Hi
I would like to know where to buy the servo control card Shield V4 for my Braccio.
There are no signs of failure on the components from the card, but something is on short circuit.
With the servo control card installed on top of the Arduino UNO and all servos unplugged, when I connect the Arduino to the PC (USB), the power drops immediatly.
When I remove the servo shield from the Arduino UNO and power it with the PC (USB), The Arduino starts-up normally and I can run programs on the unit.
Powering the Shield V4 with the 7V power supply, it goes immediatly into ERROR, whether on top of the Arduino or separated, connected to the servos, or diconnected.
It's clearly a fault on the board, and I'm totally frustrated as I can't find it anywhere.
Your assistance is appreciated.
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Thank you so much.
I will try Switch Electronics and will give feedback.
Regarding support@arduino.cc, I've tried... The answers look like AI generated...
I just want to know where to buy the card, and I'm being sent on a wild-goose chase to fault find and send videos....
Through searching, it looks to me the shield is not being produced individually, and as you may have seen, unsupported. Keep trying. Something will turn up.
I do not have a source for the Braccio Shield. It has input pins (white), servo pins (orange), serial connector (yellow) and I2C connector (green)... as well as power conditioning, communication I.C.s and connections to the Arduino Uno.
You could try running without the shield, using Hardware Serial for communications.
Thank you for the support. Really appreciated.
I've looked at the PCA9685, but I was in doubt about the current capacity of the card to feed the actual motors.
But I have been dumb... I've been focused on the Shield V4 card fault and forgot to look at the basic operation of the servos!
I can connect the +- of the servos directly to the power supply (so the current won't affect the Arduino board), and use the Arduino's PWM pins for control...
The Braccio library won'twork anymore, so it will keep me busy for some time developping a new library!
I just have to make a plan for the "Soft Start" function before the arm breaks itself on start up...
I will try to work on it over the weekend and will let you know how it goes.
Thanks
If I undertood the Braccio documentation right, the soft start is done on the servo controller board (the faulty one). On the start-up, the voltage to the servos is increased slowly to prevent full torque on the servos when moving to the home position.
On the past, with the soft start function disabled, I've broke one of the splines. It can be quite violent on the change of position.
Only 2 solutions are coming to my mind....
ensure the arm is always moved to the home position (by hand), before switching on.
use a regulated power supply to the servos, to ramp the voltage up on the start...
This is one of those toys I've bought for my kids, but it's me who has fun with it!
After you mentioned softstart, I wondered if the extra components on the Shield contained firmware that did this softstart... but as you also mentioned the violent wakeup the arm can have, it seems to me the library function Braccio.begin() is necessary for the softstart to happen... and you want to find how does the Braccio software know when to use softstart.
I did some reading (link), on a reference to waking the servos with a special PWM waveform...
long int start_time = millis();
while(millis()-start_time < SOFT_START_DURATION) {
digitalWrite(SOFT_START_CONTROL_PIN,LOW);
delayMicroseconds(450);
digitalWrite(SOFT_START_CONTROL_PIN,HIGH);
delayMicroseconds(20);
}
... so that would require "softstart" information be used after a power outage... imagining the case of a fully extended arm at power loss, wanting to power-up at "90" degrees... you would need to have variables indicating "something has occurred requiring a soft start"
I agree with you that if the presence of power can be regulated (at the full 5vdc, not a variable voltage)... which might need more hardware to hold-off individual servo power until after each servo has been written to a nice angle, then use the (above) softstart PWM to wiggle each servo to a middle range, then the next servo...
I imagine the whole sketch would be wrapped in a "DID_POWER_FAIL" variable (it probably exists in the library, monitoring Pin 12!) (link). This could be the "hardware" part of the shield that signals "IF Pin 12 is NOT_GOOD, softstart."
I think the shield library can still work for your new configuration by discovering how it works or how to make it think it is working.
I just wanted to take a moment to say a big thank you for mentioning our website in the forum thread – it really means a lot! We’re always happy to help where we can, and it’s great to know you thought of us.
If there’s ever anything we can assist you or others with, please don’t hesitate to reach out. Thanks again for the kind shoutout – it’s support like yours that makes a real difference.
