Ask Aaron: Why Not Ask ChatGPT?

Questions and Answers about Combat Robotics
from Team Run Amok

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Why Not Ask ChatGTP?
Q: You're a dinosaur. Why bother to 'Ask Aaron' if you can just ask an AI chatbot like ChatGPT? Do us all a favor: shuffle off to the old age home and get out of the way of progress. [The Beautiful Willamette Valley of Oregon]

A: Yes, I did ask and am now answering my own existential question. AI chatbots are getting a lot of press coverage with speculation that they may replace a lot of human authorship. Maybe it's time to let a chatbot take over my duties here at Ask Aaron?

Here's a recent simple question to Ask Aaron with my response:

Q: I just switched to full brushless and for the first time find myself running a setup where none of the speed controllers have a built in bec. How do I wire in an external bec? Thanks for the help. [Social Media]

A: [Mark J.] Wire the BEC in between the battery power buss and the receiver -- just like the ESCs. You may plug it into any available port on the receiver.

My response is brief, but between the diagram and the knowledge that the question comes from an experienced combat robot builder I think it was sufficient.

Let's give ChatGTP an audition: I fed the same question - adding the context that it was about an R/C robot - into ChatGPT and received the following answer:

If your new brushless motors do not have a built-in BEC (Battery Elimination Circuit) and your speed controllers also lack BECs, you will need to add an external BEC to power your receiver and servos.

Here are the steps to wire in an external BEC:

  1. Disconnect the power source (battery) from your R/C robot to prevent any accidental short circuits while you work.
  2. Locate the positive and negative wires coming from your speed controllers that lead to your receiver. These wires are usually connected to the throttle channel on your receiver.
  3. Cut the positive wire and strip a small section of insulation from each end.
  4. Connect one end of the cut positive wire to the positive input of your external BEC. Connect the other end of the cut positive wire to the positive input on your receiver.
  5. Connect the negative wire from your speed controller to the negative input on your receiver.
  6. Connect the negative output of your external BEC to the negative input on your receiver.
  7. Reconnect the battery to your R/C robot and power it on to test your setup. If everything is wired correctly, your receiver and servos should receive power from the external BEC and your brushless motors should function properly.
Make sure to follow the manufacturer's instructions for your external BEC and verify the voltage and amperage rating of your BEC matches the requirements of your receiver and servos.
Well, the general advice given is not awful, but the described circuitry won't work.

  • No brushless motors have a built-in BEC.
  • An opto (no BEC) ESC typically has no positive (red) wire in the cable to the receiver -- just a signal (white) and ground (black).
  • If an opto ESC has a red wire in the receiver cable, it is a 'dummy' that carries no power.
  • The BEC power should come direct from the battery, not thru the ESC.
  • Three critical wires remain unattached - see diagram:
  1. the BEC positive power output;
  2. the BEC input ground; and
  3. the remaining end of the hypothetical positive wire from the ESC to the receiver.

Maybe if there was a diagram to accompany the text it would be possible to make some sense of it? I re-submitted the question to ChatGPT and added "Draw a diagram":

Sure, I can help you with that!

To wire in an external BEC (Battery Eliminator Circuit), you will need to connect it between the battery and the receiver. Here's a diagram to help you visualize the wiring:

In this diagram, the BEC is represented by a rectangle labeled "BEC." The positive and negative leads from the battery should be connected to the input terminals of the BEC, which are usually labeled "BAT" or "IN." The output terminals of the BEC, which are usually labeled "OUT," should be connected to the receiver's power input terminals. Be sure to observe polarity when making these connections: the positive lead from the battery should be connected to the positive input terminal of the BEC, and the positive output terminal of the BEC should be connected to the positive power input terminal of the receiver. Likewise, the negative leads should be connected to the negative terminals.

Once you have made these connections, the BEC should provide a steady, regulated voltage to the receiver and other electronics in your R/C robot. This will ensure that they operate correctly, even as the battery voltage drops during use.

OK, the diagram is useless but the text has the BEC correctly wired to the battery and receiver. If you can figure out which receiver pins are positive and negative there is a chance you could get this to work.

I decided to try a different approach and handed the question back to ChatGPT with a request to "Reply in HTML code" so that I might just drop the answer into the webpage:

To wire in an external BEC, you will need to follow these steps:
  1. First, locate the positive and negative wires on your ESC (Electronic Speed Controller). These wires will typically be red and black.
  2. Cut the red wire, leaving enough length to connect the BEC.
  3. Connect the red wire from the ESC to the positive input of the BEC.
  4. Connect the black wire from the ESC to the negative input of the BEC.
  5. Connect the positive output of the BEC to the positive wire of your receiver.
  6. Connect the negative output of the BEC to the negative wire of your receiver.
  7. Make sure all connections are secure and insulated with electrical tape or heat shrink tubing.
So close... so very close.

2. Cut the red wire... severs the entire circuit connection to the positive battery terminal, and it never gets re-connected. If you just leave out Step 2 and provide a diagram of the correct circuit this would work.

...but it also screwed up the HTML code with tiny red and black for no reason.

It looks like I'm still needed around here.

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