Article
XXL LED VU Meter
With a wide range and high resolution
An LED VU meter is an excellent tool for keeping a close eye on the magnitude of audio voltages and so help prevent an input from being overloaded, for example when used with a mixing desk or a guitar amp. The circuit described here has an exceptionally wide input range of 60 dB and a step size of 1 dB thanks to the use of 6 LM3915 driver ICs, which control a total of 60 LEDs.
Gerber file
CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.
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PCB
Component list
Component List
Resistors
Default: 0.25 W 1%
R1 = see text and Table 2
R2 = 10kOhm
R3,R6,R9 = 820Ohm
R4a = 36kOhm
R4b,R7b = 2.4kOhm
R5,R8,R11 = 47Ohm
R7a = 9.1kOhm
R10 = 1.6kOhm
R12,R13,R14 = 680Ohm
P1–P6 = 100Ohm trimpot, horizontal
Capacitors
C1 = 1000µF 35V, low ESR, 5mm pitch, 13mm diam.
C2 = 10µF 16V, low ESR, 2mm pitch, 5mm diam.
C3 = 1µF 100V, MKT, 5mm pitch
C4 = 1nF, 5mm pitch
C5–C10 = 100nF, 2.5mm pitch
C11,C12,C13 = 22nF, 2.5mm pitch
Semiconductors
B1 = DB101
D1–D50 = 10-element LED bargraph display, green, 10.16 x 25.40 mm
D51–D60 = 10-element LED bargraph display, red, 10.16 x 25.40 mm
IC1–IC6 = LM3915N
IC7 = LM7812 (TO220)
Miscellaneous
J1,J2,J3 = 2-pin pinheader, 0.1’’ pitch
6 pcs. DIP-20 IC socket for LED bargraph displays
6 pcs DIP-18 IC sockets for LM3915 Ics
PCB # 120698-1
Resistors
Default: 0.25 W 1%
R1 = see text and Table 2
R2 = 10kOhm
R3,R6,R9 = 820Ohm
R4a = 36kOhm
R4b,R7b = 2.4kOhm
R5,R8,R11 = 47Ohm
R7a = 9.1kOhm
R10 = 1.6kOhm
R12,R13,R14 = 680Ohm
P1–P6 = 100Ohm trimpot, horizontal
Capacitors
C1 = 1000µF 35V, low ESR, 5mm pitch, 13mm diam.
C2 = 10µF 16V, low ESR, 2mm pitch, 5mm diam.
C3 = 1µF 100V, MKT, 5mm pitch
C4 = 1nF, 5mm pitch
C5–C10 = 100nF, 2.5mm pitch
C11,C12,C13 = 22nF, 2.5mm pitch
Semiconductors
B1 = DB101
D1–D50 = 10-element LED bargraph display, green, 10.16 x 25.40 mm
D51–D60 = 10-element LED bargraph display, red, 10.16 x 25.40 mm
IC1–IC6 = LM3915N
IC7 = LM7812 (TO220)
Miscellaneous
J1,J2,J3 = 2-pin pinheader, 0.1’’ pitch
6 pcs. DIP-20 IC socket for LED bargraph displays
6 pcs DIP-18 IC sockets for LM3915 Ics
PCB # 120698-1
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