More "Robust" Sonoff POW for Clothes Dryer?

[Michael Ingraham]

A Sonoff POW is only capable of handling 16A with a max power draw of 3,500W. This is fine for most appliances. But a clothes dryer exceeds these limits. I looked at ITead's product lineup. I may have missed it, but I didn't see anything with higher ratings than the POW. Is there a power monitoring smart device rated for higher power devices? Yes, a Wi-Fi connected, firmware hackable (preferably TASMOTA) device.

I just want it to monitor draw during operation so I can set up a notification on finished cycle. I've tried vibration sensors with limited (really no) success. Either there is insufficient vibration (regardless of how much I "tune" the sensor) or the washer triggers the dryer and vice versa.

Cheers!

Mike

[Phil]

for switching industrial/non domestic loads perhaps look at using a sonoff basic to switch a suitably rated power relay which in turn switches your load.  

ebay example

if power relays and associated h/w (base mounting rail etc..) sound expensive,  you could also look at employing a sonoff sv to control a dc voltage to switch a SSR.  as a 25a ssr/heatsink combo should cost circa £5..

(double your A requirement at least when looking at ssrs)

[Michael Ingraham]

I wouldn't be using the device for switching. Basically I'd leave the switch on all the time. The real need is to receive power consumption data so I can use power thresholds during operation to detect the beginning and end operation... so I can send a notification.

[Ron L]

I am just learning what type of sensors inputs the Sonoff Basic can accommodate, but if you are just wanting to know when the dryer is pulling current (on) and not (off), you might play around with a Sonoff Basic and for the sensor input, play with a few wraps of small insulated wire wrapped around 1 leg of your dryer power cable.

I would start out with just a few (say 10 wraps) of wire around 1 leg and simply read the induced voltage when the dryer is running.  Increase/decrease number of wraps until you get the desired sensing voltage.  I am not an electronics engineer, so you may need to filter this with capacitors and resistors, but the intent is to get a signal that is low when dryer is off and high with dryer is on.  You will not even be using the relay output of the Sonoff Basic, just reading GPIO14 status, between Sonoff GND pin and GPIO14.

Since you have tried vibration sensors - it would appear you have some creativity in you.  I bet you can make this work.

[roguestreak]

If you are not switching, perhaps(!) you could figure out how to remove and completely bypass the relay?  I'm not an EE and haven't checked it out properly, but I'm imagining your could leave the relay conrol pads floating (5V only I believe?), probably disabling the relay output in config to be on the "safe" side, then hard-wire the controlled pins together?
Main concern would be how much current can hard-wiring handle, you don't want it turning into a mini electric heater. [EDIT] From reading around I'm thinking about 12gauge wire would be more than enough; so say 3-4mm diameter, or as big as you can find and fit.  There might be other areas of the circuit that require beefing up, which could(!) be achieved by adding extra wire layed on and soldered (just thickening the solder can also work, but adding wire would likely be better).  Oh and the fuse may need an upgrade, don't know its rating.

A CT clamp on a Basic, Wemos etc. is another option, as a pre-bought version of RonL's suggestion; however the ADC pin (pin 6) sounds like a pain to get to and you have to jump through a few hoops to get it operational.  Normally you would ADC the output to get the current, which for proper readings you'd then need to cross-reference with a live reading of the AC voltage, but without the AC read can be usable for this sort of thing.
But, I wonder if a simple(?) external circuit could be created as a threshhold detector; anything over a certain level of current (voltage via the CT) turns the output high, otherwise it stays low.  Or do you need multiple levels of threshhold to see various "states" of the washing machine?

[Michael Ingraham]

For the washing machine, a POW is suitable and there are many examples on detecting the different cycles. All set on that front.

For the dryer there's really only one cycle... other than post "fluffing" cycles. So, a simple detection of on or off should suffice.

Ron - which is leg 1?

[Phil]

Ah my bad,  What is the load??

[Philip Knowles]

Ron's suggestion is basically sound but not sure is 10 turns round the live wire (1 leg) would produce anything meaningful without a ferrite core. The limit of the POW is the tracks and relay. In the UK we use 240V which reduces the current but my drier only draws 6A what is the rating of the one we're talking about? You can buy current tranducers which you may be able to connect to your Sonoff. However, if you think about the power is used to create heat so the easiest way may be a temperature sensor. You would just need to monitor the temperature against the cycle a couple of times to work out a suitable trigger level.

Regards

Phil K

--
You received this message because you are subscribed to the Google Groups "SonoffUsers" group.
To unsubscribe from this group and stop receiving emails from it, send an email to sonoffusers+unsubscribe@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.

[roguestreak]

Looking around this afternoon I've just "discovered" the PZEM-004, a CT-clamp and voltage module with serial (I think), for about US$6.  Could be used feeding into a nodemcu-syle ESP2866 module?

Can also get DIN-style inline consumption meters which have an S0 connector (and blinkie LED), so can achieve the same thing by counting pulses, and they have much higher current ratings than a POW.  Start at say US$10.

[Ron L]

Michael, by "leg" I mean either 1 of the 2 live wires feeding your dryer (assuming 220-240 VAC).  I agree with Phil K that my suggestion of 10 turns may not be enough.  The item that roguestreak found above would be the simplest way to achieve what I was recommending.  Depending on the size of the device, probably the best place to clamp this on 1 leg would be where the power cord connects to the dryer.

[Michael Ingraham]

Thanks to all of you for the information! I have a pretty good idea what you are suggesting. Since there isn't something out-of-the-box, this project is something that'll fall a little lower into my project queue. I'll finish my ceiling fans, then my washer, my Keurig, ... and then tackle this DIY dryer sensor. But I have the "components" of the task that I need to research and learn thanks to you guys. I'll probably be back to visit this topic a bit down the road.

Cheers!

Mike

[Phil]

Using a sonoff rf-bridge and a rf-door/window sensor and some control system either a home automation suite or something like nodered, A solution to detect when and for how long the dryer is running ( assuming the drum rotates when the dryer is on??) could be to epoxy the door sensors magnet to the dryer drum rim and epoxy the rest of the sensor to the dryer door or somewhere suitable to switch on/off as the drum rotates.

then perhaps a tasmota rule could be applied on the bridge to reduce mqtt traffic but the on/off frequency indicating a rpm>1 could indicate the dryer is on....  and when rpm = 0 the dryer is off..

duration on x power rating should provide a reasonable ball park metric for power consumption? 

[roguestreak]

Good idea Phil, there's been a recent discussion in the Tasmota github Issues on using the internal counter, you can count pulses (revs) and publish&clear them at tele intervals to avoid too many mqtt messages, I'd imagine the default 5mins would be enough if you are monitoring a dryer, ie. you don't need to know the exact second that its no longer revolving?

Could push that further and on the monitoring side publish commands to change the telemetry intervals; have it default to 5mins or more, if a published count is greater than 1 then decrease the tele period to say 30sec, then if the published count drops to 0 increase the tele period back to 5mins; resolution when you need it, less message clutter when you don't?
Hmm, I might use that one for monitoring my aircon meter...