I will order the relay & Uno rev.3 starter kit.
Can you tell me please which wifi shield will be the easiest to configure and work with?
as i dont know the parts very well, having even a link or specific model will be very helpful
e-r-a-n:
I will order the relay & Uno rev.3 starter kit.
Can you tell me please which wifi shield will be the easiest to configure and work with?
as i dont know the parts very well, having even a link or specific model will be very helpful
Never used one, but you can always Google something like "arduino Wifi control led" and find projects where people have done similar things to what you are doing and just look at which shield they are using.
e-r-a-n:
I will order the relay & Uno rev.3 starter kit.
Can you tell me please which wifi shield will be the easiest to configure and work with?
as i dont know the parts very well, having even a link or specific model will be very helpful
Just be sure to use the heatsink provided in that listing and use good heatsink compound when bolting them together. Many people don't realize that AC SSRs drop about 2vac across their output terminals when conduction and if drawing say 10 amps that is 20 watts of heat to dissipate in the package which would require a large enough heatsink to prevent damage to the SSR. Not sure what the rating for that heatsink is but be sure to check how hot it's getting when it's actually powering your heater load.
i guess its one of the reasons for taking a higher current relay for the task?
if its drawing in practice around 15A and my relay is capable of 40A, wouldnt it heat less?
e-r-a-n:
i guess its one of the reasons for taking a higher current relay for the task?
if its drawing in practice around 15A and my relay is capable of 40A, wouldnt it heat less?
No, the actual heat dissipation for the package is independent of the maximum current rating for the SSR. It's just current actually being drawn X the 2 vac constant voltage drop across the internal Thyristor device (triac or back to back SCRs) doing the switching. So any SSR packages have at least two limiting specifications, maximum current load and maximum heat dissapation for the SSR/heatsink package.
Note that the old standard electromechanical relays have no such heat dissipation problems as the voltage drop across the closed contacts has little to no voltage drop, but they too have a maximum contact current rating that the contacts must met or exceed.
Ok, well, like with computers cpu, i will just attach the heatsink provided with good thermal grease applied on it.
if the worst happens and the relay gets too hot, what will happen?
i guess its one of the reasons for taking a higher current relay for the task?
if its drawing in practice around 15A and my relay is capable of 40A, wouldnt it heat less?
Not necessarily. Any relay that has the same voltage drop that is carrying the same current will have to dissipate the same amount of heat, regardless of their rating. As stated before, but in a slightly different form
P=IV
So Power of current times voltage drop. This is always true regardless of the relay, or any other component for that matter. This will manifest in resistance heating, and needs to be dealt with accordingly. As stated above make sure you that you use a good conductive compound to attach the heat sink to the relay, this ensures that the heat can conduct away from the relay into the heat sink, which can then conduct the heat away in the form of convection. Also note that you need to put your relay in some sort of electrical box. Having open wiring, especially at such high currents, is not a good idea.
@retrolefty
Any good way to have the relay in an electrical box, but also dissipate heat appropriately.
Here are two links that should help you to understand:
For a normal relay (not a solid state one)
On the picture your boiler would be connected to the 'c' and 'no' pin of the relay.
All the other bits are necessary because the relay needs more than the ~20mA the Arduino provides to switch
Solid state relays need less current to switch, this is why you can operate many of them directly from your Arduino.
I would definitely choose a relay with a decent safety margin
Remember that for safety you can not run your 220V over your little Arduino prototype breadboard. You need to keep the relay and the 220V away from the rest of the circuit. You could buy a simple electrical box from any DIY store
I will buy the SSR I think, it seems easier isnt it?
About 220V across the arduino,
I guess that at the end I will have the arduino powered by battery, and controlling the relay which is the one that is actually connected between the boiler and the wires in my wall, correct?
Yes correct.
You have two circuits. One is the wall socket, the relay 'c' and 'no' connector and the heater
The other (Arduino) circuit has its own power supply and its own ground (e.g. 9V battery).
The only point the two circuits "meet" is the relay where the Arduino part is connected to the relay coil which performs the switching.
Check the links I posted above, especially the second one will make it very clear, it has lots of pictures
i read them both, the second one makes its very clear why a relay is the solution for my "project".
my conclusions are that I will buy the following, please advice if soemthing I'll probably need is missing:
Arduino kit:
Im actually not sure, (a) seems pretty short with items, (b) is not original arduino i think, but have the battery which is a good thing, and also screen and other things,
seems the best option, isnt it? but a tiny breadboard, maybe i should consider something else?
a. http://www.ebay.com/itm/Arduino-Uno-R3-Starter-Kit-Breadboard-Jumpers-cables-LEDs-Resistance-IR-/200864208879?pt=UK_Sound_Vision_Other&hash=item2ec47097ef
b. http://www.ebay.com/itm/Starter-Kit-LCD1602-ATmega-328-arduino-compatible-/280911458775?pt=LH_DefaultDomain_0&hash=item4167a0b1d7
c. http://www.ebay.com/itm/Arduino-Component-Basic-Element-Pack-Set-Kit-Case-For-Arduino-Starter-Beginners-/180824786469?pt=UK_Sound_Vision_Other&hash=item2a19ff4625
I still dont know about wifi card. Its hard to nevigate in ebay beacuse arduino has alot of "compatible" products,
i wish for an original one, with much documentation, so that i will not get lost in the middle and waste money for nothing.
Any suggestions what to look for exactly?
I would go to arduino official website but i need delivery for israel, which is always problematic.
I think the a) set is not bad. The others have a lot of stuff that you probably not need at the moment.
It all really depends on what else you want to do, or if you fancy doing some other pojects in the beginning to learn more about the Arduino.
Relay looks good to me, but since you are in Israel, you may find a similar relay in a local electronic shop or from an israelian distributor?
I do not have any experience with wifi shields, so maybe read around what other projects used. The shield will go on top of your uno and take up some pins but as you only need one additional pin for the relay switching this will not be a problem at all.
Ok,
And please tell me one more thing,
I found out about Electric imp, it has already wifi built in, would it go better with my needs or it doesnt really matters?