I am trying to design a system for a sap flow sensor with a heated needle in a tree. This particular sensor has a heater resistor of 50 ohms, and the application calls for a 3V input and ~0.2 W power.
I am also using a data logger that requires a 12V input to log the sensor output. I can connect the 12V battery to the logger no problem, but I am trying to find the right way to handle the 12V to 3V conversion from the 12V battery (we're using batteries like these and will be replaced and recharged as necessary)
I am starting to understand that a voltage regulator may be the right avenue, but I do not have experience building or buying these. The manufacturer that sells the sensors also can supply us with voltage regulators, but these are $500. These seem really expensive and beyond the scope of our budget. After a quick google search I see already-built voltage regulators that are less than 5-10% this price. What gives? Am I missing something here?
I am also learning that these voltage regulators release heat based on the voltage drop and supplied current and some are more efficient than others. The sensor/needle will need to be constantly heated (i.e. supplied the above 3V) for ~18 hours each day and will not receive power for the remaining hours at night. These sensors will ideally be continuously logging for weeks to months and left in a forest. I will be monitoring these sensors periodically, but not every day. I don't really know how to evaluate purchasing or building cheaper voltage regulators for my application. I just want to be sure nothing get super hot or melts(?) for the duration of our research project.
Does anyone have any suggestions how best to tackle my problem? For me, it is as much a technical problem as it is a budgetary problem. We require 10 set ups, so 10 voltage regulators at $500 each is too much for us to justify before looking into other options (e.g. other sensors, other research questions, etc).
Please let me know if any other information not in here would be useful.