This video will describe how to build three simple MOSFET circuits to get familiar with their characteristics and understand how they work. MOSFET Bootstrapping: • MOSFET Bootstrapping
Thank you. Very clear and and nicely presented. I've just received some MOSFETs with an aim to do motor speed control and your simple examples help a lot. The gate capacitance seems to be the key to correct operation. Also nice to see and hear a presentation without the music that spoils so many instructional videos.
Thanks for the feedback and also for sharing. Here are some other videos on the same subject: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-mjIubJeTRyY.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-uLA2MvKYLZs.html ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-1qing2TJWSc.html
Wow! Not only I understood everything you've explained but you've actually presented very practical circuits that can be used in real life projects. I'll borrow from you the alternating flashing lights for an emergency sign I want to build. But the most important thing is what I have learned today. Thanks man!
You can use the very common 555 timer IC to build an adjustable monostable timer that will drive the relay. The 555 timer can sink or source 100 mA at 12 volts which can drive a relay directly. If you need more drive you can buffer it with a transistor or mosfet. There are many circuits available online that you can use: 555-timer-circuits.uk/
So.... there's this guy on RU-vid... he showed an alternating flasher circuit that was much more simple and used fewer parts. You can look it up. I think he named the video 1970's GM blinker circuit...or something like that ;-p -Jake
Thank you for the video, it is well explained. I am new to electronics, so easily confused. In the touch switch you created, I have seen it done with a Z44 and he didn’t even use a resistor. I understand what a resistor does, but why is it necessary here? Also is it possible to make a dimmer touch switch for 12V supply?
Does the mosfet in the curcuit with Schmitt trigger should be special otherwise the LED does not blink? I used FQPF mosfet. The LED does not blink. No oscillation on the gate.
ive done the capacitive switch and i have changed a few mosfets when they failed....burn out..i dont have any other experience or knowledge......ive used irf540n which is almost identical to the irf44n and worked great at 12v as capaicitve switch ..couldnt get it worked with a 18650 fully charged at 4.2v...though i ve seen it happened....the gate threshold v for the gate is around 5v...anyway...i wanna ask when you use the mosfet as a switch in the classic way not the capacitive one...do you need a gate driver...i mean a logic gate a chip a microcontroller ..sorry for my terms ....dont know ...that can give the signal voltage to the gate...in order to make it work... im askin this...i have a 12v load i wanna switch...i have a 12v source....i connect the positive to the gate of the mosfet and then through a resistor to the source.....and then to the ground...i connect the load on the drain ..source.....the positive side of load ..negative side of load ...drain...if i have a switch a typical switch on the voltage i feed the gate...will it work...?willl i be able to switch the mosfet on and off and control the load?
So with the capacitance of the MOSFET holding it on, adding a 10k pull down resistor to the gate on the first example, would turn off the MOSFET as soon as your finger was removed from the top switch?
Yes .. you are correct. It is common to see a 10k resistor from gate to ground in Mosfet switching circuits. If you program a GPIO pin of a microcontroller to be an output, and then drive a mosfet to switch on a device, and then change the GPIO pin to be an input (floating) the device would be stuck in the on state. With a pulldown resistor the device would shut off. This could become a safety issue. Check out this video on GPIO interfacing: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-Iq9jPrhEGkU.html
Great video! Not sure if you're still checking comments, but I have a question. I get that MOSFETs are great for switching DC, but what about AC? Must I use a relay, or is there something analogous to a MOSFET which would allow me to switch AC on and off like this (either an AC or DC trigger would be OK)? I can only think of a relay right now, but I'm no expert.
Yes ... MOSFETS are for switching DC. To switch AC you can use a Triac. To make your circuit safe and easy I would suggest an AC SSR ( Solid State Relay). They are activated by an internal opto-isolator with 3-32 volts DC. They come in many sizes with different current ratings. Check out this video where I used a SSR to control a shop vac (mousetrap). ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-lYImd3WCjZM.html
I built the curcuit accordingly (showed in min 4 on the left) and i it does not blink. R causes that the LED goes off and does not on again. If R is greater LED goes off slower but does not light on again. Why???
That is a timer circuit not a blinker circuit. A button press will turn ON the LED and then turn OFF after a period of time determined by the RC values. The button has to be pressed again to restart the timer.
How do I allow higher volts on output to load using N channel MOSFET, zener, resistor, as zener resistor is to be called minimum load, on all the time while final load turns on and off by it's own switch in series, while MOSFET is always on also.100% duty cycle minimum load, and 40% duty for final load resistance? Vcc 28v DC or higher, 6 A final load, MOSFET type for higher gate voltage? This for series pass transistor needing 28VDC on load. The BIPOLAR type lose voltage on load with Zener. ( In other words if minimum and final resistance is together in parallel, the ohms goes down and is wrong.)
Yes .. you can use non-insulated solid wire for the sensors. In this case I cut off the leads of a resistor and bent them in a U shape and installed them on the breadboard.
It depends on your desired time interval. The resistor will discharge the capacitor until it reached the threshold value of the Mosfet. Use a calculator to determine the desired R/C combination. www.learningaboutelectronics.com/Articles/Capacitor-discharge-calculator.php
Before the diagram I was getting super confused by the "I short to VCC" (touches the blue line) "I short to ground" (touches the red line). I guess that is a lesson in itself in not trusting colours :D
I have done that a few times in my videos to see who I can catch. If someone hands you their project on a breadboard you disregard all markings and figure out the Vcc/Gnd connections. When breadboards were first introduced there were no markings. The top rails were Vcc and the bottom rails were Gnd. A diode was put across the top two rails for reverse polarity protection and the bottom ground rails were used to hook up an ammeter. The markings were put there for convenience but I have seen many projects destroyed by students making wiring errors.
I made the first circuit with 2n7000 mosfet but it turns off automatically when I remove my finger from gate and vcc touchpad any explanation or solution??🤷♂️ BTW video was awesome 🔥
The 2N7000 has a gate to source capacitance of 50pf which will discharge very quickly as opposed to the IRF1405 which has a gate to source capacitance (Ciss) of 5480pf which will hold the charge for a long period of time. Thanks for the feedback.
Your too good to not be part time homeless/rugged individual (same reason). Again... Good all in all. Of course- I speak in the name of seek Face of Higher Power, one sould fight the "stupid" ones and all not wise in their own eyes "movements."
In the beginning was the Word, and the Word was with God, and the Word was God. 2He was with God in the beginning. 3Through him all things were made; without him nothing was made that has been made. (John 1:1-3)
