Project Log
October 28, 2003: Lab Day 1
Where: Jobst 248
What got done:
We spent most of the day investigating various small motors. The problem at this point is that all the motors we've found that run at our voltage range (3 or 6 Volts) have high RPM but very low torque. We can gear them down to increase the torque, but this adds mass to the platform and greatly reduces the maximum speed. We're also pretty rusty on kinematics, so we have some nagging doubts as to whether we'll actually be able to make this thing move.
Currently we're looking at using two solar panels (from robotstore.com), which in theory each put out 55mA at 3V. Using two is a tight power budget but allows for the small form factor we want. Adding a third would ease the power constraint but makes the bugs bigger than we'd like. These panels use a polymer substrate, so they're flexible. Ideally we'd bend them lengthwise to make the bugs 3" square, but that assume we'd only be using two panels.
We also briefly looked at low-power microcontrollers. We have a fair bit of experience with the 8051 family as a result of EE365 and the miniproject, so we'd like to use that if possible. There are around a dozen companies that make 8051 clones, and most of them feature low-power modes and draw around 12mA @ 3V normally. That's a fair bit of current, but we won't really be processing continuously, so our real power usage will be much lower.
What needs doing:
We need parts. We'll need to ask Dr. Huggins to get us the solar panels and some motors to do some preliminary testing. We need to find out the realistic power output of the solar panels, and what that translates to in terms of motor torque.
We also need to find a good 8051 board. Bradley has several EMAC development boards with Siemens 80C515 chips, but they run on 5V supplies and don't have any power-management features. Before we can select a board, we need to design more of the system to figure out what the microcontroller will really need to do, which will determine the features the chip and board will need to have.