# Triggering Relay

Discussion in 'General Electronics Chat' started by Maru1, Jan 30, 2014.

1. ### Maru1 Thread Starter New Member

Nov 20, 2013
12
0
Hello,

I want a Single Pole Single Throw Relay to be triggered when the anemometer reads 17 m/s. How would I go about doing this?

Sorry if this question is too broad, if need be I will try to provide more specifics.

Thanks in advance.

2. ### MikeML AAC Fanatic!

Oct 2, 2009
5,444
1,074
Post the detailed specs on your anemometer.
Supply voltage?
Load current from relay?
Your experience level?

3. ### Maru1 Thread Starter New Member

Nov 20, 2013
12
0

My project is building a wind turbine

Basically I will have a motor acting as a generator so am I correct in assuming that voltage and current will vary depending on how fast the turbine is spinning?

Between the end terminals of the motor there will be a resistor and in parallel with that resistor there will be another resistor (2nd resistor and relay are in series)

The wind turbine won't actually power anything, just the output voltage will be measured

To power all the controls 2 9V batteries will be used.

-Sorry if I'm not making any sense here, this area isn't my strong point.

*As for the specs of the anemometer I don't have that on hand at the moment*

4. ### inwo Well-Known Member

Nov 7, 2013
2,416
314
Rather than the output level, you wish to pull in a relay at a period 17mS or about 60hz?

If that's what you looking for, then someone will come up with a circuit that can be adjusted to your levels, after you get specs or measure the output voltage across resistor.

5. ### MaxHeadRoom Expert

Jul 18, 2013
18,144
5,563
The voltage will be dependent on rpm, so it is important not to load the output anymore than necessary.
This will be a linear voltage, so do you want to detect when a single rev is 17ms?
The is a very high rpm or what is the 17ms relative to?
Max.

6. ### alfacliff Well-Known Member

Dec 13, 2013
2,449
432
probably 17 meters per second wind speed.

Nov 7, 2013
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8. ### alfacliff Well-Known Member

Dec 13, 2013
2,449
432
sounds like putting the second resistor to load the generator to limit rpm above a certain wind speed.

9. ### inwo Well-Known Member

Nov 7, 2013
2,416
314

There you go.

17mS just seemed too close to 60hz for coincidence.

10. ### MaxHeadRoom Expert

Jul 18, 2013
18,144
5,563
Its an advantage to make an anemometer with a digital source that is optically or magnetically coupled/isolated, this enables a much more friction free, lower inertia mechanism than using a motor/generator idea.
This also allows a much more accurate detection when a certain rpm is reached.
Max.

11. ### Maru1 Thread Starter New Member

Nov 20, 2013
12
0
This is as project that involves a number of people. I'm focusing on solving the problem below.

When relay is triggered the two resistors will be in parallel, this will decrease total resistance which will increase the current. I'm using the fact that torque is proportional to current. So when the relay is triggered then the motor will slow down.

I want the above to happen when the wind speed is 17 meters per second. I will use an anemometer to measure the wind speed.

So I somehow need to trigger the relay when the anemometer reads 17meters per second.

All help is much appreciated

12. ### MaxHeadRoom Expert

Jul 18, 2013
18,144
5,563
Details make it a BIT clearer.
What kind of output or signal is available from the anemometer?
Max.

13. ### Maru1 Thread Starter New Member

Nov 20, 2013
12
0
I don't have that information but I'll post it tomorrow. Can you tell me the general idea of how this is going to work?

EDIT: Also what do you exactly mean by output signal from the Anemometer. Do different Anemometer have different ratings?

14. ### MaxHeadRoom Expert

Jul 18, 2013
18,144
5,563
The exact nature of the anemometer and just how it detects the wind speed/rpm would be needed if you intend reading a value from it.
They all are basically the same, but have a different method of obtaining the data.
Max.

Last edited: Jan 31, 2014
15. ### Maru1 Thread Starter New Member

Nov 20, 2013
12
0
Guys,

I don't have the specs of the anemometer yet but for now I'm not looking for an actual value.

Can someone tell me in general how I would achieve what I want to achieve. Basically the theory and the calculations if any that I would have to do?

16. ### MaxHeadRoom Expert

Jul 18, 2013
18,144
5,563
But in order to supply some meaningful ideas, details of the equipment you intend using needs to be supplied.
Or if you have a concept and want to design the equipment for it, more detail and info as to what you want to achieve is needed.
But I would think the more practical approach is to obtain an anemometer and design around it.
Max.

17. ### Maru1 Thread Starter New Member

Nov 20, 2013
12
0
Ok let me quote the idea for the anemometer my team came up with

"The light gate and self-*‐built anemometer ideas are based
around the same concept, counting the number of
revolutions within a given timeframe and using this
frequency to work out the revolutions per minute of the
rotor and wind speed respectively. The hardware setup
chosen to implement this uses a phototransistor to detect
the light from an LED and having a spinning piece of opaque
material break this contact. This would cause a change in
voltage which can be recognised by the NI6008 board and
used for calculations."

Let's say I want the relay to activate when angular velocity of rotor is23.08rad/s or 692RPM

With that in mind what would be the general idea/concept?

Nov 7, 2013
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Nov 20, 2013
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20. ### MaxHeadRoom Expert

Jul 18, 2013
18,144
5,563
Personally I would use a small PicMicro and using a timer with an input interrupt from the photo detector.
The way an anemometer is often constructed.
The relay would be triggered from a pic output.
The DAQ route would not have been the path I would have taken.
Max.