LED fade on off improved with NPN BJT improved capacitor controlled by push button switch circuit
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- เผยแพร่เมื่อ 25 พ.ค. 2020
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Capacitors are an easy way to slowly change a voltage and thus current. Doing so directly to control an LED brightness while being turned on and off isn't near as effective as using the capacitor to control how well an NPN bipolar junction transistor (BJT) is conducting with an LED at it's collector.
#electronics #NPN #transistor - วิทยาศาสตร์และเทคโนโลยี
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Just like all of your videos, that was fun.😊 I like the way you teach.😊
Glad to hear, thanks for watching!
man, your vids are awesome. Neat little interesting chunks of information to squeeze in between my daily routine. Addictive... (thumbs up)
Glad to hear! Thanks for watching!
are there transistor where the base can be saturated to about .7 volts. it seems all transistor wont give full current flow until about 1.5 volts
What is value for 12V ?
Hi sir can we use 3.7v lipo battery with this circuit to do fade on off led effect ?
Won't hurt anything, many LEDs need about 3 volts to light brightly, so 3.7V won't be enough to power some circuits designed for 5V.
How come the cap doesn't charge to Vcc when the switch is closed?
Also, would the Cap charge to 50v if you kept the switch closed for long enough?
Thanks,
Capacitors only charge to the voltage that you apply to them. Charging through a resistor takes time, and so does discharging through a resistor. They charge/discharge based on current flow, and resistors reduce current flow.
I know I'm a couple years late to the party here, but I've been plunking at this circuit for nearly 4 hours and it's only fading off (instant on).
can this circuit be used with a 555 ?? and how and where would you set up the timer?
The 555 timer output would replace the switch. You'd have a resistor between the 555 output and where the transistor base and capacitor connect. Might need a diode to keep the 555 timer from discharging the capacitor during its low output.
@@Electronzap will give it a go thnx, looks like the circuit I'm after but not sure, need to fade in (or should I say pulse) 16 - 1watt leds in parallel, so timing is the biggest hurdle,
I want to do this w/a green laser diode and have the fade on & off cycle set at 1/4 sec or maybe a variable time between 1/4 sec and continuously on for a laser gun project. 1) How could I synchronize the 555 trigger pulses to the fade on/off rate so the quicker the switching, the shorter the fade on/off rate. 2) Why are the 150K and 220 resistors in series? Seems like this would just add a tiny more resistance to a large value or are they in series/parallel? 3) What are the formulas for calculating the fade on/off rates for determining the values of the capacitor & resistors in the circuit. I would rather do it that way than physically trying different components to try to stumble on the right combo. 4) Thanks for any reply and I will subscribe!
He has a video on that. Using a 555 and an NPN Bipolar Transistor.