If you build power transformers, coils for electric motors or chokes for filters of speakers, you know it can happen that the winding machine flayed the varnish insulation from copper wire. If a few turns are shorted, you'll never notice it. So, to detect these defects, it'll just build this unit.
Despite the high resistance of the coating deposited on the wire enamel, it is not uncommon during the winding phase nuclei the wire is frayed, causing short circuits. Search
to discover, once the winding is complete, if one or more turns are shorted by using a multimeter switched ohmmeter is virtually impossible.
Indeed, a total resistance of a few tens of ohms, it is unlikely to be able to see a difference value close 0.00000001 ohms!
The problem is not so far minor, because if the winding of a transformer has shorted turns, it will overheat so it will not even be possible to lay hands on it. If the turns are short-circuit in the coil of a speaker filter, the sound will suffer distortion.
Whoever has tried to obtain commercially a device that can detect if a coil has shorted turns do certainly will not be found.
For this reason we thought to realize that this assembly will be of great use to all who bobinent their own transformers or manufacture inductors for filters. Whoever buys
coils already done immediately want to turn the pages of this article, thinking that the device may only be of no use to him. However, you can use for other applications like, for example, a limit simple and convenient.
If, on the end of a rod you have a metal ring as soon as the bar tester comes in, the buzzer will ring (see Figure 6).
The wiring diagram
To achieve this setup we used a single integrated circuit and two transistors. For a description of its operation we start from the first NAND gate contained within a 4011 (see Figure 1 IC1-A) mounted in sinusoidal oscillator. With the number of turns that we recommend to coil on the ferrite bar L1, we can obtain the frequency of about 6000 Hz with an amplitude of 1 V. The adjusted R 2 connected to the A L1 can find the point of initiation of the oscillator stage.
The resulting signal is applied through the C4 on the second NAND IC1-B, mounted amplifier stage. At its output we find a signal of about 6 V, which is applied by C6 in DS1 and DS2 for a voltage of about 5 V. R7 in turn transmits this voltage at the base of TR1, a BC547. With this voltage the transistor is conducting and its collector connects to ground R8 and R10, thus blocking the second oscillator stage compound the other two NAND IC1 and IC1-C-D and TR2, a BC547 well. When the ferrite bar of the tester is completely inserted in a coil having one or more turns in short circuit, the NAND IC1-A stops swinging, no more signal fails on DS1 and DS2 and TR1, no longer polarized ceases to operate.
Its collector voltage rises to about 9 V (logic 1). This tension, which reaches the input of the NAND IC1-C can make it active and oscillates at a frequency of 1 kHz, made audible by the piezoelectric transducer. The oscillator stage, consisting of IC1 and IC1-C-D, as a VCO, we get a low score when the ferrite is approached our unit coil having one or more turns in short circuit and a note sharp when the bar fully inserted within the same coil.
To feed this circuit, we use a 9 V battery
Figure 1: Diagram of the tester to monitor the presence of shorted turns in a coil. The practical
The trickiest part, but certainly not impossible, for the coil of wire on the ferrite rod coil L1.
To achieve this winding must 220 turns of enamelled wire diameter of 0.15 mm (15/100). Since the coil has a plug (B) in the 25th turn of the beginning (A), we suggest you proceed as follows: With a piece of tape, attach the top of the line (A) on the bar in leaving exceed 4 to 5 cm to be able to connect to the circuit at point A. Winding 25 turns, and made a loop of 4 to 5 cm long, which corresponds to taking B to be connected to point B then the circuit board. Then, continue by performing the 195 winding turns remaining. This finished, you also have the end of the coil C is connected to point C near the condenser C3.
To prevent the windings become loose, you can keep up with a piece of tape or using a drop of cellulosic glue.
The number of turns is not critical even if you coil 25 turns between A and B and 190 or 230 turns taken between B and C, the circuit will still work perfectly.
We recall that the ferrite bar is very fragile, a fall on the ground can reduce the crumbs. After completing the winding of L1, you can focus on assembling components on printed circuit LX.1397. First, install the support of integrated circuit IC1, then every including adjustable resistors R2.
This being done, get all the silicon diodes by directing the black ring painted on their bodies as shown on the site plan in Figure 3.
Particular attention should be paid to the diodes DS1 and DS2 as if they are mounted in the wrong direction, the circuit will not work. Accordingly, point the black ring of DS2 to capacitor C5 and that of DS1 in reverse.
You may continue by soldering the single ceramic capacitor (C2) near the adjustable polyester capacitors and electrolytic capacitors in the polarity of their feet.
Now fit the two transistors in orienting the flat side of C9 to TR1 and TR2 of the flat part towards the support of IC1.
Before attaching the ferrite bar on the PCB, insert the circuit IC1 in its socket with his cue-U keyed to the capacitor C11. On the ferrite bar you need to insert the two plastic holders that are set in the two holes on the PCB.
Before welding the son marked A, B and C on the pins that you already welded on the PCB, you should scrape the veneer of son with a knife or a razor blade so you can solder and solder easily . Do
no sandpaper as you may break the thread. There is another method to remove the varnish on the thread.
It is to approach the wire from the flame of a lighter to burn the varnish. Do not insist too much.
Then, scratching is facilitated. C
wire is welded to the capacitor C3, the wire B on the ground strip and the wire A on the track that runs adjustable R2 (see Figure 3). To complete the installation, just to weld the piezoelectric transducer, the son of the battery connector and those of the switch S1. Subsequently, the cell will be set in the empty bottom of the box, the buzzer and the switch will fixed on the front of the box.
Figure 2: Pinout BC547 viewed from below and the IC 4011 viewed from above. 
PCB scale 1. 
Figure 3: Diagram of location of components of the tester to short-circuit in the windings. On the ferrite bar must winding number of turns specified in the text. The bar will be fixed on the printed circuit using two plastic clips. Iist
R1 ......... 1 MΩ
R2 ......... 20 kW Adjustable
R3 ......... 10 kilohms R4
......... R5 150 kΩ
......... 1 MΩ
R6 ......... R7 220 kΩ
......... R8 100 kΩ
......... 22 kW
R9 ......... R10 680 Ω
........ R11 220 kΩ
........ R12 330 kΩ
........ R13 15 kΩ
........ R14 100 kΩ
........ 1 MΩ R15
........ 10 kilohms R16
........ 10 kW
C1 ......... 150 nF polyester
C2 ......... 100 pF ceramic
......... C3 220 nF polyester
C4 ......... C5 22 nF polyester
......... C6 10 nF polyester
......... C7 220 nF polyester
......... C8 220 nF polyester
......... 47 uF electrolytic C9
......... 4.7 uF electrolytic
C10 ........ 15 nF polyester
C11 ........ 100 nF polyester
DS1 ........ 1N4148
DS2 ........ 1N4148
DS3 ........ 1N4148
DS4 ........ 1N4148
DS5 ........ 1N4148 TR1
........ TR2 BC547 NPN
........ BC547 NPN
CP1 ........ piezoelectric transducer
L1 ......... coil
IC1 ........ CD4011 CMOS
S1 ......... PCB switch
CI.1397 Complete kit with box LX.1397
Unless otherwise specified, all resistors are 1 / 4 W 5%.
Figure 4: Photograph of prototype circuit completely wired. Using
After installation, upon powering the buzzer sounds, the first clear sign that the circuit works. To stop the sound, turn R2 slowly until it disappears. Now, try to bring the ferrite rod in a metal ring to simulate a turn short-circuit (see Figure 6), the buzzer sounds and the notes instantly becomes increasingly acute as and as you increase penetration of the bar in the ring.
Installation in the cabinet
PCB is fixed in the cabinet with three screws on the bottom of the plastic case. On face avant en aluminium, il faut percer 4 trous : un pour fixer S1, deux pour fixer le buzzer et le dernier, en face du trou central du buzzer afin de permettre une meilleure sortie du son.
Du côté de la sortie du barreau de ferrite, il ne faut pas installer le panneau métallique. Pourquoi ? Tout simplement parce que le panneau et son trou pour le passe du barreau se comporteraient comme une spire en court-circuit!
Figure 5 : Le circuit est fixé dans le coffret en plastique à l’aide de trois vis. Dans la partie vide en bas du coffret sera logée la pile 9 volts. 
Figure 6 : Lorsque le barreau de ferrite commence à sentence to be inserted into a metal ring simulating a turn short-circuit, the buzzer begins to sound immediately. 
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