This resumes from a previous post in good shape, isolde - part 10. We have been blessed with a few days of incredible spring weather this week. Today, I was just browsing Amazon for cheap electronic DIYer's module. I thought I would search for a thermometer that can be either adjust or programmed, like a thermostat but just for the on/off control of a 12Vdc fan that is extremely low current.
Most of what came up are the usual suspects for 115Vac, bi-metal switches, or just plain old HVAC boring stuff. I then decided to try the networking devices category. Networking devices are typically the tiny electronic modules for Raspberry, or Arduino microcontrollers. Then I came across this nifty little electronic module that is a programmable thermostatic controller. There are other similar devices, but this one really stands out with it feature laden design, and the best part, for under $4 shipped from China.
I have been wanting to buy a Microchip's PIC microcontroller and program it for the automatic control of the circulation fan I made for Brunnhilde. I want the fan to turn on automatically when the ambient temperature reach a hot temperature so the circulation fan will keep the cabin cool while Brunnhilde is parked in the summer sun. For under $4 it is a no-brainer purchase just for the fun of playing with it.
the air circulation fan for Brunnhilde
I had provision a pair of wires supplying 12Vdc in Isolde circa 2003 at the skylight. My plan was to design a low power extractor fan to evacuate cooking fume. Over the years I could not avail myself to continue the project. Seeing this module and the godsend weather I wanted an excuse to go for a drive in Isolde. I was in Fry's a few week ago and saw these big computer fans. They are designed to be big so they are quiet by running at very low RPM. At the time I considered purchasing one but unsure of the application. Today is different, I now quite sure that I can implement something elegant with one for the cooling of Isolde's cabin in the summer sun.
the weather is gorgeous for the next few days - it is 71F in the late afternoon
the component section of Fry's Electronics
I am here for the big computer fans
I was very concern with the noise, the quality, and just the right CFM; these two are the finalists. Of the one with the black blade, there is a companion model that is translucent white that I would prefer as it won't get as hot sitting in sunlight. Unfortunately it is illuminated by blue LEDs all the time.
The two finalists I chosen in the above photo, the one with the white blades is more expensive, inferior built quality, but lower in current consumption, hence quieter. It was a difficult choice as I was extremely concern with noise. Fortunately I have some idea how much CFM I want based on the power consumption. I know for a fan this size around 0.2A should not be too loud. I decided to take the one with the black fan blades as it is clearly a better quality product. It cost $12.99.
coming home I could not wait to find out how well the fan meets my expectations
I did some quick bench tests to find out:
- the noise level
- the CFM and how well it handles back pressure
- operation as extractor mounted in a vertical position
- power consumption in different orientations
The test for the noise level, I wanted to find out if the fan operates quietly in my planned use. To this the fan will be mounted in vertical position sucking air from below and expelling upwards out the open skylight. As I ponder on what this mean for the fan, I realized it may not be how this fan is designed to operate. It has sleeve bearings, which is a good thing as ball bearings may not be too happy if the fan is not designed to operate with end thrust load.
I set the power supply to about 13.5V with about 250mA of current limit. As the fan is power I monitor the current draw at different orientations. Any orientations that causes higher current draw will suggest increase in friction, which is a clue that the fan may not last operating in that orientation.
the fan is set to pull air upwards and out the skylight
I like what I saw. The fan is happy in horizontal position, as would be in the intended mount in a gamer's PC. It too shows no distress operating vertically in pulling air upwards. It however shows some stress operating vertically in pulling air downwards.
I determine this by listening to the sound of the running fan, and monitoring the current consumption. Only when operating vertically in pulling air downwards that the current consumption increases the most, albeit not by much. The sound also sound not as smooth in this orientation.
bench power supply set to 13.6V
current consumption in pulling air downwards is 242 mA - suggesting the fan is straining from increase in friction
the fan is whisper quiet operating in this orientation (pull air upwards) - which is how I would use it in Isolde
I was wise not to buy the fan with half the power as it would be very feeble for the application. This one says 130 CFM but it sure does not feel like anything close. I am not one to take the spec seriously. The bench test is what I do to access it suitability for the application.
a more representative voltage while Ioslde is stationary is 12.5V
at 12.5V supply voltage the fan consumes 222mA
the fan comes with a nice extension cable with a mating connector which is perfect to make the extractor fan that can easily detached and stowed away
No comments:
Post a Comment