I plan to build the Mk2 controller (using the PCBs from Rich). I'd also like to play around with an arduino to measure a pile of (mostly undetermined) stuff. Given that I don't really know what I'm doing, I want to dedicate one arduino (aPV) to the PV controller work, and use another (emonTx) for everything else. Both arduinos would be in the same box, sharing ground and +5v. (Maybe need a bigger PSU?)
I appreciate some folk have managed to combine both functions within the same arduino, but I'd rather keep them separate, so I can play around with the emonTx without compromising the immersion control algorithm.
Given I already have the current/voltage sensor and Vref circuitry for aPV, is there any reason why I can't connect the derived signals (on an1 & an2) to both arduinos at the same time? (So I can measure imported power on the emonTx.)
Re: MK2 PV Controller + emonTx, together
Remember that if you intend to use the same input signals to both systems, you need to be careful that both systems use the same analogue reference voltage and consequently the same mid-point bias voltage. Bear in mind that the RFM12B module has a maximum recommended supply voltage of 3.8 V, which implies you must retain the 3.3 V supply for the emonTx.
Re: MK2 PV Controller + emonTx, together
Um, very good point Robert. (BTW, great name.)
I was intending to wait for the new emonTx board, and connect it using wired ethernet (I think that option is coming). But I see that the ethernet module that has been proposed is also 3.3V (although it says that 5V I/O signals are tolerated, it doesn't say about max supply voltage. Also, I suppose there's no guarantee that particular module will end up on the new board). So that wouldn't work either.
Ho hum, back to the drawing board.
Re: MK2 PV Controller + emonTx, together
I don't know what other stuff you want to measure but, unless its a lot, the arduino can be used to run the MK2 sketch and you can still do some other stuff as well in parallel with it. No issues occur then with regard to power supplies. You only need to change the pull up resistor which drives the MOC photo LED.
Re: MK2 PV Controller + emonTx, together
Before you get to far down the track, have a read through this!
http://openenergymonitor.org/emon/node/1002
Re: MK2 PV Controller + emonTx, together
Series530
Are you suggesting running the MK2 sketch on the emonTx (at 3.3V)? Would that work without any further modifications? (Except changing the pull-up resistor - I guess to ~120ohms?)
Stuart
I did look at your design, but I wasn't convinced that I understood all the proposed changes to the design, plus I've already bought Rich's PCBs, so I'm kinda committed down that track.
Thanks to both!
Re: MK2 PV Controller + emonTx, together
Sure - it runs beautifully on these units. My sketches are extensions of the MK2 sketch and one runs on the emonTX while the other runs on the emonGLCD. Just change the pull up resistor for the MOC and that's it. If you want to be fancy add in the LEDs if you use my sketch or run as it is if you use Robins MK2.