Hello everyone,
This is my first post here and I'm looking for some feedback. I designed a low voltage disconnect board for one of my ongoing project, to avoid the battery from getting damaged by over discharge. Electronics have never been by strong suit and I haven’t practiced it really much for years (the former student in me is a bit ashamed).
I wanted to be able to:
- Turn on the main power with a push button if the battery voltage is high enough
- Have the board to turn itself off if the power gets too low
- Turn the power off by pushing the same push button
As it is a low voltage disconnect board I also tried to minimize the power consumption when the main power is off.
So I tried and designed the following schematic. I'm looking for feedback on how well it will perform before ordering any component. I’m also looking for any advice, for example where to add capacitors or diodes (I suspect that freewheeling diodes on the coil might be useful).
The working principle is as follow:
- In resting position nothing is powered
- When pushing the switch, the part in blue get powered.
- The first comparator (IC2A) compares the voltage of the battery (scaled down through a voltage divider bridge) to a stable voltage from a voltage regulator (IC1) and voltage divider. If the battery voltage is high enough the comparator output is set to high and powers the set coil, turning the relay on.
- The other comparator (IC2B) is here to deactivate the relay when the battery is too low. As the relay isn’t turned on yet, the voltage of the battery is 0 and the comparator could trigger a relay shutdown while it is turning on. I added a transistor (T2) to prevent that from happening.
- The relay is turned on, connecting the load and setting the data input high on the edge-triggered D-type flip-flop.
- When the button is pushed the second time, the output of the flip-flop is set to high, letting the current go through the transistor T1 and powering the reset coil.
- If the battery voltage gets too low, the comparator IC2B output is set to high, powering the reset coil.
I included below the flip-flop time diagram to make things clearer:
Thank you for reading.
This is my first post here and I'm looking for some feedback. I designed a low voltage disconnect board for one of my ongoing project, to avoid the battery from getting damaged by over discharge. Electronics have never been by strong suit and I haven’t practiced it really much for years (the former student in me is a bit ashamed).
I wanted to be able to:
- Turn on the main power with a push button if the battery voltage is high enough
- Have the board to turn itself off if the power gets too low
- Turn the power off by pushing the same push button
As it is a low voltage disconnect board I also tried to minimize the power consumption when the main power is off.
So I tried and designed the following schematic. I'm looking for feedback on how well it will perform before ordering any component. I’m also looking for any advice, for example where to add capacitors or diodes (I suspect that freewheeling diodes on the coil might be useful).
The working principle is as follow:
- In resting position nothing is powered
- When pushing the switch, the part in blue get powered.
- The first comparator (IC2A) compares the voltage of the battery (scaled down through a voltage divider bridge) to a stable voltage from a voltage regulator (IC1) and voltage divider. If the battery voltage is high enough the comparator output is set to high and powers the set coil, turning the relay on.
- The other comparator (IC2B) is here to deactivate the relay when the battery is too low. As the relay isn’t turned on yet, the voltage of the battery is 0 and the comparator could trigger a relay shutdown while it is turning on. I added a transistor (T2) to prevent that from happening.
- The relay is turned on, connecting the load and setting the data input high on the edge-triggered D-type flip-flop.
- When the button is pushed the second time, the output of the flip-flop is set to high, letting the current go through the transistor T1 and powering the reset coil.
- If the battery voltage gets too low, the comparator IC2B output is set to high, powering the reset coil.
I included below the flip-flop time diagram to make things clearer:
Thank you for reading.
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