In years past we needed to do similar things with PLC input modules that were driven by solid-state proximity-type limit switches. The fault was that the off-state current draw of the switch was enough to convince the sensitive input module that it had a valid input. 7500 ohm, 5-watt resistors across each input solved the problem.
But it was good detective work that found the problem with the transmitter shutoffs.
I have resolved several situations with same root cause.. inputs with not enough protection from RF sources.
A CPLD IC (22v10) on a failsaft circuit. It's inputs would pick up enough RF energy from relay contacts (equ. spark gap transmitter) loaded with inductive load. Actually erased the device!.. required 1000pf caps across all inputs for this environment (couldn't put a snubber across the contacts - leaked enough to hold the smart magnetic contactor load "on" , even when contacts opened).. and we couldn't move the relay farther away from the electronics.
Always keep mechical relays / large inductive loads away from the rest of the electronics (if possible)... just asking for trouble when close to each other.
Battery powered device with GSM transceiver/processor monitoring an external device via a simple contact closure. Reduced the pull up on the contact closure in effort to reduce battery drain (resistor array - 100K) , contact was normally closed drawing current across the pullup. The external circuit - no problem. However, the other three inputs (membrane push buttons with flex cable) would normally be "open". These inputs would close when the GSM transciever transmitted. The RF energy (not that much) would be rectified by the silicon junction on the processor input and pull the input low (randomly).... net result: it "pushed" it's own buttons when transmitting (occasionally)!
Next time , will use ferrite beads on these inputs. This time , changed pull up resistor array to 10K.
A middle school team from Rochester, Mich., has again nabbed the grand prize in the annual international Future City Competition, which drew students from 37 regions of the United States, as well as from England and China.
The word “smart” is becoming the dumbest word around. It has been applied to almost every device and system in our homes. In addition to smartphones and smart meters, we now hear about smart clothing and smart shoes, smart lights, smart homes, smart buildings, and every trendy city today has its smart city project. Just because it has a computer inside and is connected to the Web, does not mean it is smart.
Are you being paid enough? Do you want a better job? According to a recent survey Manpower released just before Engineers Week, employers and engineers don't see eye-to-eye about the state of US engineers' skills and experience.
Focus on Fundamentals consists of 45-minute on-line classes that cover a host of technologies. You learn without leaving the comfort of your desk. All classes are taught by subject-matter experts and all are archived. So if you can't attend live, attend at your convenience.