From smallrobot at hotmail.com Mon Dec 12 21:21:45 2005 From: smallrobot at hotmail.com (Rick Rowland) Date: Mon Dec 12 22:31:12 2005 Subject: [WheelCommander] using the wheel commander on larger robots Message-ID: I am currently reworking an older robot built in the early eighties. I was wondering if there would be any problems using the wheel watchers adapted to the drive motor shaft, which is hooked to a 150 to one ratio gearbox driving a 10 inch wheel and using the wheel commander to control a h-bridge or a h-bridge that can use servo pulses to control? (Pololu or Picobotics) Thanks Rick Rowland From peters at nubotics.com Wed Dec 14 12:25:21 2005 From: peters at nubotics.com (Peter Skeggs) Date: Wed Dec 14 12:25:24 2005 Subject: [WheelCommander] using the wheel commander on larger robots In-Reply-To: References: Message-ID: <43A07FB1.4090500@nubotics.com> Rick Rowland wrote: >I am currently reworking an older robot built in the early eighties. I was wondering if there would be any problems using the wheel watchers adapted to the drive motor shaft, which is hooked to a 150 to one ratio gearbox driving a 10 inch wheel and using the wheel commander to control a h-bridge or a h-bridge that can use servo pulses to control? (Pololu or Picobotics) > > There should be no problem, as long as you can mount the WheelWatcher encoder circuit boards such that they are concentric with the sticker within approximately 0.01", and so that the space between the sticker and the top of the two sensor packages on each board is (ideally) between 0.8mm and 1.1mm. It may work with a larger range than that, depending on the specific batch of sensor chips used on the boards you have. Our codewheel spacers might be useful for you to mount the stickers on so they remain flat. Here's a link to some photos showing how we attached WheelWatcher encoders to modified wiper motors (we machined down the case to expose more of the shaft, so that the shaft was long enough to go through the hub of the wheels we wanted to use on a certain unfinished robot): http://www.nubotics.com/photos/wipers Also, the maximum rotation rate of the sticker needs to be reasonable. We have not tested yet for the maximum allowable speed, as they are designed for RC servos which max out at about 120 RPM. They may work fine up to, say, 300 RPM, but we're not sure yet. Good luck, and let us know how it works for you. -Pete