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Saturday, April 13, 2013

zBot 10 A Power Stage for DC Motor

If\r\n you take a look at the chassis of the zBot vehicle1, you’ll find two sections \r\nrequiring intelligent keep a watch on: the steerage servo and the DC motor. The \r\nso known as H-bridge is the normal circuit for electronic control of \r\nrevolution pace and route. The DC motor of a Tamiya automobile is powerful\r\n sufficient to propel zBot at as so much as 20 miles per hour.

The\r\n motor then consumes more than 10 A, so we make a selection high-current energy \r\nMOSFETs for the cause force stage. There are numerous totally different softwares to \r\nchoose from. The MOSFET we require has to provide the maximum motor \r\ncurrent and, importantly, it needs to be switched with gate voltages of \r\nabout 5 V. In this case, the microcontroller switches the ability stage \r\n(‘low aspect’) directly. For high aspect riding degree shifters are \r\nnecessary. The schematic of the H-bridge power stage presentations a few \r\ninverters, NAND gates and two tri-stateable drivers. These logic \r\nfunctions are essential as the better approach, i.e.., in an instant \r\ncontrolling all 4 MOSFET has a fatal disadvantage.

In\r\n case of a software crash it may well happen that two ore extra MOSFETs are \r\nswitched on incor-rectly for exam-ple, T4 and T7. In that case, the \r\ncurrent throughout the transistors is proscribed by using the interior resistors of \r\nthe MOSFETs (about 10 mO) simplest. Such a deadly error would destroy the \r\nMOSFETs. The common sense performs configured here successfully avoid illegal \r\nstates.To keep an eye fixed on the DC motor, three signals are needed: DIR, PWM and \r\nSTOP. DIR regulates the path of the motor revolution, PWM the rate,\r\n and STOP brakes the motor.

The\r\n software program module for the DC motor is called dcm.c.(070172-I) The \r\ncomplete document referred to as Zbot the Robot Experimental Platform is \r\navailable free of charge downloading from the Elektor Electronics site. The\r\n file quantity is 070172-11.zip (July/August 2007).

http://www.ecircuitslab.com

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Thursday, April 11, 2013

Class A power amplifier

Class A Power Amplifier

Examples of class A amplifier is the basic transistor circuit common emitter (CE). Amplifier type class A is made by setting dititik bias current (usually Q) on the load line. The position of point Q such a way that is right in the middle line of the load curve VCEIC from the amplifier circuit.

The is an example circuit with common emitter NPN transistor Q1.

Line load on this amplifier determined by the resistor Rc and Re from the formula VCC = VCE + ICRC + IeRe. If Ie = Ic, it can be simplified into VCC = VCE + Ic (Rc + Re). Next line load circuit can be described by a formula them. While resistors Ra and Rb were installed to determine the bias currents. Magnitude resistors Ra and Rb in related series determining how much current Ib the cut point Q. Large Ib flows usually listed on the data sheet used transistors.

Great strengthening AC signals can be calculated with an AC signal circuit analysis theory. In an AC circuit analysis of all components of the capacitor C connected brief and the imaginary connecting the VCC to ground. With In this way a series of images 1-18 can be assembled into such picture 1-20. Resistors Ra and Rc is connected to GND and all short-circuited capacitor.

Typical class A amplifier, all output signals to work on active region. Amplifier type class A is called as a reinforcement that has fidelitas a high level. Provided the signal is still working in the active region, form the output signal will exactly match the input signal. But class A amplifier has low efficiency of approximately only 25% - 50%. Its none other since the point Q is at point A, so that although there is no input signal (or when the input signal = 0 Vac) transistors to keep working in the active region with a constant bias current. Transistor is always active (ON) so that most of the sources of supply wasted power into heat. Since this is class A transistor amplifier should be augmented with extra cooling like heatsinks are more large.

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Tuesday, April 9, 2013

A Homemade Fence Charger Energizer Circuit Explained

The electric fence charger circuit presented here is basically a high voltage pulse generator. The super high voltage is derived from a commonly used automobile ignition coil. An astable multivibrator is used to generate the required frequency to drive the ignition coil. Another astable is used to control the pulses supplied to the fence.

If you have large agricultural fields and desperately need to protect the crops from uninvited guests like animals and possibly humans, then this electric fence charger device is just what you are looking for. Build and install it yourself.

An electric fence is an electrified high voltage barrier which produces painful shocks if physically touched or manipulated. Thus such fencing basically function as deterrents for animals as well as human intruders and stop them from crossing the restricted boundary.

The present circuit of an electric fence charger is designed and tested by me and has proved sufficiently powerful for the application.

The circuit is able to produce voltage pulses up to 20,000 volts, needless to say about the fatality rate involved with it. However the pulses being intermittent, provides the subject with enough time to realize, recover and eject.

The generated pulse is so powerful that it can easily arc and fly-off between short distances of around a cm. so the fencing conductor needs to be separated adequately to avoid leakages through arcing and sparking. If not tackled, may drastically reduce the effectiveness of the unit.

Here the generation of high voltage is primarily carried out by an automobile ignition coil.

The winding ratios of an ignition coil are specifically designed and intended for creating high voltage arc between a two closely spaced conductors inside the ignition chamber to initiate the ignition process in vehicles.

Basically it’s just a step-up transformer, which is able to step-up an input applied voltage at its primary winding to monstrous levels at its output or the secondary winding.

SOME POINTS OF THE CIRCUIT AND THE IGNITION COIL IS VERY DANGEROUS TO TOUCH WHEN POWERED. ESPECIALLY THE IGNITION COIL OUTPUT IS TOO LETHAL AND MAY EVEN CAUSE PARALYSIS.

Let’s diagnose the whole thing more deeply.

Circuit Description

In the CIRCUIT DIAGRAM we see that the entire circuit is basically comprised of four stages.

A DC oscillator stage,

An intermediate 12 to 230 volts step-up stage,

The voltage collector and firing stage and

The super high voltage-booster stage.

TR1 and TR2 are two normal step-down transformers whose secondary windings are connected through SCR2. TR2’s input primary winding may be selected as per the country specification.

However, TR1’s primary should be rated at 230 volts.

IC1 along with the associated components forms a normal astable multivibrator stage. The supply voltage to the circuit is derived from the secondary of TR2 itself.

The output from the astable is used to trigger SCR2 and the whole system, at a particular fixed intermittent rate as per the settings of P1.

During the ON periods, SCR2 connects the 12 volt AC from TR2 to the secondary of TR1 so that a 230 volt potential instantly becomes available at the other end of TR1.

This voltage is fed to the voltage-firing stage consisting of the SCR1 as the main active component along with a few diodes, resistor and the capacitor C4.

The fired voltage from SCR1 is dumped into the primary winding of the ignition coil, where it is instantly pulled to a massive 20,000 volts at its secondary winding. This voltage may be suitably terminated into the fencing.

The high voltage generated by this electric fence charger will need to be carefully applied across the whole length of the fence.

The two poles from the ignition coil connected to the fence wiring should be kept at least 2 inches apart.

The pillars of the fence should be ideally made of plastic or similar non conducting material, never use metal and not even wood (wood tend to absorb moisture and may give path to leakages).

Parts List

R4 = 1K, 1WATT,

R5 = 100 OHMS, 1WATT,

P1 = 27K PRESET

C4 = 105/400V PPC,

ALL DIODES ARE 1N4007,

IC = 555

TR1 = 0-12V/3Amp (120 or 230V)

TR2 = 0-12V/1Amp (120 or 230V)

BOTH THE SCRs ARE C106 OR PREFERABLY BT151,

TWO WHEELER IGNITION COIL IS SHOWN IN FLUORESCENT BLUE COLOR

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Monday, April 8, 2013

try start building a low cost Jet engine

After problems getting a turbocharger for a reasonable price, we finally got a KKK truck charger,in god condition for (kr200 / $40).Next we experiment a lot with a AUDI oil-sump pump, but ran in problem, so we decide to get the oil tank build, and because I know one who could TIG weld one in stainless-steel, the test stand was made of same material . A spring loaded sledge that run on four small bearing make it possible to measure the trust.The flame tube was also made of S/Steel, and once again I was able to obtain some 3" tubes for a sum of (kr50 / $10).So until now the budget is very fine.

The combuster was made of ordinary 4" steel tubes and welded on a 3mm plate for connecting to the turbo chargerThe top of the combuster is made (once again) of a S/Steel ring that fit into the combuster and tapped with 3 bolts.On this ring the flame holder is CO2 welded so it easily can be removed. On top we fitted a thick 8mm Alu plate that gives enough room to hold a automotive spark-plugs, and in center a hole for the gas nozzle.We use a high voltage transformer (10kV) from an old house heating unit, to ignite, and a large radial air-blower to start the engine,all found on a re cycling station for free.

A 11 Kg propane cylinder feed the system. The regulator for the propane , high pressure hose and fittings cost (dk500 / $100),expensive but a good safety investment. "Some time ago a propane cylinder explosure totally rasure a hole building block near by, because of a non legal regulator !"

6/5-97

Today I gave jan a print of Chris Barnetts home page, and after readings and his recommendation not to run the test inside , we took our test-stand outside, mounted the combuster unit and fitted the propane so we were ready to test the combuster.We get it started with a hand held propane blower, and its seems to function very good, so after reassembling and examination of the flame holder we were very pleased about the burning . A little adjust to the nozzle and we ran for more test.

7-8/5-97

The Audi pump was changed with a Escort MkII pump and fitted on a brass plate where two 10mm copper tubes where solded on,for connection to the hose. After trying with a 75 Watt motor, we soon discover we need more power, so a 0.5 Hp motor came in place. Now we have a stable pressure but the coupling between the motor and pump is to wear.

9/5-97

Today we finish the oil pump and assembled the hole turbine for the first run. After an hour we were ready. The ignition function very well after we have made a little hole in the nozzle so that a bit of gas streams backwards to the spark plugs. With the radial blower the turbine ran very slowly, but after ignition it starts to accelerate.Every time we disconnect the air blower the engine stops ! We have no EGT(exhaust gas temp.) sensor and no RPM counter, so it was a little delicate to run with to much pressure for longer time. After cooling down the turbine wheels, we tried to boost with high pressure in short intervals too extend a reasonable EGT.Now we got a further acceleration and soon we could hear the compressor start working with a loud wizzle. After disconnection of the blower it runs. !!!! Yeah..With no rews and EGT sensors we only runs for shorter times (about 30sec.) but have made about 10 starts.

13/5-97

We have start to made a RPM sensor out of a infrared diode (from an remote cont.)After cutting the diode to 3mm thins the diode and photo transistor only measuring 10mm sq. We reflect the light on the bolts holding the compressor wheel, since we got 6 pulses every rews, it can feeds a ordinary freq. counter and readout RPM/10. Its go fine with a drilling machine driving the turbine with 2600 RPM, so hopefully also with 60000 RPM or more.

14/5-97

The final finish was made today , and a control board was made to all the instruments, we also modify the flame holder by reversing it (it contain only holes in the half of the length) and we run a test only on the combuster, but it did not work, so back to the future.! It took a lot of work, so when we finally fix it and get on with the new RPM counter, it also dont work, no read out.! Now matter, the jet should run today but it would not.... great flame outs ! Could it be our modification that have mismatch the hole burning. It have been late and we interrupt for today, a real bad bad day.

20/5-97

We have got the RPM counter working by adding a amplifier to the photo transistor, it consist of a op amp (LM358) in a self adjusting coupling so it compensate for fault light influence, and it works great.Schmatic Also the diode is deliver more power (80mW). We have tested to 60000 RPM with a small DC motor and a disc, we need a larger discs to exceed 100.000 . It measure up to a range of 6 cm. We decided to test the engine with the new RPM counter. The result... it suddenly run ? . But we have figure it out .! The oil is too cold or to thick, with a temp. of 40 deg. cel. the turbine began to run much smoother, so all the problems we had the last couple of days where solved. Success, and we run it for more than an hour.

21/5-97

Our new RPM counter were mounted today and the engine started. We began heating the oil to about 35 deg.cel. (we need some thinner oil) with a pressure of 3 bar. After acceleration to 20.000 RPM the engine run by itself. With higher oil temperature (we measured 60 deg.cel.) the oil pressure lower to 2 bar. and RPM raised to 31.000. But we have too low gas pressure to go further, so we measuring the lowest self running RPM to 18000 with 60 deg.cel. oil temp. With lower oil viscosity the engine will run much better. We were surprised about the low RPM, so our concern over to high rews in the past were eliminated. It would be interesting to measure the trust, but we havent yet fitted the spring on the sledge, but our guess is (4-5Kg/50N).

5/6-97

Yesterday we re designed our flame-holder, and have build it today. With a combuster-test we notice a much cooler outlet, so we were excited to see the performance.! It works much better, than the old one, with 45000 RPM we mess only 764 deg.C EGT, and notice that when the engine excite about 35000 RPM the EGT lower from around 800 deg.C. down to 764 deg. So with more revs we will hopefully get a further decrising in EGT. We couldnt reach higher revs because the propane only aloud 2 bar of gas-pressure. Only a few experiment have been made with the diesel inj. system, but hopefully we will get more time for this system soon.

17/8-97 Sorry for the long delay, but today Sunday we made our first run on diesel fuel.
The last couple of weeks we have made some experiments with home made injector jets for diesel, but the didnt perform proberly, so we decide to buy a Danfoss injector jets for central hous heating systems. Its only cost 90Kr./15$ and could be ordered with flow from around 1 Liter to 100 Liter or more /h. We got one with a flow of (10.4 Liter/3USG)/h and it perform excellent with a very good atomisation.The high pressure pump also comes from a oil burner system, and are driven from a DC motor powered from a variable power supply. On our first attemp we have mounted a simple gas nozzle that ignite with the old sparkplug, and then by running the pump we ignite the diesel. Later we discover that the diesel have so good atomisation that it could be ignited directly by the sparkplug. The first combuster test was wery promising, but with full throttle it produce a little to mutch flame out. Mounted on the engine its soon become a problem so we made a few modification on the flame holder, and came out with a reasonable result. On the first attemp we nearly got affrait of it! It accelerate tremendes , from 3000 to over 15000 rev in a second !!. Finaly we came out with a top rev of 35000 and a EGT of 800 deg.C.
Next we will try to seal the hole compressor system because we lost to mutch air pressure, so mabe that give us more rev and lower EGT.
I have nearly forgot to mentiod that we have change the oil. Now we use automatic transmission oil that have a wery low viscosity and therfor reduce the friction in the hydropnomatic bearings, its cost about the same as normally mineral oil, so its a good alternativ to full syntetic oil.Sametime we have rearrange the drainline on the turbocharger so that it now point directly downward, that have solve our problem with oil leak into the hot turbine and eliminate the great smoke cloud that sometime appear.
The development continue, stay tuned...!

We are currently working on the new project but have no images to show, therefore I will try to explain about our plans and status right now.

The major problem our jet engine is the physically volume and the heavy weight.

We have got another KKK charger and are in the situation that we could use the old one to improve new designs and run performance test.

Its possible to start at year zero, and make a completely new design without having to scrap the old engine

and finally by changing to diesel fuel we could design the engine for that system from the beginning.

We will try to build a compact engine by mounting the combustion chamber axially to the turbine so it point parallel to the exhaust cone. The length of the combustion-chamber will be 42cm. and the clou is that we make it square, so the turbo are sitting on the one end of the square tube, inside we use a ordinary round flame holder. The problem is that the flame holder must have a 90 deg angle at the end for connecting to the turbo, and that make it a bit tricky to manufacture. The exhaust tube or cone will be as long as the combustor-chamber and give enough room for an eventually afterburner. That means that the engine will have this overall dimension.

The lubrication system will be of much smaller dimension, with a smaller pump driven with at 12 V DC motor, and the liquid oil mass will only be 0.5-1 Liter with a copper-tube cooler of up to 2 meter length maybe arranged in front of the compressor. We have also made some test with a electric starter motor couplet to the compressor nut through a silicone hose, and that seems weary promising, up to 10000 rev with a tiny high-power scale racer motor, so maybe with a gear ratio of 3:1 we could make a electric miniature starter.
Our experiment with diesel fuel on the first engine have given us some good experience that will be transform to the second.
For the diesel injection we are using a small diesel pump that have prove to be ideal for our use, and also the hose and fittings for the high pressure system we have managed to overcome in a cheap way, we simply use normally air fittings and hose with a diameter of 4mm, that managed the pressure of 15-18 bar quite well. Same time we have got control over the ignition, and are designing it for a normally spark plug that have proven to ignite the atomisated diesel extremely well. Also the injector jets are been delivered from DANFOSS, we now have 7 different with flow of 1.4 - 10.4 - 12.8 - 13.9 - 17.3 liter/h and a spray of 80 deg.

STATUS:
Our plans from now is to build the new square-tube combuster_chamber and fit it to the old 14.1 version and from there develop it to perform as well as possible. That seems to be the best choice now, since the old combuster-chamber would need a fully redesign if it should run well on diesel. If that goes well we build the new engine and move the new combuster-chamber to that engine.
Soon we will update with some images of the new 14.2 combuster-chamber.

20/9-97

Note the oil tank arranged under the turbine, that aloud us to fasten the tank directly to the drain line. the oil pump and motor will be installed behind the oil tank, (not shown on the drawing).High pressure diesel pump, fuel tank and motor will be mounted on top of the engine, the diesel tank will have a volume of about 5 liter (W25 x L20 x H10 cm)
The hole engine will be mounted in a tube frame, so It easily can be implemented in a vehicle.

20/9-97

The current status are as following.
We have build a new combuster chamber for developing use only. Its made well long (~50cm) and are of ordinary round s/s tube, but equipped with the 90 deg. angle tube we intend to use on the rectangular combuster chamber.
The first tests running on the axial blower was pretty disappointing, the tube angle glowing bright yellow and we have seriously flame out problems. There was trouble with the fuel pump since it produce a oscillating flow , so there was thing to manage.
We found a failure on the pump, so after fixing it, we then have a stable pressure from 4-18 bar.
Next we fastened the combuster chamber on the engine, well knowing we would get problem, and that s what we got. It was impossible to get self sustaining, the exhaust temp. was far to high, and there was also some nice explosions of unburned fuel collected in the combuster chamber.
Its a mystery, since the old combuster designed for gas, and running on diesel, was performing quite well.
I have lately got some good inputs from Peter(UK) to optimizing the combuster, so there will be some modifications soon, we maybe also found the major fault...? Our guess is ...! the injector jet we currently use is a S injector and the injector we used in the past was a H type, the different are unknown, but maybe by changing the injector we would solve the problems.
Thats where we are now.
so stay tuned.

21/11-97

News, mostly bad but also few improvements.First, we have got self-sustaining with the new combuster,Yeh... but first after solving different bugs, and regrettably... only on gas. Argh...We have made dramatic changes to the combuster inlet by blocking the inlet near the top and made a new in the bottom, increased the inlet area and skipped the PVC tube we first used, now we use a flex tube of larger diameter than the PVC tube and have overcoming the restriction in airflow caused by use of two 90 deg PVC tubes. So the conclusion of that must be.. dont restrict the compressor outlet by using smaller sq. area and avoid the use of bending tubes with to sharp edges. Sometime we realize that the oil sponsorship by Statoil was useless, since it cause to mutch drag on the shaft, and have change back to automatic transmission oil again.All that have improved the performance of the combustion but not yet to our satisfaction, still to high EGT. The problem is the flame front that is far away from the primary zone, and appear in the middle of the chamber, and we have realize that, after trying blocking and opening holes, adding thimbles and turbulator rings, we need a other design.We think the output speed from the injector jets is so high that the combustion is moved down the liner caused by the enormous fuel pressure. That cant be compensated with our low pressure, so with that in mind we thought of making a vaporization system instead. So... today We made a experiment with vaporization..We took a 10mm tube, 20 cm long and fitted a short silicone hose to the one end. Made a small hole in the side and feeded a brass tube (2mm) into it and bend it 90 deg. The silicone hose was then connected to a blower through a adapter. The pump was connected to the brass tube and the pressure reduced to 3-4 bar. The tube was fixed in a old vice and heated with a propane blower, so...after heating to maybe 3-400 deg.C we started the pump and let the blower ignite the fog extended at the end. By adjusting the air we got a really nice flame, with right air/fuel ratio the flame was bright blue and burned completely starting at the end of the tube and extend 40-50 cm away.That seems to be a solution thats worth to try, so please stay in touch with more updates...who will be added in a few days when the whether aloud us to test.

24/11-97

Now theres really good news:
Today we took the combuster made for atomization use and transform it to work on vaporization.Yesterday we made a hollow endcone for the flame tube and fixed it today, same time we took a piece of s/steel tube, same as used for the test 21/11, 13mm sq. and 30 cm long, bend it 90 deg. at the one end so it could fit in center of the flame tube, pointing to the top (to hollow cone), fasten it half way down the liner (combuster well long 45cm) so we now have a central vaporization tube in center and pointing against the mass flow direction.

On the vaporization tube inlet we took a pieces of brass, solded two 3mm brass tube on and fastened the plate with two 4mm screw so it easily can be removed to aloud the flame tube to be removed, because the two thin tubes stick about 10mm into the vaporization tube.The first tube is for diesel and the second for gas.

The flame tube is shortened 7 cm to aloud air to surrounding the hollow endcone for cooling, there is no connection through the top plate more. Now we were excited to see who it will perform, so after connecting the diesel pump, gas and vacuum cleaner (the old radial blower, blow) we turn on the gas for heating the vaporization tube, and ignited it at the outlet, immediately the flame front disappear inside and to our amazement the combustion took place deep into the primary zone, a core with a length of under 10cm in the primary zone and the secondary zone completely combustion free, only hot gasses.We never seen combustion so concentrated in the primary zone, and when starting the diesel pump the flame front stay in same place. Only when making a very rich mixture the flame came closer to the outlet but newer exit the combustion chamber.

26/11-97

So... here is a drawing showing our current combuster design. The drawing is not correct scale, and the holes are not arranged correctly, but it shows the principal layout.
The air enter into the bottom of the combuster to ensure the highest pressure around the secondary zone. The gas inlet tube is only needed to preheat the tube to ensure that when the diesel enter, it immediately evaporate.
As described, the combustor have only been single tested, and we will probably continue with that until we have tested some optimations ideas, one of them is to make flaps into the evaporation tube to ensure the fuel hit the hot wall several times, and another is to try ignite the diesel without having to preheat the tube. The problem is where the spark plug should be placed. Maybe by making a small "external ignition Combuster"...?

If anyone have plans for trying this design, the greatest problem must be the end cone. We took a round pieces of sheet and began hammer it out to shape, it took under 1/2 hour, so it wasnt so problematic as thought, but later we discover a soup spoon in the kitchen with exactly the same shape....!
But peace must come in first place, so maybe it was the best solution.

7/1-99

Due to I have started studying, and my friend Jan is rebuilding his house, we havent had the time in the last year to develop on our jetengine , but we are planning to continue , maybe later This year!.I you are thinking about making you own home made jet engine, the you should. It is very exciting project, but I will take a lot of you free time, but I can recommend it!

09/14-99

We have startet on our jet engine again.We have decided that we will replace the oil pressur bearing with ball bearing to reduce the resistance and make it easyer to make lubricate system.I Have contacted SKF (The inventor of the ball bearing), and asked them if they would like to sponsor some ceramic ball bearings for our project, and they would. So, now we are waiting to get them, and soon we will fit them on our turbo charger.!

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Sunday, April 7, 2013

A Low Distortion Audio Pre amplifier

In an audio amplifier the quality of sound depends upon a number of factors, e.g. quality of active and passive components, circuit configuration, and layout. To an extent, the selection of components depends on the constructor’s budget. The discrete active components like transistors have been increasingly replaced by linear ICs, making the task of designer easier. With the passage of time, the general-purpose op-amps like LM741, which were being used in audio/hi-fi circuits, have become The preamplifier circuit presented here is based on a dual precision op-amp for the construction of a low distortion, high quality audio preamplifier.

Low Distortion Audio Pre-amplifier Circuit diagram:

A dual op-amp OPA2604 from Burr-Brown is used for all the stages. The FET input stage op-amp was chosen in this context it is worthwile to mention another popular bi-polar architecture op-amp, the NE5534A. It has, no doubt, an exceptionally low noise figure of 4nV/ÖHz but rest of the specifications compared to OPA2604 are virtually absent in this IC. Also This IC is also capable of operating at higher voltage rails of ± 24V (max.). Also its input bias current (100 pA) is many orders lower than its bipolar counterpart’s. This ensures a multifold reduction in noise.

A channel seperation of 142 dB exists between In the circuit, buffer is essential for the proper working of the subsequent blocks. A nominal input impedance of 47k is offered by this stage which prevents overloading of the preamplifier. The tone control is a baxandall type filter circuit.The bandwidth limiter is basically a low-pass filter with an upper cut-off ceiling at the end of the useful audio spectrum. The gain at 10 kHz is approximately 17 dB. The design is essentially 3-pole type and the upper frequency is set at 25 kHz. This lSetting the unit is fairly simple. Check the power leads feeding the IC for symmetrical voltages. High quality audio output from the line output socket is to be fed as the input signal to this preamplifier. Output of the preamplifier is fed to the power a The whole circuit consumes about 10 mA when the above-mentioned ICs are used. Power supply requirements are not critical as the circuit works on 7.5V to 15V DC..

Source : http://www.ecircuitslab.com/2012/01/low-distortion-audio-pre-amplifier.html

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How to Make a Simple Electronic Weighing Scale Machine

Learn a super simple procedure to make a weighing scale device useful for measuring smaller magnitudes of weight. The concept is very simple, a light beam is allowed to pass through a linearly colored ribbon and fall over an LDR. The color shade of the ribbon positioned in front of the light source at any instant will depend on the weight placed over a spring loaded mechanism. The corresponding change in the light level is converted into a corresponding difference in the resistance of the LDR which is ultimately read over an Ohmmeter and the equivalent weight is determined.

A digital weighing scale is an indispensable device as far as determining smaller magnitude of weights is concerned. However these gadgets can be too sophisticated and expensive to procure. A simple design idea of a weighing scale presented here promises to be equally accurate yet very cheap.

Introduction

We all have seen this machine very commonly used with most of the shopkeeper and retailers. It is used for determining the weights of the various materials being sold to the customers so that the items may be correctly rated as per the displayed weight over the machine. This incredible device is able to detect even the minutest magnitude of weight placed over it and accurately displays it over a digital scale.

Yes we are discussing weighing scales normally used for weighing smaller weights ranging from probably mgs up to a few kgs. The commercially available weighing scales are rather too sophisticated, accurate and therefore very costly too.

The design of a simple electronic analogue weighing scale presented here has been devised by me and is pretty accurate, very low cost and can be constructed even by a layman. The idea is simple – a linearly colored semi-transparent ribbon is made to move or dip in response to the pressing weight, a light beam from a light source is allowed to pass through this ribbon and fall over an LDR. The LDR is connected across an Ohm meter, so, as the weight pushes the ribbon, it slides down and settles at a particular point and offers a particular corresponding shade in front of the light source. The light intensity is optimized according to the darkness or lightness of this shade and the LDR reads the proportionate light intensity level and directs it to the meter so that it may be directly read over its calibrated dial.

Let’s try to understand the actual functioning of the designed prototype:

Electrical and Mechanical Description of the Unit

Referring to the figure alongside, we see that the arrangement is pretty straight forward. A central pillar or shaft which forms the main and the sole moving part of the system passes through an appropriately sized hole made over the top surface of the cabinet.

The external end of this rod terminates into a flat platform which forms the base for keeping the weights under question.

The rod and the platform are held in a rigid posture by a spring positioned in between the platform and the cabinet top surface. The shaft actually passes through this spring. The spring is required so that the weights are properly optimized and the level of the platform returns to its original position once the weight is removed.

A linearly colored or darkened translucent ribbon which forms the heart of the entire mechanism is connected to the inner end of the above movable shaft.

Also a white LED (used as a light source) and an LDR (light receiving component) are positioned exactly opposite, facing each other and partitioned by the ribbon.

An analogue moving coil type meter configured as an Ohm meter or a resistance meter is integrated with the LDR.

The LED is powered through a cell and is switched ON when in use. The light beam produced from the LED passes through the ribbon and falls over the LDR and a corresponding value is displayed over the meter depending upon the opacity of the ribbon.

When there’s no weight placed over the platform, the spring mechanism keeps the shaft in a position that produces the darkest shade from the ribbon in the path of the LED beam and therefore the meter also reads a minimum or zero value over its calibration.

The moment a weight on this weighing scale is placed, the shaft dips proportionately and the ribbon slides down to produce a linearly changing shade in front of the LED light beam and finally settles down to a corresponding lighter shade level. The operation is instantly translated over the meter to provide the equivalent value of the weight being measured.

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Saturday, April 6, 2013

Making a Joule Thief Charger Circuit with Steven Chiverton

Continued from the previous article

Here is the joule thief used to test my button cells out after I successfully recharged them.

Heres my battery charger joule thief all installed into a circuit box.

Below is the front view, notice the 12 volts green light at the front panel that is modified to house a neon globe inside it.

While looking through my electronics parts draws I found another 7 or 8 more button batteries and some had charge still on them and some I recharged successfully and 2 couldn’t be charged anyhow a few small ones took a little zapping to get them to take a charge so maybe if they are got some sulphate in them if not then why did it take so long to get them to except a charge.?

Yesterday I found another button battery cell and after a few seconds charging it started to get warm so I stopped it before it got to hot otherwise it would explode

Now I have 24 button cell batteries.

Below is a picture of the bright white with pink flash of a photo flash capacitor neon circuit test

The outputs of my battery charger joule thief run to the 330 volts photo flash capacitor, and across its leads I placed a neon bulb, loosely so every so long you hear a spark jump but cant see it unless the neon leg is getting pulled in by the high voltage attraction then a short time after that the flash occurs, so if the neon is rated at 90 volts then the cap charge may be the same till it charges up more I filmed this then put it onto my pc and then I had to slow it down so much to capture the super fast flash then pause it then take a picture of it to load back onto my pc.

Heres what it looks like when it aint flashing

ive soldered one of the neon legs to one of the high voltage 330 volts photo flash capacitor legs and the other neon leg I had it just nearly touching the other capacitor terminal but I didn’t get the arc and flash after it like I got before .

next test was running one of my jumper leads to a folded peace of aluminum foil and back to the hv capacitor and the other lead I ran to the other hv cap leg to a pencil and when the neon at the 330 volts 2200uf photo flash cap come on I gently touched the lead pencil tip to the foil edge where its folded and I got flashes etc and tiny holes melted through it and when I tried to unfold the foil it was stuck like it was spot welded , and there sure was this horrible smell made by spot welding aluminum foil.

Next experiment was running the leads from the capacitor to 2x 316 grade stainless steel bolts in a jar of tap water to create any electrolysis effects and I got very fine misty vapours come up to the top of the water and no bubbles and even when the bolts slipped together I was still getting it and even when they are apart to, and the further apart the bolts are the lower the frequency of sound is emitted from the battery charger joule thief and the closer the bolt electrodes are the higher the frequency of the sound the circuit emits gets ,

My watch battery I charged before has stopped I guess the charge didn’t last long enough, I charged it on the 24^th may 2010 and it lasted till today at 8past 8 , either in the morning or last night , so it lasted a week only im gona try re charging it again . Also today at the shops I went to the place they do watches and shoes and there was thousands of button cells inside this Perspex box even large ones next to it , but no one was there to answer my questions about them .

Ive recharged my watch battery again today but I was charging it the wrong way around so I got it right after that now my watch is running again so ill see how long its lasts for this time.

Today is June the 1^st 2010 so lets see if it lasts a week, also if it lasts longer then it may be the reverse charging that contributed to the extra running time before I charged it right

I scored a packet of free button cell batteries including large lithium cells and a few small 12 volts pencil batteries for free from 2 places in Armadale that also replace watch batteries, they have thousands of them and I counted what they gave me in total I had 85 batteries mostly button cells and ive successfully recharged them all except some lithium large button cells so also my 25 batteries I had it makes 110 batteries in total including the few large lithium cells that couldn’t be charged or revived at all some of the batteries still had power in them to .

Half the button cell batteries couldn’t maintain there charge and went flat overnight

So I recharged them again so ill soon check to see if they hold there charge this time also I dismantled a lithium battery it has a thin white membrane that reacts with water and foams up and also a thicker black membrane with what looks like very thin silver wire looking cross patterns on its sides and when I dismantled that battery it sure stunk inside it to

Today Tuesday June 8^th 2010 I decided to use my 4 rechargeable batteries from my camera to power my radiant joule thief battery charger, to restore my 12 volts 7.2 amps an hour 20 hour sla battery, and so after an hour or so I used a pair of tweezers to short out the battery terminal and I got some sparks where I didn’t before that, so I left the joule thief battery charger running all day today and now when I plug in the battery charger the red charging led light doesn’t go to green after a short charge that’s trickle charge, when green its still on red so im looking forward to how it goes when fully charged then in the green when its charged so if I get plenty sparks when I short the battery terminals then I can say the battery has been revived .

My 12 volts sla battery appears to still have a tiny bit of sulphate on its plates as its voltage dropped 0.7 volts over night so when the battery is low and needs topping up ill put it back on the joule thief circuit.

Wiring panel

Saturday, April 13, 2013

zBot 10 A Power Stage for DC Motor

Thursday, April 11, 2013

Class A power amplifier

Tuesday, April 9, 2013

A Homemade Fence Charger Energizer Circuit Explained

Monday, April 8, 2013

try start building a low cost Jet engine

Sunday, April 7, 2013

A Low Distortion Audio Pre amplifier

How to Make a Simple Electronic Weighing Scale Machine

Saturday, April 6, 2013

Making a Joule Thief Charger Circuit with Steven Chiverton

Friday, April 5, 2013

How does a Flight Engine CFM56 5B work