Anemometer switch problem

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Dodulation
Posts: 2
Joined: Sat Mar 25, 2017 10:13 am

Anemometer switch problem

Post by Dodulation » Sat Mar 25, 2017 10:17 am

Hi there,
I am trying to find a piece of electronics which function as a switch operated by an anemometer. The anemometer measures a certain programable windspeed and at that particular windspeed it switches a relay. My anemometer is nothing more than a rotating magnet that passes a reed switch at every rotation. The purpose I want to use this piece of electronic for is to open vents operated by an electric linear actuator, but if the wind gets too strong the vents need to stay close. So, I need to count the rotations (pulses) of the anemometer and if it exceeds a certain (programmed) amount of pulses per second it needs to operate a relay.
Does any of you how I can easily build something like that?

magpie
Posts: 32
Joined: Sun Sep 06, 2015 11:34 am

Re: Anemometer switch problem

Post by magpie » Wed Mar 29, 2017 5:31 pm

There may be many ways to come up with a solution to your problem, but I have only been able to come up with what I would consider. That is...a 555 astable, to give a one second sample, a digital to analogue [DAC],and a window detector.However it would appear to me that you would be better off, financially, and with a lot of support, if you looked towards using a Arduino. They are cheap and if you join the forum, then you can tell them what you are trying to achieve and I am sure someone will assist.

Dodulation
Posts: 2
Joined: Sat Mar 25, 2017 10:13 am

Re: Anemometer switch problem

Post by Dodulation » Thu Mar 30, 2017 12:44 pm

Hi Magpie, thank you for the advice. Which Arduino would you think I should purchase? The UNO Rev 3?

David
Posts: 216
Joined: Sun Oct 04, 2015 6:18 pm

Re: Anemometer switch problem

Post by David » Fri Mar 31, 2017 11:38 am

This is a nice project. If you wanted to use discrete components, you could try something along these lines.
wind speed001.jpg
Basically, the reed switch generates a negative pulse every time it closes, and this pulse is differentiated to fire the 555 which gives a positive pulse with a defined width. There is no output if the anemometer happens to stop with the reed switch closed. The 555 output pulse goes via an isolating diode D1 to an integrator formed by R4 and C4. The charge on C4 is dissipated by R5+ R6, but when the voltage on C4 exceeds a certain amount (perhaps 50-60 % of the supply) the transistor turns on and activates the relay.
It is difficult to give you much guidance on the actual values of components, because so much depends on such things as the reed switch, max speed of the anemometer, and a lot of experimentation. You don't say how familiar you are with electronics, but I think that you should have a go. An oscilloscope will be hugely useful if you do experiment. Information is available on the 555 from charts on Google, and Horowitz and Hill's "The Art of Electronics" is a mine of useful circuits.
Some guesses on values to start:
R1 - 22K,
C1 small; with R2 the trigger pulse should be about 10% of the width of the 555 output pulse
R3 & C2 You need to know the minimum time between activations of the reed relay at the max anemometer speed. Set width of output pulse to about 50% of this.
R4 & C4 What voltage do you want C4 to charge up to before the relay is triggered? Start with 4K7 for R4 and vary C4.
R5 & R6 These determine how the voltage on C4 drops between the pulses from the 555. Experiment - perhaps you could use a pot here to help with setting the turn on of the transistor.
Hope this helps.
Last edited by David on Sat Apr 01, 2017 6:40 am, edited 1 time in total.

magpie
Posts: 32
Joined: Sun Sep 06, 2015 11:34 am

Re: Anemometer switch problem

Post by magpie » Fri Mar 31, 2017 5:50 pm

I would go for an Arduino Uno...I think they are up to rev 3, but I am quite sure, any one of the range will do for what you want. As this is open source, there are many companies out there that have developed their own Arduino, and may give the same results. However, you are encouraged to purchase the Arduino brand, to assist with further development. If you have not any experience with programming then don't be put off, as there is plenty of assistance and tutorials on YouTube, also many libraries you can use to download... just copy and paste into your project. With David's ideas, I think this will give the options.

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