Multi-Timer to determine 12V motor run times

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TurboDave

Joined Sep 4, 2020
1
My first post. Glad I found this site.

I'm dealing with imprecise linear actuators with 12V motors that I'm trying to match up as pairs based on the time it takes for (1) the shaft to extend then (2) retract. The idea is to measure an actuator for motor run time to extend then time to retract (from 3 seconds to 11 seconds depending on which actuator type is being tested).
Operation: Power (12V) is applied and the actuator starts to extend, once an internal limit switch is activated, the motor shuts off - shaft is extended. After a few seconds, the power supply polarity is reversed and the actuator shaft begins to retract, again once an internal limit switch is activated, the motor shuts off. This is one cycle. I want to measure the up and down travel duration (motor run time for each direction) of several actuators. I will then match them up into pairs based on closest extend/retract durations. The device probably needs to display to at least 10ths of a second. Is there something off the shelf that will digitally display a 12V DC motor run time? I'm thinking of something like a ammeter donut connected to a digital device that times only when current flows through the donut?? Maybe there is some inexpensive off the shelf gizmo? Tried to google, but don't really know what to call such a device.
 

KMoffett

Joined Dec 19, 2007
2,903
If DIY is OK, I once made a series of cheap stop watches to time the the inhalation and exhalation times of a old water filled cylinder medical spirometer. I used MOSFETs across the timers' Start/Stop button terminals. The MOSFETs were driven by CD4093 XOR gates as simple edge detectors. The MOSFETs gates were fed from a differentiator with that was connected to the patient's airway hose. This was 40 years ago, and I've lost the schematic. :( I did find this in my files:

StopwatchTrigger.png
 
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