Buddi Posted October 27, 2006 Report Share Posted October 27, 2006 Hi, I'm working on a project where I'm desigining an AC dimmer (230V/1000W) with Electro magnetic compatibility. My idea is to involve IGBTs or MOSFETs instead of more conventional triacs... Do you think that this would be a good idea? If you have prior experiences please share... Regds, Buddi Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 27, 2006 Report Share Posted October 27, 2006 Hi Buddi,Welcomr to our forum. ;DA triac is made for AC. They are used in light dimmers to quickly switch the power on and off and they dim by changing the duty-cycle. Because they quickly switch, they don't get hot. The quick switching is bad for an electro magnetic load.IGBT's and Mosfets work on DC so two or an additional rectifier bridge are needed to switch AC, then it will work exactly like a triac circuit.I hope you are not thinking of using the IGBT's or Mosfets as a linear resistance. Then they will quickly overheat and fail. Quote Link to comment Share on other sites More sharing options...
Buddi Posted October 28, 2006 Author Report Share Posted October 28, 2006 Thnx very much... This is one idea that I intend to use as a benchmark. http://johboh.csbnet.se/____BINBOSFAX001.reedbusiness.com__c$__Program%20Files__RightFax__Gateway__IN__A628c412e-b8cf-4efe-a2bd-d6c8b9a99ada.TIFThere is some extensive heat dissipation as you have mentioned... and it seems there is some problem with gate triggering and the bulb flickers instead of steady dimming...I used IRF 540 MOSFET....Buddi Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 28, 2006 Report Share Posted October 28, 2006 Your link doesn't work so I cannot see the circuit. Quote Link to comment Share on other sites More sharing options...
ante Posted October 28, 2006 Report Share Posted October 28, 2006 Here it is: Quote Link to comment Share on other sites More sharing options...
Buddi Posted October 29, 2006 Author Report Share Posted October 29, 2006 thx... so what do you guys think...?I tried with different resistor and cap values, but didnt work... Quote Link to comment Share on other sites More sharing options...
Buddi Posted October 31, 2006 Author Report Share Posted October 31, 2006 Guys,I think I foud something...I did some analysis with the oscilloscope and found out that the cap. and the R6, R5 resistors that should determine the output does not work properly... then i did a slight modification by interchanging the R5 and R6 and now the dimmer is working... :DNow two small things to sort out...1. When I vary the variable resistor the illuminance is increaesd and right at the very end there is a slight dimming that occurs after the bulb has reached the full illuminance...2. There is a slight flickering of the output when put to the full power What do you guys think of these...???Buddi Quote Link to comment Share on other sites More sharing options...
ante Posted October 31, 2006 Report Share Posted October 31, 2006 AG,Can you see the circuit now? ;D Quote Link to comment Share on other sites More sharing options...
audioguru Posted October 31, 2006 Report Share Posted October 31, 2006 Hi Ante,It is an interesting backwards dimming circuit.R5 and R6 are in series so their position shouldn't make any difference. Quote Link to comment Share on other sites More sharing options...
Buddi Posted November 1, 2006 Author Report Share Posted November 1, 2006 that is something that i also couldnt understand... but it worked... ???the circuit didnt work until i decided to put 2 vaiable resistors for both R5 and R6 just to test with different values...And now I have left the circuit as that... yep, it cannot make any different theoritically, but it did...Buddi Quote Link to comment Share on other sites More sharing options...
audioguru Posted November 1, 2006 Report Share Posted November 1, 2006 Hi Buddi,I am glad you got it working properly. ;DYou adjusted the values of both resistors so that they match the value of the capacitor, and match the threshold voltage of the 4001 IC. Quote Link to comment Share on other sites More sharing options...
Buddi Posted November 1, 2006 Author Report Share Posted November 1, 2006 That may be the reason then...thx for showing it to me...Anyway as I mentioned it has some issues still...1. Very visible flickering once the bulb is given the full power2. Limited dimming range: The bulb dims...but I expect it to dim much more when I vary the resistance...I'm trying to find a way control the level of gate Quote Link to comment Share on other sites More sharing options...
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