Well, in most designs the output is referenced to the AC neutral which still isn't safe for most consumer devices.
In these designs the only devices that need to be rated for full mains voltage are the charge pump capacitor and the diode. The electrolytic can be rated at just slightly above the zener voltage, i.e. 15V electrolytic with a 12V zener.
To further eliminate shock hazard a series resistor of about 1k ohm can be added in both the line and neutral lines and an additional series capacitor (10x larger than the pump capacitor) is placed serially in the neutral line to give DC isolation.
So the final circuit would consist of two resistors on the Line and Neutral connections, a charge pump capacitor, two diodes for the half wave charge pump, a zener, an electrolytic capacitor, and the Neutral isolation capacitor.
I only use these types of designs in primary side circuits which are isolated from secondary circuits.
Sure, this device is a half wave charge pump running at the frequency of the AC power source. During the negative half cycle the pump capacitor charges to -170Vpeak and the charge is then pumped to the electrolytic as the input AC voltage swings from -170Vpeak to +170Vpeak. The total charge pumped on every full cycle is q=c*deltaV where deltaV is 340V for 120VAC. The average current supplied is i=q*f. So for a 120V 60Hz source with a 0.1uF pump capacitor you can draw an average of i=120*2*1.414.60Hz*0.5uF or 10mA! The zener is used to limit maximum voltage at no load conditions.
For very low power loads this can be extremely efficient (>97%) The output voltage starts to collapse once the average current drawn by the device exceeds the average current that can be supplied by the charge pump.
While I'm glad to see that someone is actively working in the area, this idea is many decades old. About 20 years ago I obtained a sample kit from a vendor of the PZT and kynar type piezo films and the technical materials with the films gave formulas for computing the width, length and thickness of the films for creating voltage transormers. They gave many construction hints for increasing the output current and suggested operating at frequenccies greater than 500kHz. BTW, they are wonderful tweeters when connected to an audio amplifier. Here is a link to an IEEE artical on the history of Piezo ceramic transformers and filters. http://www.ieee-uffc.org/ultrasonics/jan1.pdf Doesn't mention the film based transformers though. Here is another link to an IBM text article describing kynar voltage tranformers from the late 60's. http://www.research.ibm.com/journal/sj/mit/section c/paradiso.txt
I bought mine off of Best Buys web site for $400 including the camera module, media modules. They shipped free to my house.
Lovely device and easy to use. Picture quality isn't so good in dim lighting but 1.3M pixel still pics outside are great. MPEG4 Video playback on my TV is really good, recorded video from camer module is OK (frame rate is not as fast as I'd like), MP3's sound awesome, etc.
Now I'm just waiting for the video feed MPEG hardware recorder module to come out.
The DTMF standard supports 16 tone pairs. Current keypads only use 12 of these and the * and # key are only used rarely, usually for voice mail commands.
Instead of having to dial an eleven digit number, why don't we start using the * and # or even the A,B,C, and D keys. (yes I know the telephone system uses A,B,C and D for other "internal" functions)
I'd much rather remember, and dial, a 6 digit hex number than an 11 digit decimal number. At least for dialing in New York City.
Oh, wait... I forgot, most people can't handle base 16 counting systems!
Why the heck are they worried about flammable alcohol in my computer when the stewardess will give me two shots of 100 proof vodka that burns quite nicely?
I've had a Nomad II for several years and recently upgraged to the IIc with 192Megs of flash on board. Luv it! Over 11 hours of continuous play on a single AA battery.
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Big deal, 3 birds a day get pasted by 7000 windmills. I'd bet that 7000 cats kill a hell of a lot more than 3 birds a day.
California ought to outlaw cats.
Didn't California recently make it illegal to use Master/Slave terminology in disk drives? They might as well make it illegal to own cats!
Well, in most designs the output is referenced to the AC neutral which still isn't safe for most consumer devices. In these designs the only devices that need to be rated for full mains voltage are the charge pump capacitor and the diode. The electrolytic can be rated at just slightly above the zener voltage, i.e. 15V electrolytic with a 12V zener. To further eliminate shock hazard a series resistor of about 1k ohm can be added in both the line and neutral lines and an additional series capacitor (10x larger than the pump capacitor) is placed serially in the neutral line to give DC isolation. So the final circuit would consist of two resistors on the Line and Neutral connections, a charge pump capacitor, two diodes for the half wave charge pump, a zener, an electrolytic capacitor, and the Neutral isolation capacitor. I only use these types of designs in primary side circuits which are isolated from secondary circuits.
Sure, this device is a half wave charge pump running at the frequency of the AC power source. During the negative half cycle the pump capacitor charges to -170Vpeak and the charge is then pumped to the electrolytic as the input AC voltage swings from -170Vpeak to +170Vpeak. The total charge pumped on every full cycle is q=c*deltaV where deltaV is 340V for 120VAC. The average current supplied is i=q*f. So for a 120V 60Hz source with a 0.1uF pump capacitor you can draw an average of i=120*2*1.414.60Hz*0.5uF or 10mA! The zener is used to limit maximum voltage at no load conditions. For very low power loads this can be extremely efficient (>97%) The output voltage starts to collapse once the average current drawn by the device exceeds the average current that can be supplied by the charge pump.
While I'm glad to see that someone is actively working in the area, this idea is many decades old. About 20 years ago I obtained a sample kit from a vendor of the PZT and kynar type piezo films and the technical materials with the films gave formulas for computing the width, length and thickness of the films for creating voltage transormers. They gave many construction hints for increasing the output current and suggested operating at frequenccies greater than 500kHz. BTW, they are wonderful tweeters when connected to an audio amplifier. Here is a link to an IEEE artical on the history of Piezo ceramic transformers and filters. http://www.ieee-uffc.org/ultrasonics/jan1.pdf Doesn't mention the film based transformers though. Here is another link to an IBM text article describing kynar voltage tranformers from the late 60's. http://www.research.ibm.com/journal/sj/mit/section c/paradiso.txt
I bought mine off of Best Buys web site for $400 including the camera module, media modules. They shipped free to my house. Lovely device and easy to use. Picture quality isn't so good in dim lighting but 1.3M pixel still pics outside are great. MPEG4 Video playback on my TV is really good, recorded video from camer module is OK (frame rate is not as fast as I'd like), MP3's sound awesome, etc. Now I'm just waiting for the video feed MPEG hardware recorder module to come out.
Hey, I bought an Archos Multimedia on Best Buys web page with the camera module and the two media modules for $400. Shipping included.
The DTMF standard supports 16 tone pairs. Current keypads only use 12 of these and the * and # key are only used rarely, usually for voice mail commands. Instead of having to dial an eleven digit number, why don't we start using the * and # or even the A,B,C, and D keys. (yes I know the telephone system uses A,B,C and D for other "internal" functions) I'd much rather remember, and dial, a 6 digit hex number than an 11 digit decimal number. At least for dialing in New York City. Oh, wait... I forgot, most people can't handle base 16 counting systems!
Damn! I remember when they were $250 a MB, course this was when a MB was 1024KB and not 1000MB. Ah, the magic of marketing!
Correction: Guns don't kill people, E=1/2mv^2 kills people
Why the heck are they worried about flammable alcohol in my computer when the stewardess will give me two shots of 100 proof vodka that burns quite nicely?
I've had a Nomad II for several years and recently upgraged to the IIc with 192Megs of flash on board. Luv it! Over 11 hours of continuous play on a single AA battery.