Week 6

Question 1

how to deal with battery usage

Answer 1

start monitoring the battery voltage: it can give a low voltage warning so the battery can be replaced.
reducing clock frequency so the arduino runs slower
use arduino low power library to shut down the aruino for a given time or until an external event wakes it up

Question 2

deep sleep and power down problems

Answer 2

it will not retain ram and will start with setu when waking up.
once in deep sleep the arduino can only wake up by an initilized interrupt
on power down mode the arduino needs a power cycle to wake up again
eeprom will help

Question 3

what to do when using lithium ion batteries

Answer 3

use a protection circuit to prevent the battery from being damaged

Question 3

digital vs analog (advanced)

Answer 3

analog works with resistance, digital works with sending digital info so is more complex

Question 4

how to protect against overvoltage

Answer 4

add a zener diode that clamps output when the voltage is higher dan 5v

Question 5

zener diode

Answer 5

zener diode: allows current to flow back when a certain reverse (zener) voltage is set

usefull for low power stabilized power supply rails
reference voltage circuits
overvoltage

Question 6

Op-Amp

Answer 6

high gain voltage amplifiers (100000x)
boasts a very high input impedance on its inputs

Question 7

input impedance

Answer 7

mostly parasitic resistance (i think this means resistance that influences the current when we do not want this to happen)

Question 8

op-amp

Answer 8

has very high impedance, so you can add output loads that are high without it ifluencing the voltage divider

you can use it as a comparator, if the voltage connected to the + pin is lower than the voltage of an input, the output voltage will be low. (if its higher the output voltage willl be low)

Question 9

level conversion

Answer 9

the sensor is using bi-directional communication ( can be achieved by using a mosFet and 2 resistors)

use when a sensor requires a different voltage than the arduino

Question 10

sensor calibration why

Answer 10

sensors are not perfect: noise, resolution, hysteresis, offset, drift

Question 11

optimal operation window

Answer 11

a window in which sensors operate the most optimal, like temperature or range. Check this

Question 12

calibrating sensors

Answer 12

non-linearity can be calibrated using a mapping function
linear offset (add/substract values) and temperature drift(meaasure the drift and compensate in the program)

Question 13

filters

Answer 13

shape input values into a desired output value, they filter out data at a certain frequency. this can be both in hardware and software

Question 14

when filters in hardware

Question 15

how filters in hardware

Answer 15

RC - filters filter certain frequencies by cutting it of at a certain value. uses a capacitator and a resistor. Loww/high refers to the frequencies that can pass this filter 1/(2piRc)

passive LC-filter use inductor and capacitator. is a second order filter (has to indents)

Question 16

time series

Answer 16

a series of values of a quantity obtained at succesive times

Question 17

buffering

Answer 17

use when:
- new data comes in during processing
- you need to store datapoints
- or you want to filter time series data

buffering = storing bulk data, they have a fixed size

Question 18

sample rate and frequency

Answer 18

largest detectable frequency in a sampled buffer is half the samplerate this can make it difficult to read values

Question 19

timeseries timing

Answer 19

exact timing is relevant, use interrupts and timers to line up timing

Question 20

filter basics (software)

Answer 20

moving average: takes an average of the data that comes in and fluctuates.

2 types: Finite impulse response (stable and used when fidelity is critical) infinite impulse response (instable but efficient)

Question 21

FIR

Answer 21

uses a buffer containing the last 5 measurements. after 5 samples the input response is 0 again. needs more memory and computationally intensive. but is very precise

Question 22

IIR

Answer 22

uses a single float as storage independent of filter size. by continuously calculating an average.

little memory not computationally intensive