This was in use all summer, so it is actually a practical device. Where we live, we do without air conditioning. It does get warm during the day, but usually cools off at night. I got 6 5" 12V computer fans as a special. and put them on a panel in our bedroom window. They are controlled by the 8M's PWM output. Analog inputs are for the ratio of 2 cheap thermistors, one inside and one outside, and a photocell. When the outside is cooler than the inside, the fans turn on. When we go to sleep and turn off the light, the fans slow so as to be quieter. It was necessary to add manual switch for override: On - Auto - Off.
Window fan controller using an 8M
- Thread starter saunj
- Start date
An interesting "practical" application, which will have many alternative uses. It sounds as though it introduces several aspects of the PicAxe and I'd suggest you move in Stages, so it can be improved as the pupils get it working.
I think its greatest benefit is that it is able to work at many levels - good.
For example, just altering the ratio of On-Off times will effectivly change the airflow ( so removing the need for thermistor curcuitry) and you will be aware that we humans react to temperature and airflow in a way that needs some explanation.
I suppose it is necessary to ask - Did this meet your requirements?
Did you mange to make it self-start next evening?
I think its greatest benefit is that it is able to work at many levels - good.
For example, just altering the ratio of On-Off times will effectivly change the airflow ( so removing the need for thermistor curcuitry) and you will be aware that we humans react to temperature and airflow in a way that needs some explanation.
I suppose it is necessary to ask - Did this meet your requirements?
Did you mange to make it self-start next evening?
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Bedroom fan reply
I don't have a photo, and now it is put away until next summer. The box is about 9x3x2", which includes the switching power supply. I would like to post the circuit and code, but I don't know how. I use RFFlow to make circuit diagrams.
As an aside, this, like most of my other picaxe (and stamp) projects, included serial code for monitoring the operation via the programming port. I have a box which plugs into any one of them and records on a Secure Digital module. It is powered via pins 1 and 6 of the 9-pin connector from the device. It uses the little board from Rogue.
That is true, but using PWM to control the airflow is quieter. It was, however, not as easy since a minimum voltage is needed to get the fans to start. The thermistors I admit were a nuisance, because I used cheap ones made to suppress startup surges, which are inconveniently low resistance, so I needed to give them low volts, requiring an op amp.
Mostly, but sometimes it did not cool down outside enough, but my wife still wanted the breeze, and turned it on manually. The fans are very effective, better than commercial window fans you can buy, and much quieter. I got 10 cheap from MPJA. They were surplus from old servers. 5" fans do not fit newer equipment.
It was left on, not having a power switch.
I don't have a photo, and now it is put away until next summer. The box is about 9x3x2", which includes the switching power supply. I would like to post the circuit and code, but I don't know how. I use RFFlow to make circuit diagrams.
As an aside, this, like most of my other picaxe (and stamp) projects, included serial code for monitoring the operation via the programming port. I have a box which plugs into any one of them and records on a Secure Digital module. It is powered via pins 1 and 6 of the 9-pin connector from the device. It uses the little board from Rogue.
See my websitepictures? code? diagram?
Click on a link to saunj's name in an above post and there's a link to his home page.
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