Powering Hexy

Joseph Schlesinger edited this page Sep 3, 2013 · 15 revisions

Powering your Hexy

IMPORTANT NOTICE: DO NOT OVER-VOLT: The voltage limits are printed onto the Servotor32 board (4.8v-7v). The logic power supply is only rated up to 10v, but nothing above 9v is recommended. Please be mindful of these limits and do not exceed them.

Alkaline vs NiMH/NiCad

Alkaline Batteries often do not supply enough current (see Battery-only Reset Problem for more information). It is highly recommended to use NiMH or NiCads instead. Its also not recommended to mix/match batteries of different power levels or types. To be more specific, Alkalines batteries aren't designed to deliver as much current as NiMH/NiCad batteries are, they have a lower 'C-rate'. This can lead to the 'dead-spider' effect even with 'full' batteries.

Recommended batteries

For practical reasons (cost and durability), it is best to use rechargeable batteries. Hexy can use a lot of batteries! The Arcbotics team recommend the Powerex 2700mAh Rechargeable Batteries.

External Power Supply

The Arcbotics team are investigating different external power supply options but have not made any formal recommendations. However, they have been using these supplies with a great deal of success:

Using LiPos

LiPo batteries are NOT recommended, as their voltage is either high enough to damage the servos (7.4v) or too low to be effective (3.7v). ArcBotics is looking to offering voltage converters.

Battery-only Reset Problem

If you're powering Hexy off of battery power only (Say, running it on bluetooth), Hexy can sometimes start to move, then suddenly lose all servo power, then reset and begin this cycle all over again. This is caused by the voltage 'dipping' too low. When the servos move, they draw power from the batteries and thus lowering the battery voltage. If this voltage goes too low the Servotor32, Hexy's 'brain', doesn't get enough voltage to keep going and resets. The reset causes the servos to stop getting signals, stop moving, and the voltage goes back up enough to let the controller boot up. But as soon as Hexy starts moving again, the voltage dips, and it starts all over again.

The fix is to power the brain from an extra power source, one that will have a high enough voltage that in case the battery dips too low, it has a backup supply to keep going. This can be seen as the 'logic' power supply port on the controller. a 4xAA, 5xAA or 9v battery pack plugged into this port will work, and keep hexy going no matter how low the servo voltage dips. The USB power supplied when plugged into a computer works as well, and this problem won't occur when Hexy is plugged in.