Monitoring Current During Competition

[Michelle]

I'm on a rookie team and have a rather pressing question concerning how best to monitor current draw during the competition. I know a DC clamp on ammeter can be used for testing, but is there a way to get an ammeter to use during competition to monitor the current draw of our drive motors? We need to make sure that the breakers won't be tripping when we are running our motors at full power. If this is a common practice, some advice on how best to do so would be greatly appreciated.

Thanks in advance!

[steven114]

http://www.allegromicro.com/sf/0750/

[Al Skierkiewicz]

Michelle,
The clamp on ammeter is a good way to start any robot check out. I recommend it to teams to check all motors, particularly multi motor drives, to be sure the currents are balance and/or one motor has not failed. Follow your first check with lot's of practice. The circuit breakers trip with a distinctive buzz and that should show up with practice sessions. A breaker that trips repeatedly will get warm to very hot so check the temperature of the breakers after a practice match. Careful, they can be hot enough to burn. The current monitor linked in the above post is another way to always check and the data can be interpreted at the dashboard output. If you are using the IFI breaker panel, it will alert you when a breaker had tripped.

Are you expecting trouble? Suspect a particular method or assy? Be aware that you can scale the speed sent to the speed controller with software so it runds less than full speed when the joystick is pushed all the way to the limit.

[BrianBSL]

I'd favor one of the honeywell "pass through" current sensors that works like a clamp-on current sensor over one of the allegro ones - they have ones rated up to 950A (rather than the 150 or 200A the Allegro's max out at), and don't require any physical connection (its just a circle you can run your main 6GA power wire through. Should be able to get them from Newark for around $40 or so.

[steven114]

The nice thing about the Allegro ones is that they're free if you ask for samples
I got a six-pack of them at no cost to me. If you're using one clamp-on for each motor at $40 a piece, that could easily add up to multiple hundreds of dollars. Depends on what you're trying to do.

[BrianBSL]

Originally Posted by steven114

The nice thing about the Allegro ones is that they're free if you ask for samples
I got a six-pack of them at no cost to me. If you're using one clamp-on for each motor at $40 a piece, that could easily add up to multiple hundreds of dollars. Depends on what you're trying to do.

Agreed - I misread the question and thought he was talking about monitoring the entire robot's current consumption. For just monitoring a single motor, the Allegro sensors are great.