Re: Best gyro for frc.
 

We'll be providing Java, C++ and Labview on the Roborio, and we also will provide sources for apps in Java (Processing) and C# on a PC.

If you would like to discuss Python development, please contact me at scott@kauailabs.com. You'll need to decide if you want to interface serially (UART/USB), I2C or SPI.

Re: Best gyro for frc.
 

What are you looking at price wise?

Available kickoff? Through andymark?

Re: Best gyro for frc.
 

Available soon after kickoff. At Andymark. Pricing details to be announced on Jan. 3.

Cool, thanks. Out of interest what arm platform are you using (Si Labs, ST etc)?

Re: Best gyro for frc.
 

STM32F411 @100 MHz; firmware developed in Eclipse C++, debuggable over SWD port with a ST/Link V2 adapter.

Re: Best gyro for frc.
 

Increasing the distance to the source of magnetic field interference is also very effective. The strength of the coupling is inversely proportional to the cube of the distance.

Re: Best gyro for frc.
 

I don't think you'd need mu-metal to shield because it's a higher frequency magnetic field. The new victors switch at 15 kHz, so copper, aluminum or preferably steel may make an effective shield. That said, if your problem is due to the DC magnetic field from something like the battery cable, copper or aluminum won't do much. However, the DC magnetic field is much weaker than the fields from the motors, which are quite noisy. The motors brushes create lots of really high frequency em fields that can be blocked by copper.

The best way to solve the interference problem is to twist the gyros signal and return cable. The two conductors act like a loop which pick up the magnetic field from your motors. Twisting these two conductors will decrease the effective loop area and greatly reduce the interference. You can prevent common mode interference with a grounded shield on the conductors.

Increasing our switching frequency to 15khz makes interferences problems 15 times worse than the 1khz.

Re: Best gyro for frc.
 

I intended to speak in very general terms only. I agree that mu-metal is of little benefit in the FRC context, but for different reasons than what you are referring to. Philso's approach (above) certainly offers the highest bang-to-buck ratio. The last time I had to buy mu-metal (~1994) I think the minimum order quantity was 1000 lb. It's also nearly the same density as lead.

Would there not also be a "low" frequency (<2 KHz-ish) magnetic field associated with the fundamental brush-pass frequency, in addition to the broad, higher-frequency spectrum you described? I'm being wishy-washy on the exact frequency because I don't recall the armature design of the CIM. I don't believe I've ever had one apart, personally.

Strongly agree. Also effective for E-field shielding.

Not sure I agree there, but that's off-topic.

Re: Best gyro for frc.
 

You're probably right here. I know that brushes can radiate a lot of electromagnetic fields over a large range of frequencies including some higher frequencies (well over 15kHz), but I don't know about the lower end and how strong different frequencies are. If the lower frequency fields are the problem, then I agree, twist and try to move farther away.

For higher RF frequency, you don't need to have a high permeability to block magnetic fields. I think the 15kHz frequency is in this higher range where it's easy to shield with conductive metals.

A higher frequency magnetic field causes more interference, both common mode and differential mode.

The noise that's induced to the gyro's signal through differential mode interference (meaning your gyro's cable is acting like a loop, picking up the magnetic field) is proportional to the effective loop area, the strength of the magnetic field, and the frequency of the field. Each time the motor's power switches from on to off, faraday's law says that some voltage induced in your gyro's signal. If the event happens 15 times more often per unit of time, you get 15 times more noise.

For common mode interference, which is when both your return and signal are affected in the same way, a higher frequency magnetic field will provide more opportunity for parasitic capacitive coupling to ground.

However, the higher frequency may be easier to shield from, but I don't think I've ever seen an FRC team use shielded cables for anything before.

Re: Best gyro for frc.
 

Sorry I'm a little late to the party on this thread. As far as this gyro goes (ADXRS453), it looks like there are two packaging options (ADXRS453BEYZ and ADXRS453BRGZ), I'm wondering which one you would recommend, and how you interface with it.

Thanks in advance.

Re: Best gyro for frc.
 

Unless you're designing your own PCB, you probably want to just get an evaluation board - EVAL-ADXRS453Z. The SPI interface pins are broken-out to through-hole contacts that are easy to solder to.

digikey product page

Re: Best gyro for frc.
 

And you'll have 6 wires in total (labeled on the breakout board): PDD, GND, CS, MISO, MOSI,CLK (Pdd = 3.3-5V). CS is held low during read/write operations, and the other pins are wired to the SPI interface on the roboRio (or Arduino, or cRio)

Re: Best gyro for frc.
 

Hey AdamHeard,

The NavX is on Andymark website for $99.00.
http://www.andymark.com/product-p/am-3060.htm

Re: Best gyro for frc.
 

They are currently showing "out of stock". Do you believe that is incorrect, or is it possible that they've sold out already? Will you be able to resupply them "quickly" if that's the case? To me, "quickly" (given that we're at the start of build season) would be within two weeks.

Re: Best gyro for frc.
 

They should be available at Andymark in about one week. Andymark is recommending interested parties click on the "email when available" link to be informed when they are available.