I was helping one of my friends build a VU meter using an LM3915, and it didn't work. I don't know what went wrong (I even built the circuit myself and it still didn't work). I think that we may have destroyed the chip so we plan on replacing it with a new one. This is the circuit that we made:**broken link removed**
The voltage supply was a PSU that had an output of 15V DC, and a current supply of 12A max. Our input was a function generator. We had an 8.2Ω resistor to simulate the speaker load.
We can't seem to figure out what went wrong, if someone could shed some light on the issue it would be appreciated.
The power supply was supplying the IC, and the LED's. The LEDs are 4 green, 3 yellow, 3 red. The green LEDs were 0.2 to 1.6W, followed by yellow and red respectively.
We tried the 3915 in both dot and bar mode. A friend took the chip out and pluged it in backwards, which is why I think that it has been destroyed (we don't usually let him touch expensive stuff like that)
The power supply was supplying the IC, and the LED's. The LEDs are 4 green, 3 yellow, 3 red. The green LEDs were 0.2 to 1.6W, followed by yellow and red respectively.
We tried the 3915 in both dot and bar mode. A friend took the chip out and pluged it in backwards, which is why I think that it has been destroyed (we don't usually let him touch expensive stuff like that)
Hi,
The LM3915 is set with that 390R to enable about 35mA thru each diode, if you use BAR mode you could fry the LM3915 as it will be dissipating well over 1.3Watts!!!
hi,
I just did a test download of the LM3914 calc, no problems.
Just left click it and it should download to your PC, change the extension from .txt to .exe
As it says you need the free VB runtime files from the web
Simply look at the three peak detector circuits in the datasheet.
I use this one on my Sound Level Indicator project. It uses a single-supply opamp so that a dual-polarity supply is not needed. It will work fine from the 14V of your car.