Switching Power Supply

[Wiggi]

Hello Everyone.

I am not a big electronics guy and have only basic knowledge about electrical circuits, relays.....and I think that's where it ends already.

To make a long story short. For a project at work I would need an AC to DC power supply (115V) that outputs 36-60V. I know that switching power supplies switch rapidly on and off. And here is my question about it.

How can I regulate the on/off times???
For the project I would need an "ON" time of about 2ms followed by an "OFF" time of 4-6ms.
Is there some kind of part out there that I can wire in or anything to regulate the on/off times?
Oh...and of course I would need to be able to adjust Voltage/Amps.

Thanks a lot!!!

 

[(*steve*)]

I think you misunderstand what a switching power supply is.

Yes, things get rapidly switched, but the output is plain DC.

Do you want to control the speed of a motor using PWM or maybe a servonotor? That's different, but your specification for on and off times then makes more sense.

 

[Wiggi]

Thank you for your reply.
I might misunderstand the meaning of a switching power supply.
Maybe it is more the direction of a pulsed power supply?
Anyway, I need several of these for electrochemical deburring ("reverse electro plating"). The best way for this process is to have a power supply that delivers DC (Voltage or better Amps depend on the deburring task) and is "on" for 2ms followed by "off" for 4-6ms.
Does that make more sense?

 

[Fish4Fun]

Hey Wiggi,

Welcome to The EP Forum!

There are numerous ways to achieve pulsed DC .... Strictly speaking all that is required is a signal source (2mS on 4mS off), a Voltage/Current source and a "Switch" ... but the Devil is in the details ;-) You mention this is a project for a work environment ..... long before any discussions about circuit design parameters the safety parameters need to be carefully considered. If the business is in the US and falls under the purview of OSHA or any other Federal, State or local agency then ensuring any proposed piece of equipment meets all of the appropriate codes and safety requirements is likely going to be the mitigating consideration.

Assuming this business is small enough and remote enough to fly under the RADAR, and that management is willing to risk future liability issues in favor of short-term equipment costs, a simple solution would be to purchase an appropriately sized CV/CC "Bench Supply" (Perhaps 60V / 5A ??) Next, you would need to devise either an analog or digital signal source and select a Mosfet or IGBT to do the actual switching. Using an Arduino for a signal source, if you Selected a "Logic Level" Mosfet, a few lines of code and a heat sink would have you pulsing in less than an hour for ~ $200. This set-up could easily earn a 6-7 figure fine from OSHA and unless carefully packaged and concealed would probably fail to pass a fire inspection; however, assuming reasonable attention to detail in assembly ****should**** be perfectly safe from an electrical point-of-view.

Fish

 

[Wiggi]

Hi Fish.

Thank you for your explanation.
It is US and it is not a small company. OSHA is a factor in this case.
What I was trying to achieve here with my question is more like what's out there to buy off the shelve that plugs in to a regular 115V outlet. The application is low DC voltage (36V or less) and high current and it would benefit the deburring process if we can adjust the on/off times....the pulsing? So....with that being said.....what do I have to look for (brand....models....the actual name of a device like this, pulsed DC power supply???).

Thank you very much.

 

[Fish4Fun]

Hey Wiggi!

I know more about electroplating theory than practice, but I know that pulsed DC is used in some electroplating processes, and I would assume that there are industry standard products readily available ..... A google search for "electroplating power supplies" yields a fair number of suppliers and manufacturers of electroplating equipment; I feel confident that a quick phone call to one of them would give you plenty of information to pass on to the engineering department OR the purchasing agent.

Fish

 

[Wiggi]

Hey Fish.

Alright....so I have to search for a electroplating power supply. That info helps.
One question came up when I was looking through some of the available power supplies (which makes me probably no look completely stupid).
When looking at the front plates of those power supplies I only saw knobs to adjust current and voltage. How could I adjust the on/off times? Would these need an additional controller or something like that to tell when to turn on and off? I think Dynatronix was the only brand I saw that gives the option to control the on/off times?

 

[Fish4Fun]

Hey Wiggi,

Again, what I know about electroplating is from reading about various processes, not from hands-on experience with industrial implementations. I would certainly **think** that any MFG offering a pulsed DC power supply to industrial customers would include both frequency and duty-cycle adjustments in addition to voltage and current adjustments; however, I don't **KNOW** this to be true.... I would suggest you call an industrial supply company that specializes in electroplating power supplies and simply ask them what is available. Assuming the process is not proprietary, there should be plenty of information about the process in the public domain, and a company specializing in this type of equipment might even point you to a specific model designed for the process you plan to use.

Hrmmmm....I guess I don't have a firm grasp on your situation. If your employer is in need of "several" of these power supplies I would think that implies the process has been tested on a small scale and is now ready to be added to an existing production line. This would generally imply that there are several engineers involved, and in my experience engineers don't generally source production-line equipment quite so casually. If I am reading this wrong and the engineers aren't involved, rather the current effort is to build a proof-of-concept unit, then perhaps it would be best to give some more details.

For instance, if you are on a tight budget, and the proof-of-concept unit can be built and tested in a place with relaxed safety codes then you might consider using a TIG welder as a current source. Even China-Cheap TIG welders offer Pulsed DC outputs with adjustments for current, frequency and dudty-cycle. Obviously a TIG welder would be problematic (from a safety-code perspective) if utilized as a power supply in a deburring segment of a production line, but that does-not imply it would be inherently unsafe .... just not likely to "pass code". Or if the plant has TIG welders on hand, you might simply "test the process" in the shop where the TIG welders are located....

I am just grasping at straws .... Perhaps if you fill in some of the blanks I might provide better suggestions ??

Fish

 

[Wiggi]

Hey Fish.

Thanks a lot for your detailed reply and your time.
You are right. I have built a small unit for proof and concept and to get this process (Electrochemical deburring/reversed electro plating) going and implemented for some a part we manufacture.
Since it is just a small unit I now like to design and built a bigger and more automated unit which should include "lessons learned". One of the improvements is to change the power supply. The small unit runs on standard switching power supplies. It works but can be optimized by using a pulse power supply.
I knew what this new power supply should do but had a hard time finding out what/how to look for it. You definitely pointed me in to the right direction and I will contact some possible suppliers.
Thank you very much for sharing your knowledge and time !!!

Wiggi

 

[bsco]

I had to do a "Non destructive" Circuit board repair course years back.....and we had to do electroplating..There was a current/voltage controlled power supply which used a footswitch to control the on/off times manually....I think it was from a company called PACE but not 100% sure...The soldering and desoldering equip were PACE brand.....you could google the company to see what comes up.....

 

[Wiggi]

Thanks BSCO.

I will look into that too.
Maybe they make a power supply with the requirements I would need.

Wiggi

 

[Fish4Fun]

Hey Wiggi!

Knowing that you are building a proof-of-concept unit (likely @ home?) changes your options considerably .... especially if your employer is not funding the project. I would suspect that an industrial power supply for production use could easily cost a thousand dollars and be more than a little difficult to source. IMHO you would be better off DIYing your pulsed DC power source for your prototype (if you are footing the bill and your prototype will not ultimately become part of a production line), and I feel confident that members of this forum will be more than happy to help.

I will draw up a schematic and build//test a DiY Pulsed DC power supply....perhaps have some preliminary info this afternoon. If you want to share details about your set-up I will attempt to mirror it and use it as a test bed, otherwise I will simply use water and potassium chloride to evolve H2 and O2 ... doubt I will be able to achieve a 5A current flow @ 36V with hydrolysis, but I will test the circuit @ both 36V and 5A to ensure component selection and heat sink recommendations are adequate.

Fish

 

[Wiggi]

Hey Fish.

Before you put work into it I want to clarify something.
We already built a proof-of-concept unit in the plant and using it. But this runs on regular switching power supplies.
To optimize the upcoming larger and automated unit I want to "update" to a pulsed power supply to be able to adjust the on/off times. That's all what I am looking for and had no idea what the name of it is or what to look for. And your advice about power supplies for electro plating was exactly what I am looking for.
So please don't spend your valuable time on drawing a schematic. We are not going to build one here (Safety Engineers, OSHA etc.) and I would probably not understand the schematic anyway.
With your posts you already gave me all information I needed.

 

[Fish4Fun]

Perfect!

Enjoy!