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Output use of PG 508 Pulses

John Ferguson
 

I bought a PG 508 to use to configure some model airplane servos whose actions are determined by Pulse Width Modulated signals.

I have one question about the CAL pots on some of the controls on the PG 508 panel. If there is any counsel in the manual on how these work, I couldn't find it.  It looks as though turning the knobs fully counterclockwise is the way to get the pulse-width (duration) shown on the panel-mine seems to work this way.  Is this correct?

I don't have a number for the power consumption of the signal input of the servos but suspect it isn't much.

So the second question:

Am I risking damage to either my 2445b or the PG 508 if I connect the output of the PG 508 to the servo and to channel one of the scope?

If this does look risky, I suppose answer is to make a transistor switch to make the the pulse signals going to the servo keeping the PG 508 and Scope on the control side of the transistor.

Is there something dumb in what I have in mind?  If so, what would you recommend?

john

Kurt Rosenfeld
 

Connecting the PG508 to the scope and the servo in parallel should be fine. I would connect it to the scope first to get the PWM voltage right, since the PG508 is capable of voltages outside of what most servos are expecting. After you have the PG508's output voltage set, then add the servo. I wouldn't expect the servo to significantly load the 50-ohm output of the PG508. Also beware of driving the servo with a weak power supply. It can make for flaky behavior. (How do I know this?)

John Ferguson
 

On 10/21/18 1:59 PM, Kurt Rosenfeld wrote:
Connecting the PG508 to the scope and the servo in parallel should be fine. I would connect it to the scope first to get the PWM voltage right, since the PG508 is capable of voltages outside of what most servos are expecting. After you have the PG508's output voltage set, then add the servo. I wouldn't expect the servo to significantly load the 50-ohm output of the PG508. Also beware of driving the servo with a weak power supply. It can make for flaky behavior. (How do I know this?)
U2?