Arduino beginner

Hi Erny,

When it comes to the math, there are plenty of examples that have already solved what you'll need to do most starter projects. Of course, there are levels of difficulty like with everything else. So if you want to figure out how to put your Arduino into orbit then you may need to brush up on your skills more

Even for things like figuring out values of resistors and such, I find that I tend to use circuits that others have already put together and made available to the public.

And if you do have the odd time when you run into a situation requiring extra math, forums like this are full of people who love math and don't mind helping out here and there.

Of course, it never hurts to brush up on your skills, and for that there are some really nice websites out there that offer free courses you can do in your spare time. Try https://www.coursera.org and Khan Academy - I noticed Khan Academy offers math right from grade 3 (basic addition and subtraction) and up, as well as computer science courses. If you want something at college level, I've noticed that MIT has a lot of great stuff available fro free online as well.

Cheers,

-Nico

Hi Nico

Thanks very much for the advice and the websites, I will definitely try to brush up my skills as I feel not only will it help me learn but one I build a project alone I will feel happier knowing that I built it without help(hopefully this feeling will keep me motivated to learn!).

Thanks

Erny  

Erny,

I suspect you are getting hung up on the 'math' related to binary and hexadecimal numbers and boolean logic.  If this is so, take heart, lots of Arduino beginners have the same problem.  Most learn as they go, but as a first step you should post a couple of specific examples that you don't understand.  Once you get one or two examples cleared up, that usually leads to further understanding.  Also, once the community on this forum gets a better idea of what your questions are, they can better guide you to suitable resources.  Feel free to PM (private message) me with some questions if you want some basic help.

Kevin H.

Erny

Don't get too hung up on the maths. It wasn't my strong subject, but hasn't stopped me.

There is certainly a time when you need to roll your sleeves up and get stuck in, but I sense you aren't there yet.

I would suggest more 'doing', and less reading.

There are plenty of tutorials and examples, and I have suggested to the students I took to try the following.

• LED's and blink example
• LED's and the BlinkWithDelay example to be able to use something other than Delay.
• Inputs with a switch, and then two switches, making one turn on and the other off.

Play with the values and try to understand how the sketch works.

Once you get your head around how the above bits work, you may want to look into temperature, and LCD Display, and I suggest the I2C displays (4 wires) and the DS18B20 temp chips.

One thing to watch out for is USE A RESISTOR in series with the LED's.

There are examples that don't and they rely on the internals of the chip.

Use a 220 or 330 ohm resistor .... its a lot easier when you change to something without limiting.

There are some basics we ran in 'The Shed' magazine that you can download (click on the picture) with the sketches here

Mark

Hi Mark

I understand the code and I know what it is doing if I were to read it, my concern came when looking at project 2 / 3 (love -o- meter) in the arduino uno starter kit's project book where by the reply signal from the temperature sensor was converted to volts and then Celsius. I cannot understand why it was worked out like that, I tried to work it out on paper and the result didn't seem correct. Unfortunately I don't have the book in front of me otherwise I would post the section I mean.

Thanks

Erny

Erny

Looking at this link Math for Project 3 Love-o-Meter - Arduino Forum

They have the following code.

void loop(){
  int sensorVal = analogRead(sensorPin);
  Serial.print("Sensor Value: ");
  Serial.print(sensorVal);
  //convert the ADC reading to voltage
  float voltage = (sensorVal/1024.0) * 5.0;
  Serial.print(" , Volts: ");
  Serial.print(voltage);
  Serial.print(", degrees C: ");
  //convert the voltage to temp in degrees
  float temperature = (voltage - .5) * 100;
  Serial.println(temperature);

The ADC value is 1024 steps, with 1024 being 5v and 0 being 0 v.

So at line 06 they are dividing the reading to work out the voltage

They have swapped the figures but essentially its 5/1024 * SensorVal/1

(I never was good with that .... but with 5v as the reference you have 4.88758 mV/step)

The datasheet for a tmp36 says it is 10mV/degreeC.

Hence once you know the voltage you should have the temperature.

I cannot understand why they do line 11, as the datasheet doesn't mention any offset voltage

It states that it is 10mV/degC and is 250mV at 25 degC.

There are lots of reasons why I don't use the analogue temp sensors and prefer the Dallas One wire devices.

The comments here  https://www.sparkfun.com/products/10988 support my decision.

Hope this helps.

Erny

Looking at this link Math for Project 3 Love-o-Meter - Arduino Forum

They have the following code.

void loop(){
  int sensorVal = analogRead(sensorPin);
  Serial.print("Sensor Value: ");
  Serial.print(sensorVal);
  //convert the ADC reading to voltage
  float voltage = (sensorVal/1024.0) * 5.0;
  Serial.print(" , Volts: ");
  Serial.print(voltage);
  Serial.print(", degrees C: ");
  //convert the voltage to temp in degrees
  float temperature = (voltage - .5) * 100;
  Serial.println(temperature);

The ADC value is 1024 steps, with 1024 being 5v and 0 being 0 v.

So at line 06 they are dividing the reading to work out the voltage

They have swapped the figures but essentially its 5/1024 * SensorVal/1

(I never was good with that .... but with 5v as the reference you have 4.88758 mV/step)

The datasheet for a tmp36 says it is 10mV/degreeC.

Hence once you know the voltage you should have the temperature.

I cannot understand why they do line 11, as the datasheet doesn't mention any offset voltage

It states that it is 10mV/degC and is 250mV at 25 degC.

There are lots of reasons why I don't use the analogue temp sensors and prefer the Dallas One wire devices.

The comments here  https://www.sparkfun.com/products/10988 support my decision.

Hope this helps.

that kind of helps, but this is what confused me even more, when i tried to work it out on a calculator line 6 seems fine i get a figure that looks correct then as soon as you do line 11 which is supposedly turning the voltage you have got from line 6 to degC  you get a very odd number which seems too high for degC

for example if sensorVal = 900 then its (900/1024.0) * 5.0 = 4.39453125

then line 11 says (4.39453125 - .5) * 100 = 389.453125

that seems wrong to me :/ but like i said not good with math so i could be being stupid

Erny

Okay after some more searching I found the explanation here on page 115

Arduino - Free Download eBook - pdf

Ladada also confirms it

http://learn.adafruit.com/tmp36-temperature-sensor

The datasheet here also confirms it.

const float get_temperature(){
- const int sensor_voltage = analogRead(TEMP_SENSOR_PIN);
- const float voltage = sensor_voltage * SUPPLY_VOLTAGE / 1024;
- return (voltage * 1000 - 500) / 10;

Hence their example gets a reading of 154 which works out to be 25.19

The issue with yours is that a reading of 900 seems very high.

I would suggest checking your connections, in particular the earth/ground to ensure its making it all the way to the tmp36.

Mark