Esp8266 arduino rgb led strip10/4/2023 or get one that will turn on with 5V on the gate (again, RdsON specified for Vgs=4.5V in the datasheet) and use a 74HCT logic gate to translate 3V3 logic levels to 5V and drive the gate. So a MOSFET can be driven at low frequencies, like your PWM, from a low current microcontroller GPIO without trouble.Įither get a MOSFET that will turn on fully with 3V3 on the gate, which is recognizable by a RdsON specification at this voltage or lower in the datasheet. TO-220 is overkill, but if you don't like SMDs, there are many in this package too.Ĭontrary to BJTs, MOSFETs don't have low current gain at low Vds: if there is enough voltage on the gate to turn it on, it turns into a resistor whose value is its RdsON. There are a lot of 50 cent MOSFETs that will do the job, with a RdsON below 50 mOhms, in convenient packages like SOT-23 or SO-8. There's no way to make this work with a 2N5550. This means your transistor isn't getting enough base current, so it isn't fully on, and its Vce is much higher than it should, so it gets hot. In saturation mode, don't expect a current gain higher than 10. The saturation characteristics aren't specified for more than 50mA, and the current gain will be extremely low anyway. As I've just read the transistor part number from the side of the component and then searched for the datasheet, is it possible that I've got a different spec'd device?Ħ00mA with a 2N5550? That's wildly optimistic. Is it normal/OK for transistors to get hot when operating within their limits?.Is the way that I've designed the circuitry reasonable/correct?.I'm just a hobbyist, but from what I can tell, the transistor should be able to handle 600 mA from collector to emitter (at least that's how I've interpreted the data-sheet). I've put my multimeter in series with the collector of the transistor and the cathode of the LED to measure the current draw and it's reading 150 mA. My issue is that the transistor on the red channel is getting quite hot, too hot to touch for more than a few seconds. This is the value I need to make each channel appear the same brightness. You may have noticed that the resistor value on the base of the transistor ( you can find the data-sheet here) driving the red channel is lower than the others a lot lower. I can PWM each channel and fade between colours as I need. That's my circuit, although it's an RGB LED strip that I'm driving, rather than three individual LEDs. Simulate this circuit – Schematic created using CircuitLab
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