Need help with project. - Page 1
Forum section: electronics / beginners

author: skillz21
author_rank: Frequent Contributor
timestamp: August 13, 2016, 01:26:35 am
content: So i have to make an electronics project for school. So I want to make a display that shows the humidity and temparature (and possibly the date and time) i will probably be using a DHT11 for humidity and temp, i want to display the data on a 16x2 display. I have to make the project so that it converts one type of energy into another. So i want to power this with a solar panel. i have a small solar panel that i am hoping to boost the voltage of so that it can charge 2 batteries,(http://www.ebay.com.au/itm/1-2-4-6-8-10pcs-18650-6000mAh-3-7V-Li-ion-Rechargeable-Battery-Charger-ID/282076923995?_trksid=p2047675.c100005.m1851&_trkparms=aid%3D222007%26algo%3DSIC.MBE%26ao%3D1%26asc%3D20140106155344%26meid%3D8c3c8e65c1ce430482cc67b7440abd40%26pid%3D100005%26rk%3D2%26rkt%3D4%26sd%3D282102655752) So what voltage will i need to charge two of these batteries? also, will i need a battery protection circuit? also i have a budget of around 10-25 aus dollars, will it fit inside that budget?Thanks in advanceskillz21

author: Audioguru
author_rank: Super Contributor
timestamp: August 13, 2016, 02:22:20 am
content: You must learn about the dangers (explosion and fire) of wrongly charging a Lithium battery. The charging current MUST be limited to the amount recommended by the battery manufacturer and the voltage must bebalancedat 4.20V per cell. A Lithium battery charger IC is usually used.The cheap Chinese no-name-brand battery has a 6000 mAh number that is impossibly too high. Its weight seems to be too low. It is probably a fake battery cell that are frequently sold on ebay. Buy Sanyo-Panasonic battery cells locally instead.Why boost the voltage of a solar panel that is too small? Its current will also be too low.

author: skillz21
author_rank: Frequent Contributor
timestamp: August 13, 2016, 02:44:20 am
content: well... i probably won't be using that solar panel, because i can't find it... anyway, will this work? (http://www.ebay.com.au/itm/Solar-Panel-0-12-0-65-1-3-5-2-3-1-5-4-2W-DIY-Light-Battery-Phone-Charger-/152103878594?var=&hash=item236a18ffc2:m:mbZ2YddWKlJ8sQHgAkpaw3wthe one with 3W/6V/520MA)

author: skillz21
author_rank: Frequent Contributor
timestamp: August 13, 2016, 11:13:41 am
content: Hi everyone!i tried to make a sketch on easy EDA(check the attachments). Easy EDA is relatively new to me so sorry about any errors that i may have made.BTW, the power source is the solar panel. So is there ant probs in the circuit design?

author: Audioguru
author_rank: Super Contributor
timestamp: August 13, 2016, 12:45:59 pm
content: Why does your schematic show two 5V batteries in series making 10V? Before you were going to use two Lithium battery cells that are 4.20V each (8.4V total) when fully charged and when their charging current has dropped low. Your circuit does not show a charging circuit but the battery will not charge anyway because the solar panel voltage is too low at maybe only 6V.Where is the detailed datasheet for the cheapo Chinese solar panel? Does it produce 6V with no load in noon sun? What is its voltage when it charges the battery with some unknown amount of current?

author: skillz21
author_rank: Frequent Contributor
timestamp: August 30, 2016, 07:51:41 am
content: ok, so, i decided not to do that, i want to build a arduino calculator(http://www.instructables.com/id/Arduino-Calculator/) oh btw, i'm not going to make the case, i will just use the circuit. so, heres the scematic(http://www.instructables.com/files/orig/FCD/XDN2/HXII577Q/FCDXDN2HXII577Q.ino) i want this to make a beep every time that any button is pressed.