Yeah...4 393's get you only 8 indicators, ok but pretty coarse. With nothing but 5K (?) and 10K resistors, you cannot build a VU meter because those are not the correct resistor values to create a group of logarithmic-spaced comparator circuits.
Is this homework, classwork, etc?
You cand show me a circuit diagram please?I designed and built a Sound Level Indicator with an LM3915 IC over 12 years ago. It has a microphone as its input and it has been in my living room most of the time but it has a rechargeable 9V battery so it has been used outside to measure the sound of dogs barking, sirens and noisy cars. It uses a fast acting peak detector to accurately show exact levels and it stretches the duration of short duration sounds to 30ms so that our slow vision can see them brightly. I added a circuit that increases its sensitivity 20dB when sound levels are low so that it has a 50dB range then it shows faint sounds and very loud sounds.
Since this is your homework, what circuits have you checked so far? Post links to a few and we can advise where to go from there.
Are your LEDs rated for a specific voltage, i.e. do they have built-in current-limiting resistors?
Thank you!That's about as simple as a non-microprocessor circuit gets (in the absence of a LM3914 or LM3915 IC) for driving a LED group according to input signal strength. However, (a) it doesn't have a VU's logarithmic response and (b) there is nothing to prevent the input being driven below the negative rail. These requirements were pointed out above. Given the limitations of the components you have, I don't see how you would adapt that circuit to meet the requirements. Consult your instructor to see if the requirements can be relaxed or additional components can be made available.