Go to Post It isn't what you're given that makes it awesome. It's what you do with it. - JosephC [more]
Home
Go Back   Chief Delphi > FIRST > General Forum
CD-Media   CD-Spy  
portal register members calendar search Today's Posts Mark Forums Read FAQ rules

 
Reply
 
Thread Tools Rate Thread Display Modes
  #1   Spotlight this post!  
Unread 04-02-2004, 21:14
Dale(294engr]'s Avatar
Dale(294engr] Dale(294engr] is offline
Mentor/Sponsor since '98
FRC #0294 (Beach Cities Robotics)
Team Role: Engineer
 
Join Date: Jan 2004
Rookie Year: 1998
Location: Redondo Beach, CA
Posts: 92
Dale(294engr] is a glorious beacon of lightDale(294engr] is a glorious beacon of lightDale(294engr] is a glorious beacon of lightDale(294engr] is a glorious beacon of lightDale(294engr] is a glorious beacon of lightDale(294engr] is a glorious beacon of light
Exclamation Allegro ACS750 Current Sensor 150uF Heads Up

Allegro engineering sent me a preliminary advisory:
Allegro advises against use of 150uF filter on output pin !

Their concern: 150uF may cause unstable output or damage output stage.
They suggest adding integrator high Rin Op Amp with appropriate feedback.
I don't see ~1000 teams going that route.

Their 2nd recommendation: 411K series w/.1uF (10nF) on the output to A/D

(411K likely cause significant voltage division error unless Rin ~5-10M)

150uF presumably was added to "filter" noise from the 2kHz PWM motor.
I have been unable to obtain output stage detail to determine actual liability.

Anyone know the input resistance of the RC A/D ?

Allegro data sheet: 1-2 ohm load spec
guided me to place a 274 ohm resistor in series w/150uF to gnd
to effect ~125 mS (3 time constant) noise filter
which was born out in scope tests.
(274 ohms serves to limit current a bit isolating Out + establish RC)

Their engineer indicated output stage is a constant current output
which I would assume should have no problem with the large Cap., TBD ??

Caution:
2nd bend of brittle lead from outward angled plastic case & they break off!!
(observe caution pulling lead out of the PCBoard to make any changes)
(better to cut than pull tiny leads)
Reply With Quote
Reply


Thread Tools
Display Modes Rate This Thread
Rate This Thread:

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Current Monitoring system questions PyroPhin Technical Discussion 44 17-02-2003 15:34
What happens / why do motors stall? DanL Technical Discussion 19 21-11-2002 07:19


All times are GMT -5. The time now is 20:45.

The Chief Delphi Forums are sponsored by Innovation First International, Inc.


Powered by vBulletin® Version 3.6.4
Copyright ©2000 - 2017, Jelsoft Enterprises Ltd.
Copyright © Chief Delphi