Regulating voltage using Solid state relay and PWM

Other Hardware General Electronics
1

Is it possible to step down a voltage using a solid state relay and PWM? I would like to control the voltage output by changing the duty cycle. Or, is using a potentiometer a better approach.

The modified voltage is then going to be an input to a DC-AC inverter. I am worried that rapid turning on-off may damage the inverter. The input voltage would be at max 24V which I plan to step down.

Any ideas?

Thanks.

2

Is it possible to step down a voltage using a solid state relay and PWM? I would like to control the voltage output by changing the duty cycle

With PWM, you are stepping-down the average voltage. Most DC solid-state relays will handle that. (AC solid state relays can't be PWM controlled because they usually use a TRIAC and they don't turn-off 'till the next zero-crossing (and some don't turn-in 'till the next zero crossing).

Or, is using a potentiometer a better approach.

Potentiometers are rated at about 1W at most, so they are not appropriate for directly controlling "power".

The modified voltage is then going to be an input to a DC-AC inverter. I am worried that rapid turning on-off may damage the inverter.

Right! It's unpredictable how a DC-AC inverter is going to respond to something like that. Bad things could happen.

What AC voltage are you trying to control? How much power/current? What kind of load, or what are you trying to do?

3

Thanks for the reply.

What AC voltage are you trying to control? How much power/current? What kind of load, or what are you trying to do?

For my expt., I am expecting an output 110V AC, and current itself could be high enough to control any appliances. While it may seem odd, but I would like to control the DC current/voltage before I give it as an input to the DC-AC inverter.

Since it may be a bad idea to do so... can you explain why things may go wrong? Is it because of the buildup of electrons if there are induction coils? Sorry asking for such noob questions.
Also, will it be a better idea to use a linear voltage regulator or buck converter?

4

Just to clarify, the input voltage is coming from a Solar Panel, which I plan to regulate.

5

Simply chopping the voltage with a PWM is rather crude and, as said may upset any circuit following it becuase the voltage will have a very large ripple. I suggest you use what is called a flywheel circuit comprising a diode, inductor and capacitor. Together with the switching element they form the basis of a 'buck' converter. These extra components help to smooth out the voltage to a DC, and then you can feed back a portion of the output to the Arduino to regulate the voltage.

Look up circuits for a buck regulator.

6

Thanks for your input.

This is where I have reached so far:

  1. Seems like using PWM with SSR may have consequences. Things may blow up depending on what you connect to. Since, I wanted this to be an independent circuit.

Nice tutorial about how to create DC-DC buck converters and also why to use a diode to prevent burning of circuits. Switch mode power supply tutorial: DC-DC buck converters - YouTube

  1. One could use buck converters: may be LM2596

My question is:

  1. what should I keep in mind when I use LM2596. It seems they have added capacitors into the circuit and I wonder why that is done (smooth out the current? ). I was expecting the LM2596 to do that.
  2. Has anyone tried regulating the LM2596? May be I can start a different thread for this.
7

I think we can conclude that building a regulated synthesised sinewave DC-AC power converter is not a beginner project and you are far better off to go and buy one. :roll_eyes:

8

Those datasheets are a little misleading. They say the chip provides everything required of a switching power supply, really they provide a set of functions which an electrical engineer could use in a power supply circuit. If you are not an electrical engineering student, then don't even attempt it. Buy a module off the shelf. (This advice also apples to electrical engineers; most of the professionals buy modules too.)

This is an unusual requirement. Most things that use 110V don't work well on 90V or they don't work at all. What are you really trying to do?

9

I wanted to control the power generated from a PV Panel. Any suggestions on how to do this? I know MPPT does this somewhat by making sure that the PV panel generates max power.

I figured that a way of doing this is to stepping down the voltage or using SSR to reduce the voltage. I am assuming the DC-AC inverter works with a range of input voltage to be able to handle rapid on-off.

10

The power generated by a solar panel is pretty much fixed by how much sun it's getting. MPPT is just extracting a few percent more power. Unfortunately, if you're driving a real load like a TV or a fridge, the power module can't control how much power the TV consumes. If you have a big enough panel, then the sun wins and the power controller can waste some energy. If there isn't enough sun to power the TV then you are out of luck and out of power.

11

Thanks for you input :slight_smile:

12

I think we can conclude that building a regulated synthesised sinewave DC-AC power converter is not a beginner project and you are far better off to go and buy one

ohh ! ,
your no fun... ;D

@OP,
Don't listen to him.
Try this:

13

raschemmel:
Try this:

Now let's see - does that implement the "Magic Sinewaves"?

14

This is the first I've heard of them. I have a sinewave generstor sketch in the MCP4725D DAC li brary.. Is thst the same thing ?