MSR1 and Encoders

John Abshier

I have tested four encoders with both the MSR1 and a Professional Development Board.· With the MSR1 I used the pins connected to the 5 volt voltage level translator.· For the PDB I used a 1Kohm resistor.· The following did not work on the MSR1 but did work on the PDB:· OAK 900 Series, Clarostat 600-128-CBL, and a surplus (from BGMicro and others) motor.·· Luckly the US Digital E4P did work with the MSR1.· I did not test it on the PDB since it it mounted in a robot and is a pain to connect.· The E4P was attached to a motor very similar to the motors the Stingray uses.· Code used for the test is attached.

John Abshier

rpdb

I had problems with the USDigital E8p encoders on the MSR1. I had long cables with a lot of capacitance, which made the translators oscillate. I installed headers and jumper on the MSR1 to bypass the translators and used a 1k series resistor. They work fine now.

John Abshier

My cable (4 wires actually) was about 8 inches long.

John Abshier

ratronic

John - although I have yet to use encoders and know nothing about them, I have figured out that the voltage translators in the msr1 need a minimum of 2ma of drive to work. Looking at the datasheet for the clarastat 600-128-CBL they have a 5.4k internal pull up resistor which would only provide for a little less than 1ma drive.·You can bypass the translator like I have shown in the attached picture.·That will make all 8 of those inputs disabled·and you can directly attach to the propeller. I found this out trying to use the parallax ir detector and also thier transceiver.··I show using p16 but you can bypass which ever group·of 8 you like and then use all of the encoder outputs connected directly to the propeller.

Edit: for clarastat encoders, I haven't looked at the other ones you mentioned·- hook those up the same way you would with the ppdb.·


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D Rat

Dave Ratcliff N6YEE

Post Edited (ratronic) : 7/20/2010 6:16:34 AM GMT

John Abshier

I understand the bypass. I was just posting the results of my testing. I am waiting for the first PCB I have ever designed. It plugs into the MSR1 and provides provides power, ground and signal pins with build in protection resistors. Since it was not a time sensitive need, I am using Batch PCB to keep cost down, 5 boards for about $30.

John Abshier

rpdb

Hi John,

Have you any pictures of your board?
I would personally like to replace the translators on the MSR1 with a 1k resistor pack on a maybe 2 banks of I/O. It would make a much cleaner connection as many sensors and outputs I have will not work with the translators.

rpdb

John Abshier

Picture of design attached.· I haven't received boards yet to check for functionality.



John Abshier

hover1

With the perceived problems with the translators on the MSR1 and Propeller Servo Controller, I designed a couple of boards to take care of Servo output problems.

With the appropriate male headers on the MSR1 board, and the female headers on the daughter board, it would automatically disable the translators, and bring the lines out through a resistor pack. This could also be used for inputs. The ability to switch between 5V and Vin would also be available on the daughter board.

The Propeller Servo Controller Daughter Board just adds the requires 5K resistor pack in DIP 16 or SOIC to run servos reliably.

Jim

John Abshier said...
Picture of design attached. I haven't received boards yet to check for functionality.



John Abshier

Post Edited (hover1) : 7/21/2010 10:13:37 PM GMT