Quote:
|
I'm very glad for your input. I had thought of auto sensors, but I didn't know anything about their range or outputs.
|
My suggestion for using Automotive sensors is they are designed to work on a low system voltage in a very harsh environment. This works to our advantage two fold. One, they will likely interact with Micros’ such as the Atmel processor in your Arduino. Two, they should function reliably over the 20-25yr system life expectancy.
An area of concern, repurposing devices, are the chemical interactions at the physical contacts. I.E. Will the membrane in the Oil-Sensor react with the Refrigerant? This may not be the case, I don’t know. I’d be willing to wager that the Hi and Lo sensors from the AC would be a good match for the Evaporator, Condenser, and Compressor.
Quote:
|
Do you have any experience with Arduino, or Machine Control, or Data Logging? I could use some help in these areas. I'd be happy to share what little knowledge I have.
|
Arduino, no and yes. I have worked with the Atmel Micros and like them very much; very handy. I have not put hands on the Arduino platform (just its core). Machine Control, yes. Data Logging, yes.
Some of your purchases and reference to Strider3700’s thread seem to be going in two different directions. Strider3700’s thread and your purchase of “one-wire” temperature sensors (DS18 series?) indicate a desire to use “digital” sensors. However, your purchase of LM355s would indicate you would like to head in the analog direction (?as well?). Combining multiple approaches tends to complicate the design...not at all un-do-able just more complex (read time consuming).
Using a Micro to read the sensor value “directly” will require an ADC (Analog to Digital Converter) and possibly an instrumentation operational amplifier (IOP) to clean–up and amplify the signal. ADC no problem, as your Micro has at least 8 of these; however, the IOP is another matter.
Personally I like to experiment but; I’d rather stand on the shoulders of giants so long as I can still clearly see the ground.
“1-wire” was designed to be a LAN based approach to gathering data. There are lots of Open-Source and Sharware programs for accessing a “1-Wire” bus directly from a PC Parallel or serial port (with some discrete components) and USB to “1-Wire” adaptor(s). I like simple as in (KISS). Eliminate as much of the system as you can and remain working at the desire level of performance.
If it were my time and money I would get a PC to dedicate to the project. An older model with a serial port (DB9 or DB25). Can be had for free or nearly free.
Build or Buy a 1-Wire interface
• DS9490R USB to 1-Wire
• RS232 to 1Wire [ www(dot)lookass(dot)ch/content_files/dthowto(dot)txt ]
Temperature
• DS18 series 1-wire
Pressure Sensor
• Misterhouse(dot)wikispaces(dot)com/1-Wire+Pressure+Gauge
Relative Humidity
• owfs(dot) org/uploads/File/humsensor(dot)pdf
Power
• Still Working on this one...but I know I have a link somewhere.
• Postpone Arduino Implementation for the time being. The PC web/cloud/etc interface to the data will be the same regardless of the source (micro data-logger or PC). One possible aside here would be using the Micro as the control system/board. My Water-Furnace uses a PIC based micro. I'm assuming when you "finish" this thing you are going to want to "set the Temp and forget it." Yes, I know "Master-pieces are NEVER really finished," But the wife may want to make use of the furnace while you out fishing.
NOTE : The suggested routes for gathering Pressure, Relative Humidity, and Power
all employ the DS2438 (Battery Monitor). This is a really flexible piece of kit that has an on-chip ADC that makes it a great work-horse for sensor development.
I'll scrounge around and see if I can't cobble some of this together and share what I find out.
Thanks again for sharing your hard work,
James