Monday, January 14, 2013

An Electrifying Issue

Troubleshooting electrical issues is often a tricky art rather than an exact science. Not only in experiments 10.2 and 10.3, but also others not posted on the blog, I noticed a certain condition coming up repeatedly. After careful thought, I became convinced that this condition is not inherent to the properties I'm measuring but rather an issue of a mismatch between the power supply and the motor load for the two motors powering the wheel sub-assemblies.

Refer to Experiment 10.3
Time Index 00:20 seconds ~ 00:26 seconds
Time Index 00:50 seconds ~ 01:10 seconds
for examples of the behavior.

During these periods, the rotation of the wheel sub-assemblies becomes frozen (even though the motors have been commanded to rotate the sub-assemblies at a uniform speed of 1 revolution per 3 seconds) or move very very slowly.

Subsequent experiments to measure the voltage across the motors during such periods revealed that the voltage had fallen to less than 5 Volts in the motors even though the power sources, the motors and the circuits were all in good order.

Careful tests confirmed that there was nothing wrong with the power sources. They could supply in excess of 60 volts no problem. It was a mystery why the motors were not pulling the current they needed from the active power sources and rotating at the commanded rate.

Further I found that during these time periods, when I leaned over and pushed the cage with just my little finger, the input voltage would shoot up past 50 Volts in a flash. At other times, if I didn't do anything to disturb it, the cage would stay frozen for a random amount of time before returning to operating at the commanded rate.

This confirmed my suspicions. My theory took firm shape after consultations with B.L. (Thank you B.L.)!!!

It seems the motors are encountering a very heavy load during periods of increasing or decreasing current. So much so that the current/voltage demand is exceeding what the power supply can put out, (which is considerable) and are tripping the over-voltage protection circuits of the power sources, resetting the voltage to a trivial value.

The above picture shows the two rather large, powerful 22,000 micro Farad capacitors I have now wired in parallel to the motor load, at the power source terminals. The capacitors act as reservoirs of electrical energy, supplying it to the motors during crucial phases, when the load spikes and 'refilling' during periods of low load.

We are now set to resume testing again!

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