A DAMPING CIRCUIT FOR A COIL

[moodz]

A DAMPING CIRCUIT FOR A COIL ABSTRACT A damping circuit for a coil includes a
voltage controlled current sink, a switch, an amplifier and a sample and hold
device. At a first instant in time when a back EMF voltage is present across
the coil the switch connects the voltage controlled current sink across the coil
and the back EMF is discharged through the voltage controlled current sink. At a
second instant in time when the back EMF has discharged, the switch disconnects
the voltage controlled current sink from across the coil and the residual
voltage across the coil is amplified and an error voltage sample is stored in
the sample and hold device. The stored error voltage level is connected to
the control input of the voltage controlled current sink to form a servo control
loop......and that's how you do it ....:-)

[WM6]

Eeehhhhh moodz ... I was just about to lodge a patent on this solution.

Can you delete your post?

[Aziz]

Eeehhhhh moodz ... I was just about to lodge a patent on this solution.

Can you delete your post?

Nice comment.
Aziz

[greylourie]

What does "servo" control loop. Control loop ... I think I know. But "servo". Thought those were little motors for radio control models.

Come on people. Help this dummy out.

[WM6]

You can take "servo control loop" as "feedback control loop".

[greylourie]

You can take "servo control loop" as "feedback control loop".

[ATTACH]26688[/ATTACH]

Thank you, WM6.

[greylourie]

Would you use one of these ? Look here :AD781.pdf

[hdphilip]

The stored error voltage level is connected to
the control input of the voltage controlled current sink to form a servo control
loop

so would the stored error voltage be used on the damping control on the next TX cycle?


curious Philip

[Aziz]

Eeehhhhh moodz,

since you have got granted the nice patent, a working circuit simulation file (spice file) would help people to understand the working principle of the invention. Would you be so kind and provide us the spice file please?


Aziz

[hdphilip]

yes, a sim would be nice, I wouldn't mind trying it out, i guess we will have to see what moodz's plans are for his patent are.


philip

[moodz]

hehe ... sim the circuit in the patent document .... its all there except for the detail on the sample and hold.... those skilled in the art ... should be able to figure this out. A constant current sink can also be called a "constant power load" ... that means that no matter what voltage is across it the load will absorb a constant amount of power ... this energy is given by IxIxRxt or IsquaredRt where I is the constant current and R is the equivalent resistance of the load and t is the duration in seconds the current flows for ... this is not watts but joules. Now lets say I want to absorb all the power contained in the magnetic field of a coil .... the energy in the coil = 0.5xLxIxI just before the TX switches off ...where L is the inductance of the coil and I is the peak coil current. To absorb this energy ( in joules ) the following equality must be established .... 0.5xLxIxI == 0.5Rxixixt ... where L=coil inductance, I = peak coil current, R=constant current load impedance, i = constant current value and t = duration that constant current load draws current for. Note that I does not = i ... I = reactive current ... i = real current. It is obvious to that the only time that the coil voltage is high enough to drive current through the constant current load is during the flyback "pulse" ... the rest of the time being in transmit or receive ... thus by adjusting the value of constant current drawn by the load during the flyback voltage period an amount of energy can be absorbed that equals the amount of energy that was "charged" into the coil during the TX current on time. ( you guys will need to get used to the concept of charging a coil as it is exactly analogous to charging a capacitor ) Thus my circuit is capable of removing all the coil energy during the flyback period ...something a resistor cannot do. Any residual energy not absorbed by this mechanism will be present itself as a voltage/current across/in the coil after the main flyback pulse. If a sample and hold / amplifier samples this voltage and feeds it back to adjust the level of current drawn by the constant current load then the constant current load will adjust itself such that the minimal energy is present in the coil after the flyback. The "balance point" for the energy charged to coil vs energy absorbed is quite critical non linear ... see the squared terms on both sides of the equations above ... any target will offset the balance point .... so this is one way of detecting a target. The squared terms result give a much higher signal to noise for targets than your old technology resistor damped coil. The signal to noise improvement is around 20db or 100 times. Testing seems to indicate a depth improvement over comparative PI units.... testing continues to confirm this more objectively. The summary benefits are much faster damping thus resulting in earlier sampling, greatly improved SNR , inherent EMI rejection, ability to "auto tune" to optimise most any coil and the elimination of all prior art claims relating to ground balance and sampling .... those squared terms in the equality equation above ??? ... they fundamentally alter the way ground balance is done and sampling target curves ... but more on this later. Note this explanation is not an endorsement for violation of any rights I or others may hold in respect of any intellectual property or patented information contained in this post.

[kt315]

about recuperation this thread
http://www.geotech1.com/forums/showthread.php?19273-PI-metal-detector-with-energy-recuperation&highlight=recuperation

[Aziz]

Eeehhhhh moodz,

20dB ain't 100 times. 20 dB = 10 times.
( 10^(20/20) = 10^1 = 10 )
But still more than what we have today.

Comeon, put a nice spice file. Please! Pleeeaseeeee!!!!
Aziz

[greylourie]

about recuperation this thread
http://www.geotech1.com/forums/showthread.php?19273-PI-metal-detector-with-energy-recuperation&highlight=recuperation

deemon used a BY359.
I found an interesting link, on "damping", a couple of weeks ago. Its here : http://www.earlytelevision.org/damper.html

[moodz]

about recuperation this thread
http://www.geotech1.com/forums/showthread.php?19273-PI-metal-detector-with-energy-recuperation&highlight=recuperation

. ....nice but you are off topic ...my cct does not recuperate power ....