CAN to PWM converter?

[Chris is me]

Originally Posted by ASD20

I'm guessing the main one is that a poorer team would not have to buy all new motor controllers if they wanted to connect everything with CAN

I mean, what is the advantage of using CAN on a motor controller that does not support it? You don't get any of the cool CAN-only features of the Talon that way. I'm not the most electrical / software guy so I think I'm missing something here.

[nickbrickmaster]

Originally Posted by Chris is me

I mean, what is the advantage of using CAN on a motor controller that does not support it? You don't get any of the cool CAN-only features of the Talon that way. I'm not the most electrical / software guy so I think I'm missing something here.

The advantage I see is being able to connect all your devices in sequence.

[asid61]

Originally Posted by Chris is me

I mean, what is the advantage of using CAN on a motor controller that does not support it? You don't get any of the cool CAN-only features of the Talon that way. I'm not the most electrical / software guy so I think I'm missing something here.

Mostly just the ease of wiring. Plus, if you already own PWM motor controllers, if one can make a CAN-PWM converter for $2 or $3, it's not a bad investment to purchase them instead of SRXs. Personally, if I wanted to do CAN control the next year, I would rather purchase a few converters before jumping on SRXs; SRXs could be used for the motion profiling, and the converters for less critical applications.

That being said, if I could get a converter working, then it's possible to increase the size of the microcontroller and add support for PID or something, although at that point we're getting into SRX territory anyway. Kind of unfortunate that the rules disallow it, although the rule makes sense.

[AdamHeard]

Originally Posted by asid61

Mostly just the ease of wiring. Plus, if you already own PWM motor controllers, if one can make a CAN-PWM converter for $2 or $3, it's not a bad investment to purchase them instead of SRXs. Personally, if I wanted to do CAN control the next year, I would rather purchase a few converters before jumping on SRXs; SRXs could be used for the motion profiling, and the converters for less critical applications.

That being said, if I could get a converter working, then it's possible to increase the size of the microcontroller and add support for PID or something, although at that point we're getting into SRX territory anyway. Kind of unfortunate that the rules disallow it, although the rule makes sense.

if it were a COTS converter for FRC it would likely be in the $20-30 range (if not more).

You also give up most of the usefulness of CAN while doubling your number of control system connections.

[Chris is me]

Originally Posted by asid61

Mostly just the ease of wiring. Plus, if you already own PWM motor controllers, if one can make a CAN-PWM converter for $2 or $3, it's not a bad investment to purchase them instead of SRXs..

I don't think people actually invest in the SRXs simply because they prefer the wiring layout of a CAN system. If you're using SRXs and CAN, it's to take advantage of the features that require the CAN bus (e.g. PID). These features don't become a thing on other speed controllers just by converting PWM to CAN. It's not a good idea.

[asid61]

Originally Posted by AdamHeard

if it were a COTS converter for FRC it would likely be in the $20-30 range (if not more).

You also give up most of the usefulness of CAN while doubling your number of control system connections.

Forgive me, but I don't know enough about CAN to see where $20 to $30 came from. I was looking up general-purpose CAN controllers and microcontrollers and found options in the $1-3 range, and PCBs should only cost $1-2 tops. What would drive up the cost?

Originally Posted by Chris is me

I don't think people actually invest in the SRXs simply because they prefer the wiring layout of a CAN system. If you're using SRXs and CAN, it's to take advantage of the features that require the CAN bus (e.g. PID). These features don't become a thing on other speed controllers just by converting PWM to CAN. It's not a good idea.

That's pretty fair. But if you could do it for cheap or wanted to try out CAN in general, a cheap converter would be useful. Plus, it would be easy to go from converter to SRX without changing much code.

[AdamHeard]

Originally Posted by asid61

Forgive me, but I don't know enough about CAN to see where $20 to $30 came from. I was looking up general-purpose CAN controllers and microcontrollers and found options in the $1-3 range, and PCBs should only cost $1-2 tops. What would drive up the cost?



That's pretty fair. But if you could do it for cheap or wanted to try out CAN in general, a cheap converter would be useful. Plus, it would be easy to go from converter to SRX without changing much code.

Not all of the profit in the per item reference frame goes to the overall business profit... Most of it is eaten up by salaries of engineers, warehouse, quality control, support etc...

I know nothing about the COTS FRC Market, but I wouldn't be surprised if the per item cost on a Talon SRX is in the $20-40 range.They need to sell it at $90 to cover all the overhead and still make a profit.

[Andrew Schreiber]

Originally Posted by asid61

Forgive me, but I don't know enough about CAN to see where $20 to $30 came from. I was looking up general-purpose CAN controllers and microcontrollers and found options in the $1-3 range, and PCBs should only cost $1-2 tops. What would drive up the cost?



That's pretty fair. But if you could do it for cheap or wanted to try out CAN in general, a cheap converter would be useful. Plus, it would be easy to go from converter to SRX without changing much code.

PCB fabrication is cheap, populating it? Less so. Add in a case, quality control, development costs... I've got a hunch COTS would be in that range if not a little higher.

[FrankJ]

Not to mention programing & design time. If you are doing it as a hobby or have students do as a project that might not be much of an issue. If you have to actually pay your programmers and engineers, it starts to add up. Quite expensive for a prototype or small production run. Obviously the per unit costs come down with the more you make.

[MichaelBick]

Originally Posted by asid61

Mostly just the ease of wiring

I'm going to agree with Adam here and add on. One of the bigger negatives of CAN is that if your first connection in the daisy chain fails, all of your motor controllers go down. Although CAN seems like the easier method of wiring motor controllers, it has its fair share of issues.