Author Topic: power depletion  (Read 2000 times)

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Offline junior000Topic starter

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power depletion
« on: February 04, 2008, 01:49:12 PM »

i have successfully completed my bot:-).
thanks to you people.

the bot is running properly initially.then after the drainage of some current from the batteries,the bot just seems to lose its way.
as the voltage levels are decreasing the bot is not working properly.
i am using differential drive configuration.the motors are 500 rpm dc motors.the weight of the bot is 2kg.
view my tutorials at

Offline HDL_CinC_Dragon

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Re: power depletion
« Reply #1 on: February 04, 2008, 02:02:17 PM »
What voltage and mAh rating is your battery?
What voltage and current(mA) do your batteries, sensors, and logic circuit each require?
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Offline Rebelgium

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Re: power depletion
« Reply #2 on: February 04, 2008, 04:17:18 PM »
How long can your robot run ok?
What do you mean by "losing it's way"?

Probably the voltage of the MCU that is getting too low, or because it's a bit lower the MCU becomes more vulnerable to voltage drops caused by motors starting.
Try placing a big and a 100nF capacitor over the power and GND.
And are you using PWM to start and stop smoothly? If not, try it.
Are you using one battery or two?
« Last Edit: February 04, 2008, 04:17:54 PM by Rebelgium »
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Offline paulstreats

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Re: power depletion
« Reply #3 on: February 06, 2008, 05:59:03 PM »
The above questions are very much valid, although there is another point that you should be aware of.

If the sensors such as photoresistors normally operate at 5v and at half light they send 2.5v to your mcu. you would measure a 128 reading if the mcu's vref voltage was also generated at 5v and you were using 8bit analog .

The problem comes is if your batteries drop to produce 4v, your mcu is still running and maybe the comparator vref charges to 5v still, but the input from your photoresistors is 4v at half light so it would appear as 2v in and therefore register 102 which is a massive difference to the 108 that you were expecting.

The best way to do this is to see if the mcu has a vref pin and use it as the comparator voltage


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