Hi guys,

I am new to MCUs(actually I am new to electrotech), just wondering how you guys power your MCUs projects.

I usually power a MCU with a 9v battery with a 5v voltage regulator, but on my simulation, the 5v voltage regulator on idle consume 47.327mW, have a idle current of 5.26mA.

With a cheap 100mAh 9v battery, it can only last for about 19hours, with a 300mAh battery, it can only last for about 57hours, which is not good enough.

here are my questions:
1) Is my calculation correct?
2) If my calculation is correct, what other better efficiency 5v voltage circuit are available.

Thanks

 

We power our dataloggers with a 5 or 6 cell NiMH pack, but they're designed to run in the bush with a solar panel.

One of our downhole instrumentation tools uses 2 x 3V AA lithium batteries (not rechargeable). These last longer than 3 days (battery test was inconclusive as piece of paper with start time was lost and the memory wrapped around).

4 x normal off the shelf lithium batteries seem to last a while too.

Some of our installations use lead acid batteries (VRLA). This would need an LVD circuit.

One the test/work bench however, you should always use a laboratory power supply. Use an old PC power supply if you don't have a laboratory power supply. This would permit the use of the 317 circuit you have (resistors look good to me). Keep in mind that the 317 is linear, it dissipates extra voltage as heat (wasted energy).

 

A tiny 9 volt battery do not contain much energy. Do you have to use a 9 volt battery. How about 3 LR6 or LR14 size batteries. And then skip the voltage regulator. Can you tell us more about your design what does it do?

 

If possible I find a battery that I can use without a regulator. I've used Lithium ion, 3xAA and 3V CR2032 coin cells.
If you need a regulated voltage then better regulators are available, the LE50CZ for example (0.5mA typical, 1mA max at low output currents), but look at the datasheets for what you have available, especially LDO regulators.

 

So form what I can understand is, it's better not to use a voltage regulator if I can get away without one?

 

If the batteries are close circuits. And your circuit board can accept a somewhat lower voltage and still function as wanted. You will not need a voltage regulator. Many micro-controllers have a broad voltage range say from 2.5 volt to 5.5 volt. But I will not be able to give an accurate answer without knowing more about your design.

 

Thanks t06afre, I haven't got a design yet(although I have a rough idea in mind), I just want to know what options are available, or maybe get some good ideas from you guys.

I always assume a voltage regulator is necessary, but I was wrong.

 

How about a switching regulator. I just had a quick look at Element14's site and the MAX750A/MAX758A from Maxim have an internal current of just less than 2mA and a shutdown current of uA's.
Much more complicated to use but possibly an option.
The LTC1474/LTC1475 have a very low current draw in the uA range.

 

after reading other people's inputs, I found some uA range of voltage regulator:

LM2936

 

How about a switching regulator. I just had a quick look at Element14's site and the MAX750A/MAX758A from Maxim have an internal current of just less than 2mA and a shutdown current of uA's.
Much more complicated to use but possibly an option.
The LTC1474/LTC1475 have a very low current draw in the uA range.

switching regulator seen to do the job too, thanks

 

It would help if tell us what you are trying to make. And what micro controller you plan to use.

 

It would help if tell us what you are trying to make. And what micro controller you plan to use.

All the tutorials I read on the internet are using Atmel AVR series MCUs, so I am going to start with that, first ATTing45 and when I get the hand of it will be using ATmega32.

I am not building any thing at the moment, but in about 6 months time I want to to build a two wheel self balancing bot (to justify my learning outcome)

MCUs is new to me(and electronics as well) and I am just in the early stage of learning. So this thread is just a GENERAL investigation about power supply options. by saying that, efficiency will be my focus area(marketing thing), that why I want to know a high efficiency method

(I probably need to explain these better in my first thread , this forum is great BTW, I always get a lot of responds, thanks guys)

 

On the bench I use a 9V switchmode wall-wart and all my set-ups use a regulator. The wall warts can usually supply an amp. I like clean stable power. For remote projects I use Lithium Ion batteries, but still use regulators. I think for your Bot the motors/servos are going to be by far the major consumer of power, so I would not worry too much about 5ma here or there.

 

Hi, bug13 . . . i have seen your post and im confusing about this voltage regulator issues. So did you finished your project ? And what solution did you choose for the best battery performance ?

 

Hi, bug13 . . . i have seen your post and im confusing about this voltage regulator issues. So did you finished your project ? And what solution did you choose for the best battery performance ?

I use a DC-DC converter