Author Topic: Inspired by LPL's new TPL5110 Breakout, I give you ESP8266 Moisture Probe  (Read 3718 times)

TomWS

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LPL's new TPL5110 Breakout board (https://lowpowerlab.com/shop/TPL5110) offers precision timing, high current switching, with nanoAmp quiescent current.

So, if you just happen to have an application where you want the convenience of a powerful, but power hungry device like the ESP8266 to take a random example AND you want it to run for years, not minutes, on a battery, this is just the baby to do it!

The TPL5110 breakout combines the very precise and extremely low power TPL5110 timer with a high current load switch.  This device will consume 35 nano amps when timing and will switch multiAmps when it times out and turns on the load.  In this application an ESP8266 WiFi load, which draws up to 225mA when connecting and can only dial down to a few milliAmps when sleeping, starts up, reads a moisture probe, connects to WiFi network, reports the result, and then tells the TPL5110 that it's done.  The TPL5110 then shuts off the load and goes back to timing - at virtually no current.

One CR123A will drive this circuit for a year.

Enjoy...

UPDATE: added photo from PDF:
« Last Edit: August 08, 2016, 10:15:43 AM by Felix »

damonb

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Tom, i am intrigued by your post. I gather from your schematic this is a capacitive soil moisture probe. Kudos to you for your design.

If you are willing to share I'd love to see the physical implementation (board/probe design) and your code.

I have built an irrigation system around vegetronix probes and JeeNodes (RFM12B). It's been operating for 3 years or so. Happy with sensor node battery life, getting around 2 years from 3xAA alkaline cells, just using JeeLabs standard library, sleep drain about 4 microamps . However, not at all happy with cost and longevity of Vegetronix probes. They tend to fail at 2 years, presumably due to moisture penetration into the exposed PCB edges. I have been thinking for a while about rolling my own, but the only thing I lack is time for the R&D.

TomWS

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Tom, i am intrigued by your post. I gather from your schematic this is a capacitive soil moisture probe. Kudos to you for your design.
I can't take credit or ownership of the moisture sensor circuit.  I simply copied the circuit from http://www.emesystems.com/pdfs/SMX.pdf  The circuit was designed for Watermark moisture probes but I've successfully used it with stainless steel bare wire probes.   It uses a soil conduction measurement method, not capacitance.
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If you are willing to share I'd love to see the physical implementation (board/probe design) and your code.
This project is to highlight an example on how the TPL5110 timer can be used to provide long life to a low duty cycle, high current application.  I quickly 'borrowed' bits and pieces from other designs I have to create the reference schematic.  I don't have a PCB implementation of this.

The one year battery life estimation is based on a one hour sample interval (more than enough for soil moisture) with a 1300mAH CR123A battery.  The current consumption of the timer is literally in the noise even at this low duty cycle.  If you were cycling Moteino sensors the circuit would exceed any practical battery life.

Tom

joelucid

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Hey Tom,

Cool idea to use the tpl timer with the esp8266. In my mind the esp8266 has never really been compatible with battery power. But in combination with this chip you actually get a workable solution for some cases.

Joe

TomWS

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Hey Tom,

Cool idea to use the tpl timer with the esp8266. In my mind the esp8266 has never really been compatible with battery power. But in combination with this chip you actually get a workable solution for some cases.

Joe
Yes, this will never give you long battery life if your sampling interval is short - it takes too long to reconnect on each start up so the duty cycle is too high - there is little benefit to optimizing power when off.

I like this timer because it is precise, consumes extremely low power when off, and can switch literally Amps when on.

Tom

Felix

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Nice work Tom!
I linked this to the product page, thanks!

@joelucid welcome back  ;)
« Last Edit: August 08, 2016, 10:18:17 AM by Felix »

syrinxtech

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@Tom and @joelucid.....you two inspired me.  I ordered 5 of these boards.

What am I going to do with them?  Who knows....but they're too cool not to experiment with.