The Portable Solar Lantern

This portable solar lantern circuit uses 6 volt/5 watt solar panels are now widely available. With the help of such a photo-voltaic panel we can construct an economical, simple but efficient and truly portable solar lantern unit. Next important component required is a high power (1watt) white LED module.

When solar panel is well exposed to sunlight, about 9 volt dc available from the panel can be used to recharge a 4.8 volt /600 mAh rated Ni-Cd batterypack. Here red LED (D2) functions as a charging process indicator with the help of resistor R1. Resistor R2 regulates the charging current flow to near 150mA.

Solar Lantern Circuit Schematic

Assuming a 4-5 hour sunlit day, the solar panel (150mA current set by the charge controller resistor R2) will pump about 600 – 750 mAh into the battery pack. When power switch S1 is turned on, dc supply from the Ni-Cd battery pack is extended to the white LED (D3). Resistor R3 determines the LED current. Capacitor C1 works as a buffer.

Note: After construction, slightly change the values of R1,R2 and R3 up/down by trial&error method, if necessary.

Soldering Iron Tip Preserver

Although 60/40 solder melts at about 200&degC, the tip temperature of a soldering iron should be at about 370&degC. This is necessary to make a good quick joint, without the risk of overheating delicate components because the iron has to be kept on the joint for too long. Unfortunately, at this temperature, the tip oxidises rapidly and needs constant cleaning. Thats where this circuit can help - it keeps the soldering tip to just below 200&degC while the iron is at rest. Oxidisation is then negligible and the iron can be brought back up to soldering temperature in just a few seconds when needed. In addition, normal soldering operation, where the iron is returned to rest only momentarily, is unaffected because of the thermal inertia of the iron. Two 555 timers (IC1 & IC2) form the heart of the circuit. 

Circuit diagram:

Soldering Iron Tip Preserver Circuit Diagram

IC1 is wired as a monostable and provides an initial warm-up time of about 45 seconds to bring the iron up to temperature. At the end of this period, its pin 3 output switches high and IC2 (which is wired in astable configuration) switches the iron on - via relay RLY1 - for about one second in six to maintain the standby temperature. The presence of the iron in its stand is sensed by electrical contact between the two and some slight modification of the stand may be necessary to achieve this. When the iron is at rest, Q1s base is pulled low and so Q1 is off. Conversely, when the iron is out of its stand, Q1 turns on and pulls pins 2 & 6 of IC2 high, to inhibit its operation. During this time, pin 3 of IC2 is low and so the iron is continuously powered via RLY1s normally closed (NC) contacts. Note that the particular soldering iron that the circuit was designed for has its own 24V supply transformer. Other irons may need different power supply arrangements. The warm-up time and standby temperature can be varied by altering R2 and R5, as necessary.

 

 

Streampowers

Soft Start For Switching Power Supply

Switching power supply whose output voltage is appreciably lower than its input voltage has an interesting property: the current drawn by it is smaller than its output current. However, the input power (UI) is, of course, greater than the output power. There is another aspect that needs to be watched: when the input voltage at switch-on is too low, the regulator will tend to draw the full current. When the supply cannot cope with this, it fails or the fuse blows. It is, therefore, advisable to disable the regulator at switch-on (via the on/off input). until the relevant capacitor has been charged. When the regulator then starts to draw current, the charging current has already dropped to a level which does not overload the voltage source.

The circuit in the diagram provides an output voltage of 5 V and is supplied by a 24 V source. The regulator need not be disabled until the capacitor is fully charged: when the potential across the capacitor has reached a level of half or more of the input voltage, all is well. This is why the zener diode in the diagram is rated at 15 V. Many regulators produced by National Semiconductor have an integral on/off switch, and this is used in the present circuit. The input is intended for TTL signals, and usually consists of a transistor whose base is accessible externally. This means that a higher switching voltage may be applied via a series resistor: the value of this in the present circuit is 22 kΩ. When the voltage across the capacitor reaches a level of about 17 V, transistor T1 comes on, whereupon the regulator is enabled.

Magnetometer

Magnetometers are scientific instruments that are used to measure the direction and strength of magnetic fields in the location that the device is located. They are used both on Earth as well on space exploration missions due to the significant variations that are found in magnetic fields based on the nature of the environment, interaction of charged particles from the sun, and the magnetosphere.

Why Are Magnetometers Used?

Magnetometers are not just used to measure the local strength of a magnetic field, however, as they can also determine their own direction and orientation. Many times the design of a magnetometer will be tweaked to match the specific quality of the device that is more important to the user. Some magnetometers are designed with a sensitivity that is great enough to detect increased sun activity before it is detectable by a visual observer which can provide an early warning of adverse effects on communications equipment. The traditional use of a magnetometer is to observe the Earth’s magnetic field that fluctuates in various locations on the planet. They are also used to conduct research on specific regions of the Earth’s crust to find minerals such as iron. More recently, the devices have been used to measure the impact of various actions taken by people have on the global and local magnetic fields of the Earth. Archaeological studies make use of the devices in order to help find ship wrecks and other sites that may have a number of magnetic substances that are collected in a single location to help start digs or recovery efforts. Some ships will also use a variation of the device in order to detect potential hazards to navigation that have moved since they were last charted.

What Are the Benefits of Studying the Earth’s Magnetic Field?

The study of the Earth’s magnetic field provides historical context to scientists regarding how the planet was created and since evolved in order to apply these lessons to the future. Historical shifts in the Earth’s magnetic field have been documented and also help determine what the impact of solar activity has been on the planet and how this will impact the future. Applications of this research range from current and future communications to ship navigation.

What Are the Types of Magnetometer?

The size and complexity of magnetometers widely vary. They can be portable or significant in size depending on the designed use. A simple compass used for land navigation is one form of the device, where those used for space exploration will be larger and more complex. The two basic types of magnetometer are: 1 – Scaler Type which is used to measure the total strength of a magnetic field, and 2 – Vector Type which has the ability to measure the magnetic field in a direction that is relative to the orientation of the device.

source[link]

A Homemade jet engine

A Homemade jet engine (The journey begins)

The 600 Watt vacuum cleaner that started it all.
Its made in China, where they obviously havent yet perfected the technique of making poor quality goods that hold together just long enough for you to lose the guarantee.
Its so powerful, it nearly twists your wrist off when you start it. And instead of the usual plastic moulding, it boasts a lightweight aluminium compressor wheel of superb design and construction.
I put a strobe light on the spinning compressor and found it was rotating at 50,000rpm!
On sale new for about £20 - I got it for £3 from a car-boot sale.


The juicy bits extracted from the vacuum. (Ill use the motor for something else)
From left to right,
The diffuser vane assembly, which stops the air spinning after it is ejected from the compressor wheel.

This is plastic so it wont stand the temperatures - pity.
The compressor wheel proper - beautifully made from light gauge aluminium sheet.
The compressor housing - galvanised steel. Slightly corroded but still useable

Bottom left, the new diffuser. Made from 1.8mm aluminium sheet with vanes cut from a bit of shim steel and glued in place with epoxy. Its a push-fit inside the housing and the springy vanes hold it nicely in place.
Those vanes are designed to catch the compressed air thats spinning around inside the periphery of the housing
and direct it back to the centre while taking out the spin. The result should be a smooth flow of compressed air.
Notice theres one more diffuser vane than there are blades in the compressor?

That is a refinement that further reduces turbulence. If they matched up, the result would be a siren.

The internal parts.
Top row, the diffuser (again) and the shaft housing. This is made from a length of tube with a bearing housing brazed to each end. The spoked ring holds the housing centrally in the outer casing.
The diffuser assembly is fastened to the front of the shaft housing using three countersunk screws and holds the front bearing in place.

The rear bearing is allowed to float axially (partly to allow for thermal expansion).
Bottom row, the partially complete turbine wheel. (The blades need shaping). The rear turbine bearing assy. The main shaft, compressor bearing assy. and the compressor wheel.


Heres a shot of the partially assembled turbine shaft.
The turbine wheel is 1.8mm stainless, sawn to a circle, the blades slotted and then each twisted to 37.5 degrees.

I really didnt think I could do this:
The outer casing is constructed from stainless steel pipe, 100mm diameter.
But the turbine end is 64mm diameter pipe, So the casing needs to come down from 100mm dia to 64mm with a taper section.
I hacksawed a sector out of steel plate (1.6mm ss), which took quite a while and left me dripping sweat. Then I spent ages more gently pounding it over a steel bar with a rubber hammer.

Im pretty proud of the result - a truncated cone that neatly joins the two cylindrical sections.


Here are the outer casing parts, ready for welding,

It will have to be welded, This part is likely to get too hot for brazing. The idea of the turbine casing coming adrift at speed doesnt bear thinking about.
The spoked ring that holds the turbine shaft is slighly larger than the casing so that it slides over it. (I cut a pice of the same pipe, split it and inserted a spacer.)
It will be bolted to the casing.
All of the dimensions were dictated by the size of the compressor wheel and housing and the available sizes of pipe I had in the workshop but it all worked out quite neatly in the end.
Theres still a lot of work to be done. The turbine needs a set of stationary vanes too (mounted in the conical section of the casing) to increase efficiency.
Those turbine blades need to be shaped to an airfoil section and the wheel balanced.
(Expected speed is 20-50,000 rpm so any imbalance could be quite exciting.)

Then there is the combustion chamber, fuel feed and a continuous oil supply for the bearings...

Construction - Turbine stator assembly

Welding up the outer casing was a mistake. More haste : less speed.
I should have put in the rear stator blades first.

Theres a bit of confusion over what to call this bit. Its a stator assembly really, sometimes (wrongly) called the diffuser which confuses with the compressor diffuser. Most people seem to settle on Nozzle Guide Vane assembly (NGV).

These blades impart a rotation to the exhaust gas flow just before the gas strikes the turbine blades, which just about doubles the efficency of the turbine.
The rotation is taken out by the turbine with the result that the exhaust gasses exit pretty well straight out of the back end.
Only problem is that they are the very devil to fit. Slots have to be cut in the conical section of the casing. And these slots would ideally be curved so that the
stator blades can be curved too. Then they must be inserted precisely enough to provide an accurate location for the turbine shaft.

On the whole, a tediously fiddly job that would have been easier if I hadnt made access almost impossible beforehand.
The inner end of the stator blades form a ring that locates the tube that in turn supports the back end of the turbine shaft.
The tube also acts as a heat shield for the rear bearing (I got this badly wrong too, but more on that later)

Combustion chamber

I hadnt the faintest idea how to make a combustion chamber. But apparently, because of the high temperature of the burning fuel, most of the air that comes into the engine is used for cooling so that the turbine blades dont melt.
Everything I found on the subject suggested that about 20% of the air is used for direct combustion, another 20% is used also in combustion but also to help stabilise the flame towards the front of the chamber (by creating a vortex).
The rest of the air flows around the outside of the chamber and is introduced gradually into the hot gasses.


So my design was for an annular chamber, consisting of a ring and two tubes (inner and outer).

The whole thing is just stitched together with pieces of stainless steel wire.
The annular ring is pierced by 16 holes (6mm dia). Propane is injected into these holes from a gas ring placed just in front.
The gas ring is just a ss tube, bent into a circle and pierced at 16 points to coincide with the holes in the ring. The tube is held in place by stainless steel wire, hooked into the ring holes.
The other (straight )tube visible just above the gas ring in the picture is the oil feed to the turbine shaft.
About 20mm along the inner and outer tubes is another series of holes. These are intended to inject air sideways into the flames, hopefully imparting turbulence and ensuring that all the available fuel is burned within that region.
At the exit end of the chamber there are more holes to allow the remaining air to enter the chamber, providing cooling.
Before mounting the chamber in the turbine, I tried some static tests, blowing air into the chamber which was mounted in a tube. When gas was added and ignited, it did seem to burn as expected, but there is no way to be absolutely sure how it will work in practice.

How to Build a Homemade Pure Sine Wave Inverter Using IC 555

How to Build a Homemade Pure Sine Wave Inverter, Using IC 555

Posted by hitman

The proposed circuit generates accurately spaced PWM pulses which imitates a sine wave very closely and thus can be considered as good as its sine wave counter part design. Here we use  two stages for creating the required  PWM pulses, the stage comprising the ICs 741 and the other comprising the IC 555. Let’s learn the whole concept in details.

How the Circuit Functions – The PWM Stage

The circuit diagram can be understood with the following points:

The two op amps are basically arranged to generate the required sample source voltages for the IC 555. 

The couple of outputs from this stage is responsible for the generation of square waves and triangular waves.

The second stage which is actually the heart of the circuit consists of the IC 555. Here the IC is wired in a monostable mode with the square waves from the op amp stage applied to its trigger pin #2 and the triangular waves applied to its control voltage pin # 5.

The square wave input triggers the monostable to generate a chain of pulses at the output where as the triangular signal modulates the width of this output square wave pulses.

The output from the IC 555 now follows the “instructions” from the op amp stage and optimizes its output in response to the two input signals, producing the sine equivalent PWM pulses.

Now it’s just a matter of appropriately feeding the PWM pulses to the output stages of an inverter consisting of the output devices, the transformer and the battery.

The Output Stage

The above PWM output is applied to the output stage as shown in the figure.

Transistors T1 and T2 receive the PWM pulses at their bases and switch the battery voltage into the transformer winding according to the duty cycles of the PWM optimized waveform.

The other two transistors make sure that the conduction of T1 and T2 takes place in tandem, that is alternately so tat the output o from the transformer generates one complete AC cycle with the two halves of the PWM pulses.

Parts List

R1, R2, R3, R8, R9, R10 = 10K,

R7 = 8K2,

R11, R14, R15, R16 = 1K,

R12, R13 = 33 Ohms 5 Watt,

R4 = 1M preset,

R5 = 150 K preset,
R6 = 1K5

C1 = 0.1 uF,

C2 = 100 pF,

IC1 = TL 072,

 IC2 = 555,

T1, T2 = BDY29,

T5, T6 = TIP 127,

T3, T4 = TIP122

Transformer = 12 – 0 – 12 V, 200 Watts,

Battery = 12 volts, 100 AH.

Dual Power Supply 78xx 79xx

Many times the hobbyist wants to have a simple, dual power supply for a project. Existing powersupplies may be too big either in power output or physical size. Just a simple Dual Power Supply is required.For most non-critical applications the best and simplest choice for a voltage regulator is the 3-terminal type.The 3 terminals are input, ground and output.

The 78xx & 79xx series can provide up to 1A load current and it have onchip circuitry to prevent damage in the event of over heating or excessive current. That is, the chip simply shuts down rather than blowing out. These regulators are inexpensive, easy to use, and they make it practical to design a system with many PCBs in which an unregulated supply is brought in and regulation is done locally on each circuit board.

Circuit diagram:

Dual Power Supply Schematic Circuit diagram

This Dual Power Supply project provides a dual power supply. With the appropriate choice of transformer and 3-terminal voltageregulator pairs you can easily build a small power supply delivering up to one amp at +/- 5V, +/- 9V, +/- 12V, +/-15V or +/-18V. You have to provide the centre tapped transformer and the 3-terminal pair of regulators you want:7805 & 7905, 7809 & 7909, 7812 & 7912, 7815 & 7915or 7818 & 7918.

Note that the + and - regulators do not have to be matched: you can for example, use a +5v and -9V pair. However,the positive regulator must be a 78xx regulator, and the negative a 79xx one. We have built in plenty of safety into this project so it should give many years of continuous service.  The user must choose the pair he needs for his particular application.

Parts :

Transformer

This Dual Power Supply design uses a full wave bridge rectifier coupled with a centre-tapped transformer. A transformer with a power output rated at at least 7VA should be used. The 7VA rating means that the maximum current which can be delivered without overheating will be around 390mA for the 9V+9V tap; 290mA for the 12V+12V and 230mA for the 15V+15V. If the transformer is rated by output RMS-current then the value should be divided by 1.2 to get the current which can be supplied. For example, in this case a 1A RMS can deliver 1/(1.2) or 830mA.

Rectifier

We use an epoxy-packaged 4 amp bridge rectifier with at least a peak reverse voltage of 200V. (Note the part numbers of bridge rectifiers are not standardised so the number are different from different manufacturers.) For safety the diode voltage rating should be at least three to four times that of the transformers secondary voltage. The current rating of the diodes should be twice the maximum load current that will be drawn.

Filter Capacitor

The purpose of the filter capacitor is to smooth out the ripple in the rectified AC voltage. Theresidual amount of ripple is determined by the value of the filer capacitor: the larger the value the smaller the ripple.The 2,200uF is a suitable value for all the voltages generated using this project. The other consideration inchoosing the correct capacitor is its voltage rating. The working voltage of the capacitor has to be greater than thepeak output voltage of the rectifier. For an 18V supply the peak output voltage is 1.4 x 18V, or 25V. So we havechosen a 35V rated capacitor.

Regulators

The unregulated input voltage must always be higher than the regulators output voltage by at least 3V inorder for it to work. If the input/output voltage difference is greater than 3V then the excess potential must bedissipated as heat. Without a heatsink 3 terminal regulators candissipate about 2 watts. A simple calculation of the voltage differential times the current drawn will give the watts tobe dissipated. Over 2 watts a heatsink must be provided. If not then the regulator will automatically turn off if theinternal temperature reaches 150oC. For safety it is always best to use a small heatsink even if you do not think youwill need one.

Stability

C4 & C5 improve the regulators ability to react to sudden changes in load current and to preventuncontrolled oscillations.

Decoupling

The monoblok capacitor C2 & C6 across the output provides high frequency decoupling which keepsthe impedence low at high frequencies.

LED

Two LEDs are provided to show when the output regulated power is on-line. You do not have to use theLEDs if you do not want to. However, the LED on the negative side of the circuit does provide a minimum load tothe 79xx regulator which we found necessary during testing. The negative 3-pin regulators did not like a zeroloadsituation. We have provided a 470R/0.5W resistors as the current limiting resistors for the LEDs.

Diode Protection

These protect mainly against any back emf which may come back into the power supply when itsupplies power to inductive loads. They also provide additional short circuit protection in the case that thepositive output is connected by accident to the negative output. If this happened the usual current limiting shutdownin each regulator may not work as intended. The diodes will short circuit in this case and protect the 2 regulators.

Source :www.electronics-project-design.com