I would like to know if there is any way to display the battery level of an arduino running off a rechargeable battery. Is there some piece of equipment or certain code I could use with an LCD? To be clear I'm looking to display the battery percentage not the voltage.
I'm using an adafruit proto board with a servo shield
Thanks in advance.
I don't know why you are avoiding the simple solution (resistor bridge into an analog input). Create a map in EEPROM to act as an interpolation table and re-scale it occasionally. Taking the voltage from that analog input and mapping it through your interpolation table will give you a percentage battery remaining for the LCD. (most batteries I have interacted with slowly decrease in output voltage as their percentage remaining drops and the slope/ curve is usually fairly repeatable)
Related
I am trying to use a MCP3008 A/D converter (see https://ww1.microchip.com/downloads/en/DeviceDoc/21295d.pdf) with a RaspberryPi to digitize an audio signal generated by some legacy audio chip.
From what I understand I could just power the MCP3008 with 3v3 (VDD) to ease connection to the RaspberryPi (or I could use higer VDD up to 7V but then I'd have to use an additional levelshifter to interface with the Raspberry). The MCP3008's reference voltage for analog input signals cannot be higher than VDD+0.6V (e.g. 3.9V or 7.6V for the mentioned scenarios.).
According to the specs of the soundchip that I want to sample the relevant peak-to-peak voltage change is only 3V but the signal seems to ride at a 6V DC level. (I imagine that means that the signal moves within the 4.5V to 7.5V range.. is that assumption correct?)
I could obviously use some voltage divider to scale the input voltage to whatever maximum reference voltage the MCP3008 will tolerate. But I would always waste most of the measurement range 0 - 4.5V due to the fact that it is never used by the original audio signal.
Is there anything I can do to make sure that a respective A/D converter (it might be a different model than the one mentioned above) uses its measurement resolution to digitize
the signal specifically within the relevant voltage range? (i.e. with a 10-bit converter a 4.5V
signal should translate into 0 and a 7.5V signal into 0x3ff).
PS: I wonder if it might be a viable approach to use a Z-diode to cut off some part of the DC level and then measure the "overflow" portion of the voltage over a 10k resistor that I'd put after the Z-diode. Or are there any reasons why this might not work well for my application?
Use a high pass filter to remove the DC bias.
Given that you are working with audio you need to be careful not to remove audio data.
Im currently trying to get an electric signal from arduino, its 5v and 1amp that i get from a powersupply.
I want to input that signal into an arduino pin, lets say pin 4.
The main powersource from my arduino is via usb, but the 5v signal is from an external device.
I just want to know the number of time that signal became active, like a switch.
As far as i know arduino can take only .04amp from 5v.
Is there anyway i can reduce the current?
Anyway to obtain the value of a resistor to make it less dangerous for my arduino?
Your question is a very common application for Arduino!
You can give your Arduino some additional protection by placing a 10kOhm resistor between the Arduino analog pin you wish to use and the positive voltage output of the power supply.
If you're worried that the voltage could increase above 5V, you can protect your arduino with a simple voltage divider using two resistors. There's a detailed tutorial for this approach here: https://startingelectronics.org/articles/arduino/measuring-voltage-with-arduino/ Here's a simplified circuit diagram with a voltage divider that reduces voltage 11 fold - making voltages up to 55V safe to measure (where the battery could be replaced by your power supply):
For your code, you can use analogread() to read the voltage of the pin. If you wired it correctly, it should return near 0 when the powersupply is at 0, and 1026 or thereabouts if it is at 5v (or whatever the maximum value your voltage divider is designed for). Here is an example to get you started :
https://www.arduino.cc/reference/en/language/functions/analog-io/analogread/
If you need any support with your code to count the number of times the voltage goes high, post that as a separate question along with the code you have so far.
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 am using 6 different sensors which are working simultaneously, but I got a problem in the readings from LM35 temperature sensor and MQ-7 Carbon Monoxide sensor. The values are changing depending on the power source.
How can I fix this problem? I'm planning to use a Sony power bank to feed my system but I am getting the wrong values especially from the temperature sensor.
Make sure that your power source is stable and continuous (i.e. make sure that your power bank is working fine and check its current output if its compatible with Arduino)
Make sure that your sensors are wired correct and working fine, try with different LM35 and MQ-7 sensors, if you have that chance.
Make sure that you are supplying your circuit with correct voltage and current, sensors may work unstable if you are supplying them directly from Arduino pins (because maximum current limit of the pins onboard may not be enough for your circuit), try an external power source such as MB102 power module.
Although, it's not a coding problem my suggestion is you can use signal conditioning to solved this. Search about low pass filter and high pass filter to filtering frequency in output sensor.
The simple method is using voltage divider, like this:
Vout = (R1/R1+R2) * Vin
R1 is your sensor, and R2 is resistor.
I have tried measuring the analog pin value using the provided standard sketch in the Arduino IDE. However even when there is no connection to the pin, it prints out random values. Is there anything that has to be taken care of?
I have a FSR sensor connected from 5V+ to analog pin 0
No connection giving you random value is completely expected. The pin is floating, and may or may not have a charge on it at any time, giving random values.
Attach the analog input to ground - it should return a number approaching zero (within the accuracy and noise of the ADC).
You have to use "Pull-up" or "Pull-down" resistor. Read here about this circuit: http://www.ladyada.net/learn/arduino/lesson5.html
Providing a path of higher resistance to ground ensures that when that portion of the circuit is open, the static electricity remaining in the portion connected to the pin gets grounded. It also splits the voltage between both paths to allow you to properly throttle the voltage to the pin.
The same problem arise to me ,
What you have to do is change the" Serial.begin(9600);"
To "Serial.beigin(115200);
Now it is showing exact zeroes without any input source.