Hi all,
I am outputting a 60hz clock signal from my Arduino to drive a pump controller that needs an input clock signal to generate a pumping frequency. When I connect the oscilloscope to the output pin and ground, I can see my 60hz square wave. With these probes still connected, I put the output pin into the pump controller and it still works great!
However, the second I remove the oscilloscope probes, my pump gets extremely loud. I believe it's still oscillating at the correct frequency but it's just REALLY loud compared to it's normal operating volume. Is the oscilloscope's internal capacitance and resistance affecting the signal (1 MOhm & 14pF)?
Also with the pump running "well" and probes connected, I do experience some discharge sounds randomly. For example, think of a car engine idling at a stoplight, every once in a while it sounds like the car engine is revved and then it drops back to it's idling frequency.
Goes from 60Hz to, maybe, double that almost instantly and then exponentially decays over 2-ish seconds back to 60Hz..
Also, I've attached to images. The first shows the 60hz signal plugged into the pump controller before connecting a 5V line to the controller, the second shows the after the 5V line is connected to the controller. See how the Vpp changes and the floor of the signal drops? Really odd
Arduino PIN9 generating 60Hz clk ----> Pump controller clk input ----> this is then sent to my actual water pump
Photos were too large, so added to imgur album, top is before, bottom is after: image order: before, after, common ground - Album on Imgur
This was hard to describe so please let me know if you need more information, thanks!