2015 Beta Testing - The Components are Here.

[jhersh]

Originally Posted by Alan Anderson

That's good information to have.

For teams that just want to use the system as a black box and care little about the details inside it, the engineering of this power supply is great. It's the teams that put a lot of effort into understanding and analyzing that could get tripped up without having a good low-level description of how it works.

Are you suggesting this should be included in some documentation somewhere? If so, please file a tracker to Kevin.

[SteveGarward]

Originally Posted by Greg McKaskle

The PWM signals from the MXP will need to provide their own power for a servo.

Everyone needs to be careful on this one. According to the answer to my question here on the FIRST forums, once you add (separate) power to PWM signals from the MXP, you have an ACTIVE DEVICE.

[FrankJ]

Originally Posted by SteveGarward

Everyone needs to be careful on this one. According to the answer to my question here on the FIRST forums, once you add (separate) power to PWM signals from the MXP, you have an ACTIVE DEVICE.

That seems to be a poorly considered response. (Recognizing that if First stays with it, that will be the rule.) The control comes over the signal pin. So where the power comes from for the power line is immaterial from a control stand point. The MXP doesn't have a dedicated power pin for each PWM. The Vex motor pulls a lot of current at stall. One reason we stayed away from them in the past.

The motor controller are pulling their power straight from the PD board. Not much different conceptually than using a separate power supply for a servo

[SteveGarward]

Originally Posted by FrankJ

That seems to be a poorly considered response. (Recognizing that if First stays with it, that will be the rule.) The control comes over the signal pin. So where the power comes from for the power line is immaterial from a control stand point. The MXP doesn't have a dedicated power pin for each PWM. The Vex motor pulls a lot of current at stall. One reason we stayed away from them in the past.

The motor controller are pulling their power straight from the PD board. Not much different conceptually than using a separate power supply for a servo

Agreed. The only difference I can see is that the PD is a known, tested, approved power source. My best guess is that an unknown (to FIRST), untested (by FIRST) power source powering servos (to make robot parts move) may be considered unsafe, or at least a risk. This would go for anything on a board - power, other circuitry. Thus the requirement for boards doing more than breaking out pins to be approved.

That's my best guess anyway. Either way, rules may change, but for now they are what they are.

My concern now is for boards that have 'prototyping' area on it - while the board may be passive, does adding components/circuits make it active? Burden of proof at inspection to show it's just sensors etc., or that PWM pins are not controlling anything? Not sure how that will play out yet.

[billbo911]

Until we hear otherwise on the power supply added to the PWM pins from the MXP port issue, would it be safe to say:

"A really good approach would be to use the MXP port PWM pins to drive motor controllers, and the MXP DIO pins for sensors, that do not get their power over the PWM cable. Use the PWM and DIO on the edge of the RoboRio for all sensors, servo, motors etc that do get their power from the PWM cable."?

Personally I believe FIRST will more than likely approve an expansion board that provides power to these connections that is sourced from the PDB. In the mean time, we need to work with what we have.

[Joe Ross]

Originally Posted by SteveGarward

Everyone needs to be careful on this one. According to the answer to my question here on the FIRST forums, once you add (separate) power to PWM signals from the MXP, you have an ACTIVE DEVICE.

I think it would be more accurate to say say "once you add an active power supply to PWM signals from the MXP ..."

This does not keep you from supplying 3.3v or 5v from the MXP header or battery voltage from the PDP to the DIO pins, It only keeps you from adding a power supply to add a different voltage.

Originally Posted by SteveGarward

My concern now is for boards that have 'prototyping' area on it - while the board may be passive, does adding components/circuits make it active? Burden of proof at inspection to show it's just sensors etc., or that PWM pins are not controlling anything? Not sure how that will play out yet.

No matter what board you use, if you claim that it is passive, you'll have to prove it at inspection. Not sure how having a prototyping area changes that. An active circuit added to a prototyping area of an otherwise passive board makes it active.

[controls weenie]

I wanted to share with you the reason I am asking about the PWM voltages. A few of the kids and I are designing a "PWM Extender" which will attach to the robot and inline with the PWM cable. The "PWM Extender" will be 2.5" x 1.5" PCB with a row of 8 LEDS to indicate the servo (or motor) command. This will allow our team to monitor (or debug) the robot health from in the stands. The "PWM Extender" is parasitic in that it will steal from the 6V supply (middle conductor) to power a ATMEGA88 uController to drive the LEDs as a function of the signal command. There is a 5V voltage regulator.

Our team would like to place as many indicators on the robot so the driver and operator do not have to look down at the laptop. We have noticed that no one ever looks down during the competition.

Yes, it is active but only for the LEDs. We would be glad to share the design, gerber files, uController code, etc with anyone who wants it. But, I have a feeling that most will reject it.

Your thoughts?

[SteveGarward]

Originally Posted by Joe Ross

Not sure how having a prototyping area changes that. An active circuit added to a prototyping area of an otherwise passive board makes it active.

From the reply on the FIRST forums, I read that to mean that once any components at all (power or otherwise) are added to the board, and the board is no longer simply a breakout, it is an active board.

[Joe Ross]

Originally Posted by controls weenie

I wanted to share with you the reason I am asking about the PWM voltages. A few of the kids and I are designing a "PWM Extender" which will attach to the robot and inline with the PWM cable. The "PWM Extender" will be 2.5" x 1.5" PCB with a row of 8 LEDS to indicate the servo (or motor) command. This will allow our team to monitor (or debug) the robot health from in the stands. The "PWM Extender" is parasitic in that it will steal from the 6V supply (middle conductor) to power a ATMEGA88 uController to drive the LEDs as a function of the signal command. There is a 5V voltage regulator.

This is definetly active. In addition this would be illegal in any previous year, as a motor controller is not allowed to connect to a custom circuit. It would be legal for you to make a seperate board and have the roboRIO communicate the values it's sending to the motor controllers to the seperate board over another communication method (I2C, SPI, CAN, serial, ethernet, etc).

Given how hard it is to see items on the robot during a match, a better option might be to have either the roboRIO log the data you want to it's internal flash or send the data to the dashboard. Both the LabVIEW dashboard and the SFX dashboard support logging by default.

[Joe Ross]

Originally Posted by SteveGarward

From the reply on the FIRST forums, I read that to mean that once any components at all (power or otherwise) are added to the board, and the board is no longer simply a breakout, it is an active board.

Are you interpreting the 4 examples of items that are ok for a passive device as the only 4 items allowed? The definition allows many more things.

PASSIVE DEVICE or CIRCUIT: Any device or circuit whose capability is limited to the conduction and/or static regulation of the electrical energy applied to it (e.g. wire, splices, connectors, printed wiring board, etc.).

[controls weenie]

Originally Posted by Joe Ross

This is definetly active. In addition this would be illegal in any previous year, as a motor controller is not allowed to connect to a custom circuit. It would be legal for you to make a seperate board and have the roboRIO communicate the values it's sending to the motor controllers to the seperate board over another communication method (I2C, SPI, CAN, serial, ethernet, etc).

Given how hard it is to see items on the robot during a match, a better option might be to have either the roboRIO log the data you want to it's internal flash or send the data to the dashboard. Both the LabVIEW dashboard and the SFX dashboard support logging by default.

Joe, I like your first suggestion to use a serial message to another device (maybe a PCDuino) to display our commands on the robot. We can set a message buffer equal to the motor (and servo) commands then send it to the PCDuino maybe somewhere high for best 'line of sight'. This would also help us debug in the pit.

We do want to try placing the commands on the robot this year with indicators such as colored LEDs. In previous years, we have spent many hours reconfiguring the dashboard but we NEVER look down at it during competition. Even the coach is too busy to look down. This way the entire pit crew in the stands can follow the driver and operator commands to educate them on component failures. This might expedite getting the robot ready for the next match.

[controls weenie]

Originally Posted by Joe Ross

This is definetly active. In addition this would be illegal in any previous year, as a motor controller is not allowed to connect to a custom circuit. It would be legal for you to make a seperate board and have the roboRIO communicate the values it's sending to the motor controllers to the seperate board over another communication method (I2C, SPI, CAN, serial, ethernet, etc).

Given how hard it is to see items on the robot during a match, a better option might be to have either the roboRIO log the data you want to it's internal flash or send the data to the dashboard. Both the LabVIEW dashboard and the SFX dashboard support logging by default.

Has anyone seen the specs on the roborio accelerometer? I searched but could not find any information.

[Joe Ross]

Originally Posted by controls weenie

Has anyone seen the specs on the roborio accelerometer? I searched but could not find any information.

It's a 3 axis, selectable +/- 2g, 4g, or 8g. MMA8452Q

[Joe Ross]

Originally Posted by SteveGarward

From the reply on the FIRST forums, I read that to mean that once any components at all (power or otherwise) are added to the board, and the board is no longer simply a breakout, it is an active board.

With today's clarification that plugging in an active component to a passive MXP makes the MXP active, I agree with you. But it sounds like they're trying to figure out a workaround.

[SteveGarward]

Originally Posted by Joe Ross

With today's clarification that plugging in an active component to a passive MXP makes the MXP active, I agree with you. But it sounds like they're trying to figure out a workaround.

I certainly hope they do - for everyone. That clarification makes the current preliminary rules much more broad that I had anticipated or understood them to be.