Tuesday, May 27, 2014

First Power Node - Prototype

Now that I have built and/or gathered most of the parts for a Power Node, I wired up a basic prototype version. Having it spread out makes it easy to make measurements but keeps all the parts stable to prevent accidents like what occurred with my first INA219 current module. I tested the new one out in this prototype and it is working fine. My other current sensor (INA169) is not fairing as well. I have had this module for a while and I had not got around to assembling it and testing it. It is just a analog device as compared to the INA219 that is I2C device. The measurements on the shunts all looked well with a DVM, but the module is just not providing a analog output. I have removed it and will attempt to re-heat the solder joints and will retest it. This is better picture of the actual wiring:

I have placed a standard Bosch relay in the prototype that allows the load to be disconnected under MCU control. The relay is driven by one channel of a L298N Motor control board. Basically this prototype provides monitoring of charge current to the battery from the charge controller and the total load current and battery voltage to the load. I am using the INA219 for the load monitor since it can measure both voltage and current so that I can track power used (watt-hours). I did not think those features were needed for the charge current monitor so that is why I just went with the INA169 device. However, I have been thinking that with another INA219 positioned in the line directly from the PV solar panel would provide useful data since I can measure the panel voltage too. Once I get all the current monitors working I can do all the charge and load tests I need to do to see how/if power transfers from other nodes will be practical.

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