The affection of this circuit is the LM3914 from civic semiconductors.
The LM3914 can faculty voltage levels and can drive a affectation of 10
LEDs in dot approach or bar mode. The bar approach and dot approach can
be evidently set and added than one ICs can be cascaded calm to gat an
continued display. The IC can accomplish from a advanced accumulation
voltage (3V to 25V DC). The accuracy of the LEDs can be programmed
application an alien resistor. The LED outputs of LM3914 are TTL and
CMOS compatible.
In the circuit diagram LEDs D1 to D10 displays the akin of the array in
either dot or bargraph mode. Resistor R4 affiliated amid pins 6,7 and
arena controls the accuracy of the LEDs. Resistors R1 and POT R2 forms a
voltage affiliate arrangement and the POT R2 can be acclimated for
calibration. The circuit apparent actuality is advised in adjustment to adviser amid
10.5V to 15V DC. The arrangement of the circuit can be done as follows.
After ambience up the circuit affix a 12V DC antecedent to the input.
Now acclimatize the 10K POT to get the LED10 afterglow (in dot mode) or LEDs up to 10 afterglow (in bar mode). Now abatement the voltage in accomplish and at 10.5 volts abandoned LED1 will glow. About-face S1 can be acclimated to baddest amid dot approach and bar blueprint mode. When S1 is closed, pin9 of the IC gets affiliated to the absolute accumulation and bar blueprint approach gets enabled. When about-face S1 is accessible pin9 of the IC gets broken to the absolute accumulation and the affectation goes to the dot mode.
Now acclimatize the 10K POT to get the LED10 afterglow (in dot mode) or LEDs up to 10 afterglow (in bar mode). Now abatement the voltage in accomplish and at 10.5 volts abandoned LED1 will glow. About-face S1 can be acclimated to baddest amid dot approach and bar blueprint mode. When S1 is closed, pin9 of the IC gets affiliated to the absolute accumulation and bar blueprint approach gets enabled. When about-face S1 is accessible pin9 of the IC gets broken to the absolute accumulation and the affectation goes to the dot mode.
With little modification the circuit can be acclimated to adviser added
voltage ranges. For this just abolish the resistor R3 and affix the top
akin voltage to the input. Now acclimatize the POT R2 until LED 10 glows
(in dot mode). Abolish the top voltage akin and affix the lower akin to
the input. Now affix a top amount POT (say 500K) in the abode of R3 and
acclimatize it until LED1 abandoned glows. Now abolish the POT,
admeasurement the accepted attrition beyond it and affix a resistor of
the aforementioned amount in the abode of R3. The akin adviser is ready.
