Easiest 5v to ~12v DC/DC converter? - Page 1
Forum section: electronics / projects

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: July 03, 2016, 04:19:19 pm
content: Other than buying one? I have a USB powered arduino based battery tester and its fan runs too slow on 5v, so I need to step up the voltage to something like 9 or 12v. Now, I could use an off the shelf step up converter (and I do have one that isnt being used) but I would rather make one because that is much more educational.I am not opposed to winding my own inductor/transformer from a small ferrite torroid. I just want to know what the easiest curcuit is that would get the job done. It doesn't have to be well regulated and doesn't need to be electrically clean (these fans can run on unsmoothed half wave rectified AC) but it wil be running off of a USB power source, and I dont want it to interfere with the arduino.Where should I start?

author: Fungus
author_rank: Super Contributor
timestamp: July 03, 2016, 04:28:47 pm
content: Quote from: iamdarkyoshi on July 03, 2016, 04:19:19 pmStart at google.comSearch for "voltage multiplier"

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: July 03, 2016, 05:28:03 pm
content: Here?http://www.digikey.com/product-search/en/power-supplies-board-mount/dc-dc-convertersI've used the TDK-Lambda CC3/CC6/CC10 series, these are isolated and a bit pricey. Others exist too (CUI, for example, makes some inexpensive ones).

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: July 03, 2016, 05:55:17 pm
content: Quote from: Fungus on July 03, 2016, 04:28:47 pmI would need to convert the DC to AC first, maybe a 555 timer? Seems a bit overkill.Quote from: radar_macgyver on July 03, 2016, 05:28:03 pmI already have a ready made board, but I was saving it for another project. Its about the size of a quarter and can work down to really low voltages. But like I said, something like this is overkill...

author: radar_macgyver
author_rank: Frequent Contributor
timestamp: July 03, 2016, 06:18:47 pm
content: Quote from: iamdarkyoshi on July 03, 2016, 05:55:17 pmSorry, missed that.What about the Joule Thief design?https://en.wikipedia.org/wiki/Joule_thiefSingle transistor blocking oscillator. You will likely need some output filtering/rectification to drive a fan.

author: poorchava
author_rank: Super Contributor
timestamp: July 03, 2016, 06:34:01 pm
content: Something based on MC34063. Can't do cheaper than that.Sent from my HTC One M8s using Tapatalk.

author: David Hess
author_rank: Super Contributor
timestamp: July 03, 2016, 09:03:32 pm
content: A faster 5 volt fan would be simpler.The current requirements of a 12 volt fan will probably exclude the lower current options like charge pumps. A two transistor push-pull inverter would work but the transformer is more complicated than an inductor so the simplest design is probably a boost switching regulator implemented by something like the suggested MC34063 which is inexpensive and comes in a DIP-8 package.

author: Fungus
author_rank: Super Contributor
timestamp: July 03, 2016, 11:48:27 pm
content: Quote from: iamdarkyoshi on July 03, 2016, 05:55:17 pmYou've got an Arduino. Just output a square wave on a pin. Feed it into an NP MOSFET pair and you've got AC.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: July 04, 2016, 12:21:48 am
content: Quote from: Fungus on July 03, 2016, 11:48:27 pmI am literally using every input and output it has XDQuote from: David Hess on July 03, 2016, 09:03:32 pmI have looked through my 440mm fan collection and could not find anything faster than the current one.

author: sleemanj
author_rank: Super Contributor
timestamp: July 04, 2016, 11:21:04 am
content: Quote from: iamdarkyoshi on July 03, 2016, 04:19:19 pmYou are thinking backwards IMHO. Instead of stepping up from your 5v to 12v for the fan, step down from 12v to 5v for the logics.

author: Kjelt
author_rank: Super Contributor
timestamp: July 04, 2016, 11:24:45 am
content: Yes or buy a 5V fan

author: Fungus
author_rank: Super Contributor
timestamp: July 04, 2016, 11:28:35 am
content: Quote from: sleemanj on July 04, 2016, 11:21:04 am12V from USB....?Quote from: Kjelt on July 04, 2016, 11:24:45 amThat would be the easiest option.

author: sleemanj
author_rank: Super Contributor
timestamp: July 04, 2016, 12:59:22 pm
content: Quote from: Fungus on July 04, 2016, 11:28:35 amSure, usb 3.0 ;-)

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: July 04, 2016, 03:27:25 pm
content: Well, I wanted to do this without buying anything. i ended up using my last DC/DC, but these things are finnicky. They pull a lot of power on startup, because they work at such a low voltage. Kept tripping the overcurrent on my USB ports. So I added a soft start. Its far from ideal, but it works...

author: mariush
author_rank: Super Contributor
timestamp: July 04, 2016, 03:28:27 pm
content: You could use a charge pump ICs with a bunch of ceramic capacitors... small area, but low current.. something like 25-40mA .. one or several connected togetherSee LM2664 or even better, see something like NCP1729 :http://www.digikey.com/product-detail/en/on-semiconductor/NCP1729SN35T1G/NCP1729SN35T1GOSTR-ND/920055Check out pages 11 to 12 in the datasheet, but you should check all datasheet, there's an example circuit showing how to make positive voltage doubler with a couple of extra diodes, or voltage trippler (3xVin - voltage drop of a bunch of diodes)See also TPS60400 :http://www.digikey.com/product-detail/en/texas-instruments/TPS60400DBVR/296-27004-1-ND/2255294(can handle up to 60mA)

author: dannyf
author_rank: Super Contributor
timestamp: July 04, 2016, 03:45:49 pm
content: Quotea faster 5v fan, or a real boost converter. The current consumption for a fan is generally too much for a multiplier / charge-pump.

author: ebclr
author_rank: Super Contributor
timestamp: July 04, 2016, 04:25:00 pm
content: http://pt.aliexpress.com/item/2-pcs-MT3608-DC-DC-Step-Up-Converter-Impulsionador-Buck-Power-Supply-m-dulo-de-Sa/32671370753.html?btsid=3980f611-737c-4e50-8627-ac3c6c698c1b&ws_ab_test=searchweb201556_8%2Csearchweb201602_4_10037_10017_10033_406_10032_10040%2Csearchweb201603_3&spm=2114.02010208.3.143.XpWdx4

author: Powermax
author_rank: Regular Contributor
timestamp: July 04, 2016, 09:33:51 pm
content: If you're after simple and DIY, Look into boost converters and charge pumps. A simple joule thief with a few small modifications can be turned into a proper boost converter.