lunalight pcb rev 2.1
DESCRIPTION
LunaLight PCB Rev 2.1. Fully Integrated Solar-Rechargeable LED Lantern and Cell Phone Charger. Mike Deagen (MATE) IME 458 May 25, 2012. The LunaLight is the result of a multidisciplinary senior project in collaboration with the non-profit organization One Million Lights. - PowerPoint PPT PresentationTRANSCRIPT
![Page 1: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/1.jpg)
LunaLight PCB Rev 2.1
Mike Deagen (MATE)IME 458
May 25, 2012
Fully Integrated Solar-Rechargeable LED Lantern and Cell Phone Charger
![Page 2: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/2.jpg)
The LunaLight is the result of a multidisciplinary senior project in collaboration with the non-
profit organization One Million Lights
LunaLight debut in Kenya (April 2012)
![Page 3: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/3.jpg)
A solar-rechargeable LED lantern and cell phone charger has three sub-circuits
IC Type Purpose
Battery Management Take the input power from the solar panel and safely charge the rechargeable batteries within the lantern
LED Driver Provide a constant current to the LEDs at the appropriate forward voltage
DC-DC Boost Increase the potential of the 3.7V Li-ion battery to meet the 5V USB standard voltage
Battery Management LED Boost Driver & DC-DC Boost for Cell Phone Charger
LT3652MSOP-12 packageCost: $4.36
MC34063SOIC-8 packageCost: $0.45
![Page 4: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/4.jpg)
Rev 1.0 of the PCB had wires leading to the batteries, the LEDs, and the switch
![Page 5: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/5.jpg)
The goal for the second revolution was to reduce overall assembly time by integrating
all the electronics onto a single board
Other GoalsUse mostly SMT components
Multiple brightness settings with a slide switchLi-ion battery instead of Nickel Metal Hydride
Ports and Switches
LEDs
Battery Holder
![Page 6: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/6.jpg)
I modeled the thermal management to see if the LED junction could rise above Tmax = 150°C
Heat Generated = 0.84 WTotal Est. θ = 102°C/WΔT = 86°CIf T∞ = 25°C, Tjunc = 121°C
81% of Tmax
![Page 7: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/7.jpg)
I used reflow soldering technique for SMT components (front side) and manual soldering
for thru-hole components (back side)
91% isopropyl rubbing alcohol removed the solder flux residue
![Page 8: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/8.jpg)
The basic functions of the PCB were confirmed with simple verification tests
Illuminance from 12” away“HI” = 473 lux“LO” = 94 lux
Solar Li-ion battery chargingVbatt_chg = 3.96 V
Ichg = 212 mA
![Page 9: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/9.jpg)
Testing the LED voltage drop over time indicated a junction temperature of 50°C
Temperature coefficient of voltage = -4.0 mV/°C [CREE XP-E datasheet]
For two LEDs in series, temperature coefficient of voltage = -8.0 mV/°C
0 200 400 600 800 100012001400 16001800 20005.6
5.65
5.7
5.75
5.8
5.85
5.9
5.95
6
time (s)
LEDVoltage
(V)
∆ 𝑇=∆𝑉
−8.0𝑚𝑉 /℃=5.75𝑉 −5.95𝑉−8.0𝑚𝑉 /℃
∆ 𝑇=−200𝑚𝑉−8.0𝑚𝑉 /℃=25℃
𝑇=𝑇 ∞+∆𝑇=25+25=𝟓𝟎℃
However, the temperature coefficient of voltage is
probably not linear!
![Page 10: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/10.jpg)
Overall, I think the design was successful, and future LunaLight teams should consider
implementing a fully integrated PCB
![Page 11: LunaLight PCB Rev 2.1](https://reader031.vdocuments.site/reader031/viewer/2022020102/56816907550346895de01a22/html5/thumbnails/11.jpg)
Questions?