T-Pain Is On A Boat: Re: [Electric Boats] Voltage converters you can make

Thursday, March 20, 2014

Re: [Electric Boats] Voltage converters you can make

Kevin,

I would also like to add my appreciation for the hints you provided!

Is this the Arduino project reference you were looking at? >> https://sites.google.com/site/wayneholder/12-volt-charge-pump

That project looks very interesting to start with and begin tinkering. I saw an article on wikipedia about boost circuits and pumps. The described the basic circuit, but didn't show how easy it was to implement with a controller, and I don't recall seeing the diode configuration shown in the Arduino project. In my previous google searches for tutorials and circuits, the references you (Kevin) suggested didn't pop up. Thank you!

Wayne's project is unfortunately limited by using the controller pins to directly charge the capacitors. So I can see that he can get from 5V to 12 or even 18V at no load, or very little load. I'm guessing that I could add switches (transistors) between the controller and the capacitors to get it to boost the current capacity a bit. One question I would have on that would be whether only (+) needed to be switched, or if (gnd) would also have to be switched (2x transistors per connection). I haven't had a chance to play with it yet....

But I'm also guessing that there's a limit to how far this can be pushed. I'm skeptical that this can be practically scaled up to the 10-15A range.

And, as you mentioned in other emails - there's definitely a limit to how much power you can suck out of one battery to produce the desired voltage.

I haven't had a chance to tinker with voltage pumps yet. They look cool, and would certainly solve some problems. But it would be no surprise to run into practical limits....

John

From: Dave Steere <dcsteere@dcsteere.com>
To: electricboats@yahoogroups.com
Sent: Thursday, March 20, 2014 10:42 AM
Subject: Re: [Electric Boats] Voltage converters you can make

Kevin, I'm fascinated by this subject but it would be very helpful if you could share a little more of what you've found in your own research. For example, I don't know what Top Spice is, or where to find it. Also the particular on line sources for other information about high current PWM DC:DC converters using Arduino would be super helpful. If you have actually gotten far enough into this to design a particular DC:DC converter using the approach, would you be willing to share the schematic and maybe a few design notes that would be helpful to others of us interested in doing a similar project? I have tinkered with analog approaches but for one reason or another, most of my attempts have shown one or more design flaws and I can't really claim to have been totally successful, esp when trying to draw 10-15 Amps of current.

On Wed, Mar 19, 2014 at 2:42 PM, Kevin Pemberton <pembertonkevin@gmail.com> wrote:

Because many of you have wanted to know more about dc to dc power supplys I have looked up some things that helped me learn more about them.

Most engineers use black box devices to put a system together rather than build from scratch. We will not build from scratch but will open the case on the blackbox.

Building an a PWM source can be troublesome so I use the arduino project to feed the buck circuit to avoid many problems. Fact is the play area of the arduino website has published a project for a buck supply with a circuit we will use.

Other tools we will use include TopSpice just download the free version.

Next we will use the text file found in the tutorial on the ecircuit website files named basic buck. Much more can be gleened there but that can get you started.

Using a p channel fet driven by a npn small signal transistor with the PWM signal, and following the project published on the arduino site, you can have any size dc to dc supply you care to build.

Use the ecircuit site to learn why it works. See the results in action using the spice file supplied in the file from ecircuit in the downloaded TopSpice program.

You will find much on voltage dividers and a voltage divider calculator online. Build a divider and test it before you connect it to the arduino board. This input is feed to an analog pin on the board. It is used to read the output of the circuit so the program can adjust the output via the PWM duty cycle.

The output voltage can be 1/4 of the supply voltage. This means that a 48 volt supply can provide 12volts.

Have fun,
Kevin