- #Lm339 battery level indicator update
- #Lm339 battery level indicator driver
- #Lm339 battery level indicator series
Note that surprises abound when constructing prototypes. The layout has not yet been carefully checked or built. These components are about as small as I like to work with. I did a SMT layout using 0805 size components, 1N753 zener and SOIC-14 IC. Related Products: Batteries | Batteries | Battery Contacts, Clips and Holders For energy conservation, connect to battery via a pushbutton (Push to Test). The overall current drain as shown is about 25mA which tends to be wasteful for continuous operation.
#Lm339 battery level indicator series
This current can be adjusted simply by varying the series resistors (R9 through R13). The LEDs are biased to operate at about 4mA which is quite bright if modern LEDs are used. As the battery depletes and the voltage begins to fade lights will begin to go off. D7 protects against reverse battery connection. Through clever use of a series of resistors and the LM339 comparator, a visual indication of the state of a battery can been seen. The comparator sections have open collector outputs that simply function as switches to operate the LEDs. U1 is an LM339 quad comparator that compares the various voltages from the two dividers. R7 & 8 form a voltage divider to that reduces the battery voltage by a factor of 3. Tied to this is a string of divider resistors (R2-6) that set the various fixed voltage levels. Of course, you may select your own colors if desired.ġ2 Volts Battery Level Indicator Circuit Schematicĭ1 is the voltage reference zener. Connecting a 33K resistor across D9 corrected this little problem without affecting anything else.This battery level indicator offers (5) LEDs that light up progressively as the voltage increases: This was traced to Zener D9 dropping out of conduction thus starving the voltage divider. Testing on variable voltage turned up an interesting bug –when the voltage was turned down to about 10V, all LEDs lit again. To reduce standby power, a push-to-test pushbutton may be used.
#Lm339 battery level indicator driver
This current can be adjusted simply by varying the emitter driver resistors (R9 through R13).
The LEDs are biased to operate at 2.3mA which is reasonably bright for high efficiency LEDs. The remaining LEDs will switch on close to the indicated voltage –accuracy of those voltages may suffer slightly, but should be close. Then adjust the calibration pot until D2 flickers.
The quad comparator compares the various voltages from the two dividers.įor calibration, connect to a voltage source that can be set to the highest LED threshold (41V in this case). R7 & 8 form a voltage divider to that divides the battery voltage by a factor of 9. While this is relatively busy, it places virtually no burden on the shunt regulator.ĭ1 is the voltage reference zener. By limiting the emitter current, the LED current is automatically limited to the same value. However, the cascode transistors may drive LEDs that are tied to a much higher voltage –up to 80V using the MPS-A16. By tying the bases of these transistors to the 13V bus, the LM339 open collector drive transistors never see more than 13V. In this circuit it offers one great property –low voltage in, high voltage out. This configuration is generally used for RF amplifiers. There are two solutions for this: increase the current rating of the shunt regulator so that it can power the LEDs, or run the LEDs via a cascode amplifier arrangement –I chose the cascode amplifier.Ī cascode amplifier is a configuration where one transistor feeds a 2nd transistor that is connected in the common base configuration. However, the LM339 open collector outputs cannot drive LEDs powered from the battery bus due to the same maximum voltage limitation. Shunt regulators are very simple, inexpensive and robust –good for this application. The solution involves running the IC power rail off a zener shunt regulator. One limiting factor is the LM339 that has an absolute maximum voltage rating of 36V –and it is not good practice to operate near that point. 36V Battery Level Indicator Circuit Diagram:.Of course, you may select your own colors if desired.Red: Power Connected (0%) (essentially always on)īlue: Greater than 41V (100%) (full charge is about 41 to 42V) While designed for 36V systems, it is easily modified to 24V, 48V or 60V simply by changing two resistors.
#Lm339 battery level indicator update
This is a update of the 24V Battery Level Indicator. This battery level indicator offers (5) LEDs that light up progressively as the battery voltage increases.
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