Electronic – Searching for a Micro controller with a battery capability

batteriesembeddedmicrocontroller

I am working on a low power design, which will have a MCU powered by my regulated DC power supply from mains(220VAC). But when the Mains fail, I intend to have a battery connected to the chip that puts the MCU in a sleep mode with some specific peripherals working (RTC). It come out of the sleep mode either when the mains is restored, or when an external interrupt occurs (in which case, it has to service the ISR and goes back to sleep).

What MCU can I use for this? Actually, i do not need a very expensive/sophisticated one. Preferably, I will like an 8051 core, 6-8k Flash, at least 512RAM, UART, I2C basically. Internal EPROM will also be nice if available.

But any suggestion, circuit diagram, application notes will be greatly appreciated.

Best Answer

You seem to be looking for an MCU that has a power failover built in as a peripheral of sorts. There may be a rare MCU available that has this, but from my memory there aren't many in a general way. For instance, I know that Atmel CortexM3s have the ability to run their internal RTC off of battery power. However, that is about as much that you can do.

Instead of looking for a single chip solution, it may be easier to look at designing a low power system out of a few different pieces, which would be easier to do.

For a microcontroller, pick something that's specifically designed to be low power. Having fine grained power control on the peripherals and the availability of low power sleep states is a plus. I've seen TI's MSP430 line qualify well in those parameters. Olin, in his comment, suggests the PIC16F1xxx series. Neither is an 8051 based solution, though. There may well be 8051 based controllers which qualify. I don't know how amenable the 8051 core is to low power states, though to be fair a lot of these other cores also do most of their sleeping by slowing down system clocks and turning off peripherals, which doesn't really need a specialized core.

In order to switchover power, you could use an IC designed for doing that, depending on the sort of battery and topology you have in mind. For a non-rechargeable coin battery sort of thing, you could look at one of the many RTC and Watchdog and Reset controller ICs, a large number of which include some way to switch over to a battery. For a rechargeable battery, assuming its voltage to high enough to be close to the supply voltage you intend to use with mains power, you're better off using a battery tied bus topology. This means that the battery is always connected to the circuit. Imagine the battery and mcu being connected in parallel. When there is mains power, the battery is charged also (using appropriate charging circuits depending on the chemistry of the battery) and when its absent, the current through the battery reverses and powers the circuit.

Related Solutions

Electronic – Measuring 0 – 1MHz ( 0.25Hz resolution) Squarewave using an MCU

If possible I'd suggest selecting a microcontroller that supports a counter operation using the timer inputs; rather than manually incrementing a counter inside an ISR (which at high frequencies quickly ends up saturating the microcontroller activity) you allow the hardware to handle the counting. At this point your code simply becomes a matter of waiting for your periodic interrupt then calculating the frequency.

To extend the range and make the frequency counter more generalised (removing the need for multiple ranges at the expense of a little more work for the MCU) you could use the following technique.

Select a periodic interrupt rate that allows for measurement accuracy at the highest input frequency; this should take into account your counter size (you need to select the timer period such that the timer counter will not overflow at the maximum input frequency). For this example I'll assume that the input counter value can be read from the variable "timer_input_ctr".

Include a variable for counting periodic interrupts (should be initialised to 0 at startup); for this example I'll refer to this variable as "isr_count". The interrupt period is contained in the constant "isr_period".

Your periodic interrupt should be implemented as (C pseudo-code):

void timer_isr()
{
  isr_count++;
  if (timer_input_ctr > 0)
  {
    frequency = timer_input_ctr / (isr_count * isr_period).
    timer_input_ctr = 0;
    isr_count = 0;
  }
}

Obviously this rough example relies on some floating point math that may not be compatible for low-end microcontrollers, there are techniques to overcome this but they are outside of the scope of this answer.

Electronic – Micro-Controller Operating System with GUI

Basically, this question is not capable of being answered. You don't need to consider what OS you're going to use at first. First, you need to consider what kind of micro-controller you're going to be using.

Various ARM CPUs will be perfectly capable of running a "OS" in .Net However, AVR and PIC and such will not be able to use even the most micro of .Net frameworks.

Second, you need to consider why you're needing to use .Net. The .Net micro framework will have a lot more overhead than a direct native program. If using .Net is only a priority because you don't want to learn C++, you probably just need to man up and learn C or C++.

And what kind of OS are you looking for? An RTOS, or a more general purpose OS, such as Linux? You're going to have a hard time finding an OS of much complexity implemented in C#, because of the reason I said above.

Best Answer

Related Solutions

Electronic – Measuring 0 – 1MHz ( 0.25Hz resolution) Squarewave using an MCU

Electronic – Micro-Controller Operating System with GUI

Related Topic