Half Wave Controlled Rectifier

[MrAl]

Hello again,


Ok that's fine then. Did you find that post with the 555 triac trigger circuit? That one is probably the best for the simplicity and accuracy. Let me know if you cant find it and we'll have to look around then.

Read this:
https://www.electro-tech-online.com/threads/ac-dimmer-circuit-microcontroller-controlled.113319/

It's actually a 555.

 

[4pyros]

Once again it is a simple DC motor controller.
Google "SCR DC motor controller circuit" You will find many of them.

 

[mufcforever7]

hi every1,

i found this circuit but dunno whether can use anot...

pls advice...

**broken link removed**

Uploaded with ImageShack.us

 

[MrAl]

Hi again,


Looks like it could work, but you should do a simulation and make sure it works the way you want it too or else ask someone else to do it for you. You also have to check power dissipation in the components for various conduction angles so you know what ratings for the parts.

Ok, another thing is that that circuit is not able to provide conduction angles less than 90 degrees. This is typical of very simple circuits like this. That means the speed will only go down to a certain amount and that's as low as it will go. This is ok if you dont need to go to lower speeds, but not ok if you do. You can help the problem a little by introducing some capacitance but then you loose the high end.
This is exactly why circuits have moved to microcontrollers and other types that use some sort of one shot like timing where the trigger pulse is sync'ed to the line but is delayed by the amount determined by the pot, and it can be continuously variable over the entire 180 degree range which means you get a full speed range adjustment from zero to full speed.

Is your line input 120vac or 240vac?

 

[mufcforever7]

hi MrAI,

i will do the simulation as soon as possible then i will tel u the result...

my supply will be 240Vac but i will use a step down transformer to step down to 24Vac...

 

[MrAl]

Hello again,


Ok sure, but i did tell you that you'll have to add some capacitance to get a low conduction angle (for low speeds), and doing that looses the high end. Maybe a switch to switch from adjusting for angles 90 to 180, and for adjusting for angles 0 to 90 if you think that would be ok.
I also dont know what kind of accuracy you need.

 

[mufcforever7]

hi MrAI,

the below attached picture was the result i got from oscilloscope... the duty cycle about 50%... is this consider a half wave rectification?

**broken link removed**

 

[Mr RB]

You own a $1400 digital scope but you don't know what that waveform is?

This is a joke right?

 

[mufcforever7]

hi Mr RB,

tat oscilloscope not i own it, i test it in my coll lab...

 

[MrAl]

Hi again,

That does not look like half wave that looks like full wave. Something may not be working right.