robotmaker
I design alot of circuils been electronic engineer and was look at are using using switching transistors to turn on lights ,relays and more
Transistors are mostly old school design ,before mosfets came out,if you look at the h-bridges now that use mostfets instead of transisors
For a few reasons one is low RDS on ,with meens they can handle higher wattage and not get hot using transistors ,plus less voltage
The most common is n-channel and have 3 pins ,GATE witch goes to digital output with a current drive resistor then SOURCE witch is the load and DRAIN is ground
Now for protection for mosfets most have a diode that protect it from EMF or inductive kickback
MOST i see use diode on transistors from collector to emitter ,NOT a good idea manly it does suppress or stop the inductive kickback and if using a microprocessor or circuits with will get resets and more induce in th system
so where the diode goes is always across the coil with cathode (black line ) to postive and NO inductive kickback
DIODES are only needed for inductive loads ,motors and relays or coils
Not for resistance loads ,lights or heaters ,leds will put up a simple circuit
second part will be how to control AC products,RELAYS are also not good slow switching and as noises on the contacts that does resets but wull give info on how to fix them
HOPE this is easy to understand if not just ask a question
yes ,but they are the old design now,all new designs use mosfets ,easy way to check it look at H-BRIDGES that did use switching transistors before and now the use mosfets,same with dc-dc converters and everything else
mosfets are a better upgrade then switching transistors,too bad not many or none ELECTRONIC ENGINEERS with a degree are on this robot forum but me
Because they would agree with me
There are so many many links on using mosfets to switch loads on and off just like there are so many links for darlington switching circuits use for switching on loads on the internet
Fred, re-read your tutorial posts before sending. When teaching, clarity is key.
See post #4. "P-channel mosfet is a npn darlington and P-CHANNEL mosfet is a PNP darlington"
I would have taken a different approach and explained in the beginning the differences in MOSFET and TIP120 switching. Then explain the virtue of MOSFETs. That way other people will start using them because they are better and not because Fred the "ENGINEER" says it's "old school" and I shouldn't use them.
As another tip, see post #1: "I design alot of circuils been electronic engineer". If you write as a professional then you will be believed as a professional. As I've said last year, you have experience to offer the forum. Please keep trying to improve your writing skills so that we may learn from you as another of many available resources.
i only do it fast and dont recheck it,doesnt meen i am not professional I know i am not a writera i am designer thats why i have a secretary to fix my mostakes at home i dont have one ,
but i guess i need to double check and re-edit some,but still my points are the same when i use the term old school it only meens that there is a better design that works better will fix the posts ,but i do see others spell ords wrong and nobody complains about them only me AND mostly RICH
TROY ok i missed one word on this See post #4. "P-channel mosfet is a npn darlington and P-CHANNEL mosfet is a PNP darlington
should be" P-channel mosfet is for npn darlington and P-CHANNEL mosfet is for a PNP darlington " missed the word FOR OR could used "used for "
Problem is that this is only forum i ever write for,even work didnt need it that much,only data,schematic and my circuit and mostly they never need that only i design and make the circuit and let them re-test it and if ok it passed but mostly it a full tester
SO In over 20 years this is my first post i did any writing for . so thats another main reason my posts are bad grammar or spelling ,been well over 20 years ,last time was in college
mosfets are made using darlington to have faster switching and lover heat dissipation without the need of a heatsink ,plus no wasted power
BUT guess in robots nobody cares about power loss and want to use to bigger battery
In my designs i look at every circuit to use less current as i can,so i dont have short run times or problems with a bigger battery
I use low current sensors ,LDO like DJ uses now ,before he used regular regulator LDO is another great example of mosfet design it uses them in the circuit for low RDS on for low drop out voltage,
SAME when i design my own servo's it uses a lot less current then ones you buy
also using lot of protection in my designs ,like DAVE said it cost more and takes up more space and said that is never fails,thats not a great idea saying it never fails
old saying goes "better to be save then sorry latter".most circuits that dont use protection ,wont go bad right away or few months ,but it may go bad latter
Thats why big companies add them in thier designs battery or ac testers
I hope soon a engineer with a degree on this forum will say the same thing about using mosfets over darlington ,thats mostly what this post it about,
The top heading word tutorial is spelled wrong ,but i could not re-edit after i saw it
So you don't see the problem with P-channel vs P-channel you posted? As it's written, NPN is the same as PNP because you listed them as having the same type channel.
I'm going to take an educated guess and say that none of us have a secretary writing our posts and we manage.
Let me say it again in a different way. If you write as the average person can, your credibility as an engineer gets better. People will wonder how you earned a college degree without writing term papers, etc. Let me get away from that title. It's not necessary to be an engineer to post on the forum.
What kind of degree is needed to satisfy your request? Is it necessary that we say the school it was from or can we just look online and find credible sources about MOSFETs?
For the record, I agree that in some applications that MOSFETs are the way to go.
LIKE I SAID COLLEGE I DID A LOT OF WRITING AND TERM PAPERS AND WAS NO PROBLEM and about 25 years ago and after 25 years you forget grammar because at least with me i never needed after college i didnt need grammar until this forum
I guess you didnt understand the posting i did on P-CHANNEL with pnp darlington
THE P-CHANNEL mosfet iin place of the pnp darlington and same with n-channel ,
and i dont have a secretary doing my posts too
people love to find mistakes in others ,witch i dont mind that much and i dont mind beening corrected also i did it the same on ther posts i see missed spelled words that person didnt use spell check also
I guess it better to show proof from the internet then write about it and others say i am wrong about it,when most dont have a degree to prove me wrong
so next posts i will put up links and do less writing
TROY why do you think that darlingtons are better MY POINTS EASY CAN BE PROVEN
Take a mosfet and turn it on and put a load on it and see if it gets hot and do the same with a darlington ,,you will see more heat on the darlington,both have to be the same wattage also try a power loss test to see about the wasted voltage.
SUPER EASY TEST under $5 to prove a person wrong also on the link on the mostfet thats close to darlington TIP120 you dont need a diode.check the data sheet same spot RICH has his diode across so you same money and space with a mosfet and its same price as TIP120 $.88
TROY if you find mistake i dont mind you point them out to me,or RICH ,i can easy re-edit my posts
i will do the same for others ,seen many posts with bad spelling.not much or any in grammar
USING bad grammar doesnt make a person less smart or doesnt know what he is talking about
J ust might make it had to read,dont really to capital letters or add periods we are beening graded for it in school or college
TROY you are lucky i like you and DAVE do give fair good advice,dont know how much you know about electronic design
And RICH you are still ok too
but from now on will find links to same stuff i talk about and post the words from it
so no more bad GRAMMAR problems will get put up,pretty easy to find my proof on the internet ,may not use the same words ,but still have the same point come across