Power

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This page summarizes our experiences with supplying power to our robots. The issue is more complex then one would think at the first glance:

  • Various parts require different voltage (see table below)
  • Motors can consume large currents, thus causing the batteries drop on their voltage, which can cause problems for othercomponents of the robot that can be sensitive on the voltage supplied, and therefore it is recommended to use different power sources for motors and the robot electronics
  • A voltage regulator (integrated circuit) can be used to convert various input voltage to stable output voltage
  • Bateries are heavy (see table below)


Power demands of various parts we work with:


Cerebot board 3,6V - 9V
Nanocon board 2,7V - 5,5V
LEGO motors (both for RCX and NXT) 9V (or at least 7.2V)
LEGO active sensors (light, compass, IR sensor, rotation sensor) 9V (or at least 7.2V)
SRF02 ultrasonic sensor 5V
SRF08 ultrasonic sensor 5V
PICAXE colour sensor 5V (or 3V if J3 jumper is connected)
SP03 Text to Speech Synthesizer 5V


The weight and parameters of various batteries:


GP Racing car NiMH Battery Pack 7.2V 3300 mAh 375 g
Pannasonic AA-size (R6) Rechargeable Battery 1.2V 1500 mAh 25 g
Energizer AA-size (R6) Alkaline Battery 1.5V  ? 24 g
Energizer D-size (LR20) Alkaline Battery 1.5V  ? 143 g
COTECH AAA-size (LR03) Alkaline Battery 1.5V  ? 12g
Energizer 9V (6LR61) Alkaline Battery 9V  ? 46g


The weight of various parts:


LEGO NXT 9V motor 80 g


Since batteries cost a lot of money, it is advisable to use rechargeable batteries. These come in different types: Older NiCd, newer NiMH, or even newer Li-Ion batteries. For applications requiring more power, when the weight is not so important, one can use the more heavy sealed Pb acid batteries. The rechargeable batteries need to be treated well and recharged using proper recharger. For the standard cell AA-size, AAA-size, and some larger NiCd and NiMH batteries, one can use any of the widely available rechargers. The newer models can recharge batteries using high current very quickly. For other battery types, we must use the recharger provided directly with the battery (for example mobile phones usually have a built-in recharger and a specialized power supply). In some cases, however, there is no recharger provided, and we have to find it or build our own. Here are some links that can be helpful:

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