How to power my ESP32 feather, compactly?

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mzincali
 
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How to power my ESP32 feather, compactly?

Post by mzincali »

We have a house that was built in the 1950s. They used to have radiant heat in the concrete slab floors, but decades ago, the pipes started leaking and they abandoned the radiant heat, leaving very little of the system. One thing they did leave, and still works, is a loop of radiant heat that goes from a pump at one end of the house, through the concrete slab, to the water heater at the other end of the house. When this pump is on, we have hot water at our showers and kithen sink within 5 seconds.

When this pump is off, it takes ten minutes to get hot water to the shower, and the hot water never really gets to the kichen sink. What seems to happen is that most of the hot water gets cooled down as it warms the floor getting to the shower or the sink. When it gets to the shower, it's not really hot anymore, and by then, the hot water tank is pretty much spent.

There is an old Honeywell thermostat attached to the pipe next to the pump. It doesn't seem to work. It's a mechanical mechanism, and the pump just runs all the time and never shuts off. I think it was designed to run the pump until the water temperature in the pipe was above 100+ and then it would shut off. It would restart the pump if the temperature dropped.

The problem with the pump running all the time is that it uses about 80watts, continuously, 24 hours a day, 365 days a year. This adds up to a few hundred dollars of electricity. The other problem, which is unavoidable, is that if we want hot water quickly, then we are also heating the floors. In the summer and the winter. I don't know how to fix this other than to run our to water pipes through the walls, with better insulation and recirculation, and not in the concrete slab floors.

I rigged up an ESP32 feather with a thermocouple and a solid-state relay. I've got a little program that checks the temperature of the pipe every so often, and runs the pump if the temperature drops too far. I also run the pump for a minute, every fifteen minutes, just in case there is more cooling somewhere else in the system, in order to equalize the temperature. I can probably vary this delay based on the outside temperature, but I haven't gotten that fancy yet. My trials show that at this time of the year, once the initial system has equalized (about 10 minutes of running the pump), it then only needs to run about a minute every 10 to 15 minutes. That's going to reduce my use from 60 minutes an hour to 4-6 minutes an hour. Nice savings.

I rewired that pump room (it used to be a boiler room, with all sorts of disconnected Honeywell relay controllers, fuse and switch boxes, and conduits, most of which I removed), and now I have a single electrical box, mounted on the rectangle of plywood that was there, housing a new GFCI outlet. There is a conduit from that box to another single gang box where the ESP32 resides. That box is connected with a conduit to the pump. When I have my laptop connected to the ESP32 and I monitor the logs, everything works well.

However, I forgot an important issue. How do I power my ESP32 so I don't have to leave my laptop plugged into it?!! I completely ignored that important need.

The old honeywell system had a transformer, a plain old one with no enclosure, like the ones you might still have in an older house, powering your doorbell, mounted on that plywood. I bet it outputs 12V or 6V and that powered the Honeywell controllers. (Those Honeywell controllers only had relays inside, and the control inputs came from thermostats around the house, and the relays would in turn turn on pumps redirecting more hot water tot he radiant loop in the room that needed it). I could use that old transformer (although ugly and very weathered). I'd still need to regulate it down to 5V.

I could plug a small USB charger into one of the GFCI outlets, and then get a USB cable from that to the single gang ESP32 box. Probably the easiest, but it would be a cable outside of conduits, and I was trying to make things look clean.

I'm not aware of any simple way to parasitically or otherwise, get power from the 120V lines going to the solid state relay that powers the pump. I'm willing to move to 2-gang box, but I'm not sure I know of anything that would be small, and safe to use right next to the ESP32. This is where I was hoping to get some ideas.

Thanks!!

(I have to misspell kittchen so that I can avoid being labelled spam)

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adafruit_support_mike
 
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Re: How to power my ESP32 feather, compactly?

Post by adafruit_support_mike »

mzincali wrote:I could plug a small USB charger into one of the GFCI outlets, and then get a USB cable from that to the single gang ESP32 box. Probably the easiest, but it would be a cable outside of conduits, and I was trying to make things look clean.
It's not only easiest, it's the safest option. It's best to be conservative with that kind of thing.

You can run a piece of CAT-5 phone/network cable in the same conduit as power wiring, and can carry power to the Feather through that.

We have DIY USB connectors you can use at both ends of the cable:

https://www.adafruit.com/?q=diy+usb&sort=BestMatch

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