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Asked — Edited

Switching Circuit Toturials For Digital Outputs

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


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As for mosfets, the IRLZ34 is a really good choice. It's logic level so it'll work with the EZ-B and other microcontrollers, it can drive 30A at 55V and it's nice and fast.
I'm currently using it to PWM dim a 3W RGB LED.
I like Mosfets. Their tough little suckers. US pinball manufacturers started using them in some of their circuits back in the 1980's because they were more reliable.However the humble switching transistor never went out of style. The only drawback I know of with them is that there is no way to test them to see if one is shorted out or open.

Ferd, what institutions did you attend and where did you earn your degree? Hope not to offend with this personal question.
first who is FERD second is U OF M COLLEGE,was going to get my masters at FIU but at that time it was too hard with work and then going to school.

I know my grammar is bad only because i havent used it in so many many years or needed it,but as you can see its much much better.

Mosfets are made from darlington transistors and its a better upgrade,one main reason it was made.

Where on darlington transistors it has very high resistance and mosfets super low ohms ,but easy to use and some are logic level ,with meeds direct connection to cpu or logic

BEST example is H-BRIDGE is you look at the long time ago when they came out they use transistors to make them ,and now they use mosfets ,so ask your self the question why did they change to mosfets ?

NEIK yes IRLZ44 is a very good choice its called a logic fet,i have some of those.

One i am using is in a smaller package 17 amps high wattage and lower cost $.77 plus no diode is needed its has one built-in

Main reason i picked this one is small size and high current without a need for a heatsink,but mostly using mosfets or transistors a heatsink is not needed on some designs.

PLUS like most guys here everyone wants to save money ,so very low cost over a transistor.

Nothing wrong with using a Transistor as a switching device.
Here is a little background on when transistors and mosfets first came out

TRANSISTORS came out in 1948 and about 10 years latter mosfets came out in 1959 s a improved replacement.

Info is on the WIKI site on both of them.
Also DAVE can i ask the same question to you about what school or college you went to ?
And RICH if he cares to answer it.
Woops, sorry. Didn't mean to misspell your name. should have been Fred and not ferd.

I was at Texas A&M for only a short while. No degree. I learned most of what I know in the school of hard knocks.;)
I know you didnt misspell my name,seems i am not the only one that doesnt use spell check :)

Some of my friends playing with me call me FERD,EVEN MY GIRLFRIEND TOO.

IT seems on this forum people without a degree knows more then ones with a degree,that not right.

IT like saying the student knows more then the teacher.

I am on many many electronic forums this is only one thats like that.
DAVE i did enjoy college alot,but i love my work alot better,free travel ,my own room with a pretty secretary and pay was more then i ever need.

But now working at home as a freelance engineer for the company ,is much better

PLUS i get to check all the parts and most of the test equipment when i retire early in under 2 weeks

Only thing bad is going to miss my pretty secretary,but my girlfriend will be there and soon getting MARRIED to her.
United Kingdom
Fred, I've often known more than the teacher - that was my main problem in school, why I didn't like it, it wasn't challenging at all and very boring... I did poorly in school and had to bluff my way on to the courses I took afterwards. Some qualifications I hold have prerequisites that I don't actually have which shouldn't happen.
When I took my AutoCAD course I knew more than the teacher and ended up teaching him a thing or two... Similar when I was an apprentice electrician. It doesn't really say much about the teachers!.. But then I do have a natural ability to pick things up almost instantly (proven by only using ARC for less than 3 months and being on these forums for 4 months).

My training has been at various places. Mainly at the technical college in my county, which no longer exists. Some has been online, some has been in the class room, some has been home study, some has been self taught by just doing.
YEP i thought that,student know more then the teacher,how come you dont have a degree.

teacher in college is professor and has the highest degree.

i also pass the course and i am licensed electrician

I GUESS you think teachers are not needed
ON teachers they get there degree from a college professor.
So teachers dont know that much.

in high school i had a very high IQ most then most in my class,and was a sub teacher for a few hors on science ,where every year i has straight A'S
United Kingdom
I don't have a degree for a few reasons;
1. Cost. There was no way I could have possibly been able to afford to go to a good university even if I had wanted to. It would leave £75,000 of debt for a 4 year course without living expenses. We did not have that kind of money but also couldn't get any grants or student loans due to both parents working and a household income above the threshold.
2. Lack of pre-requisites, I don't have good enough grades in all of the required subjects (English mainly, despite my proper use of the English language) due to not being interested at all through high school - no challenge, no interest. I did poorly in school despite having the highest IQ of anyone to have ever attended the school, as far as I know it still stands today, although irrelevant since it is not an accurate enough test to measure intelligence. From memory I believe it was 172 at 15, I'll have to dig out the results sometime, I know it was just in the top percentile which is 1/1000000.
3. A degree is worth as much as the piece of paper it's written on. I've not needed a degree to get where I have got today. My work and reputation speak louder than anything. I've not needed any qualifications to build the client base I currently have.

And for the record I don't think I got a single A in school, grades mean nothing.
so thats why you dont know very much,except for coding and software
United Kingdom
Wow... Going down the route of attempting to insult and belittle now are you? Thought you said you were always nice and never nasty to anyone? That post says otherwise with a blatant insult like that which is not only untrue but also uncalled for especially considering I'm attempting to be civil with you. Or will that post get edited shortly when you realise I wont be dragged down it? (edited it is then)

P.S. It's spelled "wonder" and don't has an apostrophe in it.
RICH college doesnt cost much ,may be a better poaying job would help.
for it was a easy cost and i really enjoy college

MY next answer to this post unless somebody has a good thing to say and not finding a faults with another person .like one missed spelled word.

With photos of my design and circuit in about 8 days from now .
YOU said you dindt get A'S i school in reading and writing i didnt too.mostly C+ or B once in while
mostly because i didnt like to read ,but after college i really like reading stuff alot on electronics.

I have big library full of electronic books that i read alot
to much garbage on this post and keeps others from find good proven info on my design.

So after 8 days we re-post the info all over again.most likely copy and paste

ALSO very rare do you see others say anything wrong with my designs or make any comments and most are really good in electronics
United Kingdom
Read this slowly... When have I said there is anything wrong with any of your designs? And it's your garbage, I tried making conversation and you turn around with an insult (that's been edited now but we both know what you wrote). I ignored you for a while so you didn't frustrate me, I tried being civil but still you continue to bang on with triple posts of useless crap. I refuse to fill the forums with this crap.
I didnt say the garbage came from you ,its all the info that has nothing to do with the post

yes i did re-edit it to be a little better like you told me to
User-inserted image

parts list
D1 - 1N4004 DIODE DIGI-KEY PART # 1N4004-E3/54GITR-ND

D1 is only needed for inductive loads like relays and motors
Also most any mosfet will do,only i pick this one because it matches TIP120 darlington and a smaller size
LINKS and prices


IN4004 DIODE $.029 EACH

Will make the board when i get back