Jumping relays

[whipdry]

Bought a esp8266 with 4 relays hoping I'd be able to switch my observatory transformer & dehumidifier on/off from my mobile. 

Got it working well with the transformer but found the relays bounce when powering 240v 10A rated dehumidifier, relays are rated at 240v 10A... would using 2 relays in parallel help? 

 

Peter 

[Dr_Ju_ju]

What do you mean 'bounce', the relay coming on-off-on or the contacts bouncing ??  if its the former then you may need to modify the hardware, usually some diodes, to 'smooth' the switching, if its the latter, then not much can be done, but wiring in parallel won't help, it may be better to use the relay output to switch an SSR (solid state relay) meant for use on AC circuits...

[whipdry]

34 minutes ago, Dr_Ju_ju said:

What do you mean 'bounce', the relay coming on-off-on or the contacts bouncing ??  if its the former then you may need to modify the hardware, usually some diodes, to 'smooth' the switching, if its the latter, then not much can be done, but wiring in parallel won't help, it may be better to use the relay output to switch an SSR (solid state relay) meant for use on AC circuits...

Switches on at first then intermediate on off on, so guess it's the latter. Will have a look for an SS Relay. 

Thanks 

[arrayschism]

On 24/01/2020 at 15:58, whipdry said:

Switches on at first then intermediate on off on, so guess it's the latter. Will have a look for an SS Relay. 

Thanks 

I would advise that you use the relay to actuate a 240V contactor. It's exactly what we do at work where we have PLCs that control large currents via 12v or 24v relay lines.

PLC switches relay, relay switches contactor.

[pete_l]

On 24/01/2020 at 15:36, whipdry said:

Bought a esp8266 with 4 relays hoping I'd be able to switch my observatory transformer & dehumidifier on/off from my mobile.

I gave up on relays for this reason among others (such as not trusting the "optimistic" power ratings).
Have you considered solid state relays such as this? There are also heftier versions for power switching, though they are recommemnded for use with a heat sink. Best reason: no moving parts!

[Gina]

240v AC up to 40A SSRs are readily available and run directly off logic levels.  Smaller sizes too.  I use mains voltage SSRs to power my 3D printer bed heaters but nothing like that much power.  1.2KW (5A) is the biggest.

[Dr_Ju_ju]

Another thought just struck me....  as the modules may not have enough on-board storage, I have seen it where the control system, re-sets all the relays before setting the required relays on. 

It could also be the application\wifi combination, especially if the board is slightly under powered, causing the wifi connection to temporarily become intermittent...

 

Your original post says your using an ESP8266 module, while I believe those types 'could' switch mains voltages, I suggest you desist using it, if it isn't fully enclosed & screened, I'd be more inclined to use a module such as this https://www.ebay.co.uk/itm/4CH-Wireless-Control-WIFI-Relay-Module-AC-220V-Smart-Switch-For-DIY-Smart-Home/352934475998?hash=item522c88b8de

Edited January 28, 2020 by Dr_Ju_ju

[MarcusH]

Are you running the whole obsy on a single circuit (i.e. 1 phase not 3 phase power) ? How far away is your obsy ?

Chances are that the starting current of your dehumidifier is so large ( can be many times more than rated current for a few 100 ms in certain appliances) that your mains voltage drops to a level where the esp8686 resets itself (I assume the esp8686 is powered from the very same circuit).

Have you tried powering on the dehumidifier with no other load powered on in the obsy ?

[whipdry]

Thanks to everyone for there help with this. 

I made the mistake wiring in an old socket from a cheap extension lead that had poor contacts, swapped out for a13amp wall socket & all good for now. 

As suggested I've ordered a more robust 240v AC 50amp SSR (will this need a heatsink with a 10amp load?) that can be switched with 12v DC, will make changes if & when needed. 

Peter 

[Dr_Ju_ju]

Like Gina, I use one for driving a 3D printer heated bed, mine can be on for hours, getting barely warm, but it is bolted to the 2020 extrusion which will act as a passive heatsink...