anyone good with electricity?

[Jay]

hi guys

anyone here competent with electrical wiring? i have a wee question to ask before i go frying myself!

I am putting together a controller for a fan system that is to be controlled by two separate sensor controlled relay cards, one triggered by temperature and the other triggered by air humidity they both run on 12vdc and switching up to 250vac, in my case in the UK 240vac, so what i want to know is if i wire them to the 240vac fan like in the below image and both conditions were TRUE would the fan receive 240vac or would i be doubling the fans voltage to 480vac frying the fan,myself and more than likely burning my mates reptile house down, killing all his beloved creatures lol

controler plan.png

Thanks for any insight!

and no lolling at my electrical diagram! it has mistakes, like 240vac in not 230vac and the temp sensor isn't wired to the humidity block, just looks that way

Best Regards

[MegaHurtz]

From what im understanding you probbaly fry the fan.

[MegaHurtz]

On second thought I think this shouldve got the potential to work.
Yust fuse it so you cant fry the fan.

why not.JPG

[MyCo]

The "circuit" will work as you want, but it's not a very secure way because a relay introduces inductance spikes when they switch, and when you switch both relays on (one after the other), the spikes flow back trough your home electronics and probably kill a fuse in your central home fuse box. Also the relays and cables introduce resistance, so one cable or relay contact, can get warm because they "burn" a voltage difference.

It's better to do the logic "or" before you toggle the relay.

[MegaHurtz]

Maybe a big fat elco before the fan?

[MyCo]

no, to do it that way you need at least 2 high power resistors, when the fan has 500W you'll need ~800W resistors... just to show you how bad that is: such a big resistor costs 75€/$ per piece and they are big (~20cm long and ~1kg)

it's way cheaper to do the "or" before the relays, there you'll need only 2 low power diodes, the costs around 20cent (both together)

[MegaHurtz]

absolutely rigt.

[Jay]

ah thanks guys! good thing i asked

I did infact see a logic board intended for the series of relay cards that i am to use! either that i will look into what MyCo is saying about making one with the two diodes!

thanks men you have saved the lives of some deeply loved scaly creatures, some of them very rare too!

Best regards