All,
I want to use the low power temperature sketch but rather than using an onboard temperature sensor (as per the low power temp node build), I want the temp sensor to be on a lead so I can position away from the TX. I may also consider having multiple sensors.
Reading around the forums there is some talk of this, but I am not clear on how it could be done. I understand that using the low power temp node requires a jumper to be soldered so that the temp sensor 5V supply can be switched to save power. Does this also work if the temp sensor is connected using the jack socket instead of hard-wiring onto the board?
Would it be possible to use both the hardwired sensor and plugged in sensor at the same time? (From the emonTX schematic I am not clear on how this arrangement works- something to do with "Q2" next to the temp sensor?
Presumably this should work because as long as the temp sensors are addressed the TX can call data from them when it is woken up periodically.
Chris
Re: EmonTX Low Power Temperature Node: multiple/external temp sensors?
The low power temperature sensor is based on the emonTx V2, and if you look at the circuit diagram of that you'll see that a sensor plugged in via the jack socket is wired in parallel with the on-board sensor, which is in fact drawn as transistor Q2! (Blame Eagle CAD for that.) So if you leave the on-board sensor position empty, you can use the plug-in sensor and the same sketch.
You've clearly realised that if you want to use both, you run into problems with the sketch and you'll need to change it to keep the part of the "emontx_lowpower_temperature.ino" sketch that switches the power to the sensor, but replace the parts that initialise and read the sensor with the equivalent parts from the "emontx_temperature_power.ino" sketch that handles multiple sensors.
And of course, running two sensors it won't be quite so low-power.
Re: EmonTX Low Power Temperature Node: multiple/external temp sensors?
Thanks Robert,
I think it was the transistor that was throwing me!
I'm actually using a full EmonTX that I intend to operate in a low power way (but also doing gas metering if I can get this to work).
As far as I can see, an EmonTX V2 can operate as a low power temp node, it's just a matter of setting up the code right, jumper for the temp sensor, and running on batteries? There are no other power consuming items that need to be dispensed with?
Chris
Re: EmonTX Low Power Temperature Node: multiple/external temp sensors?
Indeed, those are the basic steps. You also need to make sure the RFM12B is run for the absolute minimum time, as that is a big current user, and of course the processor needs to sleep a lot. I'm no expert on power consumption and interrupts, so I can't say what effect that will have on power consumption.