| T O P I C R E V I E W |
| tsikscar |
Posted - Mar 08 2011 : 6:50:41 PM
Hi all,
I need help with my design. I am designing a pure sine wave inverter to produce 60 volts ac from 12 volts dc. I used a wien-bridge for the oscillator section and calculated the capacitance and resistor values to give me a pure sine wave output @ 51 hz. My problem now is how to proceed from here. I tried connecting a transformer directly to the output of the oscillator circuit and connected a resistor as load for simulation purposes. The amplitude and voltages have gone down.
Also when i was running the oscillator simulation on it's own, it takes some time before it gradually builds up the amplitude until it gets to a pure sine wave, why is this?
Thanks.
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| 15 L A T E S T R E P L I E S (Newest First) |
| elective |
Posted - Jun 28 2011 : 06:03:13 AM
Dears infact TL494 is not meant for pure sine wave inverter this may use for modified sine wave so dont wast your time, for pure sine wave you need SPWM technique |
| elective |
Posted - Jun 28 2011 : 05:57:19 AM
Dears infact TL494 is not meant for pure sine wave inverter this may use for modified sine wave so dont wast your time, for pure sine wave you need SPWM technique |
| tsikscar |
Posted - Apr 25 2011 : 12:41:04 PM
Fair enough. |
| wasssup1990 |
Posted - Apr 25 2011 : 08:56:24 AM
quote:
Originally posted by tsikscar
You may have a point but sometimes some people find it easier to understand from a person explaining than reading text because they will be responding to specific questions. Some people take longer than others to fully comprehend hence the likes of you may find them annoying.But i don't believe anyone goes out to deliberately annoy people in a public domain like this one. On the contrary they come for whatever assistance they can get, myself included. Hope you understand.
Oh well if they are specific questions, then that's fine. But Audioguru himself told you to go and read a book. I mean if you are putting your MOSFETs in upside down then it shows you haven’t bothered to understand the basics of how a MOSFET works. That's something you don't need a forum for.
I haven’t found anyone deliberately annoying people in a public domain, except on YouTube.
I remember when I was doing my Advanced Diploma in Electronics Engineering. I enjoyed helping others as I tended to be so far ahead of everyone else that it was a nice feeling to offer my help when I wasn't busy. However I also know what it's like to be asked the same questions repeatedly. It's friggin annoying!.. but you get a laugh out of it, like I admittedly do here.  Poor Audioguru. 
I have to say that the teachers really appreciated my help. 
I'm just sticking up for Audioguru, that's all.
I can only offer my help sometimes regarding electronics on this forum because I have other things to do that keep me very busy, but most of the time I am at a computer. I don't have the time to go and do someone else’s research.
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| tsikscar |
Posted - Apr 25 2011 : 08:13:12 AM
You may have a point but sometimes some people find it easier to understand from a person explaining than reading text because they will be responding to specific questions. Some people take longer than others to fully comprehend hence the likes of you may find them annoying.But i don't believe anyone goes out to deliberately annoy people in a public domain like this one. On the contrary they come for whatever assistance they can get, myself included. Hope you understand. |
| wasssup1990 |
Posted - Apr 25 2011 : 07:47:47 AM
quote:
Originally posted by tsikscar
It's sad that you feel that way Wassup1990. What Audioguru and a lot of other people are doing on these forums is very much appreciated by many people. We are all not gurus in electronics but through these forums and sometimes making a fool of one's self one will end up understanding much much more of this vast field of electronics.These forums should be for electronics lovers, both experts and novices, i believe.
Audioguru and others, i am not alone in appreciating what you do on these forums. Please don't be discouraged, you are doing a great job.
I agree and doubt he will get discouraged. He knows how much I appriciated his help several years ago when he was helping me on a project. He has a lot of patience. I like electronics as well, but there is a point where I would get tired of being asked the same questions. It just seems that some people who come here are just plain lazy and can't be bothered to look up the information for themself. Audioguru isn't the source of all information. You've got millions of webpages to look at. He also seems to get a little annoyed with some of the new commers here, where I see him repeating himeself. Now does that sound sad, or does it sound more like I am supporting him? |
| tsikscar |
Posted - Apr 25 2011 : 04:03:20 AM
It's sad that you feel that way Wassup1990. What Audioguru and a lot of other people are doing on these forums is very much appreciated by many people. We are all not gurus in electronics but through these forums and sometimes making a fool of one's self one will end up understanding much much more of this vast field of electronics.These forums should be for electronics lovers, both experts and novices, i believe.
Audioguru and others, i am not alone in appreciating what you do on these forums. Please don't be discouraged, you are doing a great job. |
| wasssup1990 |
Posted - Apr 25 2011 : 01:29:09 AM
John, don't you get sick of repeating yourself? I mean... Every time I come up here it seems like the same thing is happening over and over again. You have a lot of patience with these noobs.  |
| audioguru |
Posted - Apr 24 2011 : 5:56:54 PM
You need to read about how a Mosfet works. Both of your Mosfets are upside down (they don't do anything and their internal diode is conducting all the time) and have nothing driving them.
You also need to read about the LM339 quad comparator or LM393 dual comparator because their output is just the collector of an NPN transistor that pulls down a negative voltage and you must add your own pullup resistor.
I don't use an inverter because my electricity is reliable. I have never seen a schematic of a good pure sine-wave PWM inverter. |
| tsikscar |
Posted - Apr 24 2011 : 3:40:37 PM
Hi Audioguru, i have tried the mosfets in the configuration shown but it seems not to work.I calculated the frequency for 30KHz but on simulating can only get about 8KHz. But being low power i suppose this will have to do? Can you please sent me a circuit that works i can use for the output stage( from comparator into the mosfets/amplifier? Also i have at my disposal 2 BUZ11 mosfets and a TIP 2955/3055 complmentary BJT pair. Can i use them in anyway in the output stage.Does this stage require a transformer? Please help me cross the finishing line. Anymore advice is welcome. Thank you very much, you have been a massive help so far.
Download Attachment:  mosfets1.PNG
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| tsikscar |
Posted - Apr 20 2011 : 5:44:34 PM
Thank you very much Audioguru. |
| audioguru |
Posted - Apr 19 2011 : 8:48:05 PM
1) Throw away the old 741 opamp and replace it with a proper comparator iC like an LM393 dual comparator.
2) Increase the triangle waveform to 30kHz using a faster opamp like a TL081 or MC34071.
3) The output of the comparator can drive complementary Mosfets that feed the LC filter. |
| tsikscar |
Posted - Apr 19 2011 : 4:04:27 PM
What can i do Audioguru please?i want to finish this circuit. |
| audioguru |
Posted - Apr 19 2011 : 08:33:04 AM
I saw your very fuzzy DOC file on another website.
Did you know that a lousy old 741 opamp is 43 years old and has trouble above only 9kHz? Most opamps made in the past 30 years go perfectly to 100kHz.
In your schematic I cannot see at what DC voltage the inputs of the 741 opamp are biased.
It looks like your PWM carrier is only 2kHz (so it will be very noisy) instead of 20kHz to 200kHz.
Your circuit with Mosfets and an extremly slow LM324 opamp will not work. |
| tsikscar |
Posted - Apr 19 2011 : 07:47:58 AM
I have resubmitted schematic using a different format now.
Download Attachment: untitled 1.PNG
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mosfets1.PNG
untitled 1.PNG