How to choose a suitable power supply for a relay

Hi there,
Iam new to this site but also have not alot of knowledge about elektronics. I hope you guys can help me a little.
I am trying to build an "auto top off system" for my aquarium. It will keep waterlevels at the same level.
I found some guides on the internet on how to build this (my main source: TopitOffKitPremiumInstruxCompDec07). Since i am from europe its not possible to buy from their shop, it would be wa to expensive).A floatswitch is connected with an relay that powers a pump when the waterlevel drops. Since float switches can not handle alot of volt (heard about voltage spikes that destroy the switch) it will be powered by a 12v power supply (wall plug).
My problem: power supply and relay have to suitable right? I choose a relay and a power supply from ebay and showed tthis to a friend and he told me that they dont work together. He told me the relay has a rated current that is below the current that the power supply will generate. Since i dont really understand what i am doing its nearly not possible to find the right relay/power supply.

Here the specs for relay and power supply:
Relay: omron 12v ly2n 10A 110VAC(datasheet https://www.electro-tech-online.com/custompdfs/2011/01/ly_dsheet_gwj002-e2-10.pdf)

Power supply: 12v 200mA DC( it might be cheaper to buy one with 500mA, ist this still safe?)
Float switch: max contact rating 50w, max switching rating 250v, max switching current 1,5A, max breakdownvoltage 300vdc, max carry current 3A, max contact resistance 100mohm
Pump: 115v, 60hz, 34ma, 3W

Do you need more specs? Is power supply ok with relay? Do you suggest other products ( preferably from ebay)? I am really thankful for every help!

Silvio

Your choice seems good to me, I think the relay you need would be part number
LY2n-12VDC. That one has a 12 Volt DC coil. The float switch you list can handle the pump without the relay, However it would be safer to use the relay to keep the 115 Volts away from the aquarium

Thank you for your fast response! So you think my friend was wrong? In the datasheet for the relay its written "max. rated current 106.5mA (50Hz), 91 (60Hz)" and the power supply has 200mA (or even 500mA). I understood this as the relay is only capable to receive 91mA and if its higher (like from rhe power supply) it gets destroyd, but since i honestly dont know anything about it i must guess you are right then.

I am very carefull with this project because i dont want to get electrocuted when touching the water haha

Is it also safe to use a 500mA power supply or is it important to keep it low?

Silvio

Donmariachi said:

So you think my friend was wrong? In the datasheet for the relay its written "max. rated current 106.5mA (50Hz), 91 (60Hz)" and the power supply has 200mA (or even 500mA). I understood this as the relay is only capable to receive 91mA and if its higher (like from rhe power supply) it gets destroyd, but since i honestly dont know anything about it i must guess you are right then.

IIs it also safe to use a 500mA power supply or is it important to keep it low?

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Your friend does not seem to know much about electricity. I suggest he not give any more advice in such matters.

The relay coil will only take the current it needs from the power supply. That's determined by the relay coil resistance and the power supply voltage using Ohms law (V/R = I).

The power supply current rating is the maximum current it can safely deliver, not how much current it forces into a load. Think of a car battery. It can deliver hundreds of amps to start a car, yet safely powers a dashboard light that only takes a few tenths of an amp. So it makes no difference how much current the supply can deliver as long as it's more than the relay requires. Either a 200mA or 500mA supply is fine.

Thank you so much this totaly helps me alot. My friend is a biomedical engineer and he told me he knows really a lot haha. I am ready to build my thing juhuuu!

Thanks
Silvio