cfb_rolley
Well-Known Member
This is more to confirm that I haven't totally lost my marbles yet after cramming a stack of coding in to a single, already busy a long weekend (high chance those marbles are actually gone though).
Long story short I'm working on another data logger/flight computer and want to use a MOSFETs to trigger e-matches for ejection. On my previous data logger I use a reed switch and pull an output pin of the Arduino Nano to high at apogee. The reed switch flows +7.2V straight from the 2s lipo to the e-match, and this has worked perfectly. But, that's in low and mid power rockets, and reed switches do have a vibration and shock limit, so I want to change to using MOSFETs. Trouble is, when testing the new logger on a breadboard with the MOSFETs, it'll light up LEDs perfectly fine but will not fire an e-match.
The two MOSFETs I've tried using (just salvaged ones) are a STP16NF06 and a 24N60C3. When testing each of these, the both pass full battery voltage, but upon checking the current, I'm, getting just 40mA with the STP16NF06 and 190mA using the 24N60C3 - not enough to reliably fire an e-match. If I instead grab a second 2s lipo and use that to apply +7.2v to the gate, e-match fires instantly.
I probably don't quite have enough experience or understanding of MOSFETs to confidently state that I know why this is, but I believe my problem is gate threshold voltage. The STP16NF06 has a gate threshold voltage of 2v minimum, 4v max, and the other is 2.1v minimum, 3v typical and 4v max. The ESP32-S3 board I'm using only puts out 3.3v on the output pins, and while that's enough to allow some current to flow, this is only enough to light and LED but not an e-match, so I'd need to use a MOSFET with a lower gate voltage threshhold.
(...Should also mention test circuit):
esp output pin >>> gate
Drain >>> e-match pin 1
e-match pin 2 >>> 7.2v+
Source >>> Ground
10k resistor between gate and source
Thoughts? Is my thinking correct, or have I got some more learning to do?
Long story short I'm working on another data logger/flight computer and want to use a MOSFETs to trigger e-matches for ejection. On my previous data logger I use a reed switch and pull an output pin of the Arduino Nano to high at apogee. The reed switch flows +7.2V straight from the 2s lipo to the e-match, and this has worked perfectly. But, that's in low and mid power rockets, and reed switches do have a vibration and shock limit, so I want to change to using MOSFETs. Trouble is, when testing the new logger on a breadboard with the MOSFETs, it'll light up LEDs perfectly fine but will not fire an e-match.
The two MOSFETs I've tried using (just salvaged ones) are a STP16NF06 and a 24N60C3. When testing each of these, the both pass full battery voltage, but upon checking the current, I'm, getting just 40mA with the STP16NF06 and 190mA using the 24N60C3 - not enough to reliably fire an e-match. If I instead grab a second 2s lipo and use that to apply +7.2v to the gate, e-match fires instantly.
I probably don't quite have enough experience or understanding of MOSFETs to confidently state that I know why this is, but I believe my problem is gate threshold voltage. The STP16NF06 has a gate threshold voltage of 2v minimum, 4v max, and the other is 2.1v minimum, 3v typical and 4v max. The ESP32-S3 board I'm using only puts out 3.3v on the output pins, and while that's enough to allow some current to flow, this is only enough to light and LED but not an e-match, so I'd need to use a MOSFET with a lower gate voltage threshhold.
(...Should also mention test circuit):
esp output pin >>> gate
Drain >>> e-match pin 1
e-match pin 2 >>> 7.2v+
Source >>> Ground
10k resistor between gate and source
Thoughts? Is my thinking correct, or have I got some more learning to do?
