Transistor vs mosfet7/30/2023 ![]() ![]() Voltage and other specs also listed so may come in handy for other DIYers.Ĭonversion from my database wasn't perfect. These were only a fraction of the ones from my day job long time ago but most likely to be of hobby interest now. Same thing couple times before so thought it might be a good idea to put up a list here. PI_SETUP.JPG (59.18 KiB) Viewed 2542 times RELAYS_TRANSISTORS.JPG (96.69 KiB) Viewed 2542 times MOSFETT.JPG (23.82 KiB) Viewed 2542 timesĬouple days ago someone offline asked what parts were actually tested with that relay circuit. I'll put scope snapshots in separate posts to illustrate subjects clearer. The pot allows me to adjust drive current which, not surprisingly, turns out to be very important for the BJTs. It has the advantage of not needing a series gate resistor. There is no reason that you shouldnt be able to use an N-Channel MOSFET as well. With a NPN transistor you would need to add a series base resistor to limit the current into the base. Chose to wiggle GPIO14 (pin 8) because of convenient proximity to 5v and ground. Depending upon the transistor gain the base drive current requirement could be 10mA or more. Last is a random diagram downloaded from google showing the basic test fixture. A collection of cheap and common 5v chinese relays and to220/to92 bipolar/MOSFET transistors. Next pic has a few examples of the relays and transistors used out of the many dozens I tried. Turns out they don't really have to be that nasty (even with bipolar) but we'll get to that. No problem getting those same horrifically noisy traces using the setup shown below in first photo. It's been a couple years since last working on this stuff so first order was to get up to speed reproducing Brandon's excellent scope captures using NPN transistor. For some odd reason there is huge resistance to abandoning the classic junction transistor circuits so popular back in the late 60's, early 70's. It quickly took on a life of it's own out here in the real world with some animated back-and-forth with a couple of my ham radio pals. This follows up on some interesting discussion in other threads on driving relays, EMF, and RFI. It's the only time with access to both hobby equipment and internet at the same time so here we go. so Friday night and as usual no game or early weekend partying for me. ![]()
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