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Wind speed
Wind speed circuit
Average speed is a determined in a standard way by measuring the revs per time interval, however the method of implementation took considerable effort to work out and the circuit and code are my own solution.
The solution is based on a low-power 4040 12-bit ripple counter chip, which is powered continously. When the PICAXE is awake, it extracts the current counter value from the 4040 by quickly filling the counter. Refer to code to get a full understanding of how the method works.
The revs of the anemometer cups are captured using a simple reed-switch. The specs for modern reed switches indicate long-life. Note the capacitor that is in parallel with the Reedswitch. This de-bounces the switch and prevents spurious count pulses hitting the 4040.
The calculation of the capacitor value is actually quite critical. Too big a capacitor will seriously limit the maximum speed that can be detected. Too low and it won't de-bounce properly.
The solution is based on a low-power 4040 12-bit ripple counter chip, which is powered continously. When the PICAXE is awake, it extracts the current counter value from the 4040 by quickly filling the counter. Refer to code to get a full understanding of how the method works.
The revs of the anemometer cups are captured using a simple reed-switch. The specs for modern reed switches indicate long-life. Note the capacitor that is in parallel with the Reedswitch. This de-bounces the switch and prevents spurious count pulses hitting the 4040.
The calculation of the capacitor value is actually quite critical. Too big a capacitor will seriously limit the maximum speed that can be detected. Too low and it won't de-bounce properly.
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