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Macspice voltage divider code4/11/2023 If your source voltage is constant and regulated, a divider is ok. If the input voltage is higher, the output voltage will also be higher, proportionally, with a divider. The main difference between a voltage divider circuit made off two resistors and a Linear Voltage Regulator (LDO or non-LDO) is that the Linear Voltage Regulator will always output the same voltage regardless of the input voltage whereas the resistor divider will only divide, not regulate the voltage. The total value between source to ground defines the power loss. In the case of signal input, in order to limit current consumption, use high value resistors in your voltage divider: 22K or more. If the goal is to provide a 3V signal to an ic input, it's also fine since it consumes very little. In another example, using a voltage divider circuit or a Linear Voltage Regulator when you need to convert 5V to 3V for an application consuming more less 100mA is fine. With a 20V difference, even 100mA can generate enough power dissipation to consider using a step-down regulator. I was wondering whether there's any problem in using the divider instead of step-down regulator.Ī step-down regulator (Switching regulator) is better or required when the Power Dissipation using a voltage divider circuit or a Linear Voltage Regulator, is too high.įor example when you are powering a device from a much higher voltage source. I have never seen this or had to resort to it, so I suspect it is not commonly needed. An option (a bit odd, but potentially workable) would be to use a low quiescent current (Iq) linear regulator (possibly an LDO) to generate the 3.3V for the pullups. In micropower designs, the divider approach may not be the wisest option for that reason. Note that the divider will consume power even when SDA and SCL are not pulled down. Simulate this circuit – Schematic created using CircuitLab The effective pullup resistance is R1 in parallel with R2, which is (R1*R2)/(R1+R2). The effective pullup voltage is V * R2 / (R1+R2) where R1 is the upper leg of the divider and R2 is the lower leg of the divider. The basic answer is, yes, you can use a divider for pullup. In your application that would be the Raspberry Pi VCC, I guess.īut it is still an interesting question. have never used a | in Arduino.Īlso final question, if I set the nano to run at 8Mhz, this adjusts everything that gets timing from the nano? So for example, I am using an nfr24l01 transceiver.The best option, when possible, especially in the case where there is a single I2C master, is to pull up to the same VCC as the I2C master. Is that pretty much all there is to it? The first post posted how but I don't understand it all. So to use the 1.1, I simply use the analogReference(AR_INTERNAL1V2) (this is a 1.2V from the page analogReference() - Arduino Reference) and divide my expected max voltage to below 1.1(with safety margin) and calculate the real voltage?Īs I understand this internal voltage is very stable but not 100% accurate from chip to chip, so I will need to test to determine a calibration number. I do know how the ADC works and the whole ratio compared to the reference. The code compares MCU supply against 1.1volt Aref internally. If you choose to power the Arduino directly from the battery (no boost converter), then only software is needed to read the MCU supply. This is of course not needed if a voltage divider is used. Never connect a battery directly to a pin. This is what you want for ratiometric sensors like pots and most current and pressure sensors,īut it's not wise to use the A/D with default settings for absolute/voltage measurements.īecause the returned value then depends on input voltage and supply voltage (which is not stable).įor voltage measurements we have a stable (but not exact) internal 1.1volt reference available, Which means that mV between steps is supply dependent. It measures ratio.Įach A/D step is 1/1024 of it's own supply, The Arduino A/D by default does not measure voltage. I am not so sure I totally understand the use of the internal 1.1.
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