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  1. hericlj

    Low-pass Filter?

    Thank you very much.....
  2. hericlj

    Low-pass Filter?

    Yes...I need that powered all the time. And as I was using a step-down transformer with a bridge rectifier to power the circuit...could I just feed the positive output of the rectifier to the transformer center tap? Cheers
  3. hericlj

    Low-pass Filter?

    No. It connects to the switched +12V side of the on-off switch. ...So what I did was to connect the center tap of the transformer to the positive node of the rectifier...How wrong was that? Is that the problem to my inverter? Could you tell me more about the switched +12V side of the on-off...
  4. hericlj

    Low-pass Filter?

    Hi, thank you so much for your help....For me, to  make the inverter seems like an endless process... Just reviewed the above post you replyed a few days ago...I just had the weird feeling maybe I did something wrong on the circuitry as well... You said that the circuit doesn't need to be...
  5. hericlj

    Low-pass Filter?

    Cheers.... I just found one in local supply...Could you have a look if it would be ok? http://www.farnell.com/datasheets/39823.pdf The online stor is: http://nz.farnell.com
  6. hericlj

    Low-pass Filter?

    oh....really.... I looked at some online electronics stores and they have transformers which are 100VA and have 2 0-12V at secondary...I only need the inverter to power a single incandescent lamp so i think 100VA should be enough for me... How do I know which type of transformer with two 12V...
  7. hericlj

    Low-pass Filter?

    Hi....Now I know why the inverter didn't work....Thank you... Could you suggest any specific transformer that I could use? I am afraid I would pick the wrong one again....And my project is close to the due day....:( I am in New Zealand, and the two large supply are either Jaycar, or RS...
  8. hericlj

    Low-pass Filter?

    sorry, i made a mistake. the transformer is rating at 60VA... I just did the measurment, the 0V terminals are not conneted together, nor they are to the frame...
  9. hericlj

    Low-pass Filter?

    Hi, thank you.... the transformer i am using is a 0-15V(multi-tapped)@2A 30VA...According to the specification, it is a type 2156 transofrmer. I can't find the data sheet...But I'll copy the specification from the supplyer here: 0 - 15V (Multi-Tapped) @ 2A 30VA - Type 2156 Transformer...
  10. hericlj

    Low-pass Filter?

    Hi...sorry I still have problem in the inverter circuit... This time i put a rectifier circuit and used the main supply to power the inverter so that current limit won't be a problem. But still, when I switched it on, nothing comes out. The transformer is shorted between one wire's 12V and the...
  11. hericlj

    Low-pass Filter?

    Thank you so much....:) Actually when I did that experiment last week, I didn't connect any load to the transformer, and I was using those 3A(max) DC Power Source to power this circuit....So when I switched it on, the power source reaches its limited output current and wouln't give 12V out....I...
  12. hericlj

    Low-pass Filter?

    Hi Audioguru: Thank you for your help...Sorry, I am a begginer in power electronics, so actually i don't know what a center-tap step up transformer looks like. I bought one with 240VAC primary  and two 12V, two 9V, two 0V output terminals at secondary, and thought I could use it to step up the...
  13. hericlj

    Low-pass Filter?

    OK.  This is the one I build my circuit. Do I common ground the two 0V terminals of the transformer and connect it to 12VDC? The collectors are connected to the 12V terminals of the transformer, am I right? Thank you....
  14. hericlj

    Low-pass Filter?

    sorry, still no output...When I connected the transformer to the collectors of those transistors. They are shor-circuited.
  15. hericlj

    Low-pass Filter?

    oh...Thank you very much... Now I know why I can't get anything from the circuit...hehe~~~ One more thing? Just wondering how does the opamp work? Is it functioning as a voltage follower? I thought the input to the opamp is 12V square wave and then the opamp should not be operating at its...
  16. hericlj

    Low-pass Filter?

    I used the 500W one...Well, I guess maybe I have some problems in connection or something. Thank you :)
  17. hericlj

    Low-pass Filter?

    Hi...I 've just built the 500W inverter circuit as part of my final year project... Without connecting the circuit to a transformer (floating the circuit output), am I supposed to get 24VAC measuring between the collectors and the 12VDC? 'cause I couldn't get anything from that... TNX
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