Go Down

Topic: Precise linear optocoupling (Read 1 time) previous topic - next topic

MorganS

I just want simple isolated microcontroler regulation that is't some insane pulsing or ugly-wave modulating but oldschool linear regulation of AC just as if it was a resistor on the knob.
Have you ever looked at an "old school" resistive power controller? Like the controls on a W-class Melbourne tram? Or any DC motor controller built before the 1950s?

Yes, they use a resistor and a knob. However the resistor weighs about the same as the motor and has about the same cooling requirements. When you're at 50% power, the 'other' 50% is waste power at the resistor. For something the size of a tram or train, the knob is a giant lever that the driver operates. If you look at a modern train control panel, they still have the giant lever because that's what the older drivers are used to. You also don't want to control a 1000-tonne train with a knob that might snap off if your jacket pocket catches it wrong.

The "old school" light dimmers you might have seen in houses are actually really clever triac circuits which don't require vast amounts of cooling for any resistor.
"The problem is in the code you didn't post."

Deous

Have you ever looked at ...
Thank you for preaching and justifying today'd electronic engineering for not having what is exactly needed or desired.

allanhurst

Various posters have pointed out that what you exactly  require is impossible without great power loss.

A variac with motor control night achieve your needs.

But far more expensively than a triac approach for a heating element.

Allan

Deous

#33
May 14, 2018, 02:11 pm Last Edit: May 14, 2018, 02:13 pm by Deous
Well ok, but unfortunately the project I am working on apparently needs a linear change of the AC in time.
I am just designing that for some complex heating process of ceramic and other materials that may take even few days and involves some complex profiles. This looks very difficult and I see there is no easy solution. Any fast switching with such power causes all kinds of EM interference. I will look at SCR and maybe some triacs that may be somehow adjusted to linear dimmers. Maybe there are some other silicons suitable for that.

MorganS

Why do your ceramics care about E-M radiation?
"The problem is in the code you didn't post."

ted

#35
May 14, 2018, 04:03 pm Last Edit: May 14, 2018, 04:07 pm by ted
He is lost in the jungle , he is expecting that TV set will work at 10V AC - similar electronics is inside of induction stove....
He is crying no simple solution - look at my posts

Deous

Why do your ceramics care about E-M radiation?
There is some various em sensitive measuring equipment around.

TomGeorge

There is some various em sensitive measuring equipment around.

Doesn't answer the question.. :o


"Around" where?
In your "laboratory"/"workshop"?


Tom.... :)
Everything runs on smoke, let the smoke out, it stops running....

ted

10m - or more, this is how far interferences can go from 1000W, 100 kHz square wave transmitter

allanhurst

#39
May 15, 2018, 12:14 am Last Edit: May 15, 2018, 12:20 am by allanhurst
10m - or more, this is how far interferences can go from 1000W, 100 kHz square wave transmitter

''

Couple it to a decent antenna and  it'll be detectable continents away.

It's called longwave radio.

Chopped ac -ie with a triac and reasonable suppression ( common mode chokes, X rated caps etc) , not very far.  and eg Murata make excellent mains noise suppression gadgets based on such techniques..

You can buy solid state relays with which you can play such tricks and contain such suppression devices for reasonable prices.

Allan

Deous

#40
May 15, 2018, 01:05 am Last Edit: May 15, 2018, 01:07 am by Deous
Good idea thanks. Switching those power elements on and off many times really affects some work on rf stuff in that small lab ) Anyways I ordered couple of power triacs and will try to experiment with them.

ted

#41
May 15, 2018, 02:08 am Last Edit: May 15, 2018, 02:08 am by ted
induction stove power module is not a resistive load for triac

allanhurst

No, but the OP says he's going to use a resistive heating element - or do I misunderstand you,Deous?

And if you're going to use a triac with suitable suppression devices, check out this forum for threads on variable phase ac control. It's been done many times before and gives you effectively near analog control with good resolution.

Allan

ted

So many times he changed his mind so I don't know what he is doing, and misleading name of the thread ......

TomGeorge

Hi,
@Deous, have you finished any of the projects from your previous threads?

Tom... :)
Everything runs on smoke, let the smoke out, it stops running....

Go Up