Heated matress pad monitor, how to sense ON or OFF status.

Thread Starter

jkaiser20

Joined Aug 9, 2016
24
Sorry, this is still in the half baked pile and I am just starting to put together a plan, but would like to solicit some feedback on direction.

objective: put a sensor on wife’s beloved heated matress pad and have the ability to check the status and send out an alert if it is not on by a specific time. Yes this a first world problem...NO interest in being able to turn it on from afar. Having the gas fireplace valve being able to be turned on from anywhere makes me nervous enough (i have a wall switch the turns off that ability...) so really I just need to be able to have an ON or OFF signal coming into a pin of a micro. The rest of the project I have enough snippets and ideas, I just need some help on how to do the sensing. I'll likely use an ESP8266 and MQTT, or direct to IFTTT. The software part I can readily do.

I thought about a temp sensor tucked under the pad. That seemed interesting, but would rather not. So I think I would like to tap into the leads just to be more complicated for me.

My first thought was to used a simple 5A ACS712 module. That would provide a decent voltage to an ADC. Add a little logic, easy. So that is a possibility that I have done that style before. It would be a simple deal to cut one of the leads to stick in the sensor module. One nice thing nere is that I would not have to worry about common grounds (i have a long standing childhood failure because of that....)

Then I wondered that since I don’t care about the current, only that there is some, is there a more creative and compact way to do it?

Taking a look at the circuit, it is fed by a 16 VDC brick. It has a little PIC IC, and a pot for the output adjustment. I would think would be a PWM system? I should have snapped a couple pictures when I had it apart earlier, rookie move.

Can anyone, based on that sparse info, give some thoughts around some ways to be able to sense that it has been turned on that I could investigate? Mild to wild is fine.

It has a simple standard tactile button for the on-off. There is an LED that signals it is on. I thought about tapping into that circuit and reading the voltage across it.

Thanks in advance for any thoughts, sorry for lack of details at this point. I’ll add more as this morphs into something.
 

Thread Starter

jkaiser20

Joined Aug 9, 2016
24
Are you and your wife separated?

If so, why worry?
Ha! No. Sorry, I probably wasn’t clear enough. This is for a preheat situation. Once we got to bed and she had forgotten to turn it on and said 'now there’s a worthwhile project you could do....'
 

jpanhalt

Joined Jan 18, 2008
11,088
Sorry. I've been married 52 years. Lived in Minnesota, and never had that problem.

Maybe someone else can relate to it and have a better solution.
 

ronsimpson

Joined Oct 7, 2019
1,337
I use Sonoff switches of different types. I have never used a "Pow R2" type but it looks like you can measure the power consumption over the internet. I think you can see "25 watts" or "0 watts" There seems to be a Pow and a Pow R2 and I do not know which type you need. Break the cord and insert the module. Then connect to the internet.
You need a wireless connection to the internet. I can see the temperature and on/off status from anywhere on my phone.
Sonoff Pow R2 Power Remote Control WiFi Switch Smart Monitor Energy Consumption
 
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Thread Starter

jkaiser20

Joined Aug 9, 2016
24
Sorry. I've been married 52 years. Lived in Minnesota, and never had that problem.

Maybe someone else can relate to it and have a better solution.
Not a problem, just an opportunity to create something. I must be missing something here...
 

Thread Starter

jkaiser20

Joined Aug 9, 2016
24
I use Sonoff switches of different types. I have never used a "Pow R2" type but it looks like you can measure the power consumption over the internet. I think you can see "25 watts" or "0 watts"
You need a wireless connection to the internet. I can see the temperature and on/off status from anywhere on my phone.
Sonoff Pow R2 Power Remote Control WiFi Switch Smart Monitor Energy Consumption
Interesting thought. I could just plug it into one of my WiFi outlets and maybe set up a smart action based on the sensed level. (All outlets currently deployed on holiday decorations, but I know the solution there...)
 

djsfantasi

Joined Apr 11, 2010
7,763
Why sense the status? Just turn it on at a specific time. In parallel with the local control. Or program an on/off time. A small micro with a real time clock (RTC) will give you a lot of flexibility. Use a relay or Triac to switch the heating pad on.
 

Thread Starter

jkaiser20

Joined Aug 9, 2016
24
Why sense the status? Just turn it on at a specific time. In parallel with the local control. Or program an on/off time. A small micro with a real time clock (RTC) will give you a lot of flexibility. Use a relay or Triac to switch the heating pad on.
Yeah, that’s a thought, but the direction I want (for various random reasons) to go is more just the ability to 'see' into the bedroom to check, or send an alert that we may or may not take action on.

the amusing part is that the bedroom is close to where we spend most of our time...and I am not really super lazy. It’s more just a chance to implement something.
 

djsfantasi

Joined Apr 11, 2010
7,763
Yeah, that’s a thought, but the direction I want (for various random reasons) to go is more just the ability to 'see' into the bedroom to check, or send an alert that we may or may not take action on.

the amusing part is that the bedroom is close to where we spend most of our time...and I am not really super lazy. It’s more just a chance to implement something.
With a microcontroller, you can host a web page with the status that you could access witha phone on the wireless network. You could actually implement the ability to turn the heating pad on/off from said web page.
 

John P

Joined Oct 14, 2008
1,903
Run wires in parallel or series or something with that LED, and send them to the input side of an optoisolator. Then you can sense the output without any risk of mixing high and low voltage circuits. Or a Hall effect sensor in the cable should work.
 

Thread Starter

jkaiser20

Joined Aug 9, 2016
24
Run wires in parallel or series or something with that LED, and send them to the input side of an optoisolator. Then you can sense the output without any risk of mixing high and low voltage circuits. Or a Hall effect sensor in the cable should work.
Duh! I thought about an opto on one of the output leads. I like the idea of tapping into that LED. The Hall sensor is also interesting.

Thanks for the ideas, time to go fiddle around with it.

Merry Christmas
 

Thread Starter

jkaiser20

Joined Aug 9, 2016
24
Thanks for the ideas (maybe not the baby monitor one....)

I decided to tap into power LED circuit. I have that part done and tested with the optocoupler. Working on the software logic now. Already have a simple local webpage built to give the statThen will solder up the simple circuit and use some velcro type fastener to stick it behind the nightstand.

here is a picture of the before and after. I was soldering upstairs without my magnifying glass. Now that I zoom in I don’t like either of those joints. Maybe after the winter I will do a gen 2 on it.

8189A1CC-64ED-4684-B3E2-B2D4BEB57E71.jpeg3B9F7C5F-1413-4083-9B2E-ED04315FD7FE.jpeg
 
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djsfantasi

Joined Apr 11, 2010
7,763
The joint on the right doesn’t look too bad. But the one on the left looks like the leads weren’t hot enough for a good joint. Reheat the joint and touch the solder to the top of the lead. The solder should flow further down the joint. If you have a hemostat or self-closing tweezers, clamp the led lead near the housing.
 

Thread Starter

jkaiser20

Joined Aug 9, 2016
24
I had actually hit that joint a second time with decent heat, so maybe it’s just the picture that makes it look that way. In other words, I already buttoned it back up and rationalized my way to 'good enough'....

Circuit is working. I do need to go back and tweak the logic, it is backwards for the alert. It sends if the heater is on but I wanted it to send it if off. I was doing testing and was going back and forth between pull up and pull down logic. So one change to an if statement. I should have set it up for OTA programming so I wouldn’t have to fish the cord out.

I can pull up a real simple webpage at any time to check the status. Then at 8pm if the heater is off (on right now) it sends an alert to IFTTT which then sends a tweet to a private twitter account. I can also adjust the time for the daily check via the web page.

Thanks again for the comments.
 
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