High Current Relay Suggestion

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KLH
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Joined: 20 Apr 2019, 01:41

High Current Relay Suggestion

#1 Post by KLH » 20 Apr 2019, 01:51

Does anyone have a suggestion for a high current relay?

I am needing to switch a 1 HP motor on 120vac. The motor will run up to 12 hours a day.

I am very wary to try these chinese knockoffs off of ebay, and would like to control it using an ESP8266 directly.

RobertM
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Re: High Current Relay Suggestion

#2 Post by RobertM » 20 Apr 2019, 10:23

SSR relay ?

Patou
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Re: High Current Relay Suggestion

#3 Post by Patou » 20 Apr 2019, 21:33

Hello,
Please use a standard relay compatible with esp 8266
The contact of this relay can switch the coil current from the contactor
For contactor see this example coil 120 VAC In 12 A :
2019-04-20_21h31_52.png
2019-04-20_21h31_52.png (214.54 KiB) Viewed 3132 times
https://www.aliexpress.com/item/CJX2-12 ... st=ae803_5
Use a flightwheel diode on the coil of the contactor in order to filter spikes due to inductance of the coil.
Patou

KLH
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Re: High Current Relay Suggestion

#4 Post by KLH » 21 Apr 2019, 02:51

RobertM wrote: 20 Apr 2019, 10:23SSR relay ?
Do you happen to have a particular one in mind?
I've seen them on Ebay and Amazon, but some of the reviews are not the greatest (leaking current, overheating, and not supporting a full load).

I do have one ordered from China, and will test it once it arrives, but I am looking for other solutions as well.

RobertM
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Re: High Current Relay Suggestion

#5 Post by RobertM » 21 Apr 2019, 10:58

" Fotek ssr-25 da " from e-bay,... or similar ;)

http://www.fotek.com.hk/solid/SSR-1.htm

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dynamicdave
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Re: High Current Relay Suggestion

#6 Post by dynamicdave » 21 Apr 2019, 16:49

This item from Banggood works fine from 3V logic (DC) and will control mains driven items.
Although this particular item is rated at 50A, Banggood have other models available.
There's also an LED on the top-face of the unit to show when the SSR is ON.

https://www.banggood.com/Solid-State-Re ... rehouse=CN

rayE
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Re: High Current Relay Suggestion

#7 Post by rayE » 22 Apr 2019, 00:57

Careful on your choice of ultra cheap SSR! i purchased some from ebay a while back and it turned out they were fakes, labeled as 30A but were more like 10A!

Shardan
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Re: High Current Relay Suggestion

#8 Post by Shardan » 22 Apr 2019, 15:51

rayE wrote: 22 Apr 2019, 00:57 Careful on your choice of ultra cheap SSR! i purchased some from ebay a while back and it turned out they were fakes, labeled as 30A but were more like 10A!
I can confirm this definitely. Had three such relays, all died quickly.

On top some points usually are not mentioned by the sellers:

- This relays need cooling! A heatsink is requiered.

- With some types the blank plate on the back is not insulated, it has mains voltage!
..so be very carefull with the heatsink!
Regards
Shardan

KLH
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Re: High Current Relay Suggestion

#9 Post by KLH » 25 Apr 2019, 02:25

Shardan wrote: 22 Apr 2019, 15:51 - With some types the blank plate on the back is not insulated, it has mains voltage!
..so be very carefull with the heatsink!
YIKES!
Thanks for all the comments. I figured these cheap chinese relays were a little sketchy, but now I know they are REALLY sketchy, and down right dangerous!

I was able to find some relays like look identical to those cheap chinese ones on mouser and digikey for around $30/piece, so I might end up going that route,but was hoping for something in the $10 range.

HvdW
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Re: High Current Relay Suggestion

#10 Post by HvdW » 05 May 2019, 11:55

I support the suggestion added by @Patou
Use the cheap Chinese as intermediate. (use isolation tape to avoid burning your fingers in case you touch the relay)
The reliable Hager I have installed can be switched manual as well, which is very handy in cases I have experimented a step beyond the limits of what my RPI accepts.
The price of the Hager rail relay is not high.
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