DIY evap A/C: Quick and dirty way to reduce power AC diaphragm pump power? - Page 1
Forum section: electronics / projects

author: rkirke
author_rank: Newbie
timestamp: March 01, 2019, 11:03:59 am
content: Hi all,Being a poor grad student and mad scientist/engineer waiting out the heatwave in Adelaide (40 today, more on the way), I've recently been playing around building evaporative air conditioners. First attempt is working really well, and I'm now working on a second unit.My situation/question is as follows:- I'm using a repurposed 240V diaphragm pump from a smoke machine to feed water into a DIY evaporative aircon. They're not really designed to run at 100% duty and it's running pretty hot. Water flow is way more than I need, so a reduction in flow is not a problem. The power consumption of 22W is also of concern - that's as much as the fan itself uses, and as I said, the flow is way more than necessary.- Obviously the "proper" way to do this (besides buying or scrounging a more suitable peristaltic pump), would obviously be to use a 555 or microcontroller plus a relay or triac to just run the pump at a reduced duty cycle. Ultimately I'll be using a moisture sensor at the bottom of the media to turn the pump on when it starts drying out, but both requires going out into the uninsulated shed and getting out the soldering iron, which I reeeeealy don't want to do just now.- My thoughts at the moment are (assuming the plunger will still move enough at reduced power and full duty):1. Using a power transformer with the secondary in series anti-phase to drop the mains voltage down a bit2. Possibly putting a capacitor in series with the solenoid? I've got plenty of experience with digital electronics, but inductance, reactance and imaginary numbers are voodoo for me, so I'd really just be trying a few different X2 or motor start caps in series and seeing if there's success, failure or smoke. The solenoid in the pump uses a diode in series already (energized for half a cycle, switched off for the other half to allow the piston to return), so I have no idea how this would impact things. Any tips please?For those interested in DIY evaporative air conditioning, here's the details of my first unit which I was pleasantly surprised at the performance of:My first attempt uses a squirrel cage blower from an on-demand hot water heater I begged from the local recycling yard, a junk box submersible pond pump, and a metal mesh "cube" reclaimed from my Mrs' collection of "disassembled because no room to put it" IKEA furniture. The metal cube (About 35x35x35cm) sits in a plastic tub full of water and is covered in Chux, with a hole in the top for the inlet of the fan. A loop of vinyl tube with holes in it sits around the top, wrapped in more Chux to disperse the water.The whole shebang sits outside, and the outlet of the the blower is ducted in through a window, with an offcut of foam to block the rest of the window.The flow rate is only good for one room, but on a 40 degree day, the air coming out of the duct was 26 degrees, and the room was around 28. Quite comfortable compared to the 38-odd degrees the room would have been with only a ceiling fan, and all for zero dollars and 55 watts consumptionNow I'm on to MKII which is the one I'm working on using the diaphragm pump uses the indoor portion of a split system A/C with the heat exchanger removed and replaced with an aluminium frame and yes, more Chuxplus some polypropylene bird netting as a spacer. I've made use of the inbuilt fan and relay board, and it turns out the inbuilt condensation catcher is perfect to collect runoff from the media to return to an external water reservoir. I'm aiming to make this one a bit more portable, since diaphragm pump is self priming, it can be built into the case and then it's just a matter of hooking it up to power and a bucket of water (always a good combo)If anyone else is working on similar things, I'd be happy to hear from you and collaborate on some energy efficient ghetto-geek air conditioning projectsThanks in advance for any ideas relating to calming down the diaphragm pump.Cheers,Rob