Hi, noob here. Got a genuine arduino to support the community, i will be asking a lot of questions, but i want to try to find out the math for myself first.
I want to power my arduino with 9v, from this i will be running 1x2 channel 5v relay, 1 x DHT11 temp/humidity, 2 x DS18B20 temp and 1 x Soil Hygrometer with LM393 driver board powering a small LED for dry soil alertness.
Giving that these are all run via bus?? I really haven't much idea of what i am talking about, thou i think i am correct in saying, they require little to none i or w, just trying to work out my power supply.
I believe that the relay must take up the most, but ebay has not mentioned how many amps thou it does state 5v. Given this is possible a solid state relay i need a little help as my knowledge stops about here.
I'm not to sure to use a generic 9v 1 amp wall PSU or if i will need something a little more powerful. If you need more detail of items please say, but everything appears generic.
Regards jon
Forget using a 9v battery unless it is made up of 6 AA cells. The small 9v battery cannot provide enough current for enough time to be of any use.
Give us links to the other devices so we can work out what current you need.
Weedpharma
chefslot:
I'm not to sure to use a generic 9v 1 amp wall PSU or if i will need something a little more powerful.
No matter how big your PSU is, the 5V regulator on your Arduino can only supply 500mA before it melts.
The sensors are relatively trivial in power consumption, but you can not operate the relay board from the Arduino regulator.
What you need is a switchmode "plug pack" 5 V power supply rated at least 1 Amp, which you connect directly to the 5 V terminal on the Arduino.
Is the relay going to be switching something that is also drawing power from your supply or from some other source? If it is switching something that also draws power from your supply, that needs to be taken into consideration as well.
Cheers guys, sorry i wasn't getting any notifications coming through. Right, so the 9v was going to be coming from a power supply adapter, looking at ones rated for about 2-3 amp. The bog standard plug into the wall jobs.
So the 5v regulator, it is recommended to power the arduino at 9v to keep a constant 5v then? Will post some links up at the bottom.
Argh i was under the impression that the arduino would control the relay directly. I was following this http://www.instructables.com/id/Arduino-2-Channel-Relay/ and yes i guess the relay is attached to something is this what you mean? Will post links below.
No the Relay will be controlling 240v external.
Sorry should say this is for a small vivarium.
Links of what i have brought so far.
http://www.ebay.co.uk/itm/161862594140?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
This is for moisture of the soil, as i want a biological set up it needs friendly bacteria etc so cannot dry out. I was wanting the arduino to power a simple red led when it reached a certain dryness to prompt me to water.
http://www.ebay.co.uk/itm/381128507366?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
To power on a fogger which produces a mist, triggered by a temp humidity sensor.
To power on a fan when the temp gets to much, triggered by two temp sensors.
http://www.ebay.co.uk/itm/181888466675?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
http://www.ebay.co.uk/itm/281216572924?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT
The lighting will be set on a reg wall timer so no need to worry about that thank god. This is more for the environment control. I dont really need it, but it's fun to learn!!
chefslot:
Argh i was under the impression that the arduino would control the relay directly. I was following this...
Arduino can control as many relays as you want, but powering them is the problem.
The onboard 5volt regulator might just be able to power two relays with <=9volt on the DC jack.
Two relays (160mA), the sensors, and the Arduino itself add up to ~250-300mA.
That could be 9volt - 0.7volt reverse protection diode - 5volt = 3.3volt *300mA = 1watt of heat in the onboard regulator. Ok open, but not ok in a box or on a hot day.
You could bypass the regulator by supplying 5volt directly to the 5volt pin or the USB socket.
A 5volt phone charger with USB socket, and your USB lead, is perfect.
The only limitaton is now the resetable onboard polyfuse. I think they are rated for 500mA.
Leo..
Wawa:
Arduino can control as many relays as you want, but powering them is the problem.
The onboard 5volt regulator might just be able to power two relays with <=9volt on the DC jack.
Two relays (160mA), the sensors, and the Arduino itself add up to ~250-300mA.
That could be 9volt - 0.7volt reverse protection diode - 5volt = 3.3volt *300mA = 1watt of heat in the onboard regulator. Ok open, but not ok in a box or on a hot day.
You could bypass the regulator by supplying 5volt directly to the 5volt pin or the USB socket.
A 5volt phone charger with USB socket, and your USB lead, is perfect.
The only limitaton is now the resetable onboard polyfuse. I think they are rated for 500mA.
Leo..
Cheers Wawa, so how do people go about controlling a group of relays, i.e 8 or so?
chefslot:
Cheers Wawa, so how do people go about controlling a group of relays, i.e 8 or so?
Best to use two separate supplies if you work with mains power.
9volt regulated on the DC jack for the Arduino, and 5volt/1A regulated for the relay board.
JD-VCC jumper must be removed for opto isolation (safer).
Relay supply is connected to relay VCC and relay ground.
Arduino is connected to opto VCC and relay inputs.
Grounds are NOT shared, because that would defeat opto isolation.
dlloyd (member here) has posted a good connection diagram in many threads.
Leo..
Smashing thanks, i will have a look around then get back if i get stuck. Apart from that, everything else appears fine then?
Regards
Note that if you have a regulated supply, the only reason to feed 9 V to the Arduino, is if you need the 9 V for something else as well.
Otherwise if you are choosing a power pack for the Arduino itself, you want a switchmode fully regulated 5 V power supply connected directly to the 5 V terminal. It makes no sense to use a regulated supply merely to feed the internal regulator. If you don't have a regulated supply, well, a 9 V unregulated supply is not too bad.
As Paul says, a switchmode regulated supply is the way to go. They are much more efficient than the linear regulator on the Arduino board (less heat produced). Jameco among others carries a number of decent ones for reasonable prices.
Quick question, it appears that i have two optocouplers in that relay shield? The only reason i'm saying this is because on another thread they said to use one, so i looked it up and then looked up another shield that said it had one (thou the one i have brought doesn't say) and it looks the same, the two rectangle black boxes in the middle of the board, with what looks like a little hole in them, i can't work out the numbers.
Regards
Also what does jd-vcc mean, i get the vcc, but not to sure of the jd part. This switchmode power supply, is that like a buck converter, or should i say it's a buck converter with a transformer/converter built in?
Many thanks guys.
Yes, typically, the switchmode supplies will have a transformer to provide isolation and drop the voltage to something above the final voltage then a buck converter to do the final drop/regulation. The buck converter is a switching type supply so it is much more efficient than a linear regulator (therefore smaller and less heat is produced).
gpsmikey:
Yes, typically, the switchmode supplies will have a transformer to provide isolation and drop the voltage to something above the final voltage then a buck converter to do the final drop/regulation. The buck converter is a switching type supply so it is much more efficient than a linear regulator (therefore smaller and less heat is produced).
Good stuff, yes a linear did turn up when i searched differences and provides more heat too. So with the relay shield does it look to you like they are optocouplers built in?
Regards.
Yes, the two little 4 pin IC's in front of the relays are the opto-couplers. They appear to be these guys (if you zoom in on one of the images on ebay, you can read the number - 817C. Here is a data sheet on that part
Swear i looked but couldnt see a decent picture, mind you had so many tabs opened!! Thanks
I cheated a little bit - one of the images you linked showed that, but hard to make out. Grabbed a clip of the image, took it into Photoshop and played with the levels and contrast then cropped it a bit. All about having the right hammer 
I suspect in that image the "1336" is the date code which would be 36th week of 2013.
LOL i should have thought about doing that myself, next time!!
I've just thought, if i was to use a PC PSU i could run the relays from a 5v, the Arduino from another 5v, a PC fan for exhaust, and i was going to get a Exo Terra Fogger but that is 24v, but ebay have done 12v ones, just need to check the amps. But that should be a one stop package surely!!
You would have to check, but I think all the 5v lines from a PC PSU all go into a common bus in the enclosure - be careful with one of those - they have enough current available to "let the magic smoke out" if you connect things wrong.