#Digital battery status indicator series#

My simple solution was to add a pair of forward-biased 1N4148 diodes in series with the yellow LED which adds about a volt of voltage drop before a current can flow.

The indicator has to have a 'turn-on' voltage between 2.5 and the reference voltage desired. Since this is below the TL431 minimum voltage, these LEDs are on all the time that a voltage above 2.0 volts is present. Note that the intensity of the LED dims as you go from the reference voltage down to the operating voltage (a 'turn-on' voltage if you wish.) After looking at several data sheets, I found that most LEDs operate at about 2.0 - 2.2 volts. So it works just fine as long as the reference voltage is greater than 3 volts. The supplied LED starts to light at something like 3 volts. Color: Quantity: Additional 3 off (3 Pieces or more) 6597 Pieces available. Now we need to have an indicator that operates in the voltage range between 2.5v and the reference voltage. Battery Gauge Car Capacity Monitor 12V 24V 36V Panel Status Indicator LCD Digital Battery Tester for Universal Auto Car Vehicle Extra 2 Off. When it enters the range below the reference voltage, the TL431 opens to allow any voltage (an open-circuit). The way this works is that the TL431 looks like a 2.3 voltage drop when the voltage is above the reference voltage (se4t by the trimmer). Okay, for those of you that want to use a different color, a smaller LED (like I do) or some other indicator, here is what I found by studying the circuit and the data sheets. The footprint of each part is clearly marked on the PCB to help you throw it together. All of the parts are through-hole and it shouldn't take long to solder together. This board comes as a 'bag of parts' kit. In order to set the appropriate reference voltage, you can use the formula found in the schematic to calculate your desired resistance and set it using the trimpot and a multimeter measuring resistance across the provided test points. KKmoon Battery Status Charge Indicator Monitor Meter Gauge LED Digital 12V&24V Features: Display of 10 segment LED bar graph. When the battery connected to the board reaches that voltage, the shunt allows current to flow through the LED, alerting you to a low battery situation. The reference voltage can be adjusted by using the trimpot on board. We've whipped up a little board to help you out with this situation: the 'Uh-oh' battery level indicator.Īt the heart of the 'Uh-oh' board is the TL431ACLPG shunt regulator diode. One way to avoid this is to keep an eye on your battery voltage and turn off the system before it gets too low (or plug it in). Brown-out conditions can cause memory to get written or overwritten in odd ways, can cause unexpected behavior in connected systems and just generally screw up your day. Under-powering a digital device can sometimes have pretty nasty consequences.