coil generator : tester of coils

[kt315]

on-line calculator. you can calculate F, L or C in resonance contour.

https://coil32.ru/calc/jslcc.html

[kt315]

UNIVERSAL LC OSCILLATOR

Radio, 1979, 5

This oscillator is designed to be used in measurement circuits. The circuit diagram is shown in the figure 1. An important advantage of this oscillator is that in this circuit can be used a resonant circuit with almost any ratio of L/C. So, this oscillator operates stable even if the inductance of the coil L1 changes from 50 uH to 100 mH and the capacitance of the capacitor C1 changes from 50 pF to 5 uF. For example, the inductance L1 = 50 uH and the capacitance C1 = 5 uF, the oscillation frequency is about 10 kHz, while with the same inductance and C1 = 50 pF we get the oscillation frequency about 3.2 MHz. In addition, the advantage of this oscillator is the low voltage across the LC circuit - it is approximately 100 mV. In some cases it is important, for example, when measuring parameters of varicaps.

schematic diagram of the universal LC oscillator

Fig. 1.
V1, V2 - BC252; V3 - BC172C; V4, V5 - 1N4148; V6, V7 - BC172B; V8 - BF241.

The oscillator is based on transistors V1 and V2. The transistor V3 is a pre-amplifier, the signal from this stage is fed to an output amplifier (the transistor V and to the AGC circuit. The AGC automatically adjusts the amplitude level of the signal. Since the pre-amplified signal is fed directly from the LC resonant tank circuit of the oscillator, the AGC maintains a constant voltage across this resonant tank circuit. The AGC circuit is composed of diodes V4 and V5, this is the doubling rectifier circuit, the DC amplifier with transistor V7 and the regulating transistor V6. If the voltage across the output of the oscillator changes, for example, the voltage became higher, it increases the bias voltage at the base of the transistor V7. This will reduce the current through the transistor V6 (hence, the current through the transistors V1, V2), and the voltage across the output of the oscillator will be reduced to the initial value.

The output voltage remains almost constant when the supply voltage changes from 3.5 to 15 V. With the supply voltage of 5 V the amplitude of the output voltage of the oscillator will be compatible with transistor-transistor logic.

In this oscillator you can use any silicon high-frequency transistors. The transistors V1-V3 should have a sufficiently large current gain (not less than 150). In this circuit the parasitic oscillations can arise, in this case increase slightly the resistance of the resistor R2 to suppress them.

?Funkshau? (FRG), 1978, 18

http://zpostbox.ru/universal_lc_oscillator.html

[dbanner]

I drove it with a isolated +5V supply, just used +5 as ground for scope measurement. It also works well at higher voltages, tested at 9V as well.

Just what the doctor ordered, a two transistor tank oscillator in the low kHz range operating with 9 volt supply. Producing a smooth sinewave with low thd.
Perfect for coil tester. The peak to peak isn't important, so low peak to peak is fine.

[moorejl57]

That's pretty awesome sinewave, looks clean as a whistle. I noticed a negative supply voltage on the scheme.

I drove it with a isolated +5V supply, just used +5 as ground for scope measurement. It also works well at higher voltages, tested at 9V as well.

[dbanner]

That's pretty awesome sinewave, looks clean as a whistle. I noticed a negative supply voltage on the scheme.

[moorejl57]

That very interesting, will the tank oscillate with say a 20n cap?(6.8mh)
Might be a good candidate for a coil tester circuit of sorts. What's the peak to peak across the tank. I need to read the article and play with the spice sim provided.

OK, tested with 6.8mH and 22nF cap. The waveform is very nice and the frequency is 12.8kHz.

Using the frequency function instead of cursors, I get 13.15 kHz which is very close to calculated.

[dbanner]

The rotary switch described above would have selections for known frequency such as for tgsl, idx, and others frequencies etc.

[dbanner]

I would like to develop a coil tester circuit for tuning home made coils, the idea goes like this:
After you have wound and shielded your coil, it is then connected to a tester. A preselected resonant tank frequency is selected by turning a rotary switch. Then a knob is turned until an LED lights, this indicates that the tank is resonating at preselected frequency. Capacitance of LC tank is then read off on a display. The heart of the circuit would be a peltz oscillator and a pic micro.

[dbanner]

That very interesting, will the tank oscillate with say a 20n cap?(6.8mh)
Might be a good candidate for a coil tester circuit of sorts. What's the peak to peak across the tank. I need to read the article and play with the spice sim provided.

[moorejl57]

Tried with 6.8mH and 100pf and got 112.4kHz and a distorted waveform.

[dbanner]

Useful little circuit, very good.

[moorejl57]

The link in post #132 includes a LTSpice file to test with. You can simulate a 10X probe (10M and 20pf in parallel) load and see what happens to the frequency.

So I breadboarded the Peltz oscillator and it works well! There seems to be a lot of additional capacitance from the breadboard and probe since the frequency is significantly lower than calculated. Used a 390uH inductor and a 100pf cap and get 543 kHz.

[kt315]

tracking number is RE1025.......LT

on the way. thank you.

[6666]

good Bruce. thank you.


Amount received

1,85 EUR

Fee 0,45 EUR

Total 1,40 EUR

Thanks

[kt315]

good Bruce. thank you.


Amount received

1,85 EUR

Fee 0,45 EUR

Total 1,40 EUR