Where is the Parallax servo controller ?
Angela-Curti
Posts: 44
Hi,
I tried to find the Parallax serial servo controller but I found just a
pdf .
If Parallax doesn't have it, do you have an alternative
to move 16 servo motors ?
Thanks.
I tried to find the Parallax serial servo controller but I found just a
pdf .
If Parallax doesn't have it, do you have an alternative
to move 16 servo motors ?
Thanks.
Comments
If you don't mind soldering a few wires and headers, you can make just about any Propeller board into a servo controller.
I've used a QuickStart board to control 32 servos and I also used it to control (a very under powered hexapod).
I think my first choice for Propeller board to use with servos would be a Propeller Project board (as soon as they get the redesigned board back in stock). The Propeller Proto board would also be a good board to use (it's on sale for $20).
I'm pretty sure the servo controller software is still available. You could load the firmware onto your own board. I'm not sure if there are any hardware changes you'd need to make (I doubt it).
I'm using a Propeller Proto board as the controller in my small hexapod. The hexapod uses 18 servos. The connectors are soldered to the bottom of the PCB.
I saw your videos. They are a very good job.
But I don't have the enogh knowledge to program a Propeller . I just used the Propeller serial servo controller with a Basic Stamp
and I think it is difficult.
I don't know how to "load the firmware" . Do you know if a Propeller with the firmware will work exactly like the Propeller serial servo controller ?
Do you have or do you know where I can read to understand how to do that ?
I looked at the code used in the servo controller but I've never used the code (firmware) in any of my projects. I'm not sure what changes are needed to use the code with a different board.
If no one with experience with the servo controller answers this soon, I'll try to answer the best I can (tomorrow).
Here's some information to get you started. You'll need either a Propeller board with a USB connection or a Prop Plug type device to program the Propeller with the "firmware" (it's a program written in Spin). I think once the code is loaded, it would work just like the original servo controller.
I think the original servo controller had level shifters to boost the 3.3V logic to 5V. None of my servo projects use these level shifters so I don't think they are necessary.
Hopefully someone knows the exact answers to your questions. I think the hardest thing about using a different board will be adding the servo connectors (which isn't very hard).
The Servo32 object from the OBEX should be fairly simple to use, but if you are depending on another processor, i.e. a Basic Stamp or even a PC to communicate wait until I get all of the files together.... the Windows.exe file that allows direct control, and the latest Firmware for the PSC. As far as loading/flashing the firmware, you will need the capability to program a Propeller (which might require a Propeller to USB adapter) ... Once you have the PSC program loaded in the IDE, it's just a matter of pressing F11. And then of course making the proper connections to the servo... Power to the Servo should be separate from the Power to the Propeller with the Grounds connected together... The signal lines or control lines to the Servo's can be a direct connection to the I/O as long as the servo's are less than 1 foot away.... longer than 1 foot it is advisable to use a 4.7k resistor in series with the servo's control line to help minimize any antenna effects that can cause interference.
The statement about the level shifters is correct (in my opinion), however occasionally you might come across a non-standard servo that expects a higher voltage than 3.3V. In that rare case, the level shifters would be necessary.
I found these files on my hard drive.
Let me know if they're out of date and I'll delete them.
I believe the file "28823_Setup PSCI.zip" is the program which runs on the PC.
I may have a version of the firmware which allows all the servo commands to be issued from a terminal window. If anyone is interested in it, I'll try to find it.
Once the archive "PSCPropellerFirmware.zip" is opened onto ones hard drive, (and with the Propeller Tool installed) double click on "PSC Propeller Firmware.spin" to open the program with the Propeller Tool. Once the program is open and the Propeller is connected to the PC pressing F11 as Beau said should load the program into the board's EEPROM.
The only time I've had trouble using 3.3V logic with servos is when I've had resistors on the signal line. So some experimentation may be needed if some brands of servos don't initially work (unlikely IMO).
Lots of servos need lots of power. You'll need a really good power source to power 16 servos.
Let us know which Propeller board you end up using and we can offer suggestions of how to add connectors for the servos.
These are on the Product Page, but are also included in the attached file....
http://www.parallax.com/downloads/psc-propeller-firmware
http://www.parallax.com/downloads/propeller-servo-controller-guide
Thanks Beau Schwabe and Duane Degn :
Beau Schwabe :
But I want to use a B.Stamp to manage the Propeller with the servo motors.
And I read the Propeller PINs have 3 volts and the BStamps have 5 Volts.
When I used the PSC there wasn't promblems with the 5 volts from the BStamp.
Please remember I want to use the Basic Stamp connected to the Propeller with
the sofware you call firmware.
This shouldn't be a problem. The Propeller will transmit with 3.3V logic which the Basic Stamp can read just fine. The Basic Stamp will transmit with 5V logic and this won't be a problem for the Propeller as long as you use a resistor in series with the communication line. The resistor should be at least 3K to keep the Propeller safe but 4.7K or 10K would also work fine. I usually use 10K when using the Propeller with a 5V device since I have lots of 10K resistors. The exact value isn't important as long as it's at least 3K ohms.
The main issue, is making sure you can load the program onto the Propeller. This won't be a problem if the Propeller board has an USB connection but if it doesn't have an USB connection you'll need something like a Prop Plug to use when programming the Propeller.