Bdale answer a similar question when I asked about the TeleMega last year. Here's the discussion:
> I've read thru all the documentation, nice job on the manualBTW, but I'm >wondering what> the current rating is on the FET outputswitch. An unrestricted > Lithium battery can pack quite a punch.Should I be adding a current > limiting resistor to protect the FET? The FETs we use can pass 19A continuously and40A pulsed. At our default firing time of 50ms, we're somewhere in themiddle of that range. If you have a 4.0V battery and a 1Ω igniter, themaximum current you'll deliver is only 4A, and that ignores all of theother resistance in the path (connectors, switches, screw terminals,wires, the FET itself (0.02Ω)). You'd have to find a way to get theresistance below 0.21Ω before you'd even reach the continuous currentcapacity of the FET. Even with a 12V pyro battery, you'd need aresistance below 0.63Ω. To add to what Keith said on the subjectalready... Even if you put a dead short on the igniterterminals of one of our boards (not recommended, but it happens),there's always some series resistance in the wiring itself, circuit boards,screw terminals, the FET channel "on" resistance, etc. Andour pyro circuit, which is designed to throttle the energy delivered toactive devices just enough to keep the processor from crashing has theinteresting side-effect of acting faster when there's a dead short on theigniter terminals, limiting the total energy delivered and thushelping to protect the FET which never really has time to warm up. > Should I be adding a current limitingresistor to protect the FET? No. I can't remember ever seeing a board comeback with a FET blown in normal use. It's just not an issue. By the way, bench testing I did myself with agood HP scope and some commercial e-matches a few years ago showed thatthey usually fired within about 13 microseconds. That's why wethink 50 milliseconds is more than enough on-time... but we made itconfigurable for those who have weird igniters, or are using our boards toswitch power to some other downstream device. Bdale -----Original Message----- From: GÖKBÖRÜ ROKET <[email protected]> To: altusmetrum <[email protected]> Sent: Thu, May 2, 2019 1:12 pm Subject: [altusmetrum] Gökbörü Rocket Team Hello, What is the maximum output ampere rating of the telemetrum v2 card?_______________________________________________ altusmetrum mailing list [email protected] http://lists.gag.com/mailman/listinfo/altusmetrum
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