Mare & Gal Electronics

2S Battery pack is very useful. It can be used to supply 5V electronic circuit without DC/DC. With help of a simple boost a 2S battery can drive 3 power LED lamp with reasonable currents. Etc…

Let’s see what is required for reliable, safe lithium polymer batter pack with two serially connected cells (2S LiPo battery pack).

Obviouslly, at least two cells are needed. Unfortunately, LiPo cells are very dangerous if used over specified limits. Most dificult is maximum cell voltage during charge. If cells are aexposed to voltages above 4,2V they can burn, but not at the charging, this could happen at any time after charging.  The absolute maximum charging voltage is 4.25V per cell. To avoid burning down the house and other troubles, a battery protection circuit board (PCB) is a must with LiPo cells.

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Many micro-controller circuits are powered from the USB port. Supply voltage is usually less than USB five volts. Supply circuit has adjustable output voltage with few jumpers. Some circuits require two supply voltages, one for digital part and second for analog part. Jumpers and resistors are selected such that when no jumper is inserted, the output voltage will be at minimum level. This prevents electronic circuit from damage when jumpers are forgotten. It’s shown in schematic:

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ST have implemented the JTAG adaptor on the STM32L-DISCOVERY board. It’s very cheap board: ~12€ at . Detailed information is available via ST web page. On-board is a STM32L152RBT6 microcontroller featuring 128 KB Flash, 16 KB RAM, 4 KB EEPROM, in an LQFP64 package. On-board ST-Link/V2 is connected to “local” microcontroller. By removing two jumpers ST-LINK could be used to program external microcontroller.

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