• on Audio/Video/Photography
  • Published in issue 3/2011 on page 68
About the article

Solar Charger

Portable energy for people on the move

Solar Charger
With renewable energy high on the agenda, this little project will appeal to everyone who would feel better charging their mobile or PDA from solar sources. A lithium-ion cell stores the sun’s energy in between charging sessions. Smart circuitry in the solar charger monitors the battery voltage and protects the battery from overcharging and deep discharge.
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Gerber file

CAM/CAD data for the PCB referred to in this article is available as a Gerber file. Elektor GREEN and GOLD members can exclusively download these files for free as part of their membership. Gerber files allow a PCB to be produced on an appropriate device available locally, or through an online PCB manufacturing service.

Elektor recommends its business partner Eurocircuits as the company of choice for its own prototypes and volume production in selected cases.

Extra info, Update
Internal Lithium-Ion battery for storing solar energy
Versatile: your choice of batter and solar panel sizes
Direct charging/operation of USB devices.
Two switchable charging outlets:
- constant voltage output (5 V, max. 500mA)
- constant current (max. 150 mA)
Battery management for internal battery:
- Overload protection
- Under-voltage protection with hysteresis regulator and load dumping
Watchdog dropout protection
Compact dimensions
Complete firmware with source code downloadable from the Elektor website
SMD0805, 0.125W, 1%, if not shown otherwise)
R1 = 270kOhm
R2 = 82kOhm
R3,R4,R9 = 220Ohm
R5,R10–R13 = 22kOhm
R6 = 4.7MOhm
R7 = 1.5MOhm
R8 = 560kOhm
R14 = 240Ohm
R15 = 1.2kOhm
R16 = 100Ohm
R17 = 3.3Ohm
C1,C3,C6–C9 = 100nF (SMD0805, 10%)
C2,C5 = 100µF 16V, 10%, tantalum, SMD
C4 = 10nF (SMD0805, 10%)
L1 = 10µH, 2.47A, 0.066Ohm, 20%, ferrite core (e.g. Coiltronics DR74-100-R)
D1 = 1N4007 (MELF), e.g. LL4007G or BAT85 (see text)
D2 = Schottky diode 3A, 60V (e.g. MBRS360T3G, On Semiconductor)
D3 = LED red, 25mA, SMD1206
D4 = LED yellow, 25mA, SMD1206
D5 = LED green, 20mA, SMD1206
T1, T2 = IRF7413 (International Rectifier)
T3 = BC847 SMD (e.g. BC847CLT1G, On Semiconductor)
IC1 = ATtiny13V-10SU (Atmel), programmed, Elektor Shop # 090190-41*
IC2 = LT1302 (Linear Technology)
IC3 = LM317LD (e.g. from ST Microelectronics)
K3 = USB-A connector, SMD (e.g. Lumberg 2410 06)
S1 = Micro slide switch, 2-pole changeover (e.g. Multicomp MCLSS22)
K5 = Connector strip 6-pin, twin-row, 2.54mm spacing (e.g. Tyco/AMP 1241050-3)
JP1 = 2-pin pinheader with jumper, 0.1 in. lead pitch
LiPo battery 2000 mAh, 15C, 3.7V, e.g. Kokam 200015-0101G (834374H)
ASI-OEM solar panel 4.8V/80mA or 5V/81mA or similar
Schottky diodes BAT85 for parallel connection of the panels (see text)
PCB, order code 090190-1
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