# Tag Info

14

simulate this circuit – Schematic created using CircuitLab The resistors divider works always exactly the same. For very precise measurement you need a low TCR value resistors. The tolerance doesn't matter if you will insert a calibration factor in the MCU, else you can use 0.1% tol. resistors. Now, what errors will be amplified? For sure the offset ...

8

DKNguyen’s answer addresses limitations on the input voltage swing, but I believe you asked about the output swing. That’s generally specified fairly directly in the data sheet as “output voltage swing” or some such, generally qualified with load. In the case of TI’s LM741 for example: This tells you that when using +/-15V rails, you can expect the output ...

7

It appears differently on different datasheets. I've seen two or three ways. Sometimes it will literally list the input common mode range relative to the voltage rails (i.e. Vcc - 3V and Vss + 3V). Other times have to infer it because it gives the maximum and minimum input voltage in a table where the voltage rails have been specified. If it does this then ...

5

Universal breakout boards usually don't have footprints for the decoupling caps the specific chip needs, so you will have to bodge it somewhere on the 0.1" headers, and you will get power integrity problems. But the main problem is not the breakout board... it's connecting it to the FPGA board with wires and sending high speed digital signals in the ...

5

Vdd is the power supply for the device. Vref is the reference voltage for the ADC. The conversions are relative to that voltage and it determines the size of the LSB. It would normally be an accurately controlled voltage, maybe from a voltage reference device. The specific relationship between the voltage at the Vref pin and the input voltage range varies ...

4

Generally single supply circuits that have to deal with bipolar inputs have some unpleasant characteristics such as the one you mention for open inputs, and outputting voltage from what is suppose to be an input. Most would likely say an ideal input circuit has a known input impedance (or extremely high input impedance), and does not output any voltage (...

3

This would mean the analog inputs could accept a voltage between -5V and +5V. No. it is stated that the analog voltaghe input range is from -0.3V to Vdd+0.3V. Let's say that the input range is 0..Vdd, positive only, so it can't accept negative voltage at the inputs. Does it mean that the -5V to +5V range is maybe between a common mode voltage of lets say ...

3

The sensor is not specified to work on 3.3V supply. It is specified to work on 5V +/- 0.5V supply, and therefore it is not required to operate in any way outside that specification. The curve you are looking only provides typical example output. The datasheet only guarantees that the output is at least 3.4V or more at 4k7 ohm load, but since it does not give ...

3

VDD is the 'main' power supply input -- it supplies the current to operate the ADC. Its value typically does not have to be particularly precise -- maybe ± 5% or even 3 to 5 V for example. VREF is the reference for the ADC and needs to be accurate in order for the whole ADC to be accurate (the ADC converts VIN/VREF to a binary value; if VREF is off, the ...

2

If you want a decent sample rate, your frequencies are definitely in the territory where signal quality matters, and trace length skew starts to matter. Given that it's a simple application that can probably be routed on a two layer board, I'd expect designing your own PCB will be both faster and cheaper.

2

The machine.I2C constructor class machine.I2C(id, *, scl, sda, freq=400000) allows you to specify: the id of the I2C bus to use the pins (scl and sda) to use So you can just create two instances of the I2C class, one for each I2C bus, and use them separately, to read each of the two ADCs. The ESP32 and associated MicroPython port does indeed support 2 ...

1

See what you think of this: simulate this circuit – Schematic created using CircuitLab It's inverting, but that's easily fixed by bitwise-inverting the ADC reading (yes, that works!), possibly by using an instruction just for that instead of the normal load instruction or whatever your MCU uses. So no performance penalty at all if you can convince ...

1

What about this? simulate this circuit – Schematic created using CircuitLab $$V_{out}=-V_{in}\cdot G + (1+G)\cdot V_+$$ $$V_{out}=-V_{in} + 2\cdot V_+$$ Note: If you supply the opamp with 12V, then you can get the output as high as 12V. EDIT: simulate this circuit ADC_{count}= \dfrac{V_{adc}}{V_{ref}}(2^N-1)=\dfrac{-V_{in} + 2\cdot V_+}{V_{ref}}(2^...

1

When you plug the jumper shorting MOSI/MISO you get the same sequence back. It is so called loopback test. As you can see there's something causing the MISO line to be recieving incorrect bits. I don't see anything wrong, the SPI device has responded. If it wasn't, you would get all bytes FF or 00. I'm a novice at this sort of thing but it looks to me ...

1

We pretty soon discover that it's a bad idea to mix this unrelated analog resistor ladder stuff with your power on/off functionality. So either you need a dedicated button for power on/off, or you need a DPST switch. This switch can then drive a MOSFET placed in series with your supply. You need some manner of latching function since the switch is momentary. ...

1

Since you are not responding, I'll only offer a very simple concept that accepts both DC and AC. It provides a very simple answer to your question: The max input is 0~24Vdc and -24V~24Vac. [...] The voltage that I want to bias is regulated by the voltage divider so the range of AC voltage coming to Arduino is between -3.3V and +3.3V. I want to get the ...

1

Turns out I am really dumb and forgot to put an |= when I simply had an =. This is the code in question: GPIOF->MODER &= ~0xFFFF; GPIOF->MODER |= GPIO_MODER_MODE9_0 | GPIO_MODER_MODE9_1; GPIOF->MODER |= GPIO_MODER_MODE7_0 | GPIO_MODER_MODE7_1; GPIOF->MODER |= GPIO_MODER_MODE5_0 | GPIO_MODER_MODE5_1; Very obvious now why I was only getting ...

1

First, your precision is 12 bit. So, at 24V, 1 step is about 6mV. At 1.8V, it is 0.4mV The errors come from: Resistor tolerance. This you can calibrate if needed. Else use a matched pair. Eg: Y0115V0522BV0L. Thermal noise in the resistors. Yes, this will be multiplied. Oversampling can help. EMI. I hope you are only needing to measure DC and hence, can ...

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