Easy travel size power supply [1.25~22V 2A] - Page 1
Forum section: electronics / beginners

author: dansku
author_rank: Regular Contributor
timestamp: January 09, 2015, 02:09:51 am
content: I needed a simple portable variable power supply.This is the easiest and cheapest way I found to have one to take with me when I travel.I'm using a AC (110/220) to DC (24V - 2A) power supply, connected to a DC-DC BUCK Step Down Power Module with output of 1.25V-36V 5A.DC-DC Power Module:Then I put the power supply with the dc-dc module connected together.Video:eBay links:[url=http://www.ebay.com/itm/171568211022?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT]http://www.ebay.com/itm/171568211022?_trksid=p2059210.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIThttp://www.ebay.com/itm/231381389930?_trksid=p2060778.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT

author: vargoal
author_rank: Regular Contributor
timestamp: January 09, 2015, 05:11:08 am
content: Maybe you could try this!http://www.ebay.com/itm/24-Volt-2A-48-Watt-Ac-Adapter-Power-Supply-For-LED-Light-Strip-5-mm-Dc-Jack-Lot-/390593759639?pt=LH_DefaultDomain_0&var=&hash=item5af133c997

author: dansku
author_rank: Regular Contributor
timestamp: January 09, 2015, 05:39:18 am
content: Quote from: vargoal on January 09, 2015, 05:11:08 amThe one I'm using is cheaper.Any advantage on using the one above?

author: vargoal
author_rank: Regular Contributor
timestamp: January 09, 2015, 05:59:54 am
content: It's just a size and form factor thing if you want more portability.

author: nowlan
author_rank: Frequent Contributor
timestamp: January 09, 2015, 06:29:39 am
content: Not a fan of the industrial psu.The laptop one looks safer (eg no mains leads).25W 9 - 24VDC Regulated Switchmode PlugpackConsider a lipo battery if you want true portability.Even a 9v battery.

author: dansku
author_rank: Regular Contributor
timestamp: January 09, 2015, 06:34:17 am
content: Quote from: nowlan on January 09, 2015, 06:29:39 amThis one is small indeed!I have a 11.1v Li-Po battery, I guess I can use that if I need 5/3.3 volts

author: PTR_1275
author_rank: Frequent Contributor
timestamp: January 09, 2015, 09:31:47 am
content: I have bought one of these for exactly the same reason. I have lots of bench power supplies, but occasionally I need a quick and easy portable power supply for checking something in a customers car. I am going to mount this into a small box with a battery to run the unit. I don't need it for huge amounts of power or for long periods of time so it will work fine for me (I hope). I am pretty sure it is only a buck converter as I cannot see any mention of a boost circuit, yet it says 6-35v input. I will give it a go once it is in my hands.http://www.ebay.com/itm/DC-6-35V-to-0-30V-3-1A-Step-down-Powers-Supply-Constant-Voltage-Current-Module-/111394890803?pt=LH_DefaultDomain_0&hash=item19efa72433

author: Evil Lurker
author_rank: Regular Contributor
timestamp: January 09, 2015, 02:08:54 pm
content: You can buy these things all day long with the LED voltmeter for around $6 and $2-3 (USD) from places like Ebay and Deal Extreme. They all are more or less the same designs however quality can vary wildly. Suffice to say you can bet every single component used on these things is a knock off as you can't even buy the switching IC itself in the US market for the cost of a fully functional barebones module from China.For example with the module shown in the first post in this thread some of the things that I don't particularly care for is the board layout and inductor selection. From the color of the toroid I'm going to guess that it is a type 26 iron powder, and from my understanding at the switching frequency of the IC (150kHz) this would suffer from greater core losses than say a green/blue colored type 52. Personally I prefer ones that have the standard shielded "box" SMD ferrite inductors as they come in higher values (that toroid I'm guessing would be doing good to push 20uH) although in theory the toroid could probably handle twice as much current. The only other gripes I have about the board is the layout... the schottky diode could be closer to pin 2 of the of the IC and since the IC is in the SMD package it is somewhat crippled by thermal dissipation limitations. Basically the board is laid out completely backwards to most designs.I'd love to do a comparison between modules to see exactly how component selection effects efficiency and performance, especially with the inductor, diode, filter capacitor, and feed forward capacitor selection but unfortunately I don't have a scope.