RE: Opensource CDI ignition
I found the following device available in small quantities from digikey FDD3672 made by Fairchild. Vds 100v rdsON 28mOhm at 44 amps with Vgs 10v. I know the Vgs isn't great for you guys who want to run on 5 v but I am running on 12v so it is fine for the LT3750 which drives the gate to Vcc-2v during normal operation. BTW I have my inverter built from your desigh BIGBOAT, it is running and I'm getting plenty of output voltage with it running at about 30KHz but the efficiency is not too great. It might be due to the core I am using which is an amidon FT-82-43. the -77 material would probably be better at 100 KHz or lower but all I had was the -43 material. Let's see what the LT3750 can do. It is supposed to deliver 90% eff or so......
Posted on: 2/17/2009 7:35 PM by Author "Phatburner" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=8488117

RE: Opensource CDI ignition
Anybody made any progress on the inverter using LT3750 yet? I got my parts now but I didn't realize the FET I bought is impossible to solder by hand. All the connections are on the bottom. How do they solder those?? Anyways I am trying to get a different FET that meets the requirements. Vds ~100v and Rdson ~20mOhm. Not so easy.
Posted on: 2/17/2009 2:29 PM by Author "Phatburner" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=8487034

RE: Opensource CDI ignition
Hi Bigboat; 6 Hours on a 2 Ah battery means an average current of 333 mA. On 6 volts 330 mA is 2 Watts right? This seems to be a decade lower than the value I figured before. Did I make a mistake on the math? Joules = wattsxseconds. 12000 rpm would be one spark every 5 msec. 90 mJ per spark means that 0.09 J / 0.005 sec = 18 W?? What did I miss here? J
Posted on: 2/3/2009 5:47 PM by Author "Phatburner" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=8434916

RE: Opensource CDI ignition
Hello everyone; I found this forum while looking for information on home made CDI. I want to thank those who have done so much work and for sharing. I would like to join in the development work with the LT3750 and am ordering it along with the DCT20EFD transformer made by TDK which is available from the local supply. I am surprised you guys can run a CDI from batteries as I did the scratch pad calculation to reveal that with 80mJ spark at 12000 rpm that means 16 watts if the efficiency is 100% so it must require around 20 watts from the battery. This is no small power and I am wondering if your engines have a generator?? Joe
Posted on: 1/8/2009 12:05 PM by Author "Phatburner" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=8334272

RE: Opensource CDI ignition
Hi Bigboat; I have been reading this forum and the related materials. Thank you for all your work and sharing. I am trying to find out what is the frequency of the free running oscillator in the inverter? Does it run fast enough to allow triggering of multiple sparks?
Posted on: 10/9/2008 8:58 AM by Author "Phatburner" in the forum "Engine Conversions"
http://www.rcuniverse.com/forum/fb.asp?m=8032876