I want to build a power supply.

[jdraughn]

how to make a power supply

I have been thinking of building a power supply which is suited for my needs. I will use it for various misc projects, mostly related to pic microcontrollers. The largest current drain will probably be some stepper motors.

I would like it to be portable and light, and these are my thoughts on the features I want it to have.

4 different voltage outputs, each one having a positive, ground and negative.
a 3.3v, 5v, 12v and an adjustable output.

It's main power source would come from simple AA or AAA batteries. I am thinking 12 of them which would get me 14.4v. I think that would be enough for a 12v regulator.

It would have a small solar panel on top so when it's not in use, or being used very lightly the panel alone would be able to keep the battery level up.

It would also have a USB input with a current limiter so I can charge it (slowly) off my notebook.

It would also have a regular DC walwart jack and/or AC plug and would run directly off those inputs if needed.

I generally just do some light experimenting for a few hours every day, but most of that time is spent building the circuit or programming the microcontroller, then I spend a few seconds at a time trying out my circuit or code.

The solar panel i want to use is a 1.5 watt one sold by harbor freight for maintaining auto batteries, so it could charge the batteries directly.

For the USB connection I would need a switching buck boost DC-DC converter to boost the 5v to 16v or so needed to charge the 14.4v batteries?

Can anyone recommend their thoughts on what components they would use to build this? This project is probably more for the fun of doing it then the practicale use of the actual power supply.

My first thoughts were using the cheap and plentiful 7805, 7812, ect... regulators, but they are very ineffecient for something that may be powered by batteries alone. But maybe it would be worth it because of the noise introduced into my power supply from a switching regulator?

Any advice or tips would be greatly appreciated. I have just been using a 5v cell phone charger or my USB port directly to power my pics on my breadboard, as I take my laptop and tons of components back and forth between home and work everyday.

In the future I may want to upgrade the power supply by adding displays and/or USB connection to my PC so I can view voltages and make adjustments via my notebook.

Thanks much.

 

[explorick]

build a power supply

I would suggest you to use buck regulators as the efficiency is critical for your application. The switching noise could be filtered through capacitors.

 

[smd_lover]

how to build power supply

Those solar panels barely give any power indoors. A waist to spent your money on that.

USB gives a direct electrical connection with your pc, not a good idea for a lab-powersupply.

Have you thought about a settable current limit? For me that is the first thing a power supply for my pic-projects must have.

 

[ark5230]

make power supply

A strange and odd demanding plan. Desktop has extra connectors with enough sourcing capacity to be suitably tuned to use. USB limits are low. Unless circumstances force, better to stay with standard batteries (may be chargable) and mains sourced supply.

 

[jdraughn]

how to make a lab power supply

Those solar panels barely give any power indoors. A waist to spent your money on that.

USB gives a direct electrical connection with your pc, not a good idea for a lab-powersupply.

Have you thought about a settable current limit? For me that is the first thing a power supply for my pic-projects must have.

Hey, thanks for you thoughts. I realise the solar panels do hardly anything indoors, but it's not quite as bad as you would think. They normally cost 20.00 but when they go on sell they are 13.00, and I work there part time which brings the cost down to a little over 10.00. not too bad.

The reasoning behind all this is because as I am lugging all this crap back and forth, I get really tired of pulling out soooo many cables. I have to have a usb hub because my notebook only has 3 usb ports, my mouse, modem and ICD 2 each take up a port which leaves none for external drives.

But unless I have the hub plugged into the wall my devices will act funny. It's just a huge rats nets I have to pull out everytime. Plus I also carry a selection of resistors, switches, caps and IC's so if I want to try a circuit hopefully I will have what I need.

It's a lot of work but seeing as how I get around 4 hours a night to play around with my circuits, it's worth the trouble, so I am just trying to ease the load a little by having the option to not have to plug in my power supply unless I need too, and hopefully just get by with a USB connection seeing as how I have a powered hub plugged in anyway.

I have thought about having current limiting also and making it digitally controlled with momentary buttons rather then pots, which will also make it easier to control through my PC.

I don't know if i will ever actually go through all this trouble, but my pics take 5v, but some of the lower voltage pics and some IC's will need 3.3v, and some motors or whatnot will need 12v, hense the reason for needing so many outputs. Plus a variable output to be safe.

I would also like to be able to set current, that was not quite a priority for me at the moment but seeing as how someone brought that up it should be a priority, I will make it a priority.