In one project I need to drive high-output leds with a microcontroller. I am a beginner in electronics so I would need advice on how to do it...
There are 10 groups of 3 high-output leds. In each group the leds behave the same.
The microcontroller must be able to control for each group of leds :
the switching frequency (on/off)
the brightness with PWM
So it is like two imbricated PWM : one drive the power frequency, and the other the brightness of the leds.
How can I do that ? I have read about LED driver but I have never used them and I do not know what the best solution would be in such a configuration.
If you are familiar with this situation I am all ears. :)
Thanks
Related
When I search online for EMG sensors, I often see these sensors are just made of a few transistors, resistors and sometimes diodes. Also I once read on a site that EMG sensors are some kind of modified voltmeters. But while I managed to make a voltmeter from an Arduino, I haven't been able to make an EMG sensor from an Arduino.
Does someone know whether it is possible to make an EMG sensor from an Arduino and how they did achieve this?
I think the biggest problem here is that of dynamic range. EMG signals are AC voltages typically in the low mV range and would need a gain of 100 or so to get them up to +/-2.5V, then a simple offset circuit to convert that to 0-5V for the Arduino analog inputs. However, that's not the whole story, since the small EMG signals can ride up and down on large low-frequency background voltages. Your AC amplifier would need a high-pass filter to remove those, or they could drive it off-scale which would prevent the EMG from getting through. If you reduce the gain to keep things in range, the EMG will be a rather small part of the 10-bit ADC range on the Arduino.
So the thing to ask is what is the point of using the Arduino in the first place? If you are going to connect it to a computer in order to look at the EMG signals, then why not just skip the Arduino and use the computer's sound card? The Mic input probably has enough gain already, and you get at least 16-bit resolution to handle any large non-EMG background that wasn't filtered out.
IMPORTANT! EMG measurements require direct electrical connection to the body. For safety, you should make certain that your recording equipment is electrically isolated. If you use only a standalone Arduino, you should power it from batteries. If you use a computer, it should be a laptop running on batteries, with no other connections to ground.
I often see these sensors are just made of a few transistors,
resistors and sometimes diodes.
That's true for pretty much all electronics devices...
Does someone know whether it is possible to make an EMG sensor from an
Arduino and how they did achieve this?
You cannot build an EMG sensor from an Arduino. But you read sensor values with an Arduino either through serial interfaces or by measuring voltages.
With a bare Arduino you can neither measure negative voltages nor can you amplify small signals. (we're in the µV range here...)
Just buy something ready or learn more on electronics
I have a GSM shield V2 for Arduino, and I want some buzzer to make some noise when there is an incoming call. At this link http://www.thaieasyelec.net/archives/Manual/M10_HD_V1.00.pdf page 44 I found that by connecting a simple transistor and a buzzer to the actual "buzzer" pin I should be able to produce sound. I tried and that does not work as expected, all I get is noise from the GND of the shield, that typical GSM noise that everyone know of.
I also tried to connect another arduino as to analog read the buzzer signal, but I get nothing that look like a ringing tone.
Has anyone any idea? Did I forget to setup some things software wise? So far it seems that the buzzer behaviour is completely unrelated to anything code wise, there is just that "buzzer" pin, and that's it, nothing more to set up.
Any help would be much appreciated !
Cheers
Here's a great beeper/alarm part I've used in a couple of recent projects. It is loud but can be muffled. It's self-driving, so all you have to do it supply it enough current at its rated voltage, like through a transistor or Darlington. It has a wide voltage range, and runs great from 3.3V up to 20, So it's ideal for microcontroller projects at 3.3V or 5V. No need to fiddle with timers or PWM to make it beep. Try out this great part.. Drive it from any output pin to a small-signal transistor with a beta of 50 or better and you'll be good to go. Turn output pin on, it starts. Turn output pin off, it stops. I made mine "chirp" like the alarm on a car security system. Easiest thing in the world.
I am currently working with a project for school in which I am building a small cart that will scan an area for the most intense source of light and drive towards it. I have programmed an SG90 180 degree servo to scan a 180 degree area, use the info I scanned to create a decision and then turn the cart and drive towards the light. The issue I have run into is that I am using the TIMER/COUNTER1 to create a PWM wave to drive the motors. My issue extends from the fact that I am using FS90R servos to drive the cart which also run on a PWM wave. My timer counter is already running the 180 degree servo and when I go to drive the continuous servos the SG90 turns and while I am scanning one of my wheels turns. This obviously is not how the cart should run. Does anyone have a way to possibly create an interrupt driven PWM wave that does not directly employ the use of the PWM capabilities of the TIMER/COUNTER1 so that I can control all 3 of the servos separately?
There are 6 PWM outputs on the Arduino, two from each timer. If you are using existing libraries to drive the outputs to the servos the libraries might assume the use of timer 1. You would have to dive into the library code to modify the libraries.
Arduino PWM Information
Ensure that you have each servo on a separate PWM output.
Hi im new to Arduino Uno
My question is how to turn a stepper motor 90 dgree clockwise only when the infrared censored a something and turn anti-clockwise when the second infrared censored something is pressed again?
Stepper motor
Infrared transmitter/receiver pair
your help will be much appreciated
Thanks
Software and hardware my friend, software and hardware.
First, you'll need to connect your sensors to the Arduino and make sure you can read them reliably. You can write a sketch that outputs the values to the serial port and monitor them on your computer.
Second, you'll need to connect your motor. A stepper motor is going to need a driver, such as the "Adafruit Motor/Stepper/Servo Shield for Arduino v2 Kit" (link). This kit has sample code you can use to figure out how to drive the motor.
Then you'd connect these two independent pieces together. Write logic that puts the motor in one position when your sensor is sensing, and another when it's not, or use your second sensor to make the second motion.
Note: Stepper motors and the drivers are expensive and maybe not what you really want. For one thing, they use relative motion, not absolute position. If they miss steps (due to hitting something or being manually moved) then they remain in the wrong position until you fix them.
A cheaper and perhaps better solution is to use a hobby servo. They are cheap and use absolute positioning, which means that when you tell them to go somewhere they will always try to get to that position. Also, you can drive them directly from the Arduino without a driver board. One of the built-in Arduino sketches shows how to run them.
Im a PIC fan. I have not used arduino. but I have got a problems when Im going to control servos with pic.
1) when PIc is controlling the servo it cannot do enything else. so during that period it cannot get the sensor readings.
2) after driving the servo to a certain position and now when the pic is doing something else, the pic does not further more generate the pwm signal in the servo connected pin. so the servo may rotate back due to the load.
now my first question is will arduino genarate the pulse continously in the attached pin after the codes
servo s;
s.attach(13);
s.write(120);
or are there eny librarys to control multi servos using PIC in mikroc to avoid the above mentioned problems.
or is it better to use two PICs one to drive servos only and the other for processing and sensor reading, and connect them using I2C.
please I need help from an expert. please reply. thank you...
Yes the Arduino is able to generate the pwm continuously.
Arduino langage is C/C++ with some build in features like analogWrite()for pwm, which make it really easy to program.
Regarding your "when something is running, it can't do anything else" problem, that's one of the major limitation of the Arduino platform as is. You can overcome those limitations by using ISR (Interrupt Service Routine), timers and hardware interrupts.
If you're comfortable with C/C++, you can also use a Real Time Operating System (RTOS) which lets you run think like a regular operating system would: allow cpu time to each task so fast that they seem to run in parallel. But that's not as easy to use as the basic Arduino features, so think carefully if you really need those functions (scheduler, "multi-task", round rubin, etc.)
Hope it helps!
I am planning a similar project, using a PIC16F872, to control a servo motor. I am thinking of using a 32 kHz crystal to have a PWM suitable, of 35Hz and pulse width centred on 1.05 mS. In my case I will first be doing A/D measurements; then when required running the motor. The motor will have a continuous signal until a 'stop' switch gives an interrupt to the PIC.
I should mention that I have modified the servo for continuous running by disconnecting the feedback pot.