Stang-Sense

[Aaron Lussier]

I was just wondering, I heard about some of the engineers on my team talking about some thing called "Stang-Sense" that was used by the Wildstangs in past years to do some funky detection stuuf with the motors So I was wonderign if any body on CD knew a little bit more about how exactly this " Stang-Sense" actually functions any info would great help. I all ready checked White Papers and there was nothing in there on it, just so you know. Thanks and have a nice day and a better one tomorrow

P.S You can IM me if its eaiser to talk about: Bldrngmn1

[Jnadke]

It's a current sensor that monitors current draw. Useful for telling when the fuses may blow, or when the main breaker may trip.

The schematic was posted somewhere around here.

[Al Skierkiewicz]

Wheelman,
Stang Sense is our name for a current monitoring system we used on this years robot. It is capable of monitoring the current supplied to all six of our drive motor speed controllers through the dashboard port of the Operator Interface. Since the robot battery voltage is also available in the dashboard stream we monitored that as well. We were able to pass the stream to a color palm pilot that would change colors on two displays to show normal(green), caution(yellow), or warning (red) conditions of current. One display was an overhead of the robot showing the motors as colors. The other was a bar graph display of each motor. Since the palm was able to store the data in each match with a rough clock tick, we were able to analyze high current activities and warn drive team and strategy of risky behavior during matches. This system allowed us, during building phase, to recognize the new FP motors and the change in power curve. With a portable version, we were able to analyze problems on other robots as well.
We offered to connect up to problem robots at both Midwest Regional and Nationals. All in all I think we analyzed 20-30 robots and these are some of the problems we were able to help correct. Dead motor in a multi-motor drive system, locked transmission, binding bearing in a steering gear, excessive voltage drop in wiring during operation (led to change in electrical layout), excessive current while turning (typical for tank drive with high friction wheels), inefficient gear train, tripping resettable breakers, slipping clutch, and assorted wiring errors, bad crimps, loose wires and high resistance connections.
This system has been discussed here before so there is probably stuff in the archives. There is also a link on our website which is in the process of changing over to a new server. Try wildstang.com
Good luck all

[FotoPlasma]

Originally posted by Jnadke
The schematic was posted somewhere around here.

http://www.wildstang.org/ws/Inventor...schematics.asp

www.wildstang.com has been down for a while... DNS trouble, I'm told...

[Matt Krass]

Yeah the stang-sense, me and my teammates are trying to design something similar. So far we've found a ciruit to do the measuring. If it works I'll post a schematic. By the way, I looked at the Stand-Sense schematics, could be my lack of electrical knowledge but I couldn't really follow it. Maybe some documents would help it. I plan to have ours output on control panle to warn us if it's gonna blow.


Soldering Away, (And most likely burning off my hand!)
Matt

[Al Skierkiewicz]

Ask questions about the schematic and I will answer.

[Dave Flowerday]

Al, Nate Troup and myself all regularly read this board and were all extensively involved with designing the hardware and software that makes up StangSense. Unfortunately we haven't really documented much of it anywhere except for the schematics, but we'd all be happy to answer questions.

[Matt Krass]

Well if your inviting me to, I was wondering, how did you measure current? I found a simple circuit that should do it but not sure, working on a test breadboard version at moment. What circuit did you use? Is it documented anywhere?

Thanks,
Matt

[Al Skierkiewicz]

Matt,
When the site comes up the schematic is at http://www2.wildstang.com/2002/inventor/schematics.asp
The archive discussion is at http://www.chiefdelphi.com/forums/sp...=&postid=99762 and you will find a full description there.

The IC we used is from Maxim, MAX 4172, it is called a "high side current monitor" and can be purchased from Digikey. The downside is it's only available as a surface mount package. Digikey sells header boards that accept the surface mount package and converts it into a SIP you can insert in any .100 center circuit board or socket.
The Maxim 4172 is designed for monitoring current in battery charge circuits and is intended for a single power supply. It measures the voltage drop across a very small resistor and converts that and amplifies it to a suitable voltage. We used a 1 foot long piece of #10 wire as the resistor (.001 ohm)which turned out to be a good compromise since it was available for no cost, we were already using it as part of the robot (speed controller wiring per robot handbook)so there was no weight increase and it didn't need to be in the custom circuit box. The whole circuit except for programming interface fit inside the required box and a palm pilot was a valid device for use at the player station to view the dashboard output. We do owe a full explanation so that might be a future white paper. I will contact the other folks and see if we can't put something together.
Let me know if there is anything else we can help with.
Al

[Matt Krass]

Thanks, we are going to try the MAX 4172 IC, but what is part number for the ehader boards? We'll need those to build circuit. TIA,

Matt

[Mike Soukup]

Originally posted by Al Skierkiewicz
Matt,
When the site comes up the schematic is at http://www2.wildstang.com/2002/inventor/schematics.asp
The archive discussion is at http://www.chiefdelphi.com/forums/sp...=&postid=99762 and you will find a full description there.

Don't count on that happening any time soon, we're having problems getting our domain name back from our old ISP For now the web site is at http://www.wildstang.org/ and you can get the schematics at http://www.wildstang.org/ws/Inventor...schematics.asp as Jim said.

Mike

[Dave Flowerday]

Thanks, we are going to try the MAX 4172 IC, but what is part number for the ehader boards?

The Digikey part number is 33108CA-ND. There's a good picture of it here. Be warned, though: those pads for the MicroMAX version of the 4172 are really small. You will need someone who is excellent at surface-mount work to solder the 4172 to the header board. The pads on the header board lift off very easily.

[Matt Krass]

Thanks, I know someone who should be able to do it.

[Rickertsen2]

exactally how did the multiplexing thing work? also what is the advantage of using the MAX4072 instead of the 4170 or MAX4071, with the internal reference?

[Al Skierkiewicz]

Rickertsen2,
We chose the MAX4172 because it was simple, low parts count, and available from Digikey. We only needed to perform a high current to voltage translation that had a response that was good enough to follow the current pulses that are normal load currents for the input to the speed controllers. Remember that the speed controllers are rapidly turning on and off (varying duty cycle) to simulate variable voltage/current to the motor. The trick was getting a sensor to use for the input. The circuit as you have seen is designed to measure across a known length and width of printed circuit trace.

Matt Krass,
There is a quick trick for soldering flat packages. Use a small iron and tin the pads of the circuit board first. Then it is a simple matter of touching the soldering iron to the lead of the IC long enough to just melt the solder underneath and you are done. Repeat for each lead. Of course there is always the solder paste, reflow method if it's available.