Secondary DC-DC module for Vision Processing

It is obvious from R42-R44

R42 The roboRIO power input must be connected to the dedicated supply terminals on the PDP shown

R43 The Wireless Bridge power must be supplied directly by the 12V 2A output of a Cross the Road Electronics Voltage Regulator Module (VRM) (P/N: am-2857, 217-4245) and must be the only load connected to those terminals.
in Figure 4-11. No other electrical load shall be connected to these terminals.

R44 The VRM supplying power to the Wireless Bridge per R43 must be connected to the designated supply terminals at the end of the PDP, and not the main WAGO connectors along the sides of the PDP as shown in Figure 4-13. With the exception of a single Cross the Road Electronics Pneumatics Control Module (PCM, P/N: am-2858), no other electrical load shall be connected to these PDP terminals.

and from this thread, that you can not use the VRM or PDB to directly power an off-board Vision processor like the Jetson or PCDuino, nor can you connect a second VRM or a separate DC-DC converter to either of these “boosted” sources.

Now, as anyone who has followed 2073 at all might know, we like using the PCDuino for Vision processing when it is appropriate, and this year we feel it is.
So, with that in mind, we will be powering the board via a DROK® DC-DC Buck Converter. As far as we can tell, this is identical to the converters provided in the KOP’s through 2014 (CLL25-24S05).

Since the above listed rules prevent us from connecting this regulator to the boost regulated +12v output on the PDB or the +12v @2A on the VRM, it really only leaves us the option of using a standard +12v wago connection to the PDB. So this raises the following questions:

  1. Does anyone know what the minimum voltage input this regulator can handle before the output drops below +5vdc?
  2. Is there a preferable source to connect our DC-DC converter to?

You can wire other electronics to the VRM, just not to the 2A connectors for radio power. If you choose though you can use other DC-DC converters, we used two last year for LEDs. Ask the q and a for sure though

Is there a rule that says you cannot connect a 2nd VRM to a WAGO connector to power non-control devices, such as cameras? R43/44 seem to be specific to the Radio, but does not prevent other VRM’s on the robot. They just can’t power the Radio.

No, I do not see a rule to prevent this. There would be no need for the DROK converter though if we just used a second VRM. The issue is, the VRM is usually driven by a “Boost” converter within the PDB. You would loose that protection if you connected it directly to a WAGO output.

Is that true? The docs for the VRM sure seem to indicate that it is a boost/buck converter all by itself.

The PDP special outputs for the radio VRM are just battery voltage.
You can test it yourself by comparing a meter reading there with a meter reading on the battery.

If that’s the case, then this has become a non-issue.
The PDB does indeed have a label that calls these outputs “VBat…”.
I’m not sure where I got the impression there was a boost regulator driving those outputs.
Thanks again Mark.