Feelers Posted June 14, 2006 Report Share Posted June 14, 2006 I am trying to build a laminar flow hepa filter - basically a small cabinet where you can work in sterile conditions - as the filter blows pure air out by blocking all the microorgansims. This is for my future plant biotech/mycology aspirations , and as always I'm trying to get there on a budget. Heres a good link on a flow hood overview... http://www.orchideenvermehrung.at/cgi-l ... /index.htm http://www.orchideenvermehrung.at/cgi-l ... /index.htm Anyways - I have gone to the wreckers and bought the fan that blows hot air around the car from inside the dashboard. - a "squirrel cage fan" The info on the motor says 140W, and since cars use 12V does this mean I need a 11.66666 Amp transformer? I am wanting to be able to adjust the speed of the fan aswell - so I will be putting a suitable vairable resistor on there too. I know practically nothing about electronics - what do I need/where do I find what transformer I need to make this thing go, and go well? How the hell do you find an 11 amp 12V DC transformer? I have rigged it up to a computer power pack - I think that its drawing too much current and shorting out, although it did go - just not fast enough. I know many of you guys have a good understand on these things, so any help would be appreciated. Quote Link to comment Share on other sites More sharing options...
ryanjury Posted June 14, 2006 Report Share Posted June 14, 2006 A squirrel cage motor is an AC motor and the squirrel cage reference is to the shape and design of the rotor (deisgned to produce a magnetic field inside it to actually react and cause the rotor to actually rotate) So your looking for something to supply you AC, I would do your research on the output from the alternator/voltage reg on the car your fan came out of to see what sort of transformer you need.. Quote Link to comment Share on other sites More sharing options...
Feelers Posted June 14, 2006 Author Report Share Posted June 14, 2006 Ummm, well it looks like a squirrel cage fan - I dont actually know if it is. As to whether it's DC or AC - surely if its from a car its D.C? Quote Link to comment Share on other sites More sharing options...
Feelers Posted June 14, 2006 Author Report Share Posted June 14, 2006 Do you know where I can get a suitable real squirrel cage fan from? Quote Link to comment Share on other sites More sharing options...
ryanjury Posted June 14, 2006 Report Share Posted June 14, 2006 Cars generate AC using an alternator maybe its using that.. I read you had put squirrel cage fan.. And I presumed it was a squirrel cage motor used for a fan. Ie a squirrel cage fan motor. All I know from my studies is that if it is a squirrel cage motor it is AC maybe someone else knows more.. Have you tried the old faithful and googled/yahoo'd it.. or maybe www.howstufworks.com? Quote Link to comment Share on other sites More sharing options...
ryanjury Posted June 14, 2006 Report Share Posted June 14, 2006 couldn't you just goto your local supermarket and get one of those cheap as fans and use that? would be alot easier than trying to make it up yourself.. Quote Link to comment Share on other sites More sharing options...
Feelers Posted June 14, 2006 Author Report Share Posted June 14, 2006 Nah it has to be able to create a failry large positive pressure in the second chamber to push the air though the hepa filter. I have made the fan go on a 5V DC computer power supply - Doesnt this mean it's definately DC? Quote Link to comment Share on other sites More sharing options...
ryanjury Posted June 14, 2006 Report Share Posted June 14, 2006 Yup sure does AC motors wont go on a DC supply so its all good computer supplys have all sorts of voltages and can supply a bit of current.. Quote Link to comment Share on other sites More sharing options...
suphew Posted June 14, 2006 Report Share Posted June 14, 2006 I think I know what you mean, I have a similar fan runnning to blow air round my fire, looks like one of those wheel things that rats run round on (well sort of). A car battery charger should give you enough juice to run the fan. plus are pretty cheap to buy now. There will be a current rating on the charger so you can check before you buy it. Good luck sounds like a fun project. Quote Link to comment Share on other sites More sharing options...
Feelers Posted June 14, 2006 Author Report Share Posted June 14, 2006 Since the motor only cost $20 its not a big deal if I can get an actual cage filter - suphew I dont spose you know how much your one cost? If they are ac that means I need to worry about getting the correct flow rate as they would not be easily altered. Where can I get these squirrel cage fans? Quote Link to comment Share on other sites More sharing options...
Ira Posted June 14, 2006 Report Share Posted June 14, 2006 Cars generate AC using an alternator maybe its using that.. What? No they don't. Car alternators produce DC. Quote Link to comment Share on other sites More sharing options...
Feelers Posted June 14, 2006 Author Report Share Posted June 14, 2006 Damn I just found out what I need to do - I need a car fan thats rated less than 140W. Suphew you were right on using the car battery charger - thats the plan but they are rated either 4 or 6 amp(as I just found out) , meaning I need a fan between 48V and 72V or thereabouts depending on the charger I get. Doing it this way (DC) makes it sweet because I can use a variable resistor to change the flow rate as opposed to trying to match the filter to the fixed flow of an AC fan. Quote Link to comment Share on other sites More sharing options...
Ira Posted June 14, 2006 Report Share Posted June 14, 2006 You'll never find a car battery charger that puts out 48-72 volts. They all put out a peak of somewhere around 14 volts. You try putting 48 volts into a 12 volt car battery and you'll end up with a nice crater in the ground. Or at the very least a destroyed battery. Quote Link to comment Share on other sites More sharing options...
Pegasus Posted June 14, 2006 Report Share Posted June 14, 2006 Looking at the links you provided.. it seems that the method you are trying to adopt will be like pushing the proverbial uphill.. as you will will "never" create enough forced air pressure using ... Anyways - I have gone to the wreckers and bought the fan that blows hot air around the car from inside the dashboard. - a "squirrel cage fan" You would get more "puff" from a 12 dollar fan from the Warehouse that runs on 240vac... and you have the speed changes built in.. The slightest backpressure on a car fan system (even the filter).. would make it ineffective. It states in your links that you need around half a meter per second to force air through the Hepa filter.. and this would need to be maintained as the filter began to clog slightly. I have done a lot of work on "clean rooms" and "sterile units".. and in all cases the air is forced via the ducting surrounding the output of the fan.. which is often very powerful and high speed. Are you trying to create a mini clean room with sterile conditions...? .. or just a sterile cabinet that you can access through sealed arm and hand units.. like they use for premature babies in hospitals...? Looking back at car parts.. one of the electric cooling fans from a modern car "might" just give you enough output.. but a mains type fan would save a lot of hassle. Bill. Quote Link to comment Share on other sites More sharing options...
suphew Posted June 14, 2006 Report Share Posted June 14, 2006 Since the motor only cost $20 its not a big deal if I can get an actual cage filter - suphew I dont spose you know how much your one cost? If they are ac that means I need to worry about getting the correct flow rate as they would not be easily altered. Where can I get these squirrel cage fans? I got mine from my mum and dad, it was in a very old fan heater, to get the proper one the fire box people supplied was a couple of hundred. Suphew you were right on using the car battery charger - thats the plan but they are rated either 4 or 6 amp(as I just found out) It doesnt matter if the charger provides more current than you need , the motor will only use what it needs. The problem would be if the charger didn't provide enough, the motor would over load it. Quote Link to comment Share on other sites More sharing options...
Feelers Posted June 15, 2006 Author Report Share Posted June 15, 2006 Are you trying to create a mini clean room with sterile conditions...? Yes - its for the whole nine yards Ira I wrote V instead of W - that should be 48 -72 watts. Bill - I'm not sure about the air pressure thing, I have a friend who is building one aswell - he's very "onto it" with projects like this, and he seems to think the one he has started building definately has enough oomph. Remember those car fans are ducted into different areas - so the flow is divided etc - they might be stronger than they appear? Quote Link to comment Share on other sites More sharing options...
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