Having trouble switching a relay for my arduino project

Gabriel;

They're trying to teach you how to find and interpret the information, so you can answer your own question.  To read a schematic you need to know some of the common lingo, and how things are annotated.  For that particular schematic you'd need to know that "Q" is a transistor, "R" is a resistor, "D" is a diode, "JP" is normally a jumper or connector, "U" is a relay, and "LED" is self-explanatory.  The number is somewhat random, but most schematics number from left to right (the circuit is taken to start on the left), and top to bottom. The model or value of component is normally placed by the identifier; so "Q2" is transistor model 2N3904.

Basic two-lead Resistors are easy - There's no wrong way to place it.  Transistors have a base, collector and emitter.  These must be connected properly, to get the desired current flow.  Similarly, a diode has to be connected correctly; normally so that it's forward biased.  LED's are just a diode, so same rules.  Relays can be a pain for anyone, as there's no standard wiring or pinout.

To further complicate things you have "Conventional Current", where the charge flows from positive to negative.  In opposition to this is "Electron Flow" (the way electrons actually move and/or transfer charge), where current flows from negative to positive.  You can thank Benjamin Franklin's mistake in current flow for the two viewpoints.

Most advertisements paint the Arduino, or whatever other microcontroller (or uC) du jour is being presented, as being "easy to use".  They are much easier than programming a bare uC in assembler using individual pin and port configurations.  That doesn't make them easy for someone not familiar with electronics.  The Arduino IDE is very simplistic (for a reason) and easier to use for a non-engineer, than TI's Code Composer Studio or Microchip's MPLab, et al.  You still need to know at least some electronics theory to hook things up yourself.  There are plenty of "this color wire goes here and here" tutorials that will show you how to make something.  I'm assuming you want to go beyond that, judging from your question.

Shabaz is trying to impress upon you that you need a foundation to work from.  When I first read your post I didn't even know if you were speaking of a Normally Open (NO) or Normally Closed (NC) relay; so I wasn't sure whether current was even supposed to flow when the Arduino sent a digital High.  I also looked at the datasheet for that relay, and it states that, for an NC relay at 5VDC, 83mA of current is required to open it.  Arduino I/O pins can't sink more than 20mA, so it's possible that your Arduino pin is now dead.  I know the great folks who designed the Uno put resettable fuses in a number of places, so the pin may be OK.  You'd just have to wait for 30-60 minutes for that line to return to a closed state.  You stated your 10A relay did just fine.  Without knowing anything else I would assume that to activate the relay coil takes <20mA; whatever type it is.

For myself, and all the other engineers I can think of, we started by taking things apart, looking at how it was put together, and then reading up on components we weren't familiar with (usually as kids, when we begun).  The book that Shabaz mentioned is an excellent start.  ALWAYS remember the basics (Ohm's law and the power triangle, especially).  There is also a great series, also by Charles Platt, called "Encyclopedia of Electronic Components", Volumes 1-3 (3 is to come out later this month).  It's better than most of my EE texts at a straightforward explanation of what XYZ component is and does, how to use it, and common gotcha's.  Best of luck with this and your future work.  There are plenty of folks on this site willing to help; but sometimes someone will be pushed toward finding their own explanation.

Gabriel;

They're trying to teach you how to find and interpret the information, so you can answer your own question.  To read a schematic you need to know some of the common lingo, and how things are annotated.  For that particular schematic you'd need to know that "Q" is a transistor, "R" is a resistor, "D" is a diode, "JP" is normally a jumper or connector, "U" is a relay, and "LED" is self-explanatory.  The number is somewhat random, but most schematics number from left to right (the circuit is taken to start on the left), and top to bottom. The model or value of component is normally placed by the identifier; so "Q2" is transistor model 2N3904.

Basic two-lead Resistors are easy - There's no wrong way to place it.  Transistors have a base, collector and emitter.  These must be connected properly, to get the desired current flow.  Similarly, a diode has to be connected correctly; normally so that it's forward biased.  LED's are just a diode, so same rules.  Relays can be a pain for anyone, as there's no standard wiring or pinout.

To further complicate things you have "Conventional Current", where the charge flows from positive to negative.  In opposition to this is "Electron Flow" (the way electrons actually move and/or transfer charge), where current flows from negative to positive.  You can thank Benjamin Franklin's mistake in current flow for the two viewpoints.

Most advertisements paint the Arduino, or whatever other microcontroller (or uC) du jour is being presented, as being "easy to use".  They are much easier than programming a bare uC in assembler using individual pin and port configurations.  That doesn't make them easy for someone not familiar with electronics.  The Arduino IDE is very simplistic (for a reason) and easier to use for a non-engineer, than TI's Code Composer Studio or Microchip's MPLab, et al.  You still need to know at least some electronics theory to hook things up yourself.  There are plenty of "this color wire goes here and here" tutorials that will show you how to make something.  I'm assuming you want to go beyond that, judging from your question.

Shabaz is trying to impress upon you that you need a foundation to work from.  When I first read your post I didn't even know if you were speaking of a Normally Open (NO) or Normally Closed (NC) relay; so I wasn't sure whether current was even supposed to flow when the Arduino sent a digital High.  I also looked at the datasheet for that relay, and it states that, for an NC relay at 5VDC, 83mA of current is required to open it.  Arduino I/O pins can't sink more than 20mA, so it's possible that your Arduino pin is now dead.  I know the great folks who designed the Uno put resettable fuses in a number of places, so the pin may be OK.  You'd just have to wait for 30-60 minutes for that line to return to a closed state.  You stated your 10A relay did just fine.  Without knowing anything else I would assume that to activate the relay coil takes <20mA; whatever type it is.

For myself, and all the other engineers I can think of, we started by taking things apart, looking at how it was put together, and then reading up on components we weren't familiar with (usually as kids, when we begun).  The book that Shabaz mentioned is an excellent start.  ALWAYS remember the basics (Ohm's law and the power triangle, especially).  There is also a great series, also by Charles Platt, called "Encyclopedia of Electronic Components", Volumes 1-3 (3 is to come out later this month).  It's better than most of my EE texts at a straightforward explanation of what XYZ component is and does, how to use it, and common gotcha's.  Best of luck with this and your future work.  There are plenty of folks on this site willing to help; but sometimes someone will be pushed toward finding their own explanation.

Wow...  Thank you so much, that's the most helpful answer i've ever gotten, not just because you answered my question, but you helped me understand that I can't just ask people for a solution everytime, then I don't learn anything.  I'll be sure to get the book mentioned by shabaz and take a look at the encyclopedia you mentioned.

Thanks again

Hi Gabriel,

It was extremely difficult to extract from you that the schematic was the issue. The original post said "I don't think a schematic is necessary so i'll just explain it." which lead me to believe you just needed a few pointers.

However, it turned out that part of the problem was that reading the schematic was causing the issues.

Hopefully the books and detailed suggestions by Brian will provide a wealth of information on how to begin reading schematics, and that will empower you to go beyond the fritzing-style diagrams (e.g this one - it would not teach a thing) that are popular with some tutorials but are actually of little use once you want to start learning.