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31  Using Arduino / General Electronics / Electric water/pipe valve? on: March 15, 2011, 05:43:16 am
Hey guys,

I'm trying to find out if there is a valve that can be electrically opened and closed that would be suitable for water. If anyone has ever heard of such a thing or can suggest to me how I build one, please let me know smiley-grin
32  Using Arduino / General Electronics / Transistors? on: March 15, 2011, 05:20:28 am
hey Ardy forum.

Just a simple question. Am I correct in understanding that a transistor changes the voltage/amperage of a current? If that's true, what are the limits? For instance, you turn 5v @ .200amp into 12v @ 2amps? How about 200amp? What are the limits?
33  Using Arduino / Project Guidance / Re: My First Arduino Project: Autonomous Solar Heat Controller on: March 14, 2011, 04:07:30 pm
Thats pretty efficient!

I think I am going to have to have a play with this. Although I suspect it may not work quite as well in cloudy north west England!

There have been some postings here on solar tracking - search for heliostat.

Good luck with it.

Thanks man! I've got some tweaks I want to do with the current design people are using. I think it may severely increase the available surface area!
34  Using Arduino / Project Guidance / Re: My First Arduino Project: Autonomous Solar Heat Controller on: March 14, 2011, 03:51:04 pm
Quote
The Solar Heater actually doesn't generate electricity

Hi, I meant KW of heat not electricity.

Now, if you could make PV cells out of coke cans, you would be a very very rich man!

The network cables are a good idea. I would imagine that you would get a good long range on them fro the temp sensors.

I was just a bit concerned that you were going to use more energy than you were capturing from the sun. Because if so, you may as well just power an electric fire from the mains.

Si.

Ahh of course. Depends on the sun light exposure. I may do up a solar tracking unit with this thing as well. We will see. But in bright sun light even in mid winter, there is nearly 1Kw of heat energy per square meter. So If i Make this thing 3m x 1m (that's a lot of pop cans) That's a lot of passive heat smiley-grin

I'm also looking into use this kind of system to heat water up, and then at night time pull the heat from the water to heat the home. I figure some kind of big truck radiator might do the trick.
35  Using Arduino / Installation & Troubleshooting / Re: Arduino Basics on: March 12, 2011, 04:20:35 pm
Thank you for explaining the LED resistor question as well. I do understand what a resistor does, I do remember Ohms law, but my lesson plan doesn't say anything about "WHY" I'm using 330ohms with the LED's. There is no make or model number on them, so I have no way of looking up what there max current is. So my question was more related to all LED's in general. Do they all have the same max current or are there different ones and where can I look up that kind of information?

330ohm is a suitable number for the 5v output from the arduino. if you want to understand more about how to calculate a suitable resistor for a led you can read about it here: http://www.kpsec.freeuk.com/components/led.htm

they do not have the same maximum current rating, but if you have no markings it's probably just a cheap no-name LED. if you have lots of them, you could experiment and see when they pop. smiley-wink but it's usually somthing like 10-30mA. when you buy more leds from, say digikey, they have info about it.

example:
http://search.digikey.com/scripts/DkSearch/dksus.dll?Detail&name=SSL-LX3044OD-ND

Current - Test   20mA
Voltage - Forward (Vf) Typ   2V (this is needed to calculate a suitable resistor too)


Ahh perfect! Thank you.
36  Using Arduino / General Electronics / Relays and Arduino? on: March 11, 2011, 10:18:33 pm
I want my Arduino to be able to turn on a 120v AC fan. Basically I had the hopes of making the Arduino turn on a relay which activated a 3 prong house outlet. What kind of relay should I be looking for? Any tips in the right direction would be incredibly useful. I went to an electronics shop today and I was dumbfounded at how many choices there were.
37  Using Arduino / Project Guidance / Re: Dough Proofer on: March 11, 2011, 06:45:36 pm
Hi everyone

First post so if I am wrong just let me know.

Here is what happened, we have a proofing cabinet and electronic board is dead, the manufacterer of course does not want to give any data or wiring diagram to fix it, he just wants to change the dead computer board for a little fortune. For now we just pulled ou the dead board and placed a temperature controler and a humidity controler to be able to use it.

First project making a new board with arduino hope it is possible. So it has to be able to deal with....

2 input one for the temperature sensor and one for the humidity sensor
Must be able to adust temp and humidity
Must be able to show actual temp and humidity
Has to control relays for the heating, compresseur and fans (there is 2 fans one for the heating and one for the cooling)
Has to control the relay for the steam maker

Second project

Same as above but must be able to be programmed for cooling  and a set time for dough ready like at 6AM for cooking, arduino will have to calculate what time overnight to sart the heating slowly and increasing temperature on a regular basis.

What is needed ???

Which arduino model (so many different)
which temperature sensor
which humidity sensor
which lcd display
which button switch
which relay card
where to buy

and all what I have forgot

Thank you for reading and helping the best you can

I'm not an Arduino pro by any means. I'm still learning the ropes as well but seeing how no one has replied I'll give my two cents. I'm using the Arduino UNO SMD Edition. It's USB equipped so that makes it pretty easy to upload your code to it. The SMD edition as I'm told just means that it has a soldered on CPU instead of a replaceable one like the previous versions.

You want your Arduino to control 120v appliances right? (fan's, dehumidifers etc?) So you will be wanting to purchase relays that the Arduino can power (I think 5vDC is what it's capable of). Of course you could always just use servo's to physically press buttons on the actual appliances themselves (sure would look funny though lol). I'm in the same arena you are in at the moment. I'm trying to find what relays I can use in a similar project although I have no clue what a Dough Proofer is.

As for your temperature sensor. I have minimal experience with the TMP36 Temperature sensor and it is very very easy to use and works quite well. Other members on the forums feel that they are decent as well.

Unfortunately due to lack of experience I can't comment on the other areas of your project, but hopefully this gives you something to think about. Good luck. Keep us posted.
38  Using Arduino / Project Guidance / Re: My First Arduino Project: Autonomous Solar Heat Controller on: March 11, 2011, 06:13:51 pm
Interesting project. Any idea how many KW you are going to get out of it?

I doubt if your fan draws 15A at 120V, that would make it 1.8KW which I am guessing would be a great deal more power than you are getting from your solar module. Its probably more like 200W or less (PLEASE CHECK - DON'T TAKE MY WORD FOR IT), which means that your relay would need to handle 2 Amps at 120V. Which it might well do!

The temperature sensor is digital and should therefore work ok on the end of a reasonably long wire. I assume the CAT5 cable is not connected to a local network, but just for the sensor - in which case, you can connect the three leads of the sensor as you like.

The Solar Heater actually doesn't generate electricity, but instead absorbs heat. The fan is powered from the house grid (which may be powered by wind eventually). The fan will just be a regular 3 prong (live, common, ground) plug. The reason I suggested a relay that could handle 120v/15amp is so I have a bit of playing room if I want to scale this thing up to someday power an 1800w fan (I may use this to heat a workshop or a green house someday).

And the RJ11/45 cable is simply used as a cheap inexpensive way to run wires that are shielded from the elements. I was also considering the headphone jack/plug style of cable as well. It will not be connected into a network of any sort.

Thank you for replying.
39  Using Arduino / Installation & Troubleshooting / Re: Arduino Basics on: March 11, 2011, 06:01:48 pm
Thank you for clarifying!

I actually ran through some more of my lesson plans and noticed that the binary size was indeed changing. I think I just somehow fluked out and did 5 lessons in a row that compiled the same binary size.

Thank you for explaining the LED resistor question as well. I do understand what a resistor does, I do remember Ohms law, but my lesson plan doesn't say anything about "WHY" I'm using 330ohms with the LED's. There is no make or model number on them, so I have no way of looking up what there max current is. So my question was more related to all LED's in general. Do they all have the same max current or are there different ones and where can I look up that kind of information?
40  Using Arduino / Project Guidance / My First Arduino Project: Autonomous Solar Heat Controller on: March 11, 2011, 01:06:21 am
Greetings Ardy forum!

I've just completed my 14 step lesson booklet and I'm anxious to start my first project. I want to create a simple thermostat that draws heat into the house from a passive solar heater (Ex: ).

The theory behind my project is to have the Solar heater only heat the house if the solar heater is warmer than the air inside the house and only if the house is colder than a desired temperature. I figure for a challenge I should put some kind of LCD display and some controls to change desired temperature.

I figure I will accomplish the project by using two temperature sensors connected via long range wires. I'm hoping to use something simple such as RJ11 cable. I will use one temperature sensors to detect the temperature of the Solar heater, and the second one to sense the temperature inside the house. I will use the Arduino and some simple logic to determine whether or not we should heat the house. When it's decided that the Arduino should heat the house, I want to active a relay which turns on a 15amp 120volt house outlet, which will have some kind of high powered fan plugged into it, which will be connected with some piping into the solar heater.

My first questions regarding the project are:

1.) What temperature sensors do I want to use for this? My Arduino Starter kit actually came with a TMP36 Temp Sensor. Can I just get another one these? Are they common? Cheap and easily available? Fairly robust? Also, how would I go about connected the TMP36 to some RJ11 Cable? Any ideas?

2.) The relay that came with my starter kit is model number JZC-11F. I believe it requires 5v DC to activate it, but I'm unsure of whether or not it could handle 15amps AC. I somehow doubt it. It's pretty small. Can you guys suggest a relay that will work well with the Arduino that can relay 15amp AC?

3.) Not sure how to use LCD screens with an Arduino, or how to build menu's etc. So any links in the direction would be great!

Thanks for reading! I'm totally loving the Arduino.

41  Using Arduino / Installation & Troubleshooting / Re: Arduino Basics on: March 10, 2011, 07:12:47 pm
Another Question

How do you round numbers to zero decimal places in the Arduino language. I have a statement that reads:

Code:
void loop() {
  analogWrite(ledPin,(analogRead(sensorPin) * 255 / 1024) );
}

And it's giving me strange results. I want the Arduino to read a value from a potentiometer and then convert the number into a integer between 0 and 255. When I twist the potentiometer it does indeed change brightness, but it's not very smooth and eventually when it should be making the LED brighter it eventually just shuts it off, and then it starts getting bright again as you twist it further. I presume this has something to do with the large number of decimal places the formula is creating.
42  Using Arduino / Installation & Troubleshooting / Re: Arduino Basics on: March 10, 2011, 05:09:39 pm
I suggest reading the datasheet for the Atmega 328 for deeper understanding of interrupts.

Here's a few quotes from it to answer your question:

"When the AVR exits from an interrupt, it will always return to the main program and execute one more instruction before any pending interrupt is served."

"The interrupt execution response for all the enabled AVR interrupts is four clock cycles minimum. After four clock cycles the program vector address for the actual interrupt handling routine is executed. During this four clock cycle period, the Program Counter is pushed onto the Stack."

"A return from an interrupt handling routine takes four clock cycles. During these four clock cycles, the Program Counter (two bytes) is popped back from the Stack, the Stack Pointer is incremented by two, and the I-bit in SREG is set."

Ok that's way over my head for now! But I'm sure I will understand it as time progresses.

Here is some simpler questions.

1.) When I upload my Sketches to the Arduino, the program tells me the binary size is 1222 bytes. It appears to be this size regardless of how big the program is (so far at least). Is 1222 bytes some kind of default size? Kind of like how windows can't address a file smaller than 1Kb (or something like that)?

2.) A bunch of LED's, transistors, resistors and a bunch of other random goodies came with my Arduino learning kit. In all of the circuit diagrams the circuit diagrams tell me I must have a 330ohm resistor for each of my LED's and they always appear to be wired on the negative side of the LED. Why do I need to have a 330ohm resistor for the LED? Will I always need that for any LED? Or is it specific to the kind that I have? The LED's I have don't appear to have any visible writing or model number on it. Also, should I always be hooking resistors on the negative side of the LED?

43  Using Arduino / Installation & Troubleshooting / Re: Arduino Basics on: March 09, 2011, 08:00:58 pm
Excellent, thank you for answering.

So if an interrupt is triggered, where in the main loop will the Arduino start back up at? Will it just begin the loop from the beginning or can it remember it's former position?

44  Using Arduino / Installation & Troubleshooting / Re: Arduino Basics on: March 09, 2011, 05:53:51 pm

1.) Is the Arduino programming language procedural? I see that everything inside the main program loop just repeats until the power is taken away. Does this mean if I create a Loop inside the main Loop, that code below the Loop must wait for the Loop to finish, kind of like PHP interpreted at run time?

it works just like C or Java or other similar languages. The main loop is just like a while(true), infinite loop. Code runs downwards yes, the stuff below gets executed after the current stuff is done.

That's what I figured. How would you interrupt a loop then? Lets say you had a motor and a sensor that you wanted to stop or start the motor? Would you just not use a Delay but a true / false condition?

I'm just going through some very basic tutorials right now, I am on a tutorial that shows how motor acceleration can be done using a 50ms delay and a for loop through an analog write. Am I correct in thinking that while this loop is executing, the Arduino is incapable of processing information from a sensor that might want to stop it?
45  Using Arduino / Installation & Troubleshooting / Re: Arduino Basics on: March 09, 2011, 04:28:41 pm
Quote
Is there some specific trick to recognizing Resistors? I see that they are color coded, but the color strips are soooo small! Do people really get good enough at recognizing the small color patterns or do they use a magnifying glass or something?
Yes. That "something" is a multimeter. You need one. You know you do.

Yes, of course!
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