We are using the new CTRE CANCoders, but I’m confused on how to wire them. Each can be supplied with 6-16V, max 60mA.
- Do I really need to use all the VRM ports?
- I think I suppose to use Y cables, is that ok by the robot rules?
- I’ve read that I can use similar device like the VRM but I cant find something of Amazon.
- How to wire 6 CANCoders? What is the technic?
So you connected all power wires into a single wago each for red and black wires?
Is that OK by the rules?
Our team did a custom circuit by using the CTRE Power Distribution Breakout PCB. This allows you to use a single VRM port and connect all 4 or more CANCoders to it.
Yes. We used two of the Wago connecters one for red and one black wire. We had one wire going to the PDP then basically used the Wago to splice the other wires in.
This is specifically allowed in the blue box in R49 in my opinion.
I am not a LRI, but am typically a robot inspector. If I were looking at a robot that had a custom circuit such as this. The main thing that I would require is that the breaker on the PDP was sized appropriately for the wiring on the custom circuit.
I would power all the CANcoders off of a single 12v 500ma port on the VRM. With them plugged into the 12V 500mA vrm port, it qualifies as both a custom circuit and a signal level circuit, which gives you a bunch of freedom in the rules. I would still recommend splicing all 6 of them together and having a single wire going in the VRM port. They each draw 60mA maximum, so power draw is not a concern with 6 of them on a single 500mA port.
My strategy has been to steer clear of the VRM leaving only the radio on it - it’s capacities are quite modest and my feeling was to avoid loading it with other loads because the radio is so crucial. The Cancoder doesn’t need regulation based on the robot’s primary power supply voltage (the battery which unloaded can get towards 14v and goes down from there)
If you’ve got a free PDP slot, powering it from there as a custom circuit (or adding it to your existing custom circuit if you are already using one for that) gives you the most flexibility. With the operating range of the device, you don’t even need voltage regulator.
If you do use a regulator, you specifically want a “Low Drop Out” type (LDO); these types of regulators will regulate higher voltages from reaching the target device but, simplistically, pass voltages lower than the regulated voltage if their input drops below the regulated voltage (to a point and with a minor voltage drop of their own). Non-LDO style regulators will just stop working (see the specs) as the voltage drops close to or below their target regulated voltage - most need the input voltage to be X volts above their regulated output voltage (2ish volts is pretty typical if my memory isn’t messed up but the spec sheet will call this out for sure).
The VRM is an LDO regulator for the record - it’s easy to see why it has be…
We splice together the Limelight, network switch, and all our cancoders into the 16th PDP slot.
It’s better than that, actually. The VRM has a pair of SEPICs (one 5 V and one 12 V). If the battery voltage drops to 8 V, for example, the VRM will boost it to provide the full 12 V on the 12 V rail.
I stand corrected. It is indeed better than I thought.
I’ll probably still keep it’s capabilities focused on the radio.
When needed, I use boost/buck converters where we want a constant voltage for just the reason @CarlosGJ mentioned - they’re all over eBay and Amazon for just a few $.
Does anyone have any suggestions about wiring CANCoders. I have done my fair share of soldering but we are finding it incredibly difficult to properly solder the wired connections and have them fit through the case.
Bend the wires before you solder, since they will be harder to bend tightly once they wick up solder. Trim them close after they cool. Other than this, it’s down to having a good iron of the right size, good solder, and technique. Try not to use more solder than you need.
Are you having trouble with the solder to the board? If so, see @nuttle’s response above. Also, don’t use anything larger than about 20 AWG, and do use stranded wire for robot applications.
Are you trying to pass a soldered-and-insulated joint through the case? Don’t. Pass the wires through the case without termination, then use whatever method you intend to connect up the power and CAN, probably Weidmullers or lever nuts. If you want to solder the daisy chain, remember to put the heat shrink tubing over one wire before soldering, and test the connection both mechanically and electrically before shrinking the tubing.
Thanks for the tips. pre-bending the wires was important and we were using 18 AWG, so that didn’t help.
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