Stereo VU Meter
I'm building the project, Stereo VU Meter, I found here: Stereo VU Meter
Since I couldn't find the BC557 and BC547, I bought the BC557C and BC547B which has a much higher hfe value.
How can I modify the circuit to work with these transistors?
Don't know if this is important, but i'm using my car battery with a 9V-voltage regulator, and not a 9V battery.
The circuit should work with a higher HFE.
I might put a resistor of 470R in series with the emitter of the BC557. It probably isn't necessary, but it would be more predictable over temperature extremes.
I would also put a 10k from the base of the last BC547 to its emitter. Again, just for stability.
de KI6RWX
Instead of using millions of transistors, resistors and diodes you could use two LM3915 bar graph driver ICs.
An LM3915 has 10 comparators and LED drivers inside so transistors and diodes are not needed. The LED drivers have adjustable current regulation so the LEDs do not need current-limiting resistors.
Uncle $crooge
Author mentions LM3915 and suggests this project is designed so it might be be built from parts already on hand instead.
An LM3915 would also be better because its comparator is logarithmic.
de KI6RWX
Thanks for replies. I live in South-Africa and I can't seem to find the LM3915 IC anywhere.
Farnell are in about 40 countries but not in South Africa.
The LM3915 is very common everywhere else and is fairly inexpensive.
Uncle $crooge
Transistor circuits can be useful even in this day and age. Apparently South Africa is one place where that's true.
de KI6RWX
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