I have looked on stack overflows forum and can't find the answer to my 2 questions. So here they are.
Can I power a motor using an arduino uno with just the outputting to the motor like I can with a led without having a motor shield?
This is based on number one but let's say the answer is yes for now until I find out the answer to question number 1. I have a max of 3 volts that my small dc motor can take and I know the arduino out puts 5 volts, so that means I am 2 volts over the limit by simple math. I have about any resistor type you can think of, so which one will I need to put into my circuit? I am confused on why I can't find anything on converting 2 volts to ohms for the resistor value.
Thanks in advance.
Powering your motor right from the output is typically not advised. The digital pins on Arduino can only souce a small amount of current. Typically far too little to drive a motor. But, it depends on the motor of course. More important than voltage of your motor is knowing how much current is needed to drive it.
For your resistor question, look into voltage dividers using resistors.
Mike
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I am trying to retrieve the current state of the motors (e.g. thrust percentage at each motor). The only state information I can find is whether or not they are on. Is it possible to get more detail about the current power setting?
The motor power level / thrust percentage is not accessible using DJI-SDK at the moment. You can however read the speed (ground speed of the aircraft) and its attitude, if that is something that might work for your calculations.
as far as i know, in the package which is sent by a beacon, it contains the information about calibrated Tx Power (or measured power - power value at 1 meter). I just wonder why beacon send calibrated Tx power, not broadcasting power (the signal power that beacon sends from the source). Because the calculation logic can be different a little bit but it makes the terms and configuration more simple.
Think about a beacon like a friend calling out to you by shouting your name. You can estimate how far your friend is away by the volume of the sound when it reaches you.
But some people have louder voices than others. A friend with a loud voice who is far away may be heard at the same volume as a friend with a soft voice who is nearby. To tell the difference, you might have each friend shout out how loud their voice is on a scale of one to ten.
This is the same concept behind beacons transmitting their "measuredPower" (also known as txPower or calibratedPower). The beacon transmits the "volume" that should be heard by the receiver (measured in dBm) if the receiver is 1 meter away. This way, beacons with strong transmitters can work alongside those with weak transmitters.
The reason 1 meter is used as a reference is because it is relatively easy to measure a signal at 1 meter. Practical considerations make it difficult to impossible to accurately measure signal levels at a distance of 0 meters. Also, physical environmental factors +like a metal cabinet behind the beacon or a wooden door in front of one) can cause reflections or attenuations that affect the signal level. A 1 meter reference point makes it easier to account for this.
The distance estimate provided by iOS is based on the ratio of the iBeacon signal strength (rssi) over the calibrated transmitter power (txPower). The txPower is the known measured signal strength in rssi at 1 meter away. Each iBeacon must be calibrated with this txPower value to allow accurate distance estimates.
i have to build a project that uses an FPGA with the software Modelsim. the project is a range finder or measuring tape.
I already know the basics of modelsim, but I've never done anything like this. the sensor that i am using is an Infra red proximity sensor. https://www.sparkfun.com/products/242 . I am aware that i will need to use an Analog to digital converter, in order for the fpga to recognize the sensor. this sensor also has to rely on is output voltage to determine the distance. the distance will then be displayed on an LCD screen. The problem i have is that i'm not sure where to start.
so if anyone can give any advice, a sample code for this problem or anything it would be appreciated.
Each of these subjects can be a large subject of their own. As it is, you should narrow down your question into something more specific -- where are you stuck? That said, here are some thoughts to help you narrow your questions.
You have correctly identified what you need to do: utilize an A/D converter, and display range (distance) on an LCD screen.
Let's break what you need to do in a little more details.
You need to interface with the A/D converter. For example, what pins are the data pins attached to on your FPGA? How do you need to clock the A/D? Basically, you need to figure out how to get digital samples into your FPGA logic.
You need to convert your digital samples from a voltage to a range. A lookup table is an excellent way to do this. The input to the lookup table will be (digital) voltage, the output will be range.
You need to learn how to interface with an LCD screen/panel. At minimum, you are going to have to learn how to draw/redraw a few characters on the screen representing the range.
Once you have these 3 components, you need to tie them together. The A/D interface in the FPGA will periodically generate voltage values, the lookup table will convert voltages to range, and then you will display the range value on your LCD.
Why do some NFC-modules have two transmitters? TX1 and TX2?
I really can't find what it's for... I was thinking about Single-end and differential signaling?
So there would be less noise?
Most NFC modules have two transmitter outputs pins. These are not two independent outputs but just the two pins of a single differential output.
The reason why a differential output is preferred by NFC modules is quite simple: It is often needed if the NFC chip only has a small supply voltage (3V is common). Since the output is capacitively coupled to the antenna, the antenna can be driven with twice the voltage compared to a single ended output.
That allows for twice the current, and hence twice the magnetic field in the antenna.
I can get the value of Wifi RSSI. but don't know how to convert it into level of Wifi strength as we can see in the menubar in Mac OSX (If I receive a strong Wifi, the wifi status will be bold black on all 4 lines of wifi icon).
Is there any methods or library that I can use to do this? Thx in advance.
I don't think you'll find anything in the API to do this.
I think you might have to Use Science™ and do a manual check, literally walking away from your WiFi access point with laptop in hand, noting down the RSSI values at which the WiFi signal indicator icon changes. Do this a few times and you'll likely find a correlation. I can't imagine it would take more than ten or fifteen minutes to get a good range of sample values.
It's probably worth trying it with more than one type of Mac, if possible.
There is no public API for this. You'll have to figure it out yourself. You might be able to use something simple like (RSSI+100)/8 and then clamp the result between 0 and 4 bars.
Also, you'll want to use a rolling average over a few seconds to keep the bars from jumping around if the signal ends up at a boundary case or jumps around.
PS: AFAIK, Apple uses a more complex algorithm which takes Transmit Rate into consideration.