It's time to bring up that old thread, again. I have designed this controller almost exactly 10 years ago for the case that the original controller of my Zevatech reflow oven broke down. Unitl now it didn't. But the conveyor speed control is getting unreliable. I got several alarms for "speed too low" recently. I've checked the encoder but it works perfectly and outputs a constant pulse frequency. So the input of the controller must be broken or the software begins suffers from "bit decay".
Anyway, I think I have to bring this project back to life. The hardware is ready and the software is almost finished. So it should take much less work and money than buying a general purpose PLC, a thermocouple analogue input converter and to program it from scratch.
Hmm, pulling all terminals from their sockets and re-inserting them again has magically cured the problem. This is good for me as it saves a lot of work, but bad for the propeller board thatt hos to wait a little longer until I finally install it.
Yeah, thermocouple currents are so small that contact resistance becomes an issue. Removing/replacing terminals 'wipes' the contacts and can cure thermocouple issues. Greater spring force on the socket connectors can lengthen the time required to repeat this procedure.
Comments
It's time to bring up that old thread, again. I have designed this controller almost exactly 10 years ago for the case that the original controller of my Zevatech reflow oven broke down. Unitl now it didn't. But the conveyor speed control is getting unreliable. I got several alarms for "speed too low" recently. I've checked the encoder but it works perfectly and outputs a constant pulse frequency. So the input of the controller must be broken or the software begins suffers from "bit decay".
Anyway, I think I have to bring this project back to life. The hardware is ready and the software is almost finished. So it should take much less work and money than buying a general purpose PLC, a thermocouple analogue input converter and to program it from scratch.
Hmm, pulling all terminals from their sockets and re-inserting them again has magically cured the problem. This is good for me as it saves a lot of work, but bad for the propeller board thatt hos to wait a little longer until I finally install it.
Yeah, thermocouple currents are so small that contact resistance becomes an issue. Removing/replacing terminals 'wipes' the contacts and can cure thermocouple issues. Greater spring force on the socket connectors can lengthen the time required to repeat this procedure.