How to Gradually Ramp 230V AC Output 0–230V Over 0–5s With Switch Control, No Relays

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#1 21668050 14 May 2013 09:21

Andrew Betts Andrew Betts

Anonymous

Post #1
21668050 14 May 2013 09:21

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
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#2 21668051 14 May 2013 09:36

Rohit Dubla Rohit Dubla

Anonymous

Post #2
21668051 14 May 2013 09:36

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.
#3 21668052 14 May 2013 09:47

Andrew Betts Andrew Betts

Anonymous

Post #3
21668052 14 May 2013 09:47

Thanks for the reply

I was hoping to keep it as as small as possible. that seems very bulky.
#4 21668053 14 May 2013 12:15

Frank Bushnell Frank Bushnell

Anonymous

Post #4
21668053 14 May 2013 12:15

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.
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#5 21668054 14 May 2013 12:42

Andrew Betts Andrew Betts

Anonymous

Post #5
21668054 14 May 2013 12:42

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.
#6 21668055 14 May 2013 13:49

Frank Bushnell Frank Bushnell

Anonymous

Post #6
21668055 14 May 2013 13:49

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We will always be here to offer the best advice and wisdom we can.
Many sites have a user forum for asking questions on any technical aspect.

Old (allegedly Chinese) proverb: “A journey of a thousand miles begins with but a single step.”
----------
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#7 21668056 14 May 2013 13:59

Andrew Betts Andrew Betts

Anonymous

Post #7
21668056 14 May 2013 13:59

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
#8 21668057 14 May 2013 14:21

Frank Bushnell Frank Bushnell

Anonymous

Post #8
21668057 14 May 2013 14:21

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..
#9 21668058 15 May 2013 00:19

Andrew Betts Andrew Betts

Anonymous

Post #9
21668058 15 May 2013 00:19

"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
#10 21668059 15 May 2013 02:32

Rohit Dubla Rohit Dubla

Anonymous

Post #10
21668059 15 May 2013 02:32

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.
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#11 21668060 15 May 2013 03:32

Andrew Betts Andrew Betts

Anonymous

Post #11
21668060 15 May 2013 03:32

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.
#12 21668061 15 May 2013 05:55

Rohit Dubla Rohit Dubla

Anonymous

Post #12
21668061 15 May 2013 05:55

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.
#13 21668062 17 May 2013 15:36

Frank Bushnell Frank Bushnell

Anonymous

Post #13
21668062 17 May 2013 15:36

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.
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Topic summary

✨ The discussion centers on designing a circuit to gradually ramp an AC output voltage from 0 to 230 V over a variable time period (0–5 seconds), controlled by a switch, without using relays. The input is 230 V AC at up to 20 A, and the output must similarly handle 0–230 V AC at up to 20 A. A variac (variable autotransformer) with a motorized wiper controlled by a linear ramp signal is suggested for smooth voltage variation, though it is bulky and may require a relay or solid-state relay for instant cutoff. The original poster prefers a compact, automatic solution and considers using a triac for power control but lacks knowledge on triggering circuits. It is recommended to use a microcontroller to generate a ramp control voltage that drives a triac-based dimmer circuit, with references to online dimmer schematics and ramp generator circuits (e.g., relaxation oscillators). The importance of starting with low voltages and building foundational electronics knowledge before attempting high-power AC control is emphasized. No specific circuit diagrams were provided, but resources for beginners and example dimmer circuits were shared.
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FAQ

TL;DR: To ramp 230 V AC without relays, use a phase‑control triac dimmer driven by a 0–5 V or 0–10 V ramp; “the terminal marked ‘control voltage input’ takes the control voltage.” Add an instant‑off path. [Elektroda, Rohit Dubla, post #21668061]

Why it matters: This FAQ shows how to get a compact, repeatable 0–230 V ramp with a start/stop signal, safely and predictably. It’s for makers and engineers exploring non‑relay AC soft‑start/power‑ramp control.

Quick Facts

Target spec from the thread: 230 V AC input, up to 20 A; ramp 0–230 V over 0–5 s. [Elektroda, Andrew Betts, post #21668050]
For pure sine output, prefer a variac; triac dimmers distort the waveform. [Elektroda, Rohit Dubla, post #21668059]
Add a solid‑state relay path for instant OFF while the ramp decays. [Elektroda, Rohit Dubla, post #21668051]
Control ramp can be 0–5 V or 0–10 V DC into the dimmer’s control input. [Elektroda, Rohit Dubla, post #21668061]
Design to repeat start/stop thousands of times; cycle window ≈ 0–3 s per the use case. [Elektroda, Andrew Betts, post #21668060]

What’s the simplest small-footprint way to ramp 0–230 V AC without relays?

Use a phase‑angle triac dimmer with a low‑voltage ramp generator (0–5 V or 0–10 V) driving the control input. This keeps size down versus motorized variacs. Add a solid‑state path to force immediate OFF on stop. “The terminal marked ‘control voltage input’ takes the control voltage.” [Elektroda, Rohit Dubla, post #21668061]

When should I choose a variac instead of a triac dimmer?

Choose a variac when you need a pure sine output, such as for sensitive transformers or induction motors. A triac dimmer chops the sine wave to control power, which changes the waveform. “If it’s a pure sine wave you need then I don’t see anything better than a variac.” [Elektroda, Rohit Dubla, post #21668059]

How do I get instant OFF while still using a gradual ramp?

Use a solid‑state relay (SSR) or equivalent solid‑state cutoff in series with the load. Drive it OFF immediately on stop, while the ramp generator resets to zero for the next cycle. This provides repeatable immediate shutdown. [Elektroda, Rohit Dubla, post #21668051]

Can this be done with a microcontroller instead of analog ramps?

Yes. A microcontroller can generate the ramp profile and timing, then command a power stage. “It can be accomplished by both analog and digital means.” Start simple and prototype at low voltage first. [Elektroda, Frank Bushnell, post #21668057]

What control‑voltage range should I design for?

Design the ramp source for 0–5 V DC or 0–10 V DC, matching the dimmer’s control input. Keep the ramp linear over 0–3 s if that’s your window. This supports clean 0–230 V transitions. [Elektroda, Rohit Dubla, post #21668061]

Does a triac dimmer keep the AC waveform pure?

No. Phase‑angle control slices each half‑cycle, so the output is not a pure sine. That can cause hum or EMI on some loads. Use a variac when sine integrity matters. [Elektroda, Rohit Dubla, post #21668059]

I need thousands of repeated start/stop cycles; is that feasible?

Yes. The thread’s use case calls for repeats every 0–3 seconds, thousands of times. Ensure your control ramp resets to zero on stop, and your power stage is rated for the duty. [Elektroda, Andrew Betts, post #21668060]

What are the baseline electrical targets from the thread?

Input is 230 V AC, up to 20 A. Output ramps 0–230 V AC over 0–5 seconds. These drive component sizing for dimmers, SSRs, heat sinking, and wiring gauge. [Elektroda, Andrew Betts, post #21668050]

Is there a ready reference circuit for the dimmer approach?

Yes. The suggested path is a voltage‑controlled AC light dimmer. Feed it with a DC ramp and gate the sequence with your start/stop. Ensure your chosen design matches your current rating. [Elektroda, Rohit Dubla, post #21668061]

What’s a variac?

A variac is a variable autotransformer. A motorized variac can move its wiper slowly with a control signal, producing a clean sine at adjustable voltage. Size and VA rating set maximum current. [Elektroda, Rohit Dubla, post #21668051]

What’s a triac dimmer, in simple terms?

It is a phase‑control circuit using a triac to delay conduction each half‑cycle, adjusting delivered power. Some versions accept a DC control voltage, enabling smooth ramps from an external generator. [Elektroda, Rohit Dubla, post #21668061]

How do I keep the solution compact?

Avoid motorized variacs because they’re bulky. Use a solid‑state dimmer plus a small ramp generator or microcontroller board. This meets the small‑as‑possible goal stated in the thread. [Elektroda, Andrew Betts, post #21668052]

Any safety advice before building?

Work at extra‑low voltage first, then move to mains with proper isolation and enclosures. “It is also wise to begin with low voltages.” Size parts for 230 V and 20 A, with margin. [Elektroda, Frank Bushnell, post #21668062]

What edge cases should I expect?

Some loads dislike chopped waveforms. Inductive loads may buzz, overheat, or misbehave with phase control. Use a variac when waveform quality matters, or validate on your exact load first. [Elektroda, Rohit Dubla, post #21668059]

Can you outline a quick 3‑step build plan?

Choose your path: triac dimmer with 0–5/10 V input, or motorized variac for pure sine.
Generate a linear DC ramp over 0–3 s and gate it with start/stop.
Add an SSR for instant OFF; test at low voltage, then scale up. [Elektroda, Rohit Dubla, post #21668061]

What if I need guidance before I have a firm application?

Clarify function, power, and load type first. Share a simple block diagram. That enables targeted, safe circuit advice tailored to your goal. [Elektroda, Frank Bushnell, post #21668053]

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