Need help!!!
juanito25
Posts: 1
Hello all,· I am new to programing and all its components.· Doing a senior project and I need help with a lot of things.· Do I need a motherboard to power the servo controller?· Does the controller give power to any motors I hook up?
I have a BASIC Stamp 2pe motherboard and a Parallax Servo Controller, USB.· From the website, I saw that these two are not compatible.· Also have two motors from Parallax that are continuos rotation.
Thanks for your help in advance.
I have a BASIC Stamp 2pe motherboard and a Parallax Servo Controller, USB.· From the website, I saw that these two are not compatible.· Also have two motors from Parallax that are continuos rotation.
Thanks for your help in advance.
Comments
The Parallax Servo Controller needs two different power sources. One, for the control logic, requires a regulated +5V power supply. Often this is supplied from the microcontroller board, but, as long as there's a common ground, can be supplied from another source. The other is the supply for the servo motors. This can range from 4.8V to about 7.2V and does not have to be tightly regulated, but needs to be well filtered. It does need to supply at least 250mA for each servo motor and peak currents of at least 1-2A. If more than one servo might be starting at the same time, this peak current needs to be higher. The Parallax Servo Controller does provide power to the servo motor through the 3-wire cable connecting the servo to the controller.
I don't know for sure why the Stamp 2pe Motherboard is not compatible with the PSC. It might be that the Motherboard is designed to operate off the 4-5V provided by the USB connection and that won't work for the PSC. The Motherboard can be configured to run off a separate +5V supply and should work with the PSC when that's done although that's not how it was designed.
The USB PSC can be used without a microcontroller and can be controlled directly from a PC if that would work for you.
Download some of the Parallax Stamps in Class tutorials from the Resources / Downloads page of their website. Start with the "What's a Microcontroller?" tutorial and look at the "Robotics with the BoeBot" tutorial as well. They'll give you some idea of what's possible and how to do it.
The reason for the incompatibility is due to the nature of the I/O input on the PSC VS the inline resistors on the Motherboard. Suffice it to say the Motherboard is unable to pull the signal line sufficiently to switch between high/low. Take care.
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Chris Savage
Parallax Tech Support
Chris is right. As it stands, the outputs of the BS2pe chip on the MoBo, in series with the onboard 300-ohm protection resistors, can't pull the input line low enough against the PSC's 220-ohm pullup and indicator LED. However, all is not lost. It should still be possible to do this via one of the MoBo's AVR coprocessors, since those do not have protection resistors in series with their pins. Can you tell me a little more about your setup, please? How were you planning to connect to the PSC? Are you using the PWR-I/O-DB daughterboard? Which port pin were you planning to use? With this info, I should be able to provide a small AVR hex file that you can upload to the MoBo to do what you want.
Thanks,
Phil
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Chris Savage
Parallax Tech Support
The beta AVR code available in this thread should allow you to communicate with the PSC from your MoBo. Download the ZIP, give it a try, and let me know how it works out.
Thanks,
Phil