dhonwyn
Posts: 3
Joined: Mon May 02, 2016 3:18 pm

RASPBERRY + RELAY + WATER PUMP 220V AC = SHORT TIME INTERVAL

Mon May 02, 2016 3:29 pm

Greetings!

This will be my first post here.. :D

As the subject itself , I want to connect the 220v ac wave maker to relay with the minimum interval of say 30 secs "ON" and "OFF".. Now my question is, will this be a safe idea to run 220v ac on and off for short period of time? I have the system running for months* as my AQUARIUM controller to controller AC and DC lights, DC fans and pump controlling from 8am to 8pm....

Your inputs is highly appreciated.

Best,
dhonwyn


tweak42
Posts: 528
Joined: Tue Mar 22, 2016 3:16 am
Location: Los Angeles, California

Re: RASPBERRY + RELAY + WATER PUMP 220V AC = SHORT TIME INTE

Tue May 03, 2016 2:04 am

dhonwyn wrote:Greetings!

This will be my first post here.. :D

As the subject itself , I want to connect the 220v ac wave maker to relay with the minimum interval of say 30 secs "ON" and "OFF".. Now my question is, will this be a safe idea to run 220v ac on and off for short period of time? I have the system running for months* as my AQUARIUM controller to controller AC and DC lights, DC fans and pump controlling from 8am to 8pm....

Your inputs is highly appreciated.

Best,
dhonwyn
I'm not sure I follow what you are asking. Is the Pi already controlling your system or are you looking to add a Pi to your current setup? Need more descriptive details.

klricks
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Re: RASPBERRY + RELAY + WATER PUMP 220V AC = SHORT TIME INTE

Tue May 03, 2016 3:03 am

The time interval is not really a concern if that is what the system was designed to do.
You must make sure the voltage and current rating (Amps) of the pump is <= the rating of the rely. Pay attention to the motors start up load rating.
Use a relay board which has the necessary control transistor and back EMF diode built in.
OR
Use a solid state relay. A SSR is quiet and has opto isolators built in.
Unless specified otherwise my response is based on the latest and fully updated Raspbian Buster w/ Desktop OS.

Goraxium
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Re: RASPBERRY + RELAY + WATER PUMP 220V AC = SHORT TIME INTE

Tue May 03, 2016 6:31 am

Keep in mind that electromechanical relays have a set number of toggles they can go through before they stop working, and you need to suppress the arcs to ensure the relay lives as long as possible. Solid state relays don't suffer from that.

As for what to switch, switch whatever is convenient for you. Just check the power rating on the relay and don't exceed it.

fsr
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Joined: Wed Jan 13, 2016 2:29 am

Re: RASPBERRY + RELAY + WATER PUMP 220V AC = SHORT TIME INTE

Tue May 03, 2016 7:54 am

You need to be aware of inrush current and design everything to handle it.

When an electrical motor starts there in an initial 'inrush' current which is much higher than the rated running current.
https://en.wikipedia.org/wiki/Inrush_current

There may be better ways to modulate the pump (e.g. something like a triac like is used in light dimmers).

[turning a pump on and off continually is called pump cycling and generally speaking it is bad. Bad for the pump, bad for your electricity bill]

JMK8
Posts: 24
Joined: Tue Apr 28, 2015 10:00 am

Re: RASPBERRY + RELAY + WATER PUMP 220V AC = SHORT TIME INTE

Tue May 03, 2016 10:20 am

Be aware that some solid-state relays will not handle an inductive load. If you do not understand what an inductive load is just stick to a electro-mechanical relay - just make sure it has fly-back suppression.

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KnightOfPi
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Location: Vienna - Austria
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Re: RASPBERRY + RELAY + WATER PUMP 220V AC = SHORT TIME INTE

Tue May 03, 2016 10:44 am

You could use a rc switch instead of the relay, that's save:
http://www.knight-of-pi.org/cheap-home- ... pi-switch/
Check out www.knight-of-pi.org for many beginner-friendly tutorials!

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davidcoton
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Location: Cambridge, UK

Re: RASPBERRY + RELAY + WATER PUMP 220V AC = SHORT TIME INTE

Tue May 03, 2016 3:55 pm

As with all things related to mains wiring, make sure you understand what you are doing -- the points above about startup (inrush) current, ratings, suppression diodes; and also your local regulations for mains wiring. If you don't understand any of that, stick to plug-in mains components (but you still need to get the ratings correct). If in doubt, get a competent local electrician to check what you are planning. Mains electricity is dangerous -- especially near water!
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