What can measure how much propane i have in two 20lb tanks?

we were discussing this in another thread but i think it deserves its own thread. i would love to see how much propane i have left in each propane tank outside my camper on my Droid or laptop computer with my Arduino mega 2560. BUT.... it was 0 degrees outside the other morning. so the only way to do it is to weigh them separately.

I suppose you could use one of those reversing cameras to check a pair of gasfuses. No need for an arduino.

great idea but i forgot to mention im off grid and low on power at night. can a backup camera see in the dark?

TrailerTrash:
can a backup camera see in the dark?

I would imagine so. I just look over the sternrail myself. You could always install a light, secure in the knowledge that it surely doesn't have to be on for long.

Most of those cameras can see infrared, so if you didn't want a light turning on to bother you when you're trying to go to sleep, you could use an IR LED as the light source. May need to check that it will properly illuminate the target. As Nick said, you could just turn it on intermittently, so you don't use too much power.

no, i need this measuring all the time. when im gone i will check it with my droid. or have it call me and wake me up. think hi tech man. plus on the same droid screen it will show all my other sensors running at Project iCamper - #11 by system - Home Automation - Arduino Forum

i dont want to wake up and find out its 45degrees inside! i wanna know at that moment its empty.

The only adequate way to measure how much gas is still in a bottle is, I beleve, by weighing the thing, so you can use this:
http://arduino.cc/forum/index.php/topic,18768.0.html

rikky:
The only adequate way to measure how much gas is still in a bottle is, I beleve, by weighing the thing, so you can use this:
http://arduino.cc/forum/index.php/topic,18768.0.html

so i need two load sensors. sweet!

You should not (polite for do not) need continuous monitoring.

What gas burning system could you possibly have that can consume say 10% of tank contents in under 10 minutes. If the electronics wake-up and taking an instantaneous snapshot once every 10 minutes or so will be more than adequate. So the whole battery system only needs to be active for say 2 seconds every 10 minutes.

Propane cylinders develop a thermal gradient as the gas is consumed so monitoring the "hot/cold" interface will give you a good assessment of content. A simple thermal image should give you what you need and a piece of "intelligence" to assess where that interface is with respect to tank volume.

TrailerTrash:
i dont want to wake up and find out its 45degrees inside! i wanna know at that moment its empty.

How about the simple solution. An alarm that goes off when the temperature reaches say 55 degrees, or whatever you set as the alarm temp? Also, as a RV owner myself, I have both tanks connected but only one turned on. When one goes empty, there's no need to switch tanks in the middle of the cold night. Just turn the other one on. The next day or so I swap out the empty tank. The only time I have both tanks on is while traveling, so the refrigerator will continue to run even if one tank runs out.

Another possible way other than a simple thermostat alarm is something that's connected to the furnace. When the furnace tries to fire up and it can't because there's no fuel it trips some sensor which you monitor and that sets off an alarm. But thinking about the last time my tank ran out while I was sleeping, I seem to remember the starter on my furnace clicking a bunch, and that actually woke me up. If you have a pilot light, that may be even easier, just monitor the temp of the thermocouple. When it's no longer hot, your pilot is out which means you're either out of fuel or you have some other type of furnace problem, which would warrant an alarm too.

Good luck and keep us updated!

Tim

This is a link in Dutch, but it translates as:
Automatic switch for gasbottles.
Once you know what to look for, you can probably find one closer to you, and for a cheaper price.