Title: Lipo to USB charging adaptor Post by: allthatido on July 12, 2012, 12:39:11 PM Hi guys
I was discussing the need for a lipo to usb adaptor with my local electronics vendor from whom I source my electronic components. He has an electronics shop and does college projects for students. So after coaxing him enough he agreed to design and get fabricated a similar circuit for me. I have successfully charged my keychain cam and an indoor IR heli with it. Couldn't check my phone as I don't have a usb charger cable for it. I asked him not to solder any connector as he didn't have xt60 or deans. He gave the bare bones circuit to me and I soldered a deans onto it. It also has a led for power indication. You can power it up with a 3s lipo too as compared to the Hk one where you need to use a 2s only. Paid 400 for it (its a little pricey i know) All in all happy with it. Now will try to make a case for it. Will put pics shortly. Title: Re: Lipo to USB charging adaptor Post by: ujjwaana on July 12, 2012, 12:58:05 PM That should not have been a big design challenge. A common place 78LM05 regulator would have done the job, even handling 3S lipos. If you dont want any loss in the Lipos due to heat, a better DC-DC step down converter could be used , even our regular 5volt BEC would have done the job.
http://www.ebay.com/itm/1PCS-LM2596-DC-Step-Down-Adjustable-Converter-Power-Module-/251088690509?pt=LH_DefaultDomain_0&hash=item3a760d5d4d Hobby King recently added exactly the same thing you want in a neat package... http://www.hobbyking.com/hobbyking/store/__24405__Hobbyking_Lipo_to_USB_Charging_Adapter.html Title: Re: Lipo to USB charging adaptor Post by: allthatido on July 12, 2012, 01:10:41 PM Hi Ujjwaana
My electronic skills are way below average. Soldering skill is a tad better. If you ask to me solder a component I will do that but if you ask me to choose a component..you will see a blank face. Yes I saw the product at HK but its consistently out of stock. Hence coaxed my vendor to make one for me. It costs approx same as HK (tad cheaper) and I get to build a custom case for it out of balsa. ;D Ankur Title: Re: Lipo to USB charging adaptor Post by: allthatido on July 12, 2012, 08:49:53 PM Pics
Title: Re: Lipo to USB charging adaptor Post by: anwar on July 12, 2012, 10:15:27 PM So now you are playing with fire everywhere you go... not just when you are going flying :giggle:
Just kidding... many (most?) newer cell phones use lipos. Title: Re: Lipo to USB charging adaptor Post by: ujjwaana on July 12, 2012, 11:20:35 PM Pics I would like to HIGHLY discourage you from using this converter. The regulator used to pull down the voltage is in TO-92 package which can max give you current rating of 100mA max.... I would again recommend you to use a 2Amp BEC instead, or at least use the 78L085 regulator in TO-220 which would give you 500mA. Title: Re: Lipo to USB charging adaptor Post by: pankaj on July 13, 2012, 07:16:06 PM Good effort Ankur Sir.IMHO i think it will overload the circuit if using it for a mobile charger(Required current is minimum 500ma). LM7805 (05 Defines the output voltage,7809 will give a constant 9V) would really be great in these kind of applications as Ujjwal Sir suggested.Also if you are using a Dean connector(where polarity reversal is not possible even by mistake) the diode can be removed from the package saving you some .3-.8 Volts.
I guess HK also has used 7805 Positive voltage regulator.That'why there max current is 1A.If making DIY Current can be increased if necessary by using multiple 7805's in parallel. Pankaj Title: Re: Lipo to USB charging adaptor Post by: sushil_anand on July 14, 2012, 10:48:24 AM I am afraid that using a 9V supply is a no-no. The USB standard specifies a 5V output voltage and the phone's internal charging circuit would, perforce, be designed around that.
Title: Re: Lipo to USB charging adaptor Post by: pankaj on July 14, 2012, 10:57:33 AM Yes 5V is standard and we should use LM7805 in this case ,i was telling that LM78XX Series are positive voltage regulators and 7809 can be used if we need a 9V constant.
Pankaj |