Diagram

Simple Automatic Load Sensing Power Switch

This circuit will automatically switch on several mains-powered "slave" loads when a "master" load is turned on. For example, it will switch on the amplifier and CD player in a stereo system when the receiver is turned on. It works by sensing the current draw of the "master" device through a low value high wattage resistor using a comparator. The output of that comparator then switches on the "slave" relay. The circuit can be built into a power bar, extension cord or power center to provide a convenient set of "smart" outlets that switch on when the master appliance is powered (turn on the computer monitor and the computer, printer and other peripherals come on as well).

Parts

Part	Total Qty.	Description
C1, C3	2	10uF 35V Electrolytic Capacitor
C2	1	1uF 35V Electrolytic Capacitor
R1	1	0.1 Ohm 10W Resistor
R2	1	27K 1/2W Resistor
R3, R4	1	1K 1/4W Resistor
R5	1	470K 1/4W Resistor
R6	1	4.7K 1/2W Resistor
R7	1	10K 1/4W Resistor
D1, D2, D4	3	1N4004 Rectifier Diode
D3	1	1N4744 15V 1 Watt Zener Diode
U1	1	LM358N Dual Op Amp IC
Q1	1	2N3904 NPN Transistor
K1	1	Relay, 12VDC Coil, 120VAC 10A Contacts
S1	1	SPST Switch 120AVC, 10A
MISC	1	Board, Wire, Socket For U1, Case, Mains Plug, Socket

Notes

This circuit is designed for 120V operation. For 240V operation, resistors R2 and R6 will need to be changed.
A maximum of 5A can be used as the master unless the wattage of R1 is increased S1 provides a manual bypass switch.
THis circuit is not isolated from the mains supply. Because of this, you must exercise extreme caution when working around the circuit if it is plugged in.

Simple DC Over voltage Protector Circuit Diagram

A very simple DC over voltage protector circuit is shown below. The transistor is set to monitor the input voltage applied to it from the left, in case the voltage rises above a specified limit, the transistor conducts, providing the required current to the SCR, which instantly fires, shorting the output and thus protecting the load from the hazard. Its also called a Crowbar circuit.
The circuit shown below is very simple to understand and is quite self explanatory.
The working may be understood with the following points:
The supply DC input voltage is applied from the right hand side o the circuit across the SCR.
As long as the input voltage remains under a certain predetermined value, the transistor is unable to conduct and therefore the SCr also remains shut.
The threshold voltage is effectively set by zener diode voltage.
As long as the input voltage stays below this threshold everything goes on fine.
However in case the input crosses the above threshold level, the zener diode starts conducting so that the base of the transistor starts getting biased.
At some point of time the transistor becomes fully biased and pulls the positive voltage to its collector terminal.
The voltage at the collector instantly passes through the gate of the SCR.
The SCR immediately conducts and shorts the input to ground.
This may look a bit dangerous because the situation indicates that the SCR might get damaged as it shorts the voltage directly through it.
But the SCR remains absolutely safe because the moment the input voltage drops below the set threshold the transistor stops conducting and inhibits the SCR from going into damaging extents.
The situation is sustained and keeps the voltage from reaching above the threshold.

Simple Oscillator Pipe Locator

Sometimes the need arises to construct a really simple oscillator. This could hardly be simpler than the circuit shown here, which uses just three components, and offers five separate octaves, beginning around Middle C (Stage 14). Octave # 5 is missing, due to the famous (or infamous) missing Stage 11 of the 4060B IC. We might call this a Colpitts ‘L’ oscillator, without the ‘C’. Due to the reactance of the 100-µH inductor and the propagation delay of the internal oscillator, oscillation is set up around 5 MHz. When this is divided down, Stage 14 approaches the frequency of Middle C (Middle C = 261.626 Hz). Stages 13, 12, 10, and 9 provide higher octaves, with Stages 8 to 4 being in the region of ultrasound.

Simple Oscillator/Pipe Locator Circuit Diagram

If the oscillator’s output is taken to the aerial of a Medium Wave Radio, L1 may serve as the search coil of a Pipe Locator, with a range of about 50 mm. This is tuned by finding a suitable hetero-dyne (beat note) on the medium wave band. In that case, piezo sounder Bz1 is omitted. The Simple Oscillator / Pipe Locator draws around 7 mA from a 9-12 V DC source.

Source: http://www.ecircuitslab.com/2012/05/simple-oscillator-pipe-locator.html

A Simple Video Out Coupling Circuit

If you want to connect a video signal to several destinations, you need a distribution amplifier to match the 75-ohm video cable. A distribution amplifier terminates the incoming cable in 75 ohms and provides several outputs, each with 75-ohm output impedance. Since this is usually achieved by putting a 75-ohm series resistor in the output lead of each video opamp (current-feedback amplifier), the opamps must be set up for a gain of 2 in order to achieve an insertion gain of 1 (0 dB). The disadvantage of this arrangement is that if the amplifier or its power supply fails, no signal is available at any of the outputs. This can be remedied by using a high input impedance amplifier, which can be tapped into a video line without having to have its own 75-ohm termination resistor.

Circuit diagram:

Video-Out Couplingw 1 A Sample Video-Out Coupling Circuit diagram

Farmula Video-Out Couplingw 2 Farmula Video-Out Couplingw

In order to eliminate hum interference and voltage differences between the cable screen and the circuit earth, the circuit exploits the common-mode rejection of the opamp. This can be optimized with resistor RG1. With the indicated LT1396 video opamp, more than 40 dB of common-mode rejection can be achieved. The signal bandwidth of the circuit can be optimized using the trimpots. It reaches to more than 10 MHz, which is quite acceptable for video signals. Thanks to the high-impedance connection to the video line, the video signal is not affected when the power for the coupled amplifier is switched off. You can learn more about the LT1396 from its data sheet at http://www.linear-tech.com.

Electrinic and circuit