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Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hi all,
I updated the faq with some debugging tips.
Jifficoil: If the receiver capacitor is overheating, do the same for it what I did on the transmitter - use several smaller caps in parallel! ALthough it gets hot in mine too, 40-50 degrees C is still ok. The wireI used for the receiver loop did get hotter though!
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
matilda wrote ...
What is the efficiency of this demonstrator and how can I measure it?
Hi matilda,
the best way to measure the efficiency of the setup would be to rectify the output, insert amp and volt meters suitably and compare the voltage and current product to one on the input. I've only made rough estimations so far by comparing the brightness of the bulb to it's brightness at rated voltage.
Hello there, I got a coupleof questions: 1. how hot will the coils become?? 2. will RFID devices in the surounding be destroyed?
also if this is the case how would i tune the original design that it only transmits For about 3/4cm and is that even posible? i need a device that wirelessly charges a device trough its airtight casing. i need about 500mA inside the device more is welcome ofc.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Hi lightscape,
1. I used 10mm pipe in my transmitter which was overkill enough not to get hot much by itself. It seemed to get warm by conducting some heat from the circuit board and heatsink more than from actual ohmic losses in it. I estimate it gets to 30 deg C or so. You could use 6mm copper pipe just fine. The whole circuit needs a lot of ventilation for mosfets and resistors though, which tend to get much hotter.
The receiver coil was of 3mm solid copper wire and got quite hot, probably up to like 50C or so. Never measured it correctly but it is painful to touch it after left running for a while. I'd recommend 4mm or 6mm copper pipe to be used there instead of wire.
2. Very unlikely, actually. If you have some RFID's to trash, you could try it yourself - I didn't. But after playing for a while with the circuit I realized it will do little harm to anything electronic that doesn't contain LC circuits specifically resonant at operating frequency of the oscillator (1.5Mhz). RFID's working at 134kHz will absorb little power from 1.5Mhz field, and they have built-in zeners which clamp the input voltage in case it goes over their ratings. Survivability depends mainly on ratings of this zener.
The circuit could probably become an efficient rfid destroyer if it operated at RFID frequency, or was just scaled up to many times it's original power.
also if this is the case how would i tune the original design that it only transmits For about 3/4cm and is that even posible? i need a device that wirelessly charges a device trough its airtight casing. i need about 500mA inside the device more is welcome ofc.
If you wanted the oscillator to start transmitting only at 4cm you would need to do it actively (infrared sensors?). You specified just the current not the power - though over just 4cm you could transfer like 10 watts quite efficiently.
Sorry about posting only the current the power thats needed in the device is between 12 an 15V, so not dramaticly much. Also i can't make a infrared loop to activate the device since the entire case is filled with oil, and must be pressure tight. Implementing an IR window can be a bottleneck in the designso any other idues to remotely get the device on? I was thinking of a simple LDR n the base socket but the problem then is that every night the device will be on also a simple switch is mechanic and i rather avoid that.
If i make the receiver coil thicker that leads to less temp i take it?
secondary question is the power supplys and LDO drivers of internal parts of the internal circuitry uses 10mH and 470mH chokes can this be a problem?
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Lightscape wrote ...
Sorry about posting only the current the power thats needed in the device is between 12 an 15V, so not dramaticly much. Also i can't make a infrared loop to activate the device since the entire case is filled with oil, and must be pressure tight. Implementing an IR window can be a bottleneck in the designso any other idues to remotely get the device on? I was thinking of a simple LDR n the base socket but the problem then is that every night the device will be on also a simple switch is mechanic and i rather avoid that.
If i make the receiver coil thicker that leads to less temp i take it?
secondary question is the power supplys and LDO drivers of internal parts of the internal circuitry uses 10mH and 470mH chokes can this be a problem?
Hi,
I'm not sure if I understood what exactly you wanted. Why do you want to ''reduce the range'' to 4cm anyway? What's wrong with simply implementing an UVLO circuit which turns the charger off if the receiver voltage falls below useful value?
I don't think the chokes will be a problem, although I'd still shield the more sensitive analog parts of the circuit. And yes, make the receiver loop thicker. 4mm refrigeration copper tubing would work great.
Making it about 4cm eliminates all possible problems that could happen in seroundings jittering tvs radio scrampling hysteresis loops on other frequentsies etc it will be a tiny transmitter that cant do any"harm" due to its limited range. 10cm is also good enough but wat i dont want is a field of 1m radious where transmissinon on 1.5Mz will be lost.
Registered Member #89
Joined: Thu Feb 09 2006, 02:40PM
Location: Zadar, Croatia
Posts: 3145
Lightscape wrote ...
Making it about 4cm eliminates all possible problems that could happen in seroundings jittering tvs radio scrampling hysteresis loops on other frequentsies etc it will be a tiny transmitter that cant do any"harm" due to its limited range. 10cm is also good enough but wat i dont want is a field of 1m radious where transmissinon on 1.5Mz will be lost.
Hi,
making the circuit turn off at a distance greater than 4cm is absolutely no cure for interference. Only a faraday cage around the whole setup is!
The tank circuit circulating tens of amps in Mhz range is still a formidable radio transmitter despite it's small size in relation to wavelength, and the signal could likely be detected from kilometers away rather than meters (despite total radiated output might be just a fraction of a watt) The best way to prevent these problems is choice of the operating frequency. 1.5Mhz would be a poor choice if you don't want to interfere with AM radio's nearby. And you would probably want to avoid frequencies used by RFID devices as well.
TY, that cleared up so many things. also indicates u design (wich is awsome i have to admit) won't be the best sollution in my project its always good to know such a thing before starting
TY for the advices and gl in further projects
PS if know any goood articles other then the ones posted plz let me know
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Miniature wireless power demonstrator
