SOLVED - Autonomous RC - using the RC battery

I have a Traxxas model whose receiver went bad, and so we've pulled that, and will just run signal to the ESC and servo.

I'm no electronics wiz, but I'm just replacing one component for another, here. I think that I need to put a resistor in the lead that sends power from the ESC to the servo. Black and red from ESC to servo, but white from PWM on the arduino. I'm getting 6v off of the ESC, but it's too much. (the servo nominally wants 4.8v or it won't move any farther than the twitch when it gets initial power) If I run it with a 5v external, it works fine. If I run it from the Arduino, it works fine. But I want to use power from the battery pack, just like the car uses today. In fact, if I could get the whole system - Arduino included - to run off of the same battery, that would be just swell...

So is this just a simple matter of one single resistor?

No.

failsafe7:
So is this just a simple matter of one single resistor?

No. But with no details of what ESC or servo or battery you're talking about it's not easy to be more definite.

Steve

Never saw an RC servo that wouldn't run off 6V

The ESC is a Traxxas Velineon VXL3M.

Servo works perfectly off the Arduino board for power and signal. When swapping to external power - in this case, a resistor on the breadboard, dropped to 4.8v - it doesn't work at all. No resistor see 6v to the servo. Nothing happens.

Never saw an RC servo that wouldn't run off 6V

Nor I.

When swapping to external power - in this case, a resistor on the breadboard, dropped to 4.8v - it doesn't work at all

  1. Don't use a resistor.
  2. Connect the grounds.

I thought I made it clear before, but if not - that’s doesn’t work.

Arduino 5v to servo - works
Battery from ESC to servo (6v) - doesn’t work
Battery from ESC to resistor on breadboard to servo (4.8v) - doesn’t work

The multimeter says I have the correct voltage in every single case.

I am running the servo test code on pin 9, in every single case.

AWOL:
Never saw an RC servo that wouldn't run off 6V

Regardless, that wasn't the question. I have a servo that isn't working in this arrangement, and the question is, why not?

My posts are thought out and purposeful, and if I miss details, I'll be back to fill in the blanks. No drive-by one liners, please. Not helpful.

Battery voltage is?

I have been, of late, building my own USB battery banks that have been doing well for powering my Arduino and Raspberry Pi projects.

There are a number of products, Amazon, that can be used to safely recharge a 18650 and to convert the battery power to 5Vs.

C=xT

C = amps per hour, x = current, T= time in hours gives me a decent idea of how long the project will run for on a battery. I put 2 or 3 batteries in parallel for longer run times; which makes for longer charge times.

I've built a test rig so that it is easy for me to hook up the project to measure its current drain. I plug various numbers in for T to get an estimate of the amp-hour needed. The T will be lower as the voltage converter will consume power and the batteries age.

I have a Arduino ProMini based GPS unit with display, sensors, and various functions, based on switch selections, that runs for 30+ hours, continuous on 2, parallel wired, 18650 2600mAh, hooked into a KNACRO DIY 3.7V to 5V 1A Lithium Battery Board Module Board Charger USB Mini USB Lithium boost module (https://smile.amazon.com/gp/product/B01HNHNE0A/ref=oh_aui_detailpage_o03_s00?ie=UTF8&psc=1)

I thought I made it clear before

What you have made quite clear is that you don't understand the power requirement for servos, which is typically 4.8 to 6V at 1 Ampere or higher.

Please identify the exact type of servo, and post one or more hand drawn wiring diagram(s) showing your attempts. Include all signal, power and ground connections.

failsafe7:
Regardless, that wasn't the question. I have a servo that isn't working in this arrangement, and the question is, why not?

My posts are thought out and purposeful, and if I miss details, I'll be back to fill in the blanks. No drive-by one liners, please. Not helpful.

I've been using RC servos since the 1970s, correctly wired and powered by four packs of AA or AAA cells, either alkaline (6V) or NiCd (4.8V), and I've never had a problem with either.

failsafe7:
My posts are thought out and purposeful, and if I miss details, I'll be back to fill in the blanks. No drive-by one liners, please. Not helpful.

Back in post #2 I suggested that details of the ESC, servo and battery you're using might help. I'm still waiting for any information about the servo or battery.

BTW when you are powering the servo from the 6V ESC/BEC are you also connecting the BEC ground to the Arduino ground?

Steve

Thank you to the person who, without any contention, whatsoever, pm'ed me, to let me know that Arduino has to see the ground from the battery pack.

One single wire, and problem solved. Works now with or without resistor.

I don't think you connected the grounds, Dave.

  1. Connect the grounds.

Helpful hint: if you continue to post on this forum, read the replies.

jremington:
Helpful hint: if you continue to post on this forum, read the replies.

And just maybe the OP will now appreciate why posting connection or circuit diagrams is so often requested.

That's the thing about knowing something about a subject; you understood what you meant, I missed it.

Had you mentioned specifically connecting the battery ground back to the Arduino, it would have been obvious.

When you are dealing with a subject that is new to others, but not yourself, details matter The person who sent me the message told me in one sentence what the problem was, then explained it.

I can't just be dismissive of you, because you took the time to reply. But I offer that as a constructive criticism. Everything is easy when you know how it's done. :wink:

Had you mentioned specifically connecting the battery ground back to the Arduino, it would have been obvious.

What part of "connect the grounds" is not clear to you?

failsafe7:
When you are dealing with a subject that is new to others, but not yourself, details matter

You were asked;

Please identify the exact type of servo, and post one or more hand drawn wiring diagram(s) showing your attempts. Include all signal, power and ground connections.

And you did not reply, do the details not matter ?

srnet:
You were asked;

And you did not reply, do the details not matter ?

Because someone with both knowledge AND tact replied before I was able to read the follow-ons.