I nearly always use MOSFETS these days instead of BJTs though as a matter of course.Īs an aside, the only other way of achieving this whilst maintaining the isolation of the ADC from the battery would be to replace the P channel MOSFET with a small relay (say a reed relay), but then you still have to build a relay driving circuit which is just about as complex as this one.Optional 100n capacitor from A1 to ground for stable readingsįloat Aref = 1.063 // change this to the actual Aref voltage of -YOUR- Arduino, or adjust to get accurate voltage reading (1.000- 1.200)ĪnalogReference(INTERNAL) // use the internal ~1. The N-channel MOSFET can be replaced by an NPN transistor if you wish, it makes no real difference. The voltage divider decreases the voltage being measured to within the range of the Arduino analog inputs. The Arduino board can be powered from a standard 9V battery pack. voltage, and IB being the battery current in response to the pulse and VBO. A PNP transistor is seen as a fixed voltage drop skewing your results. As you may well know, Arduino’s analog inputs can be used to measure DC voltage between 0 and 5V (when using the standard 5V analog reference voltage) and this range can be increased by using two resistors to create a voltage divider. It is a simple digital voltmeter, which can safely measure input dc voltages in 0 to 30V range. The Orion BMS monitors the internal resistance of each cell and tracks the. This battery pack had its own overvoltage, undervoltage, and overcurrent protection circuitry. A P-channel MOSFET, when on, looks like a very small resistor. I recently developed a product that used three 18650 cells. Note that it is important to use a P-channel MOSFET for this, not a PNP transistor. Ive got about 36 batteries that all stay between 2.8v and 3.6v, and I want to be able to accurately monitor the voltage (and therefor the state of charge) of all of them using an Arduino Nano, the two ways I can think of is use some analog multiplexers to get the 36 different batteries down to the 6 analog pins on the Arduino, or to use an. Usually arduino is powered through laptop/work station USB port and USB port is not truly outputting 5 volts. Yes, it's possible to compensate in software, but as long as you keep to a limit of 10K or so for the resistors you won't need to worry about doing such things. May be our power supply to arduino is supplying 4.8 volts and we are considering it 5 volts. The Arduino already has a built in 10 bit Voltage Sensor on the analog pins. If the divider's resistors are too large that impedance will affect the accuracy of your readings because the total resistance of the lower resistor will be skewed slightly. You should not use resistors greater than around 10K in size on the input to the ADC because the ADC itself has a resistance (the impedance) which is placed in parallel to the lower resistor of the divider. When the P channel is OFF the only circuit connected to the ADC is the connection between the ADC input and ground through a 10K resistor, so everything is happy and safe. In this tutorial, you will learn how to make a long range wireless battery Voltage monitoring system using Arduino Nano, 0 to 25V Voltage Sensor, HC05 Bluetooth Module, and the Long Range NRF24L01 Transceiver modules. We can also drop the load when the battery discharges to a predetermined value. When DOUT goes HIGH it turns on the N channel MOSFET which then pulls the gate of the P channel MOSFET down to ground which then turns it on, thus connecting the divider to the battery. R1 (Ohms) 1.25v / 1A R1 (Watts) 1.25v 1A R2 R1 ( (Vout 1.25)/1.25) A future upgrade will be a temperature sensor that stops charging (and discharging) when the battery temperature exceeds a predetermined value. That means the gate of the P channel MOSFET is being pulled up to the battery voltage by the other 10K resistor, so the P channel MOSFET is off, which isolates the whole divider from the battery. The theory is, when the Arduino DOUT is either LOW or not connected ( pulled low by 10K resistor) the N channel MOSFET is turned off. This can be accomplished by using a P-channel MOSFET which you can then drive with an N-channel MOSFET: Instead of isolating the ground ( which leaves the battery then directly connected to the Arduino) you need to completely isolate the battery from the divider. The trick, though, is to do the exact opposite of what you are doing. Simple Arduino Voltage Monitoring: In this Instructable we utilize the analog pins on the Arduino to make a simple power monitoring system that will detect the voltage on the 5v rail and perform an action if it gets too low. I use a similar system on a product I recently worked on to monitor the battery voltage - and of course I didn't want it on all the time to drain the battery.
0 Comments
Leave a Reply. |