The cheapest mosfet anti spark switch build ever, hopefully

[jonisingt35r]

ok here goes after a lot of research, my chepo diy build of anti spark switch a bear bones design, no pcb!
looking for about 100amps ish, with a fuse. going to base it on vedder design seem to work ok.
3 mosphets IRFS7530-7PPBF N-Channel MOSFET, 240 A.
4.53 pounds.

[SeanHacker]

This is definitely bare bones dude. You’ve literally just mentioned the words antispark.

[Agressivstreetlamp]

[jonisingt35r]

from what i read, loop switches work quite well

[Agressivstreetlamp]

Loopkey is really the only 100% reliable method.

Every antispark switch i’ve read of has had issues.
eventually one will come that works im sure

So go forth young man, and forge the way to a new era

[Andy87]

TIE/ad x1 evolution | Backpack MTB | Development Platform

Playing around with my loop key at work, I decided to open it up and check the solder joints, only to find this. Now I’m wondering if this is why I felt the sudden power loss last time when I thought the batteries were stuffed. I’m going to have to find a better way of doing loop keys. [image]

Nothing is perfect 100% is a strong claim

[Agressivstreetlamp]

Heres a question:

Does anybody know the internal workings of the xt90s ? Like how does it suppress the spark?

[jonisingt35r]

fitted link bars to drain and source of mosphets.
heatsink, components, and connectors to follow

[Agressivstreetlamp]

are you diode connecting these fets?
whats your schematic>

[Agressivstreetlamp]

@Andy87

100% is a strong claim

[jonisingt35r]

going to use this one

[Gamer43]

Change r2 to be 100k and add a termination resistor.

[jonisingt35r]

what a 10k across the zenner?

[b264]

@Agressivstreetlamp

Does anybody know the internal workings of the xt90s ? Like how does it suppress the spark?

Yes. These two posts shed some light on that. Ask in the loopkey thread if you want more info

Tackling the anti-spark problem (Title by a good friend)

Most “inrush limiter circuits” fail because they are operating in linear mode during inrush. It’s a design limitation on almost every one. Imagine a FET is a resistor with a variable resistance. When it’s “off” the resistance is [nearly] infinity and when it’s “on” the resistance is [nearly] zero. That’s all fine and dandy until you add capacitors to the load, like the filter capacitors on VESC and other ESCs. Right when it turns on, it’s effectively a momentary short circuit with [not really…]…

How to make an XT90 Loop Key

Arguably, the most reliable way to control power to an ESC [pair] is to use an XT90S loopkey. [20190219_024916][20190219_024931] It may not be the prettiest or the shiniest or the most foolproof, but it probably will outlast almost any other way if done correctly, and it’s certainly the cheapest. This does have antispark characteristics if you use the “XT90S” instead of the “XT90” variant of the female connector. You definitely don’t want to use the female XT90. Essentially, you make “a k…

[jonisingt35r]

or does design work better?
sorry this one
https://drive.wps.com/d/ABtXKk707MEc45aMvIqdFA
[File]Antispark Rev3 (1) - Copy.pdf

[Agressivstreetlamp]

ummmmmmmm i dont have access to your pc

[Darkie02]

From what I understand the inrush to charge the capsitors on the VESC is what blows the anti spark and if I rember right there was a post saying that was over 1kA. Could you not just double up the mosfets to make it more reliable? Put 3 more on the back or some thing? I may be completely wrong and that wouldent work for some electronics reason.

[Gamer43]

You use an RC timing circuit to limit in rush current.

Or an expensive power resistor precharge network…

[Agressivstreetlamp]

You could potentially just stack fets intil it works.
the real problem is the lack of precharge circuitry

[Gamer43]

Flipsky tried to stack 10 MOSFETs glued to a heatsink and it still failed.