Create square wave from DC power supply “without” turning off the machine

Hello,

A few of you guys might know.. but I am currently working on circuits to generate high current square waves from DC power supply.

The problem is that it seems like every time switching on and off the DC power supply also turns off. Since there is a few seconds of lagging when turning on and off the equipment, I want to keep it on if that is possible.

I am wondering what circuit design/scripts would be helpful to keep the DC power supply on continuously.

If you can share sketches and scripts with me, I would highly appreciate that!

Thanks!

Have you tried a 555?

That sounds like a problem with the power supply, or the power supply isn't capable of the "high current" you're pulling out of it. Or, something's wired wrong or you've got a bad design.

A good-regulated power supply should hold the voltage constant as long as you are operating it within specs.

Have you tried a 555?

I have not. I am not an electronics savvy since I am a polymer major. According to a quick search, it seems like it can generate a wave function. Do you happen to know any good sketches that I can use quickly?

That sounds like a problem with the power supply, or the power supply isn't capable of the "high current" you're pulling out of it. Or, something's wired wrong or you've got a bad design.

A good-regulated power supply should hold the voltage constant as long as you are operating it within specs.

The lab-scale bench top power supply is meant to supply high currents up to 20A.

I am wondering if you know any good sketches or scripts I can use quickly

Before you or anyone else can start specifying a solution,
What voltages and current are you looking at?
What is the load being switched?

Before you or anyone else can start specifying a solution,
What voltages and current are you looking at?
What is the load being switched?

The device(or load) has around 0.1~0.5 ohms.

The currents I want to supply is in the range of between 2A and 20A. The voltage will be calculated accordingly based on the load resistance.

The load is a heating element. (with a very low resistance... that's why it needs a high current. )

ok, now...
Why square waves?

ok, now...
Why square waves?

For experiments.. The heating element is not a solid-state device made of coppers or something. It is made of liquid metals.

The device's resistance goes to infinity in about a few seconds after sending high DC. I think electromigration happens... not completely sure though... and there is a paper that enhanced the device's lifetime over several orders of magnitude by using square waves instead of direct currents.

High current square waves may cause a whole lot of harmonic noise problems.

High current square waves may cause a whole lot of harmonic noise problems.

Good point which I did not know about.

I am not a programming/electronics savvy… I think that’s why lots of commercial AC generators have a very low output currents in the range of tens/hundreds of mA. Even the paper just used this machine (33220 A, Agilent) with ±0.5V with a freq of 500 Hz, corresponding to 20mA. But their application was not for heating devices which requires a lot larger currents…

20A into a 0.1 Ohm heater implies you need a 2V power supply. 2V at 20A is rare. But it should not be impossible to obtain. Prepare to pay for it.

You will need a separate supply to control your switching device, even if you use a MOSFET.

20A into a 0.1 Ohm heater implies you need a 2V power supply. 2V at 20A is rare. But it should not be impossible to obtain. Prepare to pay for it.

You will need a separate supply to control your switching device, even if you use a MOSFET.

Could you clarify what you meant by "Prepare to pay for it."

Do you think this sketch will work out for my system?

So you mean I need two DC power supplies?

“Prepare to pay for it” = expensive

Mechanical relays are not suitable and high amperage DC current will kill general purpose relay contacts in short order. A properly rated DC relay will be large, expensive and very slow to switch.

Jumping back a few posts, if a square wave works, harmonics are a non-starter since a square wave is the definition of infinite harmonics

Do you know if you need a constant current regardless of resistance? If not and fixed frequency power is okay, it would be relatively easy to create sine waves at high currents with 50/60Hz ac utility power and a 500VA, 24vac control power transformer. Supplying the fixed 24v transformer with an ac variable transformer (powerstat/variac) will provide a variable output voltage. The voltage will determine the amps based on material resistance where I = E / R or E = I * R

infinite odd harmonics, but that’s OT.

The first google result for 2V 20A power supply shows me this one: Page Missing | Acopian Power Supplies

It's $645 USD

"Prepare to pay for it" = expensive

Mechanical relays are not suitable and high amperage DC current will kill general purpose relay contacts in short order. A properly rated DC relay will be large, expensive and very slow to switch.

Jumping back a few posts, if a square wave works, harmonics are a non-starter since a square wave is the definition of infinite harmonics

Do you know if you need a constant current regardless of resistance? If not and fixed frequency power is okay, it would be relatively easy to create sine waves at high currents with 50/60Hz ac utility power and a 500VA, 24vac control power transformer. Supplying the fixed 24v transformer with an ac variable transformer (powerstat/variac) will provide a variable output voltage. The voltage will determine the amps based on material resistance where I = E / R or E = I * R

I speculate this shield consists of mechanical relays? The problem with the shield is that it can only withstand 10A theoretically..

I previously used a DPDT switch (20A) to manually change polarity. It works as I wanted it to be, but obviously I want to control the frequency with computer.

I might need to control the current accordingly as the temperature increases not to let the device fry out. Let's say if the initial current was about 2A, then the variance would be give or take 0.5A.

The first google result for 2V 20A power supply shows me this one: Page Missing | Acopian Power Supplies

It's $645 USD

Thank you for sharing the link with me. Based on reading up on the product info, it only provides DC.

CoffeeMouse:
I speculate this shield consists of mechanical relays? The problem with the shield is that it can only withstand 10A theoretically..

I previously used a DPDT switch (20A) to manually change polarity. It works as I wanted it to be, but obviously I want to control the frequency with computer.

I might need to control the current accordingly as the temperature increases not to let the device fry out. Let's say if the initial current was about 2A, then the variance would be give or take 0.5A.

Now, just wait a minute!!!!!

You begin this thread about square waves. Now you write about manually changing polarity. Which is it?

Paul

Maybe we need to ask what frequency range is required?