Friday, May 15, 2015

uC Board is Misbehaving on Brown Out

I'm working on a project which involves battery  Ni-Mh 4x1.2v, 2100mAh], which power-ups the boards. The current consumption is about 150mA. Now what I wish to do is disconect the load when my battery voltage falls down to 4v or so

Because now when my battery reaches this voltage the instrument misbehaves & fails to work, sometimes my program gets corrupted. And battery reaches a critical voltage level like 1-1.2(summation of all 4 batt). what else can I do so prevent this?

Mail from MO

Depending on your budget you can solve this, a watchdog and power management chip from maxim may work for these types of problems.

You can even build your own watchdog and power management with logic and comparators.

When the uP malfunctions it has to be reset by a watchdog timer which monitors if the uP or uC is pulsing in the way expected.

Battery Backup for SRAM or Microcontroller

And when the power goes down slowly like a Brown out, you have to save all RAM on a Flash chip and shutdown system and wait. Or have another backup for RAM and use a low power RAM. Make sure that you write a start sequence and shutdown code in your program.

When you start start with a clear ram ( if not batt backed up) then load values from flash. Make sure power up, power down resets are ok.

Digital to Analog Converter with uC Watchdog

Internal comparators implement undervoltage/overvoltage warnings and windowed-reset functions.

Supervisory Circuits Keep Your Microprocessor Under Control

Supervisory Circuits Keep Your Microprocessor Under Control

Abstract:

"Understand the value of a ┬ÁP supervisor to ensure proper system operation during power-up, power-down, and brownout situations (undervoltage monitoring). In addition, provides information about overvoltage and windowed monitoring. Describes additional features such as manual reset, watchdog timer, battery backup, and chip enable gating. Discusses the need for multi-voltage monitoring."

In an industrial environment your card it may malfunction due to EMI RFI. If your Board controls a huge Motor, when motor starts your Board could hang or Boot. You have to study and work out a solution.

The circuit or code is not everything, it is the Engineering that matters.

delabs