Schematics > Power > Instrument panel lamp dimmer control
Instrument panel lamp dimmer control
This circuit uses an MC3392 low side protected switch and an MC1455 timing
circuit to form an automotive instrumentation panel lamp dimmer control. The
brightness of incandescent lamps can be varied by Pulse Width Modulating the
input of the MC3392. The modulating signal can be obtained directly from the
MC1455 timer (or a microprocessor). The MC1455 is configured as a free-running
clock having a frequency and duty cycle control. The typical timer frequency is
approximately 80 Hz when the frequency potentiometer is adjusted to 1.0k. This
frequency was chosen so as to avoid any perceptible lamp flicker. The duty cycle
potentiometer controls the duty cycle over a range of about 3% to 97%. When at
3% the lamps are essentialy off, at 97% the lamps are essentially full on. Any
number of lamps can be control, so long as the total load current is less than 1
amp. The LED is used to signal the existence of a system fault (overvoltage,
current limiting, or thermal shutdown).
Title: Instrument panel lamp dimmer control
Source: www.electronics-lab.com
Published on: 2005-02-03
Reads: 224
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