Miniature USB power supply with display - Page 1
Forum section: electronics / projects

author: knivd
author_rank: Newbie
timestamp: September 27, 2015, 04:27:27 pm
content: A few months ago I ran a small and unpretentious kickstarter project for a miniature USB power supply. The project can be seen herehttps://www.kickstarter.com/projects/knivd/pocket-usb-powered-power-supply-for-the-hobbyistUnfortunately it failed but up to this day people occasionally keep asking me how to make or buy one of those. I have lost interest in this project in favour of others at the moment, and decided to release it free to everyone the way it is at the moment. The hardware is tightly routed on a two-layer PCB in order to keep the cost low. That was fun. The files are for Altium Designer.The board is relatively easy for manual assembly with the components large enough to be handled. If you assemble the board properly, it should start working immediately. The full working parameters are still yet to be determined.The firmware however is unfished (again, because I turned my attention elsewhere). It is close to completion and if someone else is interested in picking up from here on, please be welcome. The only condition - keep the project open source.You can download the pack from my own website:http://dimitech.com/hamster/USBminiPower.zipComments or questions - please let me know.Thanks!

author: Kilrah
author_rank: Unknown
timestamp: September 27, 2015, 08:20:51 pm
content: Very very nice! Would probably be worth relaunching a kickstarter after presenting it to a couple of forums like this one, sure you'll get enough people this timeMaybe just a little expensive though.

author: knivd
author_rank: Newbie
timestamp: September 28, 2015, 12:09:54 pm
content: ThanksI am not planning to re-launch it or do any further work on it, but hopefully someone else might find it interesting.As to being a little expensive - my calculations were based on Digikey/Mouser BOMs, probably can be made much cheaper...

author: zapta
author_rank: Super Contributor
timestamp: September 28, 2015, 03:41:44 pm
content: How does it regulates Vout voltage and current limie, though the MCU and the PWREN signal? If so, what is the sample rate of that loop?Also, anything special about the selected MCU (PIC16F1783) or can it be done with AVRs such as the ATMEGA328P?(I am thinking of using this as the starting point for a similar power supply that is Arduino IDE compatible, no fixed 3.3 and 5V output, an SPI 1.3" OLED display, and a rotary encoder).Edit: I see it now, the voltage regulation loop goes through digital pot. What about the current limit loop?

author: Mechatrommer
author_rank: Super Contributor
timestamp: September 28, 2015, 05:22:59 pm
content: it seems like he's using boost convertor like the plethora of china 5V to boost module these days i believe... the nice feature though is the need for mcu and voltage display all in one pcb... otoh, you maybe snap these 2 to get portable hobbiest psu, ymmv...http://www.ebay.com.my/itm/DC-DC-Converter-USB-Step-Up-Boost-Power-Supply-Module-5V-to-5V-12V-Adjustable-/171540701206?hash=item27f09f6016http://www.ebay.com.my/itm/New-Mini-Digital-Voltmeter-0-100V-Red-LED-Vehicles-Motor-Voltage-Panel-Meter-FO-/111754213123?hash=item1a0511f703but i wont dare to plug those into my pc or laptop usb port. i prefer to connect it to 5v wallwart that are humongous these days..

author: zapta
author_rank: Super Contributor
timestamp: September 28, 2015, 05:34:56 pm
content: Quote from: Mechatrommer on September 28, 2015, 05:22:59 pmI think his is buck boost that can go down to 1v. A small graphical OLED may be a nice addition. Also I prefer a micro USB connector that can be connected with ausb cable to a 5v charger.

author: knivd
author_rank: Newbie
timestamp: September 29, 2015, 11:07:33 am
content: The device uses SEPIC design, so the output can go lower or higher compared to the input. It can go down to 1V which is the feedback reference voltage for the selected converter. The upper limit is just over 14V due to other factors. Due to the fact the output current is fairly small, it is not regulated at the moment, only the voltage. The current can be monitored, though.You can make some sort of current regulation by using the PWREN signal in a software feedback-based loop.As to the selection of MCU - I use Microchip because I know them and I like them. The footprint also allows use of a few different models, some of them with USB, others with other features. For sure it can be made with Atmega328 as well, but it will be a totally different design.