| Electronics > Beginners |
| INA 219 current sensing maximum wattage |
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| lots o tots:
I have an INA 219 and want to calculate the current, but i dont know if it is too high for the INA219. https://www.adafruit.com/product/904 According to the specs it can monitor at up 26V and up to 3.2A. the current sense resistor is 2W. The voltage in the circuit will be 19.5V. i wanted to be able to run current through this at up to 3A. exact current value is unknown at the moment. The load will probably be 50% to 75% duty cycle. Does the current sense resistor at 2W mean that if i run at 19.5V, i cant sense more than 0.1A without burning the sense resistor? (0.1A x 19.5V = 1.95W). if i cant monitor anything past 1.95W, i will have to use a low value load only through the resistor like a small LED and just add a correction factor to the real load. i dont really want to do that if it can be avoided. Is there something that i can wire into the circuit that has a precise load that will provide a constant voltage, constant current that the INA219 can safely sense. Also(there will actually be 2 seperate circuits and i want the loads in those 2 circuits to be as close as possible to each other.) thanks -LOT |
| paulca:
To work out the maximum through the resistor you need to know it's value. It will drop a certain voltage (used to sense the current) for a given current. Multiple that voltage by the current to get the power dissipated by the resistor. So if it's a 0.1Ohm resistor at 3.2A it will drop 320mV. That is 3.2*320mV ~= 1W. You might note you can just do Current2 Amps * Resistance Ohms = Power Watts dissipated Ohms law. |
| lots o tots:
I see, so we muliply the current by the voltage drop and not the voltage for the voltage in the circuit, as the rating is for the heat it can dissipate. interesting Thanks |
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