
EthanSparky

Full Title: EZ-B Robot Controller Treats 7.4 Volt Supply As Too Low For Operation, Uncontrollably Restarts When Servos Under Strain
Hello! I am the other half of the duo working on the robot featured in this question. Our robot is basically a scaled-up JD with wheels rather than legs.
Our new question isn't very much specific to our robot, but it's one we've only been experiencing very recently -- our EZ Robot Controller restarts during times of great servo stress (like calibration & performing arm motions) and it relays the dreaded "my battery is low" message even when we are positive that it is receiving a constant supply of 7.4 volts, which should be exactly what the Controller requires. To our knowledge this message is only relayed when power supply drops below 6.6v, which subsequently causes the Controller to shut off.
Here is a layout of the power inputs we've tried and the components which cause strain on the power:
Attempted Supply Inputs 6 AA battery holder (came with the developer kit) - though this did do the trick last week, our Controller will no longer accept it. Regardless of whether we plug 6, 5, or 4 NEW batteries into the holder, the Controller always relays "my battery is low" after a few seconds of robot action before shutting itself down. Voltmeter measurements from the barrel head of the power connector which plugs into the Controller tell us that the AA batteries are supplying voltage ranging from 8.4 to 7.1 depending on their number and charge, which are much too high for the Controller to relay the low battery message. Also, it is preferable that our solution not include batteries which need to be swapped out every hour or so -- we prefer power plugs.
7.4v wall socket power plug (recommended by DJ Sures) - for a few sessions, the Controller would work with this indefinitely, never relaying the low battery message, though the Controller would uncontrollably restart quite often whenever we had all of the arm servos firing at once (during calibration & while performing most JD Auto Position actions). Now, this power plug acts just like the battery holder, relaying the message after mere seconds of use. Voltmeter measurements from the barrel connector here give us a constant 7.4v supplied, which also does not warrant said low battery message.
Power Straining Components The only components connected to the Controller which may be straining its power supply are as follows: 7, eventually 9 Hi-Tec (HS-5685MH) servos which are rated to operate on a range of 4.8v-7.4v. Some of these rotate against a high force of torque whenever performing arm movements. The developer kit camera which of course is built to function with the EZ Robot Controller. JD's I2C components (JD's head is plugged in to our Controller because we couldn't seem to connect to ARC without it).
So the crux of our problem is that somehow the Controller is interpreting a signal of 7.4v as below 6.6v and that our components have only recently started causing the Controller to force restart (assumed do to power issues) despite there being no recent changes in the power straining components and multiple attempts at varied supply inputs.
Any help would be greatly appreciated!
I know this topic has been done to death, but I am getting the dreaded "my battery is low" message with a 40amp 7.4v regulated power supply whilst moving one servo. I can only assume this is because the servo is under too much strain. It can't be voltage or exceeding 40 amps, surely. Any ideas?
What kind of servo are we talking about here? Large?
Just a standard EZ robot HDD 19kg servo. The arm is weighty but not overly.
https://www.ez-robot.com/Shop/AccessoriesDetails.aspx?prevCat=9&productNumber=7
I can lift the arm for 2 secs no problem. More than 2 secs and I get the error message.
This is the power supply: https://www.alliedelec.com/product/tdk-lambda/sws300a7r5/70564409/
Alright, that supply can definitely handle more than a full robots worth of servos, never mind just one. Check what the voltage is measuring coming off of that supply. It may be adjusted too close to the 7V threshold for a low battery warning. There’s a potentiometer on most supplies like that which can trim the voltage.
I did adjust the pot when I first set up the power supply so that my multimeter read 7.4v. But I will adjust it slightly and see if it eliminates the low power message.
You can also adjust the voltage threshold via software in the connection skill: https://synthiam.com/Support/Skills/General/Connection?id=16041
After some testing using my power supply, I noted that when moving the arms, the voltage drops momentarily well below 7v. Using the pot I can increase the voltage to 9 or more volts, but I am loathed to do this. Can the EZB handle 9v+ without damaging servos or other peripherals? I am thinking a regulator of some sort is required to ensure the voltage stays at 7.4v. I thought this power supply was doing that but readings suggest otherwise. What do you think?
Something like... https://www.mrpositive.co.nz/dc-dc-7-4v-44-4v-20amp-step-down-voltage-regulator-sbec/
The EZ-Robot servos are only rated up to 8.4V. You could try a regulator with it. That’s very weird that a 40A supply would dip so much.