Sim Project Links

Home

   

Order Cards & Software

   

Motion Software

Motion Hardware

   

Cockpit 1

Platform 2

Mini Platform 3

DIY Linear Actuator

   

DIY FFB Flight Yoke

DIY FFB Hardware

DIY FFB (Control Loader) Software

EV & other Stuff

 

Component Info

Electric Motors

Speed Controllers

Batteries

Adhesives

Ball & Sockets Joints

Bearings

Gears

Chains & Sprockets

Shaft Collars

Shaft Steel

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Component Search

Component Information

Order Pages

Contact

Conditions

I2C Noise Isolator Card

 

BFF I2C Isolator Card - Data Sheet

64SPU-1 Noise Protection - for added system reliability

 

With three drive motors connected to a single battery supply, and the battery ground connection shared through the motors, motor speed controllers and 64PSU-1 (or other) drive controller there is always the possibility of electrical noise from the motors affecting the DIY servo system operation. This is most likely to happen in systems using higher powered motors and/or inexpensive lower quality noisy motors.

 

Steps can be taken to reduce motor noise related voltage spikes within the system such as fitting snubbing capacitors to motors, making sure ground return lines are robust, avoiding ground wiring loops and physically separating the low voltage electronics from the high current motor drives. However some electrical noise, especially that present on the electrical ground lines, can be very difficult to remove.

 

If this noise if heavy enough it can affect the smooth operation of the microcontroller IC on the 64SPU-1. Symptoms can be intermittent black-outs of the 64SPU-1 or encoder read errors and interrupts to the servo drive operation.

 

The BFF I2C Isolator card is a simple and effective way to fully isolate the 64SPU-1 from the noisy end of your DIY servo drive system and to help trouble-free operation of the SPU. It is connected on the low voltage logic lines leading from the 64SPU-1 card to the MD03 motor controllers and allows the 64SPU-1 to be operated from a completely separate (clean) 5V power supply from that powering the MD03 speed controllers. When fitted there is no electrical path between the MD03's SDA, SCL, 5V and 0V lines and the 64SPU-1. A typical system layout with the BFF I2C Isolator card fitted is shown below.

 

 

IMPORTANT - Although the isolator card will protect the 40SPU-1 from the effects of electrical noise, electrical conditions can still arise in which the I2C comms can seize with the I2C Isolator card fitted. This can happen, for example, when heavy vibration effects are configured (eg runway vibrations) and the MD03 controllers attempt to drive very fast reversing movements against the inertia of the platform and/or heavy unbalanced load. On my platform for example configuring heavy runway vibration then running the platform unloaded (ie against the full unbalanced load of the bungee spring) can cause problems for the MD03 controllers and the I2C Isolator card. So the MD03's and the I2C comms can be affected by heavy and erratic motor drive conditions - take care not to configure too heavy runway vibration effects in your DIY motion platform and avoid running it in a heavily unbalanced condition.

 

The BFF I2C Isolator Card uses the Silicon Labs Si8400 I2C Isolator chip to provide the electrical isolation. Two-way data communications between the 64SPU-1 and the MD03 speed controllers are maintained across the card so allowing the 64SPU-1 to continue to both send motor speed and direction commands and read-back data from the controllers whilst remaining unaffected by noise on the lines.

 

An on-board voltage regulator allows the isolator card to provide the 5V supply for the MD03 logic inputs from its 9V DC input supply. Alternatively the motor controller 5V supply can be provided separately. In either case the 64SPU-1 logic supply (5V and ground) should NOT be connected to the 5V and logic ground of the MD03 speed controllers.

 

If you wish to use the BFF I2C Isolator in your system please read the data sheet carefully.

 

The BFF I2C Isolator card is now available to buy - see the order page here.

 

If you use the isolator card remember to ensure that your feedback pots or encoders do not provide a separate electrical noise path back to the 64SPU-1. If they are fitted to motor or gear box drive shafts make sure they are electrically isolated from the metal of the shaft. Otherwise any ground noise on the motor shaft will travel back along the pot 0V line to the 64SPU-1. MA3 encoders are not so much of a problem as their casings and shafts are electrically isolated from their electrical connectors.

IMPORTANT WHEN THE ISOLATOR CARD IS FITTED TO YOUR SERVO DRIVE DO NOT POWER DOWN THE 64SPU-1 CARD WHILST THE SERVO SYSTEM IS MOVING.

ALWAYS STOP THE DRIVE FIRST BY CLOSING THE PID SERVO CONTROLLER SOFTWARE ON THE PC BEFORE CUTTING THE POWER TO THE 64SPU-1 CARD.

ON SYSTEM SHUT-DOWN POWER DOWN THE ISOLATOR CARD BEFORE POWERING DOWN THE 64SPU-1 CARD.

With the isolator card fitted the 5V 40SPU-1 supply no longer provides the MD03 5V logic supply. The logic elements of the MD03 controllers are powered by the I2C Isolator card and will therefore remain active until the I2C Isolator card power supply is removed. Closing the BFF PID Servo Controller software before powering down the 64SPU-1 card will allow the card to instruct the MD03 controllers to stop driving before it is made inactive.

Powering down the I2C Isolator card will cut the logic supply to the MD03's and stop them driving (so long as the 5V is supplied by the voltage regulator on the I2C Isolator card).

 

 

This site is copyrighted, If you'd like more information or have any comments please contact me at

 

 
Copyright © 2006-20012 BFF Design Ltd All Rights Reserved.