Higher capacity batteries are larger and heavier than smaller ones, so you'll need to trade off size and weight vs. The higher the capacity, the longer your project will run. ![]() The other number is the capacity of the battery, or how "big" it is. Usually we'll recommend a specific battery, such as two 1.5V AA cells for our Simon game. You'll of course want to pick a battery that matches your project's requirements (too much or too little voltage isn't good). One of these is how many volts the battery provides. When you buy a battery from SparkFun (or anywhere else), you'll decide which one you want based on two important numbers: Voltage, Current, Resistance and Ohm’s Lawīefore we talk about coulombs, let's talk for a minute about batteries.If you start with a full battery, you'll always know exactly how much of it is left! Neat, huh? Suggested Reading: By counting the pulses and direction, you can maintain an accurate count of how much power your circuit is removing from (or putting back into) your battery. With each pulse, you'll also get a "polarity" signal, which tells you which direction the current is flowing (great for rechargeable batteries!). It constantly monitors the current your circuit is using, adds it up, and gives you a pulse each time a given amount of amp-hours have been used. This is the odometer's job it constantly monitors your speed, accumulates it over time, and tells you how far you've traveled.Ī coulomb counter is like an odometer for current. The speedometer is like an ammeter - it shows you your instantaneous speed, which is good to know, but it can't tell you how far you've gone unless you're constantly keeping track of it. The Coulomb Counter uses under 1mA when it’s running, and you can use the SHDN (shutdown) input to reduce its power consumption further (though it will not be able to keep track of current use while shut down).Consider the speedometer and odometer in a car. This is so that the small amount of power used by the Coulomb Counter itself is included in its measurements for maximum accuracy. Note that the Coulomb Counter is powered by the IN header (usually your battery) and not by the VIO pin, which is used only as a voltage reference for the output pins. Thus, if you see a signal named RESET, you must provide a low signal to reset the part, and keep it high at other times. In negative logic, a low logic level means the signal is asserted or active. PROTIP: When you see a signal name that contains an asterisk or has a line over it, that’s an indication that this signal uses “negative logic”. This pin can be left disconnected if you do not need the shutdown function. There is a pullup resistor from this pin to VIO, so if you leave it disconnected, the board will remain active. If SHDN is low, the chip will be held in reset. This pin can be left disconnected if SJ1 is closed and you are using interrupts to sample INT. This is done automatically if SJ1 is closed (ties CLRand INT together). If INT is low, make CLR low to reset INT. High = current from OUT to IN (charging). Low = current from IN to OUT (discharging). Is cleared (goes high) when CLR goes low. ![]() Goes low when 0.0001707 amp-hours have passed through the board. Note that you may need to change jumper settings (see above). Depending on what you want to do, you’ll need at least the first four pins: NameĬonnect to 3.3V or 5V depending on your system. ![]() These are the pins you’ll need to connect to your microcontroller. Indicates Charge Quantity and Polarity.Īt the other end of the Coulomb Counter, you’ll find a header with six pins.Simply install this breakout out between your power source and your circuit, that way all the current your circuit uses needs to pass through the Coulomb Counter to be measured. These are the pins you’ll need to connect to your microcontroller and include VIO (Voltage Input), INT (Interrupt), POL (Polarity), GND (Ground), CLR (Clear), and SHDN (Shutdown). At the other end of the Coulomb Counter you’ll find a header with six pins. Connect your battery or power supply to the IN header or JST battery connector (they’re identical), and connect the OUT header to your project. When used effectively and if you start with a full battery, you’ll always know exactly how much of it is left!Īt one end of the Coulomb Counter Breakout are headers labeled IN and OUT. This breakout is capable of constantly monitoring the current your sensor is using, is able to add it up, and will give you a pulse each time a given amount of amp-hours have been used. If you are wondering: a coulomb is defind as, to put it simply, one amp for one second. Odometers are extremely useful for cars, they tell you how far you have gone, wouldn’t it be nice if you were able to have a device that does the same for electrical current? The LTC4150 Coulomb Counter Breakout is here to be your odometer for current.
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