• on Miscellaneous Electronics
  • Published in issue 10/2014 on page 28
About the article

Dot Display Driver

Dot Display Driver
There are situations when it is useful to scale the dynamic range of a signal down to a few coarse sub ranges. As an example you can think of an indicator that does not show the exact speed of a motor, but only a few values like Off, Slow, Medium, Fast and Too Fast. Such signals can easily be obtained by averaging (i.e. low-pass filtering) amplitudes, frequencies or pulsewidths of signals produced somewhere in the system that you want to keep an eye on.
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Component List
(0.25 W)
R9,R10,R11,R12,R13 = 390Ohm
R1,R2,R3,R4,R5,R6,R7,R8 = 4.7kOhm
R15 = 47kOhm
R14 = 1MOhm
P1 = 100kOhm, trimmer
C2 = 100nF
C1 = 1µF
D1,D2 = 1N4148
IC1 = LM324
LED1,LED2,LED3,LED4,LED5 = LED, red, 3mm
T1–T4 = BC557C
K1 = 3-pin pinheader, 0.1” pitch
PCB # 140111-1
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