solar dc power supply

[sybergoosejr]

hi new here to the ee forums and I have been working on a small power supply for my hobby projects and would like some tips and pointers.

first here is what my current solar panel setup is like
each panel is rated for 6v 250ma. I have 6 panels in total wired to provide 12v at 750 ma (full sun ideal draw ect...) using only 2 wires going from a screw terminal strip at the panels to another screw terminal strip inside.

right now I have my current design on bread board but I plan to solder a more permanent version onto one of those grid pcb's (I don't plan on etching my own at this time)

my end design goals are to have 2-3 output rails with a few accessory outputs/inputs for controls.
rail 1 would be 12v
rail 2 would be 5v
if I can figure out how I would like to add a negative rail without running 3 wires in-between my junction strips. (for +6v gnd -6v)

accessory ins/outs would be for input voltage sensing and I plan to add 2 3pin male headers on the board tied to 12v rail (with a transistor and dip switch) for 12v pc fans with having a total of 6-7 female pins for all the IO of the supply  2 for individual control of the fan ports via onboard transistors (dip switch override) for micro controller use. a pin for input voltage detection and the rest for the actual supply rails.

I have made a video of my current setup and it works ok so far.


some parts I used in my current setup
10000uf 16v cap (12v rail)
1000uf 35v cap (5v rail)
2 100uf 16v caps (voltage divider)
3 10k ohm resisters (voltage divider)
2 5v regulators (power 5v rail)

my 12v rail is not regulated at this time and I don't have any current limiting resisters (smallest value resistors I have are 330 ohm)
I would like to add a current limiting resistor on the 12v cap side of things to limit current to about 1-2A without a lot of voltage drop.
I have already made a few of my transistors go bad by trying to use them with this large cap on the rail.

now that cap is most likely way huge for this project but I wanted something that I don't riley have to worry about charge and discharge life like a battery and can supply power on it's own (unplugging panels) for a second or more (not micro seconds)

now the cap that is rated for 35v 1000uf would I be killing it life expectancy by running at such a lower voltage than it is rated for?
should I add a 12v regulator to help solve my over current issues or is there a magic value resistor that will give me a workable amount of current and still keep the supply at about 12v (full sun)

and as my only part source for this project so far everything (except the 10k uf cap) came from radio shack. (I get the feeling that there stuff is looked as if it's the lowest end)
if you guys need me to I can go find the part numbers for the solar panels I used as well as some of the other parts.

[David Hess]

now the cap that is rated for 35v 1000uf would I be killing it life expectancy by running at such a lower voltage than it is rated for?

No, the capacitor will work fine at lower than it rated voltage.  Typical applications derate capacitor voltage for higher reliability.

should I add a 12v regulator to help solve my over current issues or is there a magic value resistor that will give me a workable amount of current and still keep the supply at about 12v (full sun)

A resistor may be acceptable to limit fault current but is not going to work if you want the 12 volt output to be stable with different loads.  A simple 12 volt regulator would be a good choice.

[Ziltoid]

Hi,

check Julian Ilett Channel on YT. He has done something similar, he used cheap modules from china. What you want is a Buck converter so you dont waste Energy. The Post Apocalyptic Inventor made some nice Videos about SMPS.

https://www.youtube.com/channel/UCDbWmfrwmzn1ZsGgrYRUxoA/videos
http://en.wikipedia.org/wiki/Buck_converter
https://www.youtube.com/user/julius256/videos

[sybergoosejr]

thanks for the info ill do some research into the buck converters and get my hands on a 12v regulator in the mean time.