Tl431 low voltage cutoff


  • A Simple 24V Li-Ion Battery Low Voltage Disconnect W/ Hysteresis Using Six Parts
  • Over-Voltage Automatic Switch off Circuit
  • Battery discharge indicator on TL431. What is the battery discharge indicator for?
  • Ode To The TL431, And A LiFePO4 Battery Charger
  • 3 Tested 220V High and Low Voltage Cut OFF Circuits Using IC LM324 and Transistors
  • TL431A Adjustable Zener
  • Electronic – TL431 Low battery cut-off
  • A Simple 24V Li-Ion Battery Low Voltage Disconnect W/ Hysteresis Using Six Parts

    Its output voltage can be set to any value between 2. With very sharp turn-on characteristics, the TL is an excellent alternative to a zener diode in many applications. In this article we will look at how a TL can be used to make a very simple battery status monitor illuminating an LED when the input voltage is above a user set value. Click here to view our article on making a battery status monitor with a zener diode.

    Using the TL The TL is most commonly found in the TO packaging pictured at the start of the article — a piece of black plastic out of which emerge three legs.

    Below the connections are labelled — REF is the voltage reference. The aim of the monitor is simply to light up an LED when a target voltage is reached — perfect for a solar battery charger to let you know when the batteries have reached full charge.

    The simple equation displayed above gives the high limit — in this case the voltage at which the LED will light up. Since the reference voltage Vref is fixed at 2. The R3 resistor is there to protect the LED from excessive current with the value selected depends on the specification of the LED used, the brightness required, and the maximum likely input voltage. The resistor labelled R4 in parallel with the LED prevents the LED from glowing softly when the input voltage is still below the switch-on voltage.

    We used a 1K Ohm resistor. The lower the resistance value used for R4 for sharper the switch-on — i. A 1K5 and a 1K resistor were used as R1 and R2 respectively to achieve the desired 6. A variable voltage source was then used to test the circuit. When the input voltage was 6. For example, if you think you may want to be able to set the LED to come on at voltages from You could then use 2. Turn it all the way one way to make the LED come on at All the voltages in between those maximum and minimum values would be at different position of the potentiometer and can quickly be calibrated using a variable voltage source and a multimeter.

    More Information The accuracy of the voltage monitor depends on the accuracy of the resistors used. Fine tuning can be achieved using a low value variable resistor in series with R2. Note that the TL is also often labelled as a LM and may also be described as a programmable voltage reference. Blog Categories.

    Over-Voltage Automatic Switch off Circuit

    Short Link: Copy Nerd Ralph loves cheap and dirty hacks, and for that we applaud him. Although we think he really made it for the fun of making it. The circuit is centered around a TL programmable shunt regulator , which is an awesome and underrated chip in its own right. TL Despite its misleading electrical symbol, think of the TL as being a voltage-activated switching transistor. When the voltage on the reference pin is lower than 2.

    When the voltage on the reference pin is higher than 2. If you tie the reference pin to the cathode, the TL does behave like a zener diode that has a breakdown voltage of 2. The TL is a full-fledged IC with a precision voltage level reference, a comparator, and the active transistor all bundled up inside. The ability to put different voltages on the reference pin and the cathode make it interesting.

    Then, when the voltage on the reference is higher than 2. You can add a voltage divider to increase the threshold to any value above 2. Shown here is an LED that only lights up when the input is 5V or greater.

    To make a voltage regulator from the LED circuit shown here, all you need to do is add a transistor in place of the LED; have the TL turn the transistor on when the voltage drops below a target voltage and off when the voltage rises above.

    Indeed, this cheap and cheerful voltage regulator application is where almost all of the TLs end up — providing voltage regulation in switching power supplies. He chose the voltage-setting resistors R1 and R2 to give him 2. Current flows from the power supply through RB1 and into the transistor, turning it on.

    The voltage at Vout increases, the battery charges, and the voltage in the middle of the voltage divider increases proportionately.

    When it reaches the 2. He tested the output current into a half-charged battery to verify that he was in the right ballpark. The basic circuit is a voltage regulator, after all. Constant enough. If you need a voltage-triggered switch anywhere in your project, you now know where to look. Ken Shirriff has written a very nice dissection of the TL that includes die images. Do you have any favorite tricks for the TL? What piece of silicon would you rate as an unknown gem in the rough?

    Battery discharge indicator on TL431. What is the battery discharge indicator for?

    Ode To The TL431, And A LiFePO4 Battery Charger

    The TL is a full-fledged IC with a precision voltage level reference, a comparator, and the active transistor all bundled up inside. The ability to put different voltages on the reference pin and the cathode make it interesting.

    Then, when the voltage on the reference is higher than 2. You can add a voltage divider to increase the threshold to any value above 2. Shown here is an LED that only lights up when the input is 5V or greater.

    3 Tested 220V High and Low Voltage Cut OFF Circuits Using IC LM324 and Transistors

    To make a voltage regulator from the LED circuit shown here, all you need to do is add a transistor in place of the LED; have the TL turn the transistor on when the voltage drops below a target voltage and off when the voltage rises above. Indeed, this cheap and cheerful voltage regulator application is where almost all of the TLs end up — providing voltage regulation in switching power supplies.

    He chose the voltage-setting resistors R1 and R2 to give him 2. The aim of the monitor is simply to light up an LED when a target voltage is reached — perfect for a solar battery charger to let you know when the batteries have reached full charge.

    The simple equation displayed above gives the high limit — in this case the voltage at which the LED will light up. Since the reference voltage Vref is fixed at 2. The R3 resistor is there to protect the LED from excessive current with the value selected depends on the specification of the LED used, the brightness required, and the maximum likely input voltage. The resistor labelled R4 in parallel with the LED prevents the LED from glowing softly when the input voltage is still below the switch-on voltage.

    We used a 1K Ohm resistor. The lower the resistance value used for R4 for sharper the switch-on — i. A 1K5 and a 1K resistor were used as R1 and R2 respectively to achieve the desired 6. The accuracy is so high that virtually the thresholds can be separated and sensed within 5 volts range. The incorporation of opamps in the circuit equips it with the above feature and therefore the whole idea become very much reliable. The IC is outstandingly reliable and easy to configure and hardly poses a problem with its functioning, in short it has robust specs and is too flexible with most of the configurations.

    The four opamps are rigged as voltage comparators.

    TL431A Adjustable Zener

    Op amp A2 and A3 are configured as window comparators, meaning the outputs of both these opamps will be zero volts or logic low, as long as the input AC is within the normal range, as set by the presets P2, P3.

    A2 controls the low voltage cut-off while the A3 monitors the high voltage cut off point. The remaining opamps A1 and A4 are simply rigged as voltage indicators along with the associated yellow, orange, green, red LEDs. How to Setup Setting up of the presets P1 to P4 are implemented by first evaluating the various DC levels that would match the corresponding AC mains voltage levels.

    This is elaborately explained under the "Calculating the Cut-off Thresholds" section below. Initially keep the transformer disconnected, and the relay also disconnected from the transistor. Using a variable power supply, set a voltage of 10 V across the op amp circuit, and adjust the P4 preset until the yellow LED just illuminates.

    Electronic – TL431 Low battery cut-off

    Next, increase the supply to 11 V, this should instantly shut off the yellow LED. Now tweak and shuffle the P3 preset until the orange LED just light up. Increase the voltage supply to 12 V, this should instantly shut off the orange LED. Next, increase the DC supply to Finally, adjust the DC level to After this, tweak and shuffle the preset P1, until you see the red LED just illuminating.

    This completes the Setting up procedures, now you can connect the relay with the transistor collector, and the transformer input with the mains, and expect the circuit to work exactly as per the settings. Please refer to the diagram given below; it's self-explanatory and very simple to understand.


    thoughts on “Tl431 low voltage cutoff

    1. I consider, that you are not right. I can defend the position. Write to me in PM, we will discuss.

    2. I recommend to you to visit a site, with an information large quantity on a theme interesting you.

    Leave a Reply

    Your email address will not be published. Required fields are marked *