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Sat, 23 Sep 2006
improving SRV-1 battery performance ...
There have been a few discussions about the heat of the voltage regulator on the SRV-1 controller board on the Surveyor Robotics Forum, and some users have added heat sinks to the board's LM7805 +5VDC linear voltage regulator. While this is a simple solution, there's actually a more efficient alternative, changing the linear regulator to a switching regulator.
Linear voltage regulators achieve their voltage drop by dissipating the difference between the input and output voltages as heat, so it's not unusual for 30%-50% of the battery's power that passes through a linear regulator to be wasted. A switching regulator moves small chunks of energy at a time in such a way that the voltage drop is not lost as heat, and switching regulators typically achieve 90%+ efficiency.
Switching regulators are not simple circuits, usually requiring a number of external components. They are also quite a bit more expensive than linear regulators (typically $9-$10 vs $0.25). As such, we don't use them on production versions of the robots, but encourage users to consider them as an after-market upgrade. There are several manufacturers building switching regulators that are pin-compatible with the standard LM7805 regulators, and we gave one of these a try ...
Here are a couple of photos of a Recom R-785.0-0.5 +5VDC switching regulator, installed in place of the LM7805 (U4) on the SRV-1 controller.
We ran some tests, and found that nominal power draw dropped from 170mA-240mA with the LM7805 to 100mA-150mA with the switcher. We're not running motor power through the regulator - that comes direct from the battery, but this does measure the power usage of components that run off the regulator - processor, camera, radio, IR, etc. Excluding motor usage, changing the regulator effectively extends the duration of a battery charge by 50%+.
Here are information links for the Recom and Datel parts -
- Recom R-785.0-0.5 -
- Datel 7805SR -
Posted Sat, 23 Sep 2006 01:18 | HTML Link | see additional stories ...