About blanchae

Eugene Blanchard's Website
Calgary Alberta Canada
Jan. 9, 2009
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Natural born DIY, if there's a hard way to do something, I'll find it. Nickname: "cut twice and still too short". Abusing the web since 1993. I'm to blame for "Using the Internet for Education". Sorry
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  • Designing a Dual 40A PWM Speed Controller for Brushed Motors

    Very nice write-up, well done! Some things to consider: - When selecting MOSFETs, select RDs(on) to be the lowest value you can find. This will reduce the heat dissipation on the mosfets. Usually this will correspond with a higher Id(max) value.- You shouldn't immediately switch the direction from FWD to REV or vice versa. There should be a small idle period in between. MOSFETs turn on incredibly fast and if there is any capacitance charging or discharging in the circuit (stray or component) then there could be a period where the MOSFETs are still transitioning logic states and are in the analog region. If the MOSFETs are in the analog region then they are going to drop a LOT of current and dissipate a lot of heat consequently blowing. They fry fast too!- MOSFETs have an incredibly high input impedance Zin and the Gate is very static sensitive. The first thing that I do is to connect the Gate/Source resistor - this simple step will protect the Gate.Back in the 90s, I was in autonomous sumo robotics competitions and everyone said that you can't create a H bridge using MOSFETs. I thought that just didn't make sense and designed several circuits and posted them to the robotics newsgroups. After receiving countless emails asking questions, I posted the designs on my website: http://www.cadvision.com/blanchas/hexfet/intro.htm...Of course this is all 90s info and content.

    I've put a voltage divider instead of just a pull-up or pull-down resistor. This forces the Gate voltage to whatever voltage that I spec.

    I would be concerned with the internal capacitance of the Zener diode and its affect on the transition time Ton.

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  • blanchae commented on soilwork's instructable Heatsink for Diy laser engraver1 month ago
    Heatsink for Diy laser engraver

    Yes I agree, don't hold the piece with a glove on - use a vise or plyers. I put a bolt in the drill press plate and rest the part against it to stop it from spinning . A second point is that you should drill a pilot hole that is just bigger then the web thickness (chisel edge) which is the tip between the flutes. Then go to the final size. Slowly stepping up through multiple drill sizes dulls the drill bits.

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  • How to build a foam teardrop trailer. rot proof, well insulated and super lightweight

    My concern is the fire hazard with foam. It can burn very easily and when on fire, the ceiling melts in flaming droplets. The smoke can be deadly also. Test by lighting a small piece on fire. You can coat the outside with fiberglass to give it strength and to reduce the fire hazard.

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