For the first time in several years, I was standing in my driveway a few days ago during the day, and found myself attacked by a mosquito. Other family members had been reporting mosquito bites, but it seemed too early in the season for that, so I ignored them. However, after 2-3 more attacks plus two bites, that was enough. Time to fire up the traps!
My 16 year old daughter has taken an interest in machines, including small engines and legacy computers, so I invited her to help me set up my un-trusty circa 2002 Defender, modified a couple of years ago with the substitution of a ESP32 WiFi module to replace the Defender’s PIC controller, which I had stupidly blown up troubleshooting the trap’s many problems. The modification was done in a slipshod manner, and has not and was not expected to withstand the elements for prolonged periods of time. Compared with my newer unmodified Patriot, this unit is far more interesting and complicated, more can go wrong, so it was first, with the other on deck.
She plugged it in, and the fan started to spin. I opened my MQTT snooper app, and there was the Defender reporting its status. Nothing wrong with the electronics! I asked her to then attach the propane tank, and turn on the gas.
After a few minutes, the temperature rise was only 4°C or so. I waited for a while for the trap to enter the error state and turn off the gas, and restarted. I remembered that a new tank of propane in which the air is not bled after filling can take several attempts until the air finally bleeds out into the trap, and the propane is sufficiently pure to sustain combustion.
Well, I tried that 4 times, with the same result: only a very modest temperature rise. I then decided to try to bleed the tank like I saw my local hardware store (which charges a fortune for a tank refill), so I went to the tank. The bleed valve looked like it took a standard slot screwdriver, nothing fancy. However, finding a slot screwdriver took some time; it seems they are very popular with the tool “borrowing” crowd. Finally, I returned to the tank, inserted the screwdriver, and turned it to release the air.
Nothing! Nothing came out, not air, not propane. What? I used the screwdriver on an adjacent tank, which spitted air and propane, just like at the store. What could be wrong? I decided to substitute the propane tank. Picking up the Defender’s tank, I suddenly realized that it was empty! My (now long deserted) daughter followed my directions and connected the tank without mentioning that it was very light. I wanted her to do all the steps, so I never touched the tank. I thought that I had filled all the tanks at the end of last season, and could not imagine that there was an empty tank in line to be used. Moral of the story and new rule of thumb: you cannot start a trap with an empty tank.
This now highlights the need for an additional sensor to weigh the propane tank and hose so that a trap can have a new tank before it goes stop (with quick replacement action, the trap can keep going without restarting). Such a sensor would have alerted me immediately to the empty tank. Or I should follow my standard practice of weighing every tank before putting it on a trap. But the mosquitos were biting. I am ashamed to say I still haven’t weighed the tanks… Fear? Laziness? Both?
I had made some weighing scale design progress, but have not solved the issue of weatherproofing the strain gauge sensors on which the tank would sit. Any recommendations (via the forum) would be appreciated. How can we reliably weigh the tank in real time?