is it possible to use a little servo with Duet 2 WiFi?

TheDragonLord

Good morning, I was think (just for fun) to project a litte "purge arm" for my nozzles with the Duet 2 WiFi....my goal would be "simply" to have the cabability to manage the rotation to put an "arm" below the nozzles and then retract it....I see the documentatiuon for the M280 to use in conjunction with the M950
The questions are: first, are there particular ports that can be turned in servo port using the M950 or any free port should be used? second, what model of servo is best suitable?

I was forgetting to say that I already have a BLtouch installed

Thanks

o_lampe

@thedragonlord As long as the servo reaches it's endposition without buzzing it won't draw much current while it isn't moving. So, you could use BLTouch and Servo, (but not at the same time) without an external 5V supply.
A hobby servo from the 9gram clas will be fine.
You can use any PWM pin or fan output.

Is that your way to avoid oozing?

TheDragonLord

@o_lampe said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord As long as the servo reaches it's endposition without buzzing it won't draw much current while it isn't moving. So, you could use BLTouch and Servo, (but not at the same time) without an external 5V supply.
A hobby servo from the 9gram clas will be fine.
You can use any PWM pin or fan output.

Is that your way to avoid oozing?

As I said it's just an experiment, just for fun...PWM pin could be an unused heater pin? Didn't they "work" at 3,3V? So it is possible to configure two servos (BLtouch and the servo) but not to use them at the same time, right?

Thanks

o_lampe

@thedragonlord said in is it possible to use a little servo with Duet 2 WiFi?:

PWM pin could be an unused heater pin? Didn't they "work" at 3,3V? So it is possible to configure two servos (BLtouch and the servo) but not to use them at the same time, right?

We can't use the heater or fan output terminals, because they supply 12-24V. If you refer to the pins on the expansion port, then yes a servo usually works with 3.3V on the control pin.
If you also have a panelDue, it might be better to use an external 5V circuit for the servo.

TheDragonLord

@o_lampe said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord said in is it possible to use a little servo with Duet 2 WiFi?:

PWM pin could be an unused heater pin? Didn't they "work" at 3,3V? So it is possible to configure two servos (BLtouch and the servo) but not to use them at the same time, right?

We can't use the heater or fan output terminals, because they supply 12-24V. If you refer to the pins on the expansion port, then yes a servo usually works with 3.3V on the control pin.
If you also have a panelDue, it might be better to use an external 5V circuit for the servo.

I also have an external 5V circuit so this is not a problem. I thought to use a heater pin in the expansion board but can a servo be driven with 3,3V?

droftarts

@thedragonlord see https://duet3d.dozuki.com/Wiki/Using_servos_and_controlling_unused_IO_pins

Ian

TheDragonLord

@droftarts said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord see https://duet3d.dozuki.com/Wiki/Using_servos_and_controlling_unused_IO_pins

Ian

Uh, I completely missed this page!!

Thanks a lot!

TheDragonLord

@o_lampe said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord said in is it possible to use a little servo with Duet 2 WiFi?:

PWM pin could be an unused heater pin? Didn't they "work" at 3,3V? So it is possible to configure two servos (BLtouch and the servo) but not to use them at the same time, right?

We can't use the heater or fan output terminals, because they supply 12-24V. If you refer to the pins on the expansion port, then yes a servo usually works with 3.3V on the control pin.
If you also have a panelDue, it might be better to use an external 5V circuit for the servo.

I saw that the servos have 3 wires, I suppose +V, Gnd and Signal, for +5V and GND i use the external power, but could the 3,3V signal from the heater pin in the expansion board drive the servo's signal pin?

T3P3Tony

@thedragonlord said in is it possible to use a little servo with Duet 2 WiFi?:

but could the 3,3V signal from the heater pin in the expansion board drive the servo's signal pin?

yes

TheDragonLord

@t3p3tony said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord said in is it possible to use a little servo with Duet 2 WiFi?:

but could the 3,3V signal from the heater pin in the expansion board drive the servo's signal pin?

yes

excellent, thanks, what other pin in the expansion connector can I use for it? Heater 3 is already allocated by the BLTouch

T3P3Tony

@thedragonlord to add, ensure your grounds are connected between the external supply and the Duet,

TheDragonLord

@t3p3tony said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord to add, ensure your grounds are connected between the external supply and the Duet,

Yes, the external supply is a stepdown wich input is the 24VDC from the board's power supply so it's already ground-connected with the board itself. I've modified my previous post so maybe you haven't read my last question: what expansion connector pin can I use to drive the servo? heater3 is already allocated by bltouch

TheDragonLord

@t3p3tony said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord to add, ensure your grounds are connected between the external supply and the Duet,

I have installed the servo using the heater 7 pin in the expansion connector, correctly configured it and it works but now the bltouch doesn't work at all... I though that two servos can be configured in the same board but they can't work at the same time. Have I misunderstood? Only one servo can be configured and working?

dc42

@thedragonlord you can configure and run more than one servo but they must have different GpOut port numbers. The port number is the S parameter in the M950 command and the P parameter in the M280 command.

TheDragonLord

@dc42 said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord you can configure and run more than one servo but they must have different GpOut port numbers. The port number is the S parameter in the M950 command and the P parameter in the M280 command.

excellent, thanks

o_lampe

@thedragonlord said in is it possible to use a little servo with Duet 2 WiFi?:

but they can't work at the same time

To clarify that: they can work at the same time, but it might overload the internal 5V supply. (I wouldn't dare to try, since it can kill the Duet)
With a strong external 5V source, you could drive more servos

TheDragonLord

@o_lampe said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord said in is it possible to use a little servo with Duet 2 WiFi?:

but they can't work at the same time

To clarify that: they can work at the same time, but it might overload the internal 5V supply. (I wouldn't dare to try, since it can kill the Duet)
With a strong external 5V source, you could drive more servos

I have an external 5V step down connected to the main 24Vdc power supply to power them

TheDragonLord

@dc42 said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord you can configure and run more than one servo but they must have different GpOut port numbers. The port number is the S parameter in the M950 command and the P parameter in the M280 command.

is it possible to change the angular speed for the movement?

o_lampe

@thedragonlord Angular speed of a servo depends on Voltage. But a low voltage makes it weaker, too.
You can also slow it down by writing a macro that changes the angle step_by step with a pause between, but that's not a smooth slow move.

TheDragonLord

@o_lampe said in is it possible to use a little servo with Duet 2 WiFi?:

@thedragonlord Angular speed of a servo depends on Voltage. But a low voltage makes it weaker, too.
You can also slow it down by writing a macro that changes the angle step_by step with a pause between, but that's not a smooth slow move.

ok, thanks

achrn

@thedragonlord said in is it possible to use a little servo with Duet 2 WiFi?:

is it possible to change the angular speed for the movement?

There are plug-in gizmos to slow down servos, used by radio-control planes that want (for example) the undercarriage to retract at something like a realistic scale speed even if teh transmitted signal is just 'up' or 'down'. They simply plug between the receiver and the servo, so I don't see why you couldn't plug one between the Duet board and the servo.

See https://www.youtube.com/watch?v=oGJ7ymBBa2c from about 1:45 for example (but I have no idea what he's saying - maybe he's saying this unit is no good at all).

o_lampe

@achrn Right, they do the same as described above. It's just a matter of super-fine steps and shortest pauses, how smooth it looks. It's worth a try with Duet MPU clockrates.
I've seen videos of "lynxmotion hexapods" where a similar mpu controls 18 servos fluently