I’m trying to integrate a 40+ year old ac motor and remote controller with a device using modern ADC controllers to remotely manage the motor turning process.
The legacy gear is an old CDE Ham-M amateur radio antenna rotator which converts maximum voltage (26 VAC) to a compass heading. The tower mounted rotor includes a 500ohm resistor (wound on a 360 degree platter on the motor axis) which reports the voltage to a meter converted to a compass direction.
The issue at hand is some of the windings on the 500 ohm pot in the remote motor aren’t in perfect condition. When the rotor is turned with the legacy controller, the meter spikes in voltage around some compass headings, which gives the ADC circuit fits. Apparently, the device with the ADC samples so frequently, that when the legacy devices reports momentary voltage spikes (1-2VAC), the ADC device gets so many different values so quickly, that it sends many different relay commands to stop, reverse or advance the motor. The relays in the digital device chatter rapidly, sending commands to turn CW, then CCW and then brake, that finally high current in the motor exceeds the fuse rating. When this occurs, the motor is stalled/paralyzed, often resulting in a blown fuse.
The motor xformer is rated at 26VAC protected by a 3A 3AG (fast blow) fuse.
I’d like to implement a circuit change that will smooth these spikes/variations and reduce the ADC measurements that cause the relays to send CW, CCW and brake commands in rapid succession.
I’m wondering if a decoupling cap across the circuit reporting voltage would smooth the voltage reported to the ADC? If so, what would be a likely uF value? This variability in voltage is for no more than 2-2.5 seconds and less than than 3VAC, until the swiper on the 500 ohm pot reports steady voltages and the ADC is “happy”.
Or do you recommend a different solution to smooth the voltage?
