WC8, 8ch relay board and safe Mains manipulation

So, I have finished my WC8 12 chicken temperature project - chickens still alive, nothing burned down and all low voltage of course.
Now that the ElectricBug has bitten, would like to move on to controlling main electric 110V gadgets, such as lights, 110v, 50W aquarium heaters, 20W aquarium pumps.
 
having read a ton on relays, mostly from sigehts such as Ardunio, it makes it all sound somewhat simple: run the black wire of your electrical component through the ground and AlwaysOpen or AC portion of relay, apply 24V tot he relay board (mine is a 24v) and plug in power last (I am putting this here to prevent the ' make sure you don't cu wires while plugged in responses, although I am sure I will not think of something that should have been logical).
 
The board I purchased for trial and error is:  amazon.com/dp/B00GGKLFX0/ref=pe_385040_30332190_TE_3p_dp_1   a generaic 8CH relay board using SRD-24VDC-SI,C  relays by ? songle ?
 
My question: Is there nothing else needed, no diodes no nothing?
 
Rainer

Could not find this item
 

B00GGKLFX0

There are a post on this forum mentioned a few relay boards working fine, directly driven by the TTL output, relay board will need to be powered by separate DC supply.

TY very much!
 
Will continue to read, though glad it does work in principle!
 
Happy New Year!
 
Rainer

You forgot to include the fuses -- when doing any sort of project like this, it's a very good idea to include a low-current fuse as close to the point where you plug into the mains as possible.  Select the fuse value based on the anticipated load, of course.

That, I would not have done, but sounds good so I will!
Appreciated!
 
Silly question: does the fuse break the positive or negative? I will check on what type of fuse holder/assemblies are available, but if negative is interrupted with fuse, can it be applied just after exiting the relay?

RAiner

Fuse mostly put in positive side for DC. For AC, put on hot wire side.

CAI_Support said:

Fuse mostly put in positive side for DC. For AC, put on hot wire side.

Click to expand...

In AC systems the neutral is grounded at the service entrance for safety reason. You put the fuse or circuit breaker on the hot lead. That why if there is an over-current power is removed from your device. In the US 240V systems have two hots so need a two pole breaker for safety. In DC circuits it is common to connect the negative lead to the, vehicle chassis and if possible Earth ground. In that case the fuse/circuit breaker goes on the plus lead, for the same reason as fusing the hot in AC systems. 
 
If you are using the WC to control multiple outputs need to decide if you fuse each output, or the entire box. For AC projects something else to think about is either adding a GFCI to the circuit if it does not already have on or adding one to the controller. GFCIs detect an imbalance between current in the hot and neutral wire. At a low current they trip removing power and making the  circuit safe.
 
I just did an aquarium controller for my wife, it supports two tanks to control lighting and heaters. I added GFCI protection to reduce shock hazard, standing on basement floor with hands in the tank.
 
/tom

Excellent! TY CAI_Support and TSchmidt!
 
Tom, have to say your explanations are always pretty inclusive!
 
The whole chicken coop is on a 15A system with the main inlet controlled by GFCI, so that much I was able to think of when I built it.
I will now check online to see what I can find on fuses - I don't think they could be expensive, so, I will most likely use one per Relay output.

TY both again,

Rainer
p.s.: used to have 3 Reef tanks - after a few years questioned my sanity when I informally tallied the time and money spent on maintenance - though I have to say that period of time taught me a lot about water properties, Algae/ cleaning/ pumps/ some electricity and even relays (but not the electronic type).

So,
did a search on Google and Granger and other electrical online stores.
Initially I thought an 8 block Blade fuse holder would work, but found that they do not make them for 110V.
Then I searched for 110v fuse holders - got pretty much nothing other than some items in the hundreds (dollars, yes).
Is this an easy thing I am overlooking?
I really don't think having exposed fuse holders, 8 in a row, is not a good idea

Rainer

You can use a panel mounted fuse holder like one of these:
http://www.ebay.com/itm/10PCS-CB-radio-Auto-Stereo-Chassis-Panel-Mount-AGC-Glass-Fuse-Holder-15A-125V-/361169298504?pt=US_Car_Audio_Video_Fuses_Fuse_Holders&hash=item54175e2448
 
Wire the feed to the terminal distal to the cap. That way the end near your fingers is not live when inserting the fuse or when it blows.
 
 
Circuit breakers are nice if you know what level of "fusing" you need.
http://www.ebay.com/itm/4-Schurter-5-Amp-Fuseholder-Thermal-Circuit-Breaker-5-A-240-VAC-48-VDC-/181623458056?pt=BI_Circuit_Breakers_Transformers&hash=item2a499a0908
 
I used a 15A version if this circuit breaker to protect the aquarium controller I did for my wife. Use 12AWG line cord and a 15A breaker.
 
/tom

Appreciated - I did find fuse holders (probably the same as your top example) on eBay last night and now am sure to get those.
Wiring at distal cap end: would not have thought of that! TY for the extra tip!

Rainer

Don't forget to buy fuses. I have parts bins full of different values so I can tweak the design after the fact.
 
/tom

Will do - cheap enough for sure to actually get multiple amperages.
Would it make sense to get fuses for 12V DC as well? I am really only running computer fans with this - blowing hot air from basement (wood stove) into LR

Common AGC fuses are rated for 250V AC, not DC, however they are available for 32V DC applications. The issue with fusing DC is quenching the arc formed when the fuse blows. DC, unlike AC, has no self commutation where the voltage goes to zero during the cycle.
 
http://www.cooperindustries.com/content/dam/public/bussmann/Electrical/Resources/product-datasheets-a/Bus_Ele_DS_2001_AGC_AGC-V_Series.pdf
 
My concern with using 32V AGC style fuses is accidentally mixing them up and using them for AC line voltage. I'm an old fart and prone to senior moments.  :mellow:  Given the low voltage and current I'd just use an AC rated fuse. I have not fused the DC side of any of my projects. The DC power supplies are relatively low current and I make sure everything in the chain is able to withstand PS short circuit current. That way if there is a problem the SMPS overcurrent protection kicks preventing overheating and potential fire.
 
If you think there is a need to protect the DC secondary I suggest using circuit breakers or automotive ATC blade style fuses to make your design idiot proof.
 
http://www.cooperindustries.com/content/public/en/bussmann/consumer/products/automotive_circuitprotectionprdandacc/automotive_fuses/blade_fuses_atmatcmaxid.html
 
/tom

Good point about possibly mixing up the fuses.  DC ratings are often less than AC for the reasons stated. But some fuses that size are good for both AC and DC  (could still mix them up if the current ratings were different though).  For example, here is a Littelfuse part that is good for AC and DC:
 
http://www.littelfuse.com/~/media/electronics/datasheets/fuses/littelfuse_fuse_314_324_datasheet.pdf.pdf
 
 Another thing to watch out for is interrupt rating.  On the Bussmann fuse linked the interrupt rating for 250V is only 35A.  The applications in this post I think are 115V and lower so perhaps not an issue but these are not (IMHO) suitable for mains fusing at 250V.  You will blow the end caps off the fuse if any severe short happens because the current will be much greater than 35A.  Been there, done that in product testing.
 
Not saying Littelfuse is better than Bussmann - I just grabbed a data sheet I was familiar with.  I suspect Bussmann has a similar part.