Current Sensor
 

Has anyone figured out/found the schematics for the current sensors? We have been trying to figure them out but without the schematics or a larger picture than the one on the wiring diagram we can't really do too much. If you have had better luck, can you post the links/info?

Re: Current Sensor
 

We were having trouble with them as well. From the picture, it looks simple enough to assemble, but it looks as if the spot where the pwm cables are supposed to connect won't fit. Anyone have any suggestions for making that connection? Thanks.

Re: Current Sensor
 

Where is this picture? Is it on usfirst or somewhere else?

Re: Current Sensor
 

what are u guys planning to do with these? for all of u with 2 speed trannys, this is a nice way to set up a relatively easy auto transmition


:] <--- i never really got this smiley

Re: Current Sensor
 

I can't really say for everone else but I think a general agreement would be to use it to regulate motors. In the past, many (I know mine has) teams have experienced problems with the breakers flipping due to improper gearing and strain on the motors. With the sensors you can use the program to automatically reduce the motor outputs when the current goes too high.

Re: Current Sensor
 

The sensors are Allegro ACS750SCA-075 chips. A sheet of paper came in the same bag with a schematic of how to assemble the sensors. They output an analog value according to the amperage through the large terminals.

Here is the manufacturer's product page, and here is the datasheet.

Re: Current Sensor
 

Really? We didn't get one! Would it be possible for you or somebody to scan the sheet and upload it to the papers section?

Re: Current Sensor
 

I'll see what I can do, tomorrow.

Re: Current Sensor
 

All the teams I've worked with got the circuit diagram in the programming box inside the plastic with the Nuts & Bolts magazine. Oddly enough it wasn't in the Sensor bag.

Data sheet link
 

Hi all,

I am very hopeful that this addition to the kit will be useful to teams.

I work with Allegro on my day job from time to time. I was very excited to see this chip in their "what's new" junk mail they send out every so often.

Anyway, after sending the data sheet to FIRST along with some samples and lots of leg work by Charlie Jost of FIRST, here they are.

For some reason the data sheet must have missed some of the kit packing.

See this link for your very own pdf data sheet: http://www.allegromicro.com/datafile/0750-075.pdf

Good luck using them.

Joe J.

Re: Current Sensor
 

So does anyone understand how those pwm connections are working? Like I said before, either we're reading the schematic/picture wrong, or it looks as if we're going to have to cut the pwm cables to make them fit where they're supposed to. I hope someone can get back to me on this one.

Re: Current Sensor
 

I only got to see the sensor parts briefly while inventorying our kit but I thnk that there was a plastic piece with three holes for the pwm cable on one end and pins on the other to fit the circuit board. I am not certain, but that may be the piece you are looking for.

Re: Current Sensor
 

Well the PC board came with 3 rows of 3 pins. Each row is obviously connected together.

The first row (closest to center) is for the chip itself. It should fit snug in those 3 holes with the big leads in the holes on the other side of the board.

In the next row we put the capacitor. I can't remember exactly what pins it should go in, refer to the sheet included in the kit for that (pay attention to polarity).

The last row is where we put the pwm cable. You may have to trim a few strands from each wire to get it to fit in the holes. Make sure you get the wires in the right pin (white -> output, red -> Vcc, black -> ground). See the datasheet for what each pin on the chip is for.

One problem we had was soldering. The small pins were easy, but the bigger leads were more difficult. It was impossible to do with some of our 850 F irons, but mine at home was hot enough to do.

We also were not sure how to solder the 10 AWG wires in those holes (which are much bigger than a 10 AWG wire). We ended up running a wire through the holes and along the back of the PCB. Then we removed the insulation around where the wires touched the metal rings and soldered it there. Then we cut the wire short and added connectors on the ends. Finally we used liquid electrical tape to seal off the bare metal. Once again it was difficult to solder, but we managed.

I think this thing is great. The first day we set up a simple experiment where we had the CIM reverse directions at full speed (no load) every 500 ms. When the motor changed directions, we were reading current of up to around 60 - 70 amps. Then the 30 amp breaker started getting hot and it started tripping. We plan on doing more experiments and hopefully use it to determine problem spots in our drive train (tripping breakers has always been a problem with us).

Re: Current Sensor
 

When I first saw these terminals, I thought of ring connectors with nuts and bolts. I don't have them in front of me right now, so I can't say how effective my thoughts would be, but I have a hunch that we weren't supposed to solder the 10AWG wires to the board, itself.

I have yet to do anything involving the current sensors, sadly.

Re: Current Sensor
 

If you look at the Robot Power Distribution diagram, you'll see the the positive wires running from the motors are routed through the large holes in the sensors.