Quote:
Originally Posted by edward
Hi mr franco and thank you for your help
I tested bc548, bc547 b , bc 238b , bc 547c , and the results was same, my pcb is self oscillation, i have to use 20 pf capacitors for c13 , c14 to avoid from self oscilation
I think when i increase total value of c2 , c3 , c4 for increasing output voltage the lrl sensivity decreases
Now i have 2 question mr franco
1- how much is maximum amount that can be used for r10 and r12
2- does your lrl dont work with low voltage in output? ( for example 0.5 volts or 0.6 volts)
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1 -Usually it is chosen for R10 / R12 a value lower than that of R9 / R13. I made several copies of my lrl and I always managed to eliminate self oscillation. Try to remove C13 / C14, in this way it should stop oscillating, if so, decrease R10 / R12 until it oscillates again, then increase again R10 / R12 until the oscillations cease. For example R10 / R12 = 1 K no oscillations, R10 / R12 = 680 ohms no oscillations ... R10 / R12 = 220 ohms no oscillations, R10 / R12 = 100 ohms yes oscillations, choose R10 / R12 = 220 ohms. This difficulty in eliminating self oscillations makes me think of a defect in the pcb, there may be some parasitic coupling. I always recommend using a double-sided pcb.
2 - my lrl works also with low voltage output but for me it's better at least 2V, in fact it could happen when the installation was completed or in the field that the tension lowered further, in this way it would also greatly reduce the sensitivity, since it could not regulate the threshold effectively.