RE: Science fair project results -test for viability

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Dale Hall by way of Terry Fritz <twftesla-at-uswest-dot-net>" <Dale.Hall-at-trw-dot-com>

Hi Joshua, Michael,
I emailed Michael directly regarding relevant to power transfer using TC's.

Joshua here is my assessment re: LED illumination using Michael's data:
~Data, Red LED's have lowest threshold turn-on voltage
	and are the most efficient (require least power to light): 
  rated typical ~1.6v 20mA 
	There are some rated for ~6mA that are visible at 2 mA
	Using Ohms law:	Pled = IE = .0032 W = 3.2 milliwatts
				Rled = 1.6/.002 = 800 ohm (proposed load)
	(note the LED IV characteristic is nonlinear - it's a diode)

	practical note: LEDs illuminate noticeably well at infrequent
	high peak power bursts, such as typical 120 PPS TC break rates.
	HP35 calculator used Hi current pulses to increase LED power efficiency.

Joshua's highest output measurement: 
	1.4vdc into 10000 ohms with a parallel DMM ~10Mohms
	P = E^2/R = 1.4^2 * 10000 = .000196W = .196 milliwatt = 196 microwatts

Conclusion: 
There appears to be insufficient power available to 
illuminate the LED in his present test configuration.

Hypothesis: The current Tx - Rx configuration can be optimized.

Furthermore, the lower resistance presented by an active LED (800 ohms)
would likely reduce the available voltage to less 
than is required to overcome the 1.6V LED threshold to illuminate.
 (<1.4V measured at 10000 ohms likely a lot less V -at- 800 ohms)

Impedance transformation (RF,AC) before 
peak detection can optimize power transfer 
to match requirements of a lower impedance load (DC).

Comment:
Power transmission via an alternating electric field 
such as the resonant non breakout TC requires an efficient 
and matched impedance antenna on both the transmitter 
and receiver - diode rectifier detector to a load resistance.

Furthermore, impedance matching is required for optimum results;
i.e. to obtain the most power transfer, greatest efficiency.

Some other measurement considerations:
 The diode detector being used is a peak detector charging a capacitor,
 so RC time constant a consideration. 
   Assuming a break rate of the TC is 120 BPS 
   then charging occurs relatively infrequently, 
   every 1/120 = .0083 sec = 8.3 mS.

TC radiated Power is delivered as relatively 
infrequent impulses of high peak power.
  What are the consequences of power delivery this way ?
  Hint: users of power are interested in RMS or Average, not peak power.
      i.e. the "heating" value of the power supplied = work function.

Regards, Dale
========================
--- since there seems to be interest here is more of our exchange:
--- (SLAP = Scientific Laws and Principals)
What was the TC's:
  average input power ?

  estimated output power ? 
 (tougher but you could estimate based on efficiency approximation)

  What kind of antenna was used ?  
	untuned receivers and antennas may be expected to be very inefficient.
	  Even the signal diode switching characteristic at 200kHz merits
consideration.

	SLAP: efficient antenna is required for efficient power transfer,
	1/2 wave dipole antenna Length feet = 468/f_MHz = 468000/F_kHz
	example 468000/200 = 2340 feet (This is very long)
	What can be done to get good efficiency at a shorter length ?
	note: the Transmitter and Receiver both need efficient antennas.

  Was the receiver a tuned circuit ?
  What affects receiver efficiency ?
  Was there TC break out ? Is that desirable or not & Why ?

  Was all the energy received radiated from the secondary electrostatic
field ? 
		Does that matter ?? Why ?
	Could a portion of the received energy be due to direct
	magnetic field induction coupled from the Primary 
	due to the close proximity of the receiver ?
 
What were your 3 measured voltages across 10K expressed as average powers ?
 Power, a product of voltage * current in a load,
 is the proper quantity to compare.
  (scientific law involved: ohm's law, Efficiency = 100*Pout/Pin, 

   DC detector voltage = average if there is no droop due to RC 
	(note: your diode detector is a voltage peak detector)

   convert your measured voltage and load to power (watt) 
   E=IR, I=E/R, P=IE, P=E^2/R;  P=1/t, t=1/P (waveform Period = 1/time)
	(Prcvd-at-0.5M = 1.4^2/10000 = 0.000196 W = .195 milliwatt - 196 microwatts)

   other relevant SLAP: two fields, Electric and Magnetic displaced 90 degrees.

   Time Constant =RC sec = time to charge or discharge to 63% of applied
voltage):
	What is Time Constant affect on values chosen for receiver detector ?
	Hint: If you have an oscilloscope, 
		how does the receiver detector waveform appear ?
	If you don't, then speculate. 
	(TC output = impulses of TBD duration 120/sec 
	(assumes break rate = 120/sec, needs verification)
	  which is once every 1/120 0.0083 sec, = 8.3 milliseconds.
	  RC = .1 e-6 volt * 10000 ohms = .001 sec = 1 millisecond
		(assumes DVM (10Mohm?) does not significantly lower 10,000 ohms
		i.e. does not introduce significant test error)

If you understand any of this you are ahead of the project, 
else some study is still appropriate to understand and explain your
experiments.
....snip
(lots more, like what Judges look for, student education of Judges, etc.
  email me direct if you would like a copy)
	
-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Monday, December 11, 2000 6:29 AM
To: tesla-at-pupman-dot-com
Subject: Re: Science fair project results

Original poster: "by way of Terry Fritz <twftesla-at-uswest-dot-net>"
<MaverickIce00-at-aol-dot-com>

Hi Michael, Everyone, 

>My results were: 1.4 V -at- 0.5 meters, 0.335 V -at- 1 
>meter, and 0.007 V -at- 2 meters (as measured from toroid). 

Good work with your science fair project, I am just curious about something. 
First, do you think it would be possible to connect a small LED across the 
output of the receiver to show that the energy from a TC can have a somewhat 
practical use? (even though it's not entirely too efficient to power a tiny 
LED with a couple hundred watts, even if it is from a distance :-)) Did you 
measure the current output as well? I am not even sure if it would work, but 
if there is sufficient current at 0.5 meters, the 1.4 V should be able to 
illuminate the LED, if it has a small enough voltage requirement. I just 
think it would be kinda cool... 

Just a thought... - Joshua -