DIY Controller Board Power Supply

[Fish4Fun]

I have been reading through the controller board threads and am very impressed by the level of sharing, cooperation and teamwork. I particularly enjoyed the thread about uli’s servo driver. I had thought about designing and building a similar controller, but this seems very done, but I had planned on starting with the Power Supply, and this doesn’t seem nearly so ‘done’. Obviously a line frequency transformer, a rectifier and some filter capacitors will do the job, but with the price of copper and the current focus on higher efficiency this solution is costly both initially and long term. A better solution would be a SMPS (Switch Mode Power Supply); however, SMPSs, while fairly simple in theory, present a great number of challenges to the average DIYer, and so the only available option is a commercial power supply to the tune of $200~$600.

Perhaps the greatest single challenge involves the transformer(s). Choice of wire size, core material, turns etc, etc can be a bit overwhelming. Even if all of these parameters are properly selected, obtaining transformers or even transformer cores in small quantities can be both difficult and expensive. I followed a thread in another section here where microwave transformers were used in an attempt to build a welding power source. It was fairly obvious to me that while a great deal of thought went into the project, the ultimate failure of the project hinged on an incomplete knowledge of the properties of the transformers.

With this in mind, I have been considering a completely different approach to a high VA supply. Unlike most SMPS designs this supply will need a great deal of flexibility with respect to the primary transformer. To achieve this flexibility I plan to use a micro-controller to optimize the switching elements based on feedback from the actual operating conditions. From a commercial SMPS design perspective this is an absurd expense; however, from a DIY’s point-of-view it offers tremendous flexibility at a considerable savings. That is, from a commercial design perspective a $50k investment in engineering R&D to minimize component cost is a trivial concern, but from a DIY point-of-view using a $10 component to allow flexible selection of other components is trivial.

Obviously a simple micro-controller is not going to take a $10 transformer from Radio Shack and magically provide us with an 800VA supply, but with some experimentation we might be able to come up with an easily fabricated transformer that will provide us with a 500VA to 1500VA supply. I have not begun experimenting with these transformer cores yet, and it may turn out that ‘off-the-shelf’ core materials simply cannot handle the flux densities requisite for a high-power supply and we have to fall back on a commercially available torrid core, but it is my hope this won’t be the case. Even if it were the case, having the ability for a single design to accept a range of available cores would allow DIYers a much better chance of success at a reasonable cost.

If anyone is interested in this project, either from a pure ‘user’ point-of-view or from a ‘wanting to help’ point-of-view chime in and let’s see if there is sufficient interest to move forward with this project.

Fish

[servocontroller]

You have come up with an idea which most of the DIY'ers have not even thought of and also admire your interest in this project This thread will also help those who know little about about SMPS and as far as the micro controller for controlling the PWM module is concerned an AVR will be the best choice for it.

Your idea is indeed interesting for all the DIY'rs concerned with power supplies for there motor controller.

[Fish4Fun]

ServoController,

Thanks, I was beginning to think no one even knew what I was talking about, lol. Yes, an AVR would be my first choice in uControllers. I have a great deal of experience with them, but there are many suitable uController choices if someone wanted to pursue something different than the AVR family. The cool part about this approach to an SMPS is that you should be able to use essentially the same supply for a wide range of current/voltage applications by simply changing either settings or firmware. Essentially we will be designing and building a bench supply without regard to the tight ripple and regulation parameters.

Thanks for your response

Fish

[max_imum2000]

our company has a dept which is specialized in switching power supplies only.
i wish i can have a us distrbuter that can buy in bulk and resell them again.
we really have great prices and i can help in getting even better prices for the zone users. the quality is great and i can offer free replacment of any defective unit immeditly
just to give you a hint
a 500watt , 48v power supply can range from 60$ to 100$ . depending on the features you require.
we also have 1000watt, 1500watt as well.

[Fish4Fun]

Originally Posted by max_imum2000 our company has a dept which is specialized in switching power supplies only. i wish i can have a us distrbuter that can buy in bulk and resell them again. we really have great prices and i can help in getting even better prices for the zone users. the quality is great and i can offer free replacment of any defective unit immeditly just to give you a hint a 500watt , 48v power supply can range from 60$ to 100$ . depending on the features you require. we also have 1000watt, 1500watt as well.

While those prices are certainly within reason and perhaps even cheaper than a DIY SMPS I understand all too well how the distribution chain works. Your company likely needs an order for 50, 100, 1000 or even 10,000 units. Next these units need to be paid for and shipped to another country where import tarrifs are applied. From there the person who has recieved these units needs to store them and begin selling them. By the time this process is finished a $60 power supply is selling for $180~$360. This doesn't mean that anyone along the way is 'getting rich', its just the way things work. The key to low pricing is volume, and the problem here is that there just isn't much volume in specialized power supplies. For instance, a 500W PC power supply can be sourced for < $20, but a 500W 80Vdc power supply, though of much simpler design, typically runs $150 to $300.

All of this being said, if you can offer 500W to 1500W custom power supplies to the members here for $60 to $100, then you will surely be a hero and there is no reason to continue forward with a DIY project. In fact, if these prices are firm, I'd like a couple.

Fish

[max_imum2000]

you are correct in every word, but offcourse 1000watt and 1500watt power suppliers are more expensive.
i can offer a price of 67$ for 50units 500watt 48volts PS. the voltage can offcourse be from 40 to 50volt adjustable.
if anyone wants to buy <50 units, it will not only cost more, it will also take a bit longer time as we source components for batch orders.
i can ask about the best prices for a units less than 50 units.
but i think it will be about 85$ price range.

however 1000watt 48volt powesupply will be much higher (185$-200$ range)
let me point out that increasing the voltage will not increase the price range.
but increasing the wattage will increase the price
ie: 500watt 24volt is the same price of 500watt 48volts.