Mains voltage increase from 0 – 230V AC

Just starting out...

I am looking for a circuit that will increase the output voltage from 0 V - 230 over time
( 0 -5 secs, if possible variable).

Input voltage 230v Ac 20A max
Output voltage 0 -230v Ac 0 -20A

When a "switch/trigger" is present the voltage increases from 0 - 230v over the "set" time if at any time the "switch" is switched off the voltage drops instantly to 0 V. and keeps repeating when the switch is/not present.

I wish to avoid using relays.

Can anyone help

You probably need a variac (basically it is a variable auto-transformer) - the kind that is used in servo-stabilisers. This has a built-in motor or similar mechanism that positions the variac's wiper with a control signal input. In your case this input would be a linear ramp that causes the wiper to gradually move from zero to the required position slowly. Mind it that the maximum available current will depend on the variac's VA rating.

For instant switch-off, I guess a relay will still be needed along with simultaneous ramp-down of the variac. A solid-state relay should work well here.

Thanks for the reply

I was hoping to keep it as as small as possible. that seems very bulky.

Hi there Andrew,
If you could explain a bit more about your application, it would help us to figure out possible solutions. A circuit or system diagram that you have developed for the ideas so far would help also.

Hi,

To be honest i don't really have an application just yet, just floating ideas in my head.
I think i need to use a Triac, but it's the "switching/pulsing" i don't know how to do,

well to be honest the whole lot!!

All i wish to do is increase the output voltage slowly if the "start signal" is present.

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Many sites have a user forum for asking questions on any technical aspect.

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Thanks for the advise,

but i would like to know if it's possible to achieve what i'm after., and if possible how??

I have been looking on other sites some you have mentioned above,

but as usual i want to run before walking... so it's this project i want to solve/make

It is good to have high aims ! But as your knowledge grows, you will be able to frame your question more precisely, which is the first step on the road to the solution.

It can be accomplished by both analog and digital means. Most simply it could be done with a microcontroller, for which you only need to specify the changing output to a port, and then amplify that to the required power level

Build simple things to start. Growing your knowledge is easy in this age with all thats available free on the internet. Microcontroller based digital oscilloscopes are now incredibly cheap, I think I've even seen them as kits..

"It can be accomplished by both analog and digital means. Most simply it could be done with a microcontroller, for which you only need to specify the changing output to a port, and then amplify that to the required power level"

Okay do you have a circuit?

Like i said just wish to increase the output voltage from 0 to 230 volts over 3 seconds

If its a pure sine wave you need then I don't see anything better than a variac, However, if its just for the sake of power control such as a dimmer then there are a myriad of circuits available on the internet.

Okay i need this circuit to be as small as possible, and automatic.

The start signal will start the voltage rise and at some point the "stop" signal will be given (variable) and the process will stop, then repeat 1000's of times continuously

The circuit will switch on/off every 3 seconds, or any point up to 3 seconds

So i was thinking of using a Triac but it's the triggering circuit i need to solve.

Okay - since you have a triac in mind it probably means that you want to control power...seems to me to be some kind of lighting application.

Here is a suitable dimmer: http://www.pcbheaven.com/circuitpages/Voltage_Controlled_AC_Light_Dimmer/

In the schematic, the terminal marked "control voltage input" takes the control voltage - probably 0-5V DC (or perhaps 0-10V DC). The next problem is generating a suitable ramp voltage for this - search for "relaxation oscillators" or "ramp generator" on the net and find one that has a suitable output (0-5V or 0-10V DC). When this generator is ON your the dimmer ckt will receive a ramp and when the generator is OFF the dimmer will be OFF too. You need to determine a suitable frequency for the ramp generator and turn it ON/OFF every 3 seconds as required.

I don't have a circuit, I am generalising ideas. Before you can design a circuit, you need a clear idea of the purpose and function and power ratings of your application. To use a microcontroller, you need to learn the basics of programming the particular one you intend to use.

To repeat my proverb and yours,
"Learn to walk before you run " and "A journey of a thousand miles begins with a single step."

It is also wise to begin with low voltages. It may not seem so exciting, but you may live longer.