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Topic: Reverse a pwm signal to negative ? (Read 641 times) previous topic - next topic

Gadgeroonie

Hi guys,

I have a signal to drive a servo motor

The signal is a pwm and a direction pin (0 or 3.3v)

The servo driver I have is not compatible and requires a negative voltage to turn counter clockwise and a positive voltage to turn clock wise

If there a way to flip the voltage to negative when the direction pin is enabled ?

Perhaps I could use a simple h bridge and use that to flip the signal ?

MarkT

[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

JCA34F

Arduino cannot produce negative voltages, post a link to that controller.

Gadgeroonie

The servo driver is a d200s

Uses the same manual as the d100s

https://www.manualslib.com/manual/1640073/Dvs-Ds100s-Series.html

Gadgeroonie

It appears it works with negative voltages when in torque mode

Paul_KD7HB

It appears it works with negative voltages when in torque mode
The schematic shows all input signals are opt-isolated, you statement makes no sense. Are you sure you are using what you linked to?

Paul

Gadgeroonie

The schematic shows all input signals are opt-isolated, you statement makes no sense. Are you sure you are using what you linked to?

Paul
Er yes

4 inputs are optoisolated the rest are not

Regardless, i am asking how to reverse a signal voltage

Do u have any suggestions ?

Paul_KD7HB

Er yes

4 inputs are optoisolated the rest are not

Regardless, i am asking how to reverse a signal voltage

Do u have any suggestions ?
I see the following inputs:

1. servo enable
2. Pulse signal
3. Direction signal

No fourth input on the document.

But to answer your question about reversing a signal voltage, a single transistor will invert the digital signal.

Paul

AJLElectronics

Regardless, i am asking how to reverse a signal voltage

Do u have any suggestions ?
Ignoring all the other sensible advice you have been given, a simple inverter will turn a digital signal "upside down".

The other piece of advice I can give you is to check your keyboard, as the Y and O keys appear to be intermittent.

Wawa

Didn't read the document, but an opto could be normally off when connected between pin and ground, and normally on (inverted) when connected between pin and VCC.
Leo..

MarkT

Hi guys,

I have a signal to drive a servo motor

The signal is a pwm and a direction pin (0 or 3.3v)

The servo driver I have is not compatible and requires a negative voltage to turn counter clockwise and a positive voltage to turn clock wise
Well that's not the case is it - the position mode wiring diagram on page 4 clearly shows a standard
step/direction opto-isolated interface....
[ I will NOT respond to personal messages, I WILL delete them, use the forum please ]

TomGeorge

#11
Aug 03, 2020, 04:38 am Last Edit: Aug 03, 2020, 04:40 am by TomGeorge
Hi,
Have you tried a connection where the direction terminals are either connected to 5V or left open.

-5V is not the case, it is a simple logic HIGH/LOW to give you the two directions.
The terminals are polarised to make sure you activate the opto.
The wires are shown zig-zagged because they represent twist pairs.

It will be interesting to see if 3.3V will be enough.

So forget about -5V needed.

Tom.... :)
Everything runs on smoke, let the smoke out, it stops running....

Gadgeroonie

The diagram in the manual is for position mode

Torque mode uses different pins

Pin 5 is for the torque voltage

‐‐-------------------

What i want to do is flip a 'analogue' voltage to negative

Ie 0.15 volts becomes -0.15 volts when the direction pin is enabled

AJLElectronics

What i want to do is flip a 'analogue' voltage to negative

Ie 0.15 volts becomes -0.15 volts when the direction pin is enabled
Except that the concept of 0.15V is nonsense in this case. PWM is a digital signal. It stands for Pulse Width Modulation. It moves between logic 0 and logic 1 only.

Gadgeroonie

Except that isnt the case

The voltage is cleaned from a pwm to a smooth analogue voltage using a DAC

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