Precise sensing of the null point seems an over complication to me.
A simple optical sensor will give you a reference point, a simple adjustable electronic delay (555 timer?) will allow you to adjust the timing of your electromagnet to give a kick.
Almost anytime at or after the null point will do the trick. (Unless I'm missing something here?)
Del

I'm with Del. Definitely, I'd go for a optical sensor to check the pendulum position. In addition, depending on how small and how many optical sensors you may be able to install, you could even do a minimum-target-maximum position sensor, so you could make your magnet to be turned on or not, depending if the pendulum movement is too small or too large as a result of the last turn movement, air movement, some tricky colleague trying to jump your project, ... I appreciate your approach to the pendulum theory. Frequency will be the same, but you'll be able to compensate for the total travel as energy dissipates. This sensor could also add you in calculating time, frequency, act as a counter, whatsoever...

Reply to Del Cat & Bhrescobar:

In my post I should have mentioned some conditions that I felt needed to be considered before proceeding in my project (power pendulum).
If I was certain that the swing arm would traverse only 180 degrees for a full swing then I could place the EM at a specific position and a simple magnetic proximity switch would trigger action of the EM. But, the load condition on the axis of the pendulum may cause the swing arm to be less than 180 degrees at full swing (i.e. 120, 130, 140, etc.).
I would have to position more than one EM along the swing arm path. This would be cost prohibitive.
I could mount the EM on end of the swing arm as part of the weight. Several permanent magnets could be placed along the swing path at far less cost. Special flexible wiring could run from the EM along the arm lever to a connector at the axis. The pendulum is a slow moving device with desired high torque at the axis and I don't forsee any problems with movement of the cable carrying the wiring.

Here some additional things I felt needed to be considered:

(1) The placement of permanent magnets along the arm swing path covering a path 120 to 180 degrees. Some type of sensor system detecting zero (or near zero) motion triggering action of the EM.
The length of time before the arm moves downward may be too short for a motion detector to respond.
(2) Since it is desirable for the arm to have a full swing of 180 degrees, electrical current to the EM should be increased when the arm swing degree is less than 180 to force the swing to 180 degrees.

I will explore the possibilty of the use of optical sensors in my project.
Thanks for your replies.

Place a small magnet part way up the pendulum's shaft and use an analog Hall Sensor to capture the motion as the pendulum swings to it maximus.

The biggest challenge is discrimination of that exact point. In theory, you can never do that because it occurs at a finite moment in time.

You need to derive specifications for your project with realistic requirements and tolerances before you go any further. Those requirements will determine what pathways are open to you.

As Dell stated, it may not be important to determine the exact momemnt that the null is reached. So be sure before you set off on a bad path.

The other way to do this accurately is to build a circuit with an accelerometer on it and attach it as part of the pendulum. It would need to have a battery and a wireless RF link since a wired link would create drag.

At that point, the velocity is zero and is sinusoidal. You can't detect that change by anything that looks like a tach.

The acceleration signal is too broad to detect accurately with an accelerometer.

A tilt switch would capture a preset point. If you added an adjustable delay, you could make it dependable.

I missed your second post. How large a budget do you have? You could use a synchro.

What the heck is this thing? Sounds like a motor?

You might consider locating the EM at the bottom of the arc rather than the top, as it will always pass that point whatever the total arc. An optical sensor could control the switching.

Then a linear sensor located at the the horizontal position could measure the arc length. If you used an integrating controller on the EM power, it would automatically adjust the power level for variable loading.

I agree with DaveR's post 7, especially if this is something akin to a Foucault pendulum, since the pendulum will always pass over the same bottom location, regardless of the angle of swing. You use attraction, which is easier than repulsion, since no permanent magnets are required. all you need is an optical sensor 'looking' straight up at the exact bottom dead center, and a timing device to time the duration of the magnetic pulse so it only pulls on the way in, not on the way out.

An electromagnetic Impulse Variator triggered by a LASER doppler null detector.

Hi,

any magnetic weight compensation will not work completely: either generate forces in unwanted directions or moments (torques) around the three axes.

If you want to use this arrangement as a precise oscillator (old fashioned pendulum clock) then the null sensing shall be very accurate as symmetry of the driving pulse with respect to zero amplitude is of utmost importance.

Between 1940 and 1960 the "Riefler" pendulum clocks gained an accuracy and stability of 1 to 3 milliseconds per day (or 10^-9!!!), some earlier without the electromagnetic drive were near this.

Look at the vast patent literature, there are multiple solutions to use the driving coil as a sensing coil.

A good approach to overcome friction is to use a flexible suspension and to operate the device inside a good vacuum.

Flexible suspensions are orders of magnitude better than magnetic suspensions because no eddy currents generated.

Vacuum is a necessity because at Q-factors (resonance amplification) above 500 the gas friction at normal pressure will be dominant in frictional losses.

I tested an oscillator (not a pendulum, but small, robust and massive) in air showing Q=400 and in vacuum showing Q = 50000).

RHABE

Yes, I do fall into the "free energy enthusiast" class. Some time ago I posted a project that I had planned to pursue but decided not to proceed. Instead I became interested in experimenting with a power pendulum. For years many have attempted to build devices using gravity purported to do some useful work. But in my research while wading through many devices with wild claims, a power pendulum surfaced as a device I felt would be something I would want to experiment with.

I strive for challenges, have an abundance of time to experiment, and, fortunately, have a good funding source. My goal is to get the power pendulum to produce useful work. I am stubborn enough to attempt to prove that with input energy from an outside source (EM and components) will maintain oscillations of the pendulum under varying load conditions. All the reason to find a practical way to fire the EM at the precise time the pendulum swing arm is at its upmost position so that the input power is minimal.
Although the axis (shaft) will oscillate in rotation, I will explore means to convert rotation of the shaft to either clockwise or counterclockwise at a higher speed. Obviously, frictional forces in the device design must be minimal.
The shaft power output could drive a low speed generator similiar to a DC motor generator used as a turbine in smaller wind power devices.
My goal is to generate elecrical power to charge a network of storage batteries. Some of the output would be used to activate the EM. Even if I had only enough power for this feedback, I would consider my project successful. The device would be for my own use if it proved to be of practical use. I could use solar cells or even wind power instead of gravity but, with the power pendulum I wouldn't have to depend on either.

The Pendulum powered generator will not produce enough continous energy to sustain the Pendulum swing. However the momentum of a huge swinging pendulum powered generator would provide a small period of uninterupted power as would a huge spinning mass powered generator or a dam full of water for a water wheel.

I knew a couple of guys who were trying to weigh the difference of a capacitor that was charged and uncharged. They had quite an elaborate weighing structure.

Experimenting is fun but these types of free energy experiments are as illuminating as a snuffed candle.

You can keep trying to get a desired response by shining your intellectual light on it but it will always prove to have as much response as the black in the eye of a dead ant.

What leads you to believe that you can get more, or even as much, energy out of the pendulum than you put in?

Like a flywheel, a pendulum could take low power input over a relatively long time and provide pulses of higher power output over shorter time, but the average power out will always be less than the average power in. There are always losses!

If you are not going to use solar or wind to power your electromagnet(s), what do you plan to use instead?

I wish you well in your endeavors. No matter what you learn, it will be fun doing the experimentation.

Some of the output would be used to activate the EM.

In fact, all of the output plus an amount to overcome frictional losses will be required even if your entire generation and storage system is 100% efficient (which is not possible).

Even if I had only enough power for this feedback, I would consider my project successful.

If you can do that, we will all cheer, for never in recorded history has it been done before, and no one with an education in physics would expect it ever to happen. But successful or not, you will have fun trying. Be aware that one reason the scammers throw in energy conversions is for confusion value, not for efficiency or efficacy. Every energy conversion comes with associated losses, so you should try to minimize the number of conversions. Just making a mechanical perpetual motion machine would be historical enough. To make one that also suffers the losses of converting mechanical to electrical to chemical... back to electrical and back to mechanical would be absolutely astounding, making Einstein's work look like child's play. You have quite a task ahead of you.

Have fun.

If this is a fixed axis of swing (not Foucault) then an optical encoder could be part of the bearing providing the swinging motion. Looking at the two pulse streams for a direction reversal will tell when briefly after downward motion starts. While never precisely at the peak, it will permit knowing which direction to add your impulse force and have a predictable maximum error.

If you are doing a Foucalt pendulum then the mechanics will be much more complicated to detect in which axis of motion your pedulum is now in to impart a force that doesn't mask the Coriolus at the top of the swing. I like sombody elses suggestion of timing and stopping at the detected mid swing position.