Hi folks,
according to
, I have some very beginner questions.
(how can I ensure that the video is not embedded? :/)
I'm searching for a step down converter which also is a constant current source for
3 Cree XM-L U2.
- Input should be 4 LiIon 18650 Cells in series, which will be charged individually (a complex switch will ensure this).
- Output current should be 620 mA (I just want to increase the lifespan of the LEDs, nominal current is 700 mA)
- The circuit should take care of the LiIon cells to not deep discharge
- The circuit should also take care of the LED's temperature and throttle the current or shut them off (with "temp. too high" LED indicator)
- The circuit should of course monitor its own temperature and also throttle or shot uff (with "temp. too high" circuit indicator)
- On normal temperature, it should remain on full brightness till the end and go off with a red indicator LED "Charge me!"
Goal is a small PCB with surface mount devices that fits in my stainless steel pipe.
- Inner diameter is of the pipe: 2.5 cm
- Length of the pipe: 36cm
- Could also be 2 PCBs stacked together
For charging, I have bought 4 of these circuits, that can fit into the pipe:
http://www.ebay.com/itm/New-1PCS-5V-Mini-USB-1A-Lithium-Battery-Charging-Board-Charger-Module-EP98-/121089857674A switch will connect the cells in series when in ON state, and in OFF state it will connect the cells individually to the charger circuits that will be stacked. LED indicators goes with acrylic plastic rods to the side of the pipe, so that the charging status of each cell is visible.
What I need to know:
- What should I know to build such a circuit?
- How to create a PCB surface mount modell with free software?
- How to PLAN a compact PCB even when I have tested a circuit on a breadboard?
- Thermal issues?
- Which type of connection should I use to connect any 5 Volts, 4 Amps power supply for charging?
- I have a beautiful big 7.5 Volts/ 4 Amps power supply in europe plug style! Is it suitable to be used with a step down converter to 5V / 4 Amps?
- The charging current of each charger is not constant till the cell is full. The moment where 1 Amp is pulled is a very short time span and I don't think that the cells would be so empty that 1 Amp ever will flow for each cell.
Edit:
Forgotten to mention which cells I will use:
http://lygte-info.dk/review/batteries2012/LG%2018650%20D1%203000mAh%20%28Pink%29%20UK.htmlSo no china crap.
They will be charged till 4.2 volts, so 2.5 Ah are guaranteed I think.
Edit 2:
Found better ones:
http://lygte-info.dk/review/batteries2012/Panasonic%20NCR18650B%20Protected%203400mAh%20%28Green%29%20UK.htmlCosts me 50 EUR for 4.
I have to decide....
Thank you in advance!