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The voltage throughout the regulator is restricted by using the mix of T1 and zener diode D1 to a price that lets the regulator to work properly with loads up to the most rated load. R1 professionalvides an enough operating present for D1 and the bias present for T1. It’s a excellent suggestion to use a Darlington kind for T1 to be able to maintain the worth of R1 reasonably excessive. The current thru D1 is simplest 10 mA with an enter voltage of 60 V. Naturally, we additionally measured what the circuit does when no load is connected. Surprisingly sufficient, the nominal output voltage of 5.02 V increased to best 5.10 V (with a 60-V input voltage). In our scans, we used a BDV65B for T1 and a value of 4.7 kΩ for R1.

If you are having a look to have to be sure that the circuit is really brief-circuit professionalof with an enter voltage of 60 V, you should use a transistor that is still within its safe working house at the maximum enter voltage with the brief circuit current of the regulator (which can exceed 2 A). The BDV65B and TIP142 do not meet this requirement. The maximum voltage for the BDV65B is actually 40 V, and for the TIP142 is 50 V. If the transistor spoils down, the regulator may even spoil down. We verified that experimentally. One risk is so as to add SOA professionaltection for T1, but that quantitys to professionaltecting the professionaltection. Another possibility is to chill out the requirements.

For that objective, R1 must provide enough current to ensure that T1 receives enough current in the event of a brief circuit to maintain the voltage across T1 decrease, however that doesn’t make various distinction in apply, and it additionally increases the minimal load. Besides that, it should be evident that adequate cooling for T1 and IC1 should be provided in maintaining with the load. Ripple suppression is only marginally littered with the professionaltection circuit, since the enter is already neatly stabilised by T1, however the current via D1 does go with the flow in the direction of the output. The presence of C2 should even be taken into account.

In this circuit, with an adjustable voltage regulator one of theses the LM317 and an output voltage greater than 40 V, C2 will cause the voltage to be in brief larger than 40 V in the experience of a brief circuit, which can additionally result in the IC to be damaged. In that case, it'll be important to discover a completely different solution or use a distinct type of voltage regulator.

Here’s a project that could be useful this summer on the beach, to stop anyone touching your things left on your beach towel while you’ve gone swimming; you might equally well use it at the office or workshop when you go back to work. In a very small space, and powered by simple primary cells or rechargeable batteries, the proposed circuit generates a low-energy, high voltage of the order of around 200 to 400 V, harmless to humans, of course, but still able to give a quite nasty ‘poke’ to anyone who touches it.

Quite apart from this practical aspect, this project will also prove instructional for younger hobbyists, enabling them to discover a circuit that all the ‘oldies’ who’ve worked in radio, and having enjoyed valve technology in particular, are bound to be familiar with. As the circuit diagram shows, the project is extremely simple, as it contains only a single active element, and then it’s only a fairly ordinary transistor. As shown here, it operates as a low-frequency oscillator, making it possible to convert the battery’s DC voltage into an AC voltage that can be stepped up via the transformer.

Using a centre-tapped transformer as here makes it possible to build a ‘Hartley’ oscillator around transistor T1, which as we have indicated above was used a great deal in radio in that distant era when valves reigned supreme and these was no sign of silicon taking over and turning most electronics into ‘solid state’. The ‘Hartley’ is one of a number of L-C oscillator designs that made it to eternal fame and was named after its invertor, Ralph V.L Hartley (1888-1970). For such an oscillator to work and produce a proper sinewave output, the position of the intermediate tap on the winding used had to be carefully chosen to ensure the proper step-down (voltage reduction) ratio.

Here the step-down is obtained inductively. Here, optimum inductive tapping is not possible since we are using a standard, off-the-shelf transformer. However we’re in luck — as its position in the centre of the winding creates too much feedback, it ensures that the oscillator will always start reliably. However, the excess feedback means that it doesn’t generate sinewaves; indeed, far from it. But that’s not important for this sort of application, and the transformer copes very well with it.

The output voltage may be used directly, via the two current-limiting resistors R2 an R3, which must not under any circum-stances be omitted or modified, as they are what make the circuit safe. You will then get around 200 V peak-to-peak, which is already quite unpleasant to touch. But you can also use a voltage doubler, shown at the bottom right of the figure, which will then produce around 300 V, even more unpleasant to touch. Here too of course, the resistors, now know as R4 and R5, must always be present. The circuit only consumes around a few tens of mA, regardless of whether it is ‘warding off’ someone or not! If you have to use it for long periods, we would however recommend powering it from AAA size Ni-MH batteries in groups of ten in a suitable holder, in order not to ruin you buying dry batteries.

Warning!
If you build the version without the voltage doubler and measure the output voltage with your multimeter, you’ll see a lower value than stated. This is due to the fact that the waveform is a long way from being a sinewave, and multimeters have trouble interpreting its RMS (root-mean-square) value. However, if you have access to an oscilloscope capable of handling a few hundred volts on its input, you’ll be able to see the true values as stated. If you’re still not convinced, all you need do is touch the output terminals...

To use this project to protect the handle of your beach bag or your attachecase, for example, all you need do is fix to this two small metallic areas, quite close together, each connected to one output terminal of the circuit. Arrange them in such a way that unwanted hands are bound to touch both of them together; the result is guaranteed! Just take care to avoid getting caught in your own trap when you take your bag to turn the circuit off!

 

 

Source by : Streampowers