coil generator : tester of coils

[dbanner]

KT, thanks for the translation. I think I will be able to make my own little layout single layer. Thanks again for giving circuit. I want to make coil for my home made 1210x, but dont have enough wire for two 9.5mH coils. Now I know what to do, I think.

[kt315]

Where is top layer? The tiny blue lines?

the blue lines were still not traced lines.

[kt315]

may be anybody from Germany will also give the text in german because a primary source was in german magazine.

[kt315]

crude google translation Melbeta... i see the article in text form so its easely to get.

UNIVERSAL LC GENERATOR

Radio, 1979, No. 5

The generator, the circuit of which is shown in the figure, is intended for measuring equipment. An important advantage of this generator is the ability to use resonant circuits with virtually any L / C ratio. So, it works equally steadily if the inductance of coil L1 varies from 50 μH to 100 mH, and the capacitance of C1 is from 50 pF to 5 μF. For example, with an inductance of L1 = 50 μG and capacitance C1 = 5 μF, the generated frequency will be about 10 kHz, and with the same inductance and C1 = 50 pF - 3.2 MHz. In addition, to the number of advantages of this generator should be attributed a small voltage on the LC-circuit - about 100 mV. In some cases this is important, for example, when measuring varicap parameters.

The generator is made on transistors V1 and V2. The cascade on the transistor V3 is a preliminary amplifier, the signal from which is fed to the output amplifier (transistor V8 ) and to the automatic level control unit of the output signal of the generator. Since the preamplifier comes directly from the generator oscillator circuit, the AGC unit maintains a constant voltage and on this circuit. The automatic level control unit consists of a rectifier on the diodes V4 and V5, made by the doubling circuit, the direct current amplifier on the transistor V7 and the regulating transistor V6.

As soon as for some reason the voltage at the output of the generator changes, for example, it will increase, then a mixture on the basis of the transistor V7 will increase. This, in turn, will lead to a decrease in current through the transistor V6 (and hence through the transistors of the generator V1, V2), and the voltage at the generator output will decrease to the original value.

The output voltage remains practically constant when the supply voltage varies from 3.5 to 15 V. It is convenient to choose it equal to 5 V. In this case, the signal level at the output of the generator will be compatible with the devices of transistor-transistor logic.

In the generator, you can use any silicon high-frequency transistors, and transistors V1-V3 must have a sufficiently large current transfer ratio (not less than 150). In the event that parasitic high-frequency oscillations occur, the resistance of the resistor R2 should be slightly increased.

"Funkshau" (FRG), 1978, No. 18

The transistors KT361B, G (V1, V2, V3) and KT315B, G [V6, V7, V8 ] can be used in the generator, the diodes (V4, V5) can be of the KD503A type.

[Melbeta]

KT315
I would be interested in building it, and then using it to see if I can read coils. Is there anyway one could get an English Translation of the article? Maybe a link with an English translation?
Melbeta

[dbanner]

Where is top layer? The tiny blue lines?

[kt315]

[dbanner]

according the original article generator with L= 50uH and C=50pF gives 3.2MHz. a range of connected L from 50uH to 100mH.

I like this little circuit, thanks for sharing. It's range is perfect for testing any coil. Would be nice to have article in English.

[kt315]

I'm not sure that the 6 transistor circuit will be stable when changing the power supply.
Why are you looking for another circuit - the Foma generator is stable and checked.

changing the power supply for what? article says the output voltage is stabile in wide range of power supply.

[kt315]

according the original article generator with L= 50uH and C=50pF gives 3.2MHz. a range of connected L from 50uH to 100mH.

[dbanner]

Your rationalization is sound. Maybe first, a fixed cap of known capacitance, then the possibility of switching in a varicap for CX to tune for same frequency. What is the range of oscillation of circuit?

[kt315]

DB

yes, you search unknown coil for the resonance. also you can choice cap for coil you do. or retune your coil for another detector with different frequency.
for example you need to get 18kHz in 6.59kHz IDX. how you search resonance of RX coil?

[dbanner]

For a novice like myself, the implication here is startling. Are you inferring that a search coil can have correct resistances and inductances( measured) for tx and Rx, and still be defective? The only way to know is use coil tester circuit to measure resonance frequency with Cx. Please explain. In other words, the coil measures good(correct resistances, inductances) but metal detector still not working as it should, is the problem your coil or is it the control box?(scenario for factory made brand metal detector)

[dbanner]

Measuring inductance varies alot depending on quality of inductance meter being used, but measuring frequency with coil generator circuit gives vital characteristics if you want to build another coil of different sizes. Then all you would need is to measure resistances of Rx and tx. Then you could develop some sort of tables for different metal detectors and there respective coils. After which using your coil generator, you could quickly test any coil with reference to data from tables. How's that.

[dbanner]

You forgot to show power supply connection in post #3. I take it you measure frequency of resonance and then what? Must compare to some table showing correct frequency for that coil? What is your goal here? Are you saying this is better way to measure coil characteristics? By measuring coil resonance rather than inductance? Please explain.
Can't read document.