Back to Home

ATM Forum Message

Forums: Atm · Astrophotography · Blackholes · Blackholes2 · CCD · Celestron · Domes · Education
Eyepieces · Meade · Misc. · God and Science · SETI · Software · UFO · XEphem
RSS Button

Home | Discussion Forums | Amateur Telescope Making | Post
Login

Be the first pioneers to continue the Astronomy Discussions at our new Astronomy meeting place...
The Space and Astronomy Agora
Power Converter

Forum List | Follow Ups | Post Message | Back to Thread Topics | In Response To
Posted by Robert May on February 9, 2002 21:59:52 UTC

The Modified Sine Wave is usually a sort of square wave where the power isn't on all the time over the 1/60sec. cycle. If you compare the waveform to the true sine wave, you will see that when the sine wave hits about 70% of it's max voltage, the power goes on with the modified sine wave. The power goes off again at the 70% point where the true sine wave is dropping and then turns back on the opposite polarity again for the second half of the cycle at the 70% points again.
This technique gives about the same resistive power and peak voltage (~180V) that a 120V sine wave gives.
FWIW, those inverters aren't that accurate with the 60Hz (and are often quite temp sensitive) but to someone who knows electronics, you can easily add a speed paddle box to control the actual frequency of the output section.
If you have the lightweight ones, there's two sections to the inverter - a 12V - 180V inverter (running at a very high frequency) and then a H bridge switching circuit that drives the output line at the 60Hz. The chip that controls the output driver has a frequency determining circuit in it that can be modified easily. With these designs, I usually go to 10Hz and 120Hz for the two button controls of fast and slow and a pot to control the exact resistance that the chip wants to put out 60Hz.
I might also note that the output is usually fully isolated from the input and the ground pin on the 3 prong connector is tied to the ground of the 12V input.

Follow Ups:

Login to Post
Additional Information
Google
 
Web www.astronomy.net
DayNightLine
About Astronomy Net | Advertise on Astronomy Net | Contact & Comments | Privacy Policy
Unless otherwise specified, web site content Copyright 1994-2024 John Huggins All Rights Reserved
Forum posts are Copyright their authors as specified in the heading above the post.
"dbHTML," "AstroGuide," "ASTRONOMY.NET" & "VA.NET"
are trademarks of John Huggins