Encoders for 2015 Season

[juchong]

Originally Posted by marshall

It's true. I also want a pony.... perhaps even a striped one with a horn on it.

YAY PONIES!

Every time that we've used encoders for swerve drive, we've coupled them with a 360 degree potentiometer for initial calibration. This way, you (almost) always know where your wheels are pointing and how much you're slipping.

If you throw a well-calibrated Gyro into the mix then you've got field-oriented drive + drift compensation!

We've also had great results using the US Robotics encoders included in previous KOPs. One for steering, and one for drive.

[ozrien]

That's an interesting idea.

With a custom breakout/cable you could wire out both the potentiometer and quadrature encoder for each wheel for each Talon SRX (since SRX decodes both at the same time and puts both on CAN bus).

Originally Posted by juchong

YAY PONIES!

Every time that we've used encoders for swerve drive, we've coupled them with a 360 degree potentiometer for initial calibration. This way, you (almost) always know where your wheels are pointing and how much you're slipping.

If you throw a well-calibrated Gyro into the mix then you've got field-oriented drive + drift compensation!

We've also had great results using the US Robotics encoders included in previous KOPs. One for steering, and one for drive.

[marshall]

Originally Posted by ozrien

That's an interesting idea.

With a custom breakout/cable you could wire out both the potentiometer and quadrature encoder for each wheel for each Talon SRX (since SRX decodes both at the same time and puts both on CAN bus).

That's a complicated mess though. Mounting one of these widgets is bad enough. I really just want someone to start selling 3.3v absolute encoders instead of 5v ones.

We are already building a custom breakout to do the conversion... it's just extra circuitry that I'd love to get rid of.

[jman4747]

Originally Posted by marshall

That's a complicated mess though. Mounting one of these widgets is bad enough. I really just want someone to start selling 3.3v absolute encoders instead of 5v ones.

We are already building a custom breakout to do the conversion... it's just extra circuitry that I'd love to get rid of.

Are the MXP/0-9 GPIO not 5V tolerant?

[James Kuszmaul]

Originally Posted by jman4747

Are the MXP/0-9 GPIO not 5V tolerant?

The Talon SRX analog pin isn't.

[marshall]

Originally Posted by jman4747

Are the MXP/0-9 GPIO not 5V tolerant?

They are but the Talon SRX is not. The goal is to offload PID control to the Talons. We just need more options for 3.3v absolute encoders that output a 3.3v analog values.

[ToddF]

In 2013 I put together a group buy for sealed US Digital encoders. You can see all the details in this thread:
http://www.chiefdelphi.com/forums/sh...d.php?t=116899

We absolutely love them.

Despite what the product page says (http://www.usdigital.com/products/en...otary/shaft/s4) these are available for purchase. I just got off the phone with the sales rep I worked with on the group order, and they are available for same day shipping.

If someone wanted to put together another group buy to get the price down, we would be interested in participating. But, fair warning, during build season might not be the best time to put one of these together.

[Monochron]

Originally Posted by marshall

They are but the Talon SRX is not. The goal is to offload PID control to the Talons. We just need more options for 3.3v absolute encoders that output a 3.3v analog values.

Just to put me at ease, the quadrature input pins on the Talon ARE 5V tolerant correct? It is only the analog input that needs 3.3V?

[marshall]

Originally Posted by Monochron

Just to put me at ease, the quadrature input pins on the Talon ARE 5V tolerant correct? It is only the analog input that needs 3.3V?

That is correct. I highly recommend the awesome datasheet for the Talons that CTRE has: http://www.crosstheroadelectronics.com/Talon%20SRX%20User's%20Guide.pdf

[Monochron]

Originally Posted by marshall

That is correct. I highly recommend the awesome datasheet for the Talons that CTRE has: http://www.crosstheroadelectronics.com/Talon%20SRX%20User's%20Guide.pdf

Yeah I didn't see any specifications for what voltage was allowed on the quadrature pins. Thanks!

[ayeckley]

We typically use our Automation Direct voucher towards the purchase of the TRD-family ("light duty") encoders they offer. I believe they are re-branded Koyo units.