I'm planning to use the basic model of an arduino bike speedometer to count the amount of chain that I let out when I anchor my boat. However if I only have one sensor it would only work for the chain counting one way.
My theory is to have two sensors on the wheel so that if sensor A counts first then the chain is going out but if sensor B is counts first then the chain is coming in.
Only problem is I am much better at coding in python than I am in the arduino IDE. I would be super grateful if someone could give me an idea of how to do this?
From you application description, you really wan't to track the position of the wheel holding the chain, not the speed (or velocity). If you read how rotary encoders work, you can apply that technique to the wheel. Rotary encoders have two digital outputs which are out of phase by 90 degrees so you can not only detect motion, but direction.
See http://playground.arduino.cc/Main/RotaryEncoders for a detailed explanation
Would it not be more useful to count chain out and count back in?
Only 1 magnet on the chain gypsy that counts out your chain from the stowed position, picking up a 12v signal from the windlass direction solenoid lowering feed, stores this value at rest. When raising pick another 12v from the windlass solenoid raising feed to count the value back down to zero at the rest position?
This negates the need to determine direction by interpreting motor direction as count positive and count negative IO signals?
Related
I wanted to know if there is any efficient way of finding the distance between 2 devices(a transmitter and a receiver) which is accurate to atleast the order of a couple of inches.
I am basically want to detect the movement of the transmitter from the receiver and how far it has moved from its original position.
I was thinking in terms of using a wireless hotspot/bluetooth connection. I cannot Use some form of audio/medium which can be detected by humans.
Could anybody help me with this?
To my mind, assuming there is no common synchronisation signal between the devices, there are 2 differents way to do this (not really easy):
1. Measure received power : some receivers provide RSSI (Received Signal Strength Indication). RSSI is a measure of how much power you received. If you know the transmitted power, you can estimate the transmission loss (from the transsmission channel) by taking different measure of RSSI at different distance. It will really depends on the channel (environment, frequency, throughput, ..), so don't change it for the measure. Once you got enough points, try to fit it by a curve. You can now predict distance by having RSSI.
2. Measure round trip time : this is called RADAR, and is really more difficult but is the classic way to measure distance and speed. Broadband systems (like WiFi) are better for this kind of measure. By the way you also can do the same with audio for short distances (SONAR), without being detected if you use frequencies higher than 20kHz.
I'm trying to measure the distance an object is pulled along a pulley track using arduino (or Rasp Pi) sensors. I have an object that is manually pulled, from a resting position, on a pulley system and I need to be able to track the distance it travels over one pull.
Example: The object traveled 90% (example) of the total pulley distance for 5/10 pulls.
Example: The object traveled 11.53 ft along the pulley.
See the image below for a visual diagram. I have two ideas, but I'm not an Arduino sensor expert. I'd love input on an elegant solution.
Use an arduino sensor to sense how many times the pulley rotates, and then use an equation to determine the distance.
Use a sensor that senses the distance pulled in cord, maybe each direction, and record that distance. I got this idea from pump sensors, no idea if a comparison exists.
Really just looking for advice on what sensors to use, how to implement them (general), and what type of metrics I could record.
There are at least two ways of doing this:
Use a rotary encoder, which will tell how many rotations the pulley did. There are two disadvantages: line can slip on the pulley, resulting in inaccurate measurement, and there is no way you can now at what actual position the object is. Rotary encoder will give you only position relative to the starting position (unless you only need one rotation of the pulley - then you can use absolute encoders)
Use a distance sensor (ultrasonic, or IR) to measure at what height is the object. That way you will know the exact position of the object, but you may have a problem if your object is too small, has a shape or surface that will impact the measurements, or if the space is limited and a sensor can pick up walls, or other surrounding objects. Also if the objects may swing on the rope, there will probably a problem.
Software implementation for all of these solutions should be pretty simple, just decide on type of sensors - there are plenty of tutorials for all of them.
Both task 1 and 2 can be done easily using a digital rotary encoder at very nominal cost. It can sense direction and distance of travel quite accurately.
I want to ask about I Beacon advertising, especially Tx Power.
I used two BLE module HM10 and HM11. I make one as a ibeacon (HM10). and other one used to connect and listen to HM10 broadcasting.
I used MCU ATmega32 AVR tied with HM11 and I used scanf function to read the broadcast. I want to extract the last byte (Tx Power). I want to measure the distance with AVR programming.
Could you tell me the algorithm?
The formula Apple uses to calculate a distance estimate to an iBeacon is not published. There are a number of alternative formulas including this one, based on a best fit power curve, that we wrote for the Android Beacon Library.
Further research we have done shows that the formula above basically works, but it has two main imperfections:
It does not work well for weaker beacon transmitters. With weaker broadcasts, the distance is underestimated.
It does not account for varying signal gains in receivers. Different receivers have different antennas and receivers which measure the same signals differently.
There is an ongoing discussion of the best formula here.
A bit late but hopefully useful to others. I have given up on Apple's "Accuracy" number; as #davidyoung points out, different devices will have different signal gains. Now I am not an engineer but more of a math and statistics person, so I have gone down the route of "fingerprinting" an indoor space instead. Essentially I read all RSSI from all beacons installed in a certain "venue". Some might not be within reach and therefore I just assume, in such cases, an RSSI of -95 dBm (which seems to be the floor past which a signal is not read any more). Such constituted array has the same beacons in the same positions at all times (even across app launches). I compute a 5 seconds moving average for each beacon (so a I se 5 arrays to do that). The resulting avg array is then shifted up by 95 units and normalised so that the sum of all of its values is one. If you want to tag an an indoor "point" you collect many of these normalised average arrays on that specific spot. I go ahead and construct a database of "spots". To forecast your proximity to any spot in a database you simply compute a quadratic distance of your current reading and the all of the fingerprints in the database.
Which beacons to use? At least class 2 in power. How many? At least a couple per room (put them in two adjacent corners, on the ceiling or high up).
The last step that you need to do is match the fingerprints with an x,y coordinate on your map. I never did this step, because I am mainly interested in proximity applications and not fully fingerprint and indoor space.
Perhaps the discussion above will serve you as a guidance on a technique that is used by many indoor location companies.
Disclosure: I have recently open sourced my code doing the above calculations.
I am using Arduino UNO board. I have 24 analog channel which gives me 0~5v analog out put. Now my problem is I have only 5 analog channel. I wanted to read value from each channel for every 2 min and then switch to other channel. Can anyone suggest me in Hardware how can get analog value ?
I am planning to use 8:1 multiplexer or 16:1 multiplexer . Will it is correct way of doing it. Can you suggest other way of doing it in hardware ?
74HC4051,74HCT4051,ADG708,MD14051B,
IC I am planning to Use.dep[end on so,s1,s2 just switch the channel
As a start, you might need to know that even Arduino Uno also have internal MUX. In my experience of reading multiple analog channel, this is the approach that I take. However by taking this approach, I suggest you to recheck the analog value so adding MUX will not generate any error or bias.
This could be done by comparing the output of measurement with the MUX and output of measurement without the MUX. I used 74HC4051 and it works brilliantly, just make sure not to leave any pin floating. The only disadvantage of this method is that you will need to use some I/O to control the MUX, but if that is not an issue for you, then go ahead.
Any other method could be more complicated. It would require your analog channels to correlate with each other, and you need to find a way method to combine multiple analog channel into a single channel.
e.g: if your aim is to compare two analog value, instead of measuring the value and comparing the value in software, you could make use of op-amp comparison circuit to compare the value for you and take the comparison result instead.
Use the photon-pixel coupling method, it is a new approach in science for sampling an unlimited number of sensors in parallel.
Basically, each sensor output is an LED. If you have 10000 sensors, the output of all of them is inserted in a LED array, a LED matrix as the authors say. After that, the LED array is filmed by a video camera and the images are processed in real time by a computer. A software reads one pixel from each LED from the LED array and converts it to numerical values. So, your LED array will be converted in a matrix (with 10000 elements) filled with numbers that can be processed as you wish in your software. I don't know if I was explicit but you can read their article here: https://www.sciencedirect.com/science/article/pii/S2215016119300901
Note that classic multiplexing is serial, this approach is parallel.
The photon-pixel coupling method is truly ingenious because it solves two main problems in engineering: an unlimited number of sensors and their parallel sampling at video rate frequencies. Just imagine, we can read as many sensors as we wish. What I wander is if we can adapt the photon-pixel coupling to Arduino. I am new in the world of microcontrollers but I know Arduino can support a cam, so it should be possible.
If you are a PhD student then:
P.A. Gagniuc, C. Ionescu-Tirgoviste, R.G. Serban, E. Gagniuc. Photon-pixel coupling: A method for parallel acquisition of electrical signals in scientific investigations. MethodsX, 6:968-979, 2019.
To read more analog channels than inputs you have, an analog multiplexer is a good option. All the ones you suggested will work, but personally, I like the Analog Devices ICs for analog circuits, so I would take the ADG708, but this is just a personal preference.
I have two buggies moving around a track, both of which use ultrasonic measurement modules to detect obstacles in their paths and are controlled by Arduino microcontrollers. The two ultrasonic sensors operate at the same frequency and this frequency cannot be changed. The two ultrasonic sensors are interfering with each other. How can I reduce this interference, or prevent it, by adding something to the Arduino code. The hardware cannot be changed. Thanks for your help
There are in general six ways to reduce interference between two channels (see for example http://en.wikipedia.org/wiki/Multiplexing) - two of which don't apply to sound. That leaves you with four:
space - don't operate in the same space (e.g. cell towers): not applicable for you
frequency - (e.g. channels) you said you can't change that
time - don't operate at the same time
code - send out different amplitude patterns
In a sense, "code" is a bit like "time", but more complicated. With "time", you try to time it so the two transducers don't transmit at the same time. With "code", they send complex pulse sequences and use these to eliminate the interference.
I think your best bet (simple, but effective) is "time". This is going to depend a little bit on the frequency of update that you need, but you could make one buggy the "master", sending a short chirp every 100 ms (say); then have the second buggy wait until it hears the master chirp, and send its own pulse 50 ms later (when it knows the other buggy will be quiet). In this way each will have 10 updates per second, but they will not interfere.
To be more robust, the "slave" buggy could decide (after not hearing a pulse from the "master") to send its own pulse after 100 ms - this way it can operate when there is only one buggy present. And they could in fact each use this algorithm - then there is no "master" and "slave" and they have the same code (usually a good idea). As a final tweak, if you make this "wait for n ms" interval random, you will have implemented a version of "carrier sense multiple access with collision detection" - see http://en.wikipedia.org/wiki/Carrier_sense_multiple_access_with_collision_detection
Good luck.