Small Power Supply for Digital Systems? - Page 1
Forum section: electronics / beginners

author: Matir
author_rank: Contributor
timestamp: May 04, 2017, 06:36:09 pm
content: I'm a software (security) guy just getting into embedded systems (or, as marketing would call it, the "Internet of Things"). Consequently, most of the systems I'm dealing with are operating at either +5V or +3.3V (or some mix of both). For my home workspace, I don't have much space at all (really just an Ikea desk in my home office) and so I'm thinking "small" for my tools. Consequently, I'd like to find a small power supply for working on these systems.At a minimum, I need to support:+5V/+3.3V outputs (probably single output is fine)Current limiting for when I do stupid things~2A outputIdeally, I'd also like:Voltage/current displayOutput on/off switchMaybe as high as 12V/3A on occasionSpace and price are premiums, but I don't want to blow up the DUT, so safety/correctness first.

author: TheUnnamedNewbie
author_rank: Super Contributor
timestamp: May 04, 2017, 07:00:56 pm
content: Are you looking for a simple fixed supply or a full-on bench supply? If you are looking for the latter, last I heard the entry rigol ones are pretty good. They perform well, and are not that expensive (I think around 400 EUR?)If you really need simply low power/size, it might be interesting to wire up a handfull of LM7805 or similar with a small transformer. They could fit in really small boxes.

author: john_c
author_rank: Contributor
timestamp: May 04, 2017, 08:47:29 pm
content: Given that you want to focus on microelectronics, and keeping in mind all your requirements, I'd say you have two options. #1 would be something like a Tekpower TP1803D.#2 would be a 12V fixed power supply (available as a cheap "brick" at currents up to 5A or even a bit more) plus a small adjustable step-down DC converter. You could also go up to 19V or 24V for the fixed voltage, or use an old laptop power supply for that part. This would be very easy on work space. There are a ton of converters on Ebay. Here's one with an enclosure and a display:http://www.ebay.com/itm/351824924923

author: Matir
author_rank: Contributor
timestamp: May 04, 2017, 10:13:49 pm
content: The problem with the converters is that they're not current limiting. I would like to, at some point, design a current-limiting power supply, but I'm not sure I'm at that stage yet.I'm often supplying power to chips in unusual ways (trying to hold a MCU in reset to read out serial flash, for example) and I'm hoping current limiting will save me fromsomeof my mistakes.The TP1803D looks like a not bad option.

author: john_c
author_rank: Contributor
timestamp: May 04, 2017, 10:52:22 pm
content: There are some DC converters I've seen (mostly step up converters for LEDs) that have a screw-pot adjustable current limit. None that I've seen that also have a display, though.

author: ez24
author_rank: Super Contributor
timestamp: May 05, 2017, 04:49:22 am
content: Quote from: john_c on May 04, 2017, 08:47:29 pmLooks interesting so I ordered one of thesehttps://www.aliexpress.com/item/New-DPS3003-LCD-Constant-Voltage-volt-current-Step-down-Programmable-control-Supply-Power-module-converter-DP30V3A/32684948592.html?spm=2114.01010208.3.1.0x1hiN&ws_ab_test=searchweb0_0,searchweb201602_5_10152_10065_10151_10130_10068_436_10136_10137_10157_10060_10138_10155_10062_10156_10154_10056_10055_10054_10059_10099_10103_10102_5140020_10096_10147_10052_10053_10142_10107_10050_10051_10084_10083_10080_10082_10081_10178_10110_10111_10112_10113_10114_10181_10183_10182_10078_10079_10073_10070_10123,searchweb201603_1,ppcSwitch_3&btsid=a3f1c547-32aa-45a7-8256-dc62dc78ccf8&algo_expid=9625bc3b-b5ec-466a-8487-88914d7249e1-0&algo_pvid=9625bc3b-b5ec-466a-8487-88914d7249e1Oh brother - what a link. I will drive it with a 19v laptop supplythanks

author: rdl
author_rank: Super Contributor
timestamp: May 05, 2017, 05:48:10 am
content: Quote from: ez24 on May 05, 2017, 04:49:22 amJust whack off the ? and everything after it. All that extra stuff is of no benefit to anyone but Aliexpress.https://www.aliexpress.com/item/New-DPS3003-LCD-Constant-Voltage-volt-current-Step-down-Programmable-control-Supply-Power-module-converter-DP30V3A/32684948592.htmlIt works for ebay too.