Power Supply

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Beiträge: 431
Registriert: Fr 5. Aug 2011, 12:09

Power Supply

Beitragvon Kabelitz » Mi 3. Okt 2012, 09:20

Power Supply is needed for
  • charge circuit of internal Li-Ion Akku
  • DC-DC conversion between external supply and internal power supply
  • supply of PIR Sensor

external voltage range: 6V ...24V, e.g. lead battery 12V or solar panel (open circuit voltage up to 24V)
internal voltage: 5V DC
current: >= 0,5A

use as internal power supply:
Rohm, Bp5220a, Sip9, 1A, 8V-38V, 5,58 Euro, http://www.voelkner.de/products/270283/ ... -Sip9.html,
Recom, R-785.0-0.5 Sip3, SIP3, 0,5A, 6,5V-34V, 7,57 Euro, http://www.voelkner.de/products/82214/D ... -Sip3.html
Recom, R-785.0-1.0 Sip3, SIP3, 1,0A, 6,5V-18V, 8,32 Euro, http://www.voelkner.de/products/82218/D ... -Sip3.html
Recom, R-78b5.0-1.0, SIP3, 1,0A, 6,5V-34V, 10,00 Euro, http://www.voelkner.de/products/82224/D ... 0-1.0.html

use as internal Charge Circuit:
Microchip, MCP73831T-2ACI/OT, 738-6360, SOT-23, 3,75V...6V, 0,82 Euro, https://de.rs-online.com/web/p/batterie ... s/7386360/

Use as (external) Charge Circuit?
(for 10...20Ah Li-Ion, charge from external power supply)
Artesyn, LDO03C-005W05-VJ , 461-947, SIP5, 3A, 3V-13,8V, 9,04 Euro, https://de.rs-online.com/web/p/dc-dc-wa ... t/0461947/
Artesyn, LDO06C-005W05-VJ, 461-979, SIP5, 6A, 3V-13,8V, 12,54 Euro, https://de.rs-online.com/web/p/dc-dc-wa ... t/0461979/

charge circuit LM3622:

Simplest solar charger: series resistor! and zener diode for voltage limitation:
http://electroschematics.com/4310/batte ... r-cells-3/
Voltage limitation may be improved with adjustable precision shunt TL431...
Figure 24: High Current Shunt Regulator: http://www.ti.com/lit/ds/symlink/tl431.pdf

IC, 2A output current, 4.75V to 32V input

best choice: Power Tracking 2A Battery Charger for Solar Power
IC, 2A output current, solar panel input:
Demo Board:
http://cds.linear.com/docs/Demo%20Board ... 1568Af.pdf

Beiträge: 431
Registriert: Fr 5. Aug 2011, 12:09

Re: Power Supply

Beitragvon Kabelitz » So 14. Okt 2012, 18:58

i tested
Recom, R-785.0-0.5 with Microchip, MCP73831;
With this parts it is possible to connect an external power supply, like lead battery 12V (or even solar panel) or a 230V/12V Wall Power supply;
for trickle charge MCP73831 is ideal. To recharge an empty Li-Ion with 10Ah will about 24 hours...due to 0.5A max charge current of MCP73831

The final pcb should contain power supply an trigger-circuit and connectors for PIR sensor, PIR-LED, Charge LED, USB-Cable, and PIR Output.
A draft of the pcb is attached



Re: Power Supply

Beitragvon Gast » So 14. Okt 2012, 22:59

I found an interesting chip. It can convert step up voltage from a single solar cell to charge LiPo. Ver low self use current. Ordered it as a free sample. Will try.


Re: Power Supply

Beitragvon janisalnis » So 14. Okt 2012, 23:17


Not optimised for maximum power tracing.

A 10 W peak solar panel placed on a garden house is shaddowed by some tree.
Energy-efficient switching step-down regulator converts voltage to 5V.
Direct charging with 5 V via USB made phone very energy inneficient.
Because of that the LiPo is charged directly.
USB LiPo charger chip Max1811 takes 5V as input and charges cell.
Wires from chip are soldered directly to phone's Lipo cell + and - leads.

As experiment I use only phone accu, no extra LiPo.
During night charge is lost to 70 % and during day LiPo recharges full.
Phone is inside a garden house. It sends garden pictures via WiFi to house router.
Now works ca 1 month autonomously. See it live here:


Beiträge: 431
Registriert: Fr 5. Aug 2011, 12:09

Re: Power Supply

Beitragvon Kabelitz » Mo 15. Okt 2012, 14:56

thanks for this information.
a) How do you optain these resolutions? Is it with "custom size"?

b) yes, i agree: I dont think the actual schedule is ideal. 0.5Amps is not enaugh for charging with solar panel, and the charge current must be adapted to the actual power.
The LTC3652 (http://www.linear.com/product/LT3652) is ideal in my opinion. I ordered a demo board with LT3652, but first, i want to finish all works with the (simple) design of Recom Switching regulator and microchip MCP73831. The PCB will be layouted and available in this forum in about 3 weeks

Max1811 seems to be comparable to MCP73831
LTC3105 - 400mA Step-Up DC/DC Converter with Maximum Power Point Control and 250mV Start-Up
seems to be similar to LTC3652: With Automatic Power Adjust. Main Difference: LTC3105: 400mA, LTC3652: 2A

I agree: if the charging circuit is efficient with automatic power Adjust, a capacity of 2Ah should be more than sufficient....

If you want to use actual circuit with Recom Switching Regulator: C1 must be augmented, greater than 470µF. If not, circuit will oscillate...


Re: Power Supply

Beitragvon janisalnis » Mo 15. Okt 2012, 22:52


LTC3652 seems to be ideal if some kind of a standard solar panel is used like 20V. And would be good for charging external battery pack with 2A.

Step-up charger could be used for some miniature single solar cell. Sometimes tree shaddow is a problem for solar panels. If one cell is in shaddow the whole panel current is limited. I will try it out soon step-up regulator and write experiences.


Re: Power Supply

Beitragvon janisalnis » Mo 22. Okt 2012, 23:08


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