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Registered Member #4465
Joined: Wed Apr 18 2012, 08:37AM
Location: Bucharest, Romania
Posts: 145
KrystaL wrote ...
Hello guys , i want to ask can we use 1.6MHz oscillator , and amplify its amplitude to that level , becoz these compionents are not easily available in my area
No, that's more complicated solution than the original version. However, try to use other types of transistors. I have managed to test in circuit various MOSFET transistors. (Empirical tests only, not claim to scientific value. )
The initial setup: • Vcc = 12V • Rg = 100 ohms (R1, R2) • Diode D1,D2 = STTH3R02 -ultrafast 200V/3A • DiodeD3, D4 = SR810 schottky 100V/8A • L = 1 turn/ 210 mm diameter/13 mm Copper tube • capacitor C = 22nF/ FKP type 1000V
I have measured for each transistor: •current consumption without external load = ' Io' •the on load current = 'Is' ,(for a 50 mm clearance between transmitter and receiver coils). •the maximum distance for light bulb filament still glowing => 'dmax'
• Next, the power supply voltage tests. I have kept one pair of IRF520 on place, then start increasing the power supply voltage up to 30V. Maximum distance for the 12V/5W load (light bulb steady on condition) has increase up to 750mm, and the 'no load current' increase up to 0.8A. The only problem Rg=100 ohms went on fire!... By the other hand the minimum required voltage for the power supply: 7V-7.5V.
• The 'Rg' resistor test ('R1' and 'R2' in the actual schematic) I have keep the original circuit configuration (IRF520, Vcc= 12V), and I have managed to increase 'Rg' value up to 720 ohms for a 'no load current' =0.23A. Finally all the IRF 520/530/540/630/640 and 740 transistors do the job using a 680 ohms (0.25W) standard resistor value.
• The diode test. I have run some test for the diodes used to discharge the MOSFET gates, same setup circuit IRF520, Vcc=12V and Rg= 680 ohms. The following diodes types were tested - STTH3R02, those are running very cool, Io= 0.23A - 1N4148. Not all the diodes I have tested can manage the situation OK, some are very hot, some were destroyed and 'Io' (the 'no load current') increase up to 0.35A - MBRS1100T3G, running cool, 'Io' = 0.25A - BA157, BA159 series, running OK, just a little warmer, 'Io'= 0.35A - BYV27, running cool, 'Io' = 0.28A
And my final conclusion for these tests: at 12V power supply we get perfect results using any of the transistors and diodes mentioned above. This allow to increase the 'Rg' resistors value and hence reducing power losses in resistors. In any situation need to use always some very good capacitors, as the recommended FKS/FKP/MKS or MKP foil polyester series.
Registered Member #4267
Joined: Fri Dec 16 2011, 09:17AM
Location:
Posts: 16
mister_rf wrote ...
In order to power up a small DC fan you need to use a rectifier bridge. The purpose of the rectifier section is to convert the incoming alternating current from the AC power source to some form of pulsating DC. By the way, at this high frequencies some schottky diodes need to be used for. For example I have managed to modify a small mobile phone in order to be recharged wirelessly form the Royer oscillator. See a video here:
I have a few of these laying around:
BYW29-200-E3/45 - Ultrafast Rectifier Diode
are Schottky Diodes essential in this application. Im guessing the slight amound of stored charge will delay a standard diode and create alot of head.
Registered Member #3888
Joined: Sun May 15 2011, 09:50PM
Location: Erie, PA
Posts: 649
very nice data mister rf. So basically everyone can change their resistor value to save a little power and not have it affect the results. pretty useful. I'm also surprised that such different mosfets yielded approximately the same results. One question though: what was your power supply and was it current limited?
Registered Member #4465
Joined: Wed Apr 18 2012, 08:37AM
Location: Bucharest, Romania
Posts: 145
For the initial tests I have used a variable regulated power supply, 0-30V output, 3A current limiting. Later I have used a 12V/2A power supply. (But you can use almost any 10-15V/1A power supply for this purpose).
Registered Member #1938
Joined: Sun Jan 25 2009, 12:44PM
Location: Romania
Posts: 701
mister_rf wrote ...
In order to power up a small DC fan you need to use a rectifier bridge. The purpose of the rectifier section is to convert the incoming alternating current from the AC power source to some form of pulsating DC. By the way, at this high frequencies some schottky diodes need to be used for. For example I have managed to modify a small mobile phone in order to be recharged wirelessly form the Royer oscillator. See a video here:
Yes but you still use a wire connected to the phone, so why not plug it to the wall directly?
The idea is to use a modified battery that also includes a small receiver coil, a capacitor and a fast rectifier.
Registered Member #4465
Joined: Wed Apr 18 2012, 08:37AM
Location: Bucharest, Romania
Posts: 145
There are no wires outside the phone. That’s a wireless charger. All items were included in the phone case = receiver coil + capacitor + schottky bridge rectifiers + 5V step-down converter (LM2678-5).
There’s only one major problem, because of the circuit high frequency (~1.6MHz) you need to place the receiver coil (that it’s inside phone case) very near to the transmitter coil.
Registered Member #4465
Joined: Wed Apr 18 2012, 08:37AM
Location: Bucharest, Romania
Posts: 145
Need to mention this sort of experiment was not properly prepared at that time. Normally, to get the best results, we may first try to adapt some sort of LC antenna into the phone case and second step to modify the transmitter frequency to match the receiver one. Otherwise it’s time consuming just finding proper capacitors to boost more energy.
Here are some phone pictures, (you can see this was not prepared for marketing ).
First a dc-dc converter assembly was squeezed in the place of the old speaker (no PCB, just wired on place, and the old speaker replaced by a smaller one). Second, a picture of the first coil I have made the initial receiving tests. And the last one, a picture of the new antenna made of some copper foil.
Registered Member #3680
Joined: Wed Feb 09 2011, 12:48PM
Location: Porto Alegre - RS - Brasil
Posts: 3
mister_rf wrote ...
I have tested this circuit and it works very well. In use : -STP60NF10 power MOSFET transistors -diodes: SR810 (100V/8A) and STTH3R02. -Rg = 68 ohms/3W , but later increased to 100 ohms /2W -Radio frequency chokes ~ 150uH. You can see the results here:
Did you used on the video project the 12 relay and the capacitor C7? This itens are on the schematic but I 'cant find it on the video.
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Miniature wireless power demonstrator
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