Breezy

Hi all. Thank you much for the help you have given to me about PWM PWM_Speed_Controller.zip

Are you my Hero999 ;) ??? I wrote most of the following to reply to another post and the issues are similar, so I cut and paste this msg together. If I understand this right, the MOSFET should be turned totally on then totally off for a switched mode. Partially on is the linear mode and what causes excessive heat. The purpose of this circuit is for use in an electrolyzer a boyfriend is wanting to build. He knows even less than I do about electronics, but I said I would try to help him out, (I want to make him THE boyfriend, get my meaning? :D ). I am not supposed to say what it is for specifically, but the site I got these from are both about use for electrolysis in water to get H2O and that is apparently a hot - nasty - very much disputed use. This is not for water. Can you tell me what either circuit would need to be changed to make a switching mode operation for the MOSFET? :D And I can also say that the target is about 50 amps or so. Thank you Hero999

I am a new girl in electronics here and I hope this is the right place. I used to play with my grandfather when he worked on building electronics. I learned a lot about building PCB's, but not to much about theory or how electronics works for that matter. I can usually follow a schematic and get something built. I hope to learn more because this is fun for me, building anyway. I am in college now and do not take any electronics or related courses, so this is just a hobby for me. I found a circuit from a guy called "Zero Fossil Fuel" that is a PWM with constant current ....... parts???? And I found other similar circuits out there too. But this one has my attention cause I need a circuit that has constant current, but then I found another web site where a man says the "Zero Fossil Fuel" PWM is good, but has problems. This is what he says about the 1st attached circuit: The Circuit designed by "Zero Fossil Fuel" is better than normal PWM, however when it goes into the Current Limiting Mode, it operates in a Linear mode that causes the MOSFET's to Over-heat. So you require a VERY LARGE HEATSINK to try to keep it from overheating. This is where I run into a problem, I have no idea what all that means. And he says his design of the "Zero Fossil Fuel" circuit is modified and better working than the original Zero has. I attached both of these schematics to let you know what I am refering to. And this guy says he has a PWM circuit that does what the Zero one does, but with no heat or any other problems. Bit he wont let anyone know what that is and you can buy it but it is covered in resin or epoxy or some sort of thing. So my main question is can anyone explain what Current Limiting Mode is and what does operate in a Linear mode mean. And if you can answer those questins maybe you can give me an idea how to make the circuit so it does not have those problems. Thank you all, Brianna Rose