help with a project 3.7v to 12v - Page 1
Forum section: electronics / beginners

author: squire
author_rank: Newbie
timestamp: June 05, 2012, 03:30:34 am
content: hello i look forward to being a part of this form!so bare with me im going to explain this the best i canim trying to start a small project. im trying to make a battery operated pack for a motor that i have. i would like to use a 3.7v(small) lithium ion battery with a high Mah for longevityok heres the parts i need help with. i would like to boost the 3.7v to the max around 12v. if at all possible with i would like it to last 1-2 hours max(is that possible if ran constant ?) it will not be a set at 12v i would like it to be adjustable from 3.7 to 12v. i would like to be adjust remotely via bluetooth or rc,rf what ever can be the smallest. im looking to build this the smallest way possible. im not that familiar with parts and builds of this type and any help would be greatly appreciated or if you can point me in the right direction. my first start was herethe reason i went with the 3.7 battery is im trying to stay small. i want it to be as small as i can. the 3.7v battery cell phone size is perfect... is this feasible?if it helps im trying to build something along the lines of this but wanted the the adjustments to be made remotely. see how the dials are on the back of the machine. a tattoo machines runs from anywhere to 4v to 12v and thats constant power. i noticed they used a 3.7 lithium ion battery for theres.http://www.jokertattoo.net/tattoo-machines-20/freewire-tattoo-machines-113/freewire-tattoo-machine-970.html?zenid=8a5de2ed1503a4bfba505ca605f20398

author: T4P
author_rank: Super Contributor
timestamp: June 05, 2012, 04:45:28 am
content: use a DC-DC boost converter...Bluetooth?You kidding me right?

author: squire
author_rank: Newbie
timestamp: June 05, 2012, 01:20:11 pm
content: Is Bluetooth to big? Or just a bad idea? Also would the dc to dc boost converter be able to be purchased Or would I need to build it? Like I said trying to make it as small as I can. Around an inch or two Thank you do much for you help!

author: PA0PBZ
author_rank: Super Contributor
timestamp: June 05, 2012, 01:25:04 pm
content: Can't go much cheaper than this:http://www.ebay.com/itm/DC-Boost-Converter-3-24V-to-5-25V-Battery-Step-Up-Switching-Power-Supply-Module-/270974011214The big question is: what is the power consumption of the motor?

author: digsys
author_rank: Unknown
timestamp: June 05, 2012, 01:54:22 pm
content: QuoteHiya, Firstly Voltage doesn't determine size. Total AH determins size. For example, lets say you want (haven't indicated how much power you need)5WH of energy. You get that with EITHER 3.7V x 1.35AH OR 12V (say) x 0.4AH. The Volume (size) of the battery is exactly the same (close enough).BUT the advantages are - 1/ Higher efficiency (lower currents) and a 200X+ greater selection of DC-DC converters to chose from. Step ups are notpopular. So now you adjust down, instead of up.2nd component - "radio" control. Best bet would be a say 4 button "garage door controller" kit. Hunderds out there and good to 100-200mtrsBlutooth is VERY short range, complex to set up / use etc, so forget that idea. You can get radio kits with more buttons (IO) but not necessary.You can set the button up as either - UP/DN/RESET/OFF or 4xpreset Voltages, that's up to you. For longer range, there are different frequency kitsthat do 100's metres+, just search "garage door kits". It's just a popular generic name.As for Voltage control, you'll need to look for DC-DC modules that have an adjust pin, shouldn't be too hard to find.Good hunting

author: squire
author_rank: Newbie
timestamp: June 05, 2012, 05:54:15 pm
content: you guy rock!im not to sure of the power consumption.its is basically a dc circuit containing two magnetic coils in series with a capacitor in parallel which operate an armature on a spring contact. Think doorbell. there is a adjustable supply feeding the power via a cord positive and negative. the supply is adjustable from 1v-12v higher voltage faster the machine goes. i hope that helps, the link supplied from my last post says the machine will run at a constant at13.6v for 2 hours.. im wondering how they achieved this.

author: digsys
author_rank: Unknown
timestamp: June 05, 2012, 11:55:05 pm
content: QuoteYou NEED the current rating to calculate the Total storage energy required. A coil is probably ~ 100-200mA,unless it has to move WEIGHT. Assuming 100mA, you need ~2.8AH, add 10% min at the ends = ~3.0AHAt 200mA constant current draw, you need 6.0AH of storage energy. so - a 12V battery x 0.5AHStraight maths (+~10% for slight losses)

author: squire
author_rank: Newbie
timestamp: June 06, 2012, 01:58:14 am
content: if you look at the picture here there runnnig a 3.7 battery i want to keep it small all the 12v battery seem to large..i guess the main question is how do you think they did this?

author: digsys
author_rank: Unknown
timestamp: June 06, 2012, 03:16:53 am
content: OK, maybe I wasn't clear.THEY have unlimited money (compared to you), so THEY chose to use a lower voltage and STEP-UP.Everything on the control PCB is custom designed, an option you DON'T have (due to cost).What I am saying, the battery VOLUME is EXACTLY the same, whether you go ~3V and step up OR12V and step down. All you need to do is find a perfect fit battery, maybe a laptop type instead.Because you have limited technical assistance, I suggested you go for STEP-DOWN, as it is easier todo. The application couldn't care less. Either way, you will NOT achieve their small size, unless youspend a LOT of $$ to custom design it. Using Off-the-shelf parts, you have limitations.Hope that a bit clearer.

author: T4P
author_rank: Super Contributor
timestamp: June 06, 2012, 12:20:09 pm
content: STOP looking to use a 3.7v batteryUse a 7.4V battery and be done with